High Engine Temp! Need Help Asap Guys!
 

My 86 560 SEL has up until now been running just fine at a steady 82 to 85 degrees whether or not the a/c is on unless its about 90 outside and I'm standing still in which it climbs to fluctuate just above/below 100 degrees. At that time the car just had distilled water in her system (because I was waiting for MB coolant to arrive) I recall that when I did replace with the MB coolant, she'd spit it up through the radiator cap and that was why I just put the water in it as a temporary fix.

I just replaced the coolant system with PEAK 50/50 pre-mixed antifreeze (which is also orange in color like the MB fluid) and ever since, she's been running at 100+ regardless of cruising at speed and almost 110 when stopping in traffic. She's been sitting since last Thurs because we left town and upon leaving for work this morning, I noticed that the radiator light came on/off and when I went to fill the car with gas, topped her up with water (again) but when on the highway,the temp shot up to 110+ and as I parked her, went up to damn near 120 and the aux fan kicked in.

Once parked I left her on (because the aux fan STOPS when you remove the key) but noticed the orange fluid bubbling out from the expansion tank area (leaking from the cap). This only happens when I've put antifreeze in her but she ran just fine with water. Any suggestions or advice how to get her back down to normal? I'm wondering if air is in the system. How do I check this and should I just go back to the distilled water? It has a new radiator and cap that have only been installed within the last six months. I'm paranoid that something is screwed with running her with such high temps if this is the case. I've been told that the 560's are supposed to run between 95 and 105 anyway but I've seen on threads that some run just above 80 (which mine did before now- with the water). Need suggestions as quick as you guys can get it to me before I leave here. I'm tempted to tow her home I'm so nervous. Thanks in advance and wish me luck!;)

Alan

I'm not a 560 owner, but have gone thru similar situations with another 126 car.

Coolant raises the boiling pint and lubrictates various cooling sys. components. By running straight water, you are lowering the boiling point and providing no lubrication for your system.

It's possible that you have an excessively high concentration of coolant. Too much coolant can cause overheating. Should be no more than 50/50. It's also possible you have air in the system. Perhaps someone will chime in with 560 air-bleed procedures.

How about your thermostat. Is it installed correctly. There's an air-bleed valve on most that needs to be at the highest position.

Yea the thermostat is working fine. This has only happened since I changed the coolant. I'm "hoping" it is just air in the system since the car hadn't been through anything to prompt me to change the coolant except me just wanting to put coolant in instead of just water. I also have a pretty steep hill from my driveway/garage area and thinking the slight incline didn't get all of the coolant to the system preventing it from keeping the air pockets out. Hopefully I can get some "expert" advice as far as testing to see if air is in the system and getting this air out if this is the case. Thanks for your input...

Alan

also, the antifreeze is supposed to be a 50/50 mixture that needs no water to be added (although I've had to keep topping up with just that).

I had dealt with this grief a year ago and it might sound stupid...

...is the coolant cap on securely?

Coolant will spill out of the overflow tube, but not from the cap...unless the cap isn't on properly. You may have to give it another 1/2 turn.

If it's not on tightly, the system doesn't have sufficient pressure...result: premature overheating!

Check that little detail first...switching coolant brands shouldn't create this much havoc!

I had dealt with this grief a year ago and it might sound stupid...

...is the coolant cap on securely?

Coolant will spill out of the overflow tube, but not from the cap...unless the cap isn't on properly. You may have to give it another 1/2 turn.

If it's not on tightly, the system doesn't have sufficient pressure...result: premature overheating!

Check that little detail first...switching collant brands shouldn't create this much havoc!

I thought about the cap isssue too and its on there pretty good (and its new). I just went out for lunch and saw where the antifreeze ran out and down the ground in the parking garage. I topped her up with water and took a 10 min drive in stop and go traffic with the cap off to see if perhaps she'd "burp" any air out of the system and so far the temp is back to about just below 80 cruising to about 82 standing still in 80 degree weather. I'm suspecting the air pocket issue and only the hot rush hour ride home will tell me something else (as this is going to be at least an hour and a half of stop and go in the sun).

I hope there's someone here to shed some light on their normal operating temps. I'm thinking I'll have to replace the coolant (again) with just the 50/50 premixed antifreeze and running her for about a half an hour without the cap to make sure the air is out. Also, I remember that before I changed the coolant, a tech from the MB dealer said to just fill it at the expansion tank and it would go into the radiator with no problem which I did. The last time I changed it to the water, I actually took the top radiator hose off and filled it that way (and didn't have these issues afterward). Could this also be the culprit? Any other ideas? It seems that its pretty much cured so far with the cap off but still weary at this point.

Alan

An easy burb tecnique is to feel for heat at the hose from the thermo neck to rad. When it gets hot, you know the thermo has opened. Now, with the fill cap off, grab the hose with a gloved hand and firmly squeeze several times [ with eng running].
This will burb the system.................

The way I do it is as follows:
Disconnect the top radiator hose and turn the hose "up" at the engine end. Pour coolant/water/water wetter mix in at the reservoir until water starts running out at the block. You will get a little water coming out at the radiator end of the hose too based on how tight your clamp is. Anyway, pour a little more water in the reservoir and then rotate the hose and attach at the block end and tighten both clamps. Once you start running it you will want to run the heater on full blast to make sure you circulate through the heater core.
The mix is as follows:
1 bottle of Redline Water Wetter
40% MB coolant (coolant of your choice, please don't get started on a coolant brand discussion)
Remainder of distilled water.
I use a one gallon clear plastic jug and pay close attention to the mixture. It is WAY easy to get too much coolant in the mix. Go purchase yourself one of those Prestone mixture testers and use it to get the mix to approximately 40 coolant/60 water and use the Water Wetter.
oh yea - I do what AD says to do too with the burp thing.

Is the hose from the reservior to the overflow tank in the fender intact? You will have to remove the fender cowling to be sure, but that's only about 6 screws. I didn't think it to be anything but cosmetic/neatness until I replaced the hose. Ran at 90-110 prior and stays at 82-84 since.

Alan,

After 4K miles in the 560 I find 80-82*C to be the norm in temps up to 100*F. You need to get a coolant mixture tester, like $2 at the local Pep-Boys. Like Jim suggested aim for a 40-45% coolant to 55-60% water mix, and a bottle of water wetter (I run 45/55 on the 560).

Also check that hose that Earl suggested.

Thanks Mike, Guys! I'm on my way outta here to see how she acts on the way home. I was contemplating doing the radiator hose up thing when I get her home later tonight (and I'll stop at Pep Boys to check on that mixture tester deal). Will update ya in the morning when I get back to work. Wish me luck and thanks for coming thru (again). I was just wondering if my thoughts of how to go about this was in sync with what the "super forum" would also do. Have a safe and blessed day guys! :)

Alan

My mechanic showed me a car, that the cap was on tight, but the connection of the metal neck for the cap, would twist on the water bottle a bit.

So it wasn't making a proper seal. Replacement of the bottle worked.

If you tighten the cap, and feel any movement of the cap after it is secure and tight to the water bottle, check the water bottle filler neck to see if its loose. if it is, replace that bottle.

Alon

I've been thru almost 6 gallons of antifreeze since last night. I've removed the top hose to get the coolant directly into the radiator, etc and it worked for a while as I drove around my subdivision but immediately would spit the coolant back out as I was trying to top her up with the car running and the heater on. She went up to 120 again and after I shut her off, I'd hear the gurggling sounds in the cabin (from the heater coils I assume).

I would then just let her cool down enough to top off again, replace the cap and run her a while...repeating this until she was "full" in the expansion tank. I filled the containers with water last night and loaded her up just in case she wanted to act up this morning.On the way in, she was at 80-82 steady on the highway drive in (about 74 outside) but as soon as I got off at my exit, she shot up to 110 and stayed there although I cruised at about 35-40 mph to my building. Upon pulling up to my usual spot in the parking deck, she's got a bit of a coolant smell and a very small amount of steam coming up from under the hood by my pass side window (by the battery tray).It's funny that you mention the bottle Ash because I was noticing some bubbling around the neck where it actually connects to the bottle which--no matter how tight the cap is, its seeping. I was in my trusty "560 parts catalog" (Mike knows the one) looking for a replacement.

Anyway, the saga continues as she sits in the parking deck until I can get to her again later on today.Another MB tech has said that the car is SUPPOSED to run at between 90-102 degrees and this is driving me nuts! I picked up the mixture tester although I was unable to do any testing because of time or lack of it. The dang thing wouldn't hold any coolant down (I still think its air along with the bottle issue) and seems this will be a battle for now. I'm thinking I should've just left well enough alone with just the distilled water because EVERYTHING was seemingly just fine and now has become a PITA! I didn't think it would really be a mixture issue since the coolant was already a 50/50 mix and at this point has quite a bit of water added to the mixture. Still welcome any suggestions and thanks for the advice so far.

Alan

Just a thought - Check your viscous fan. When the temp. starts to climb - rev up the motor and see if the fan turns at full speed - if it lazily spins at higher revs - change the fan. I have changed the antifreeze several times in my 88 560sel for various reasons and never had the problems you have. Sounds like the engine is overheating from lack of cooling. Since the aux fans are working - that leaves the viscous fan as a possible suspect. Another possibility is the rad - feel the surface of the rad at different places and look for cool spots that indicate a plugged rad.One other possibility (Ihope not though) is that you have a leaking head gasket that is pressurizing the cooling system creating the air bubbles. The coolant container and cap could give problems as described but be prepared to go farther a field for the solution.

Well it SEEMS that the viscous fan is alright and the radiator is still brand new.What I actually did was blast the heater last night and let the windows down and open the sunroof and the temp would go down. I guess the heater "trick" helped to lower the temp to just above 85 degrees until I got it back on the highway and could cut it off. I really hope that it isn't a head gasket (and so far no smoking nor water in the oil, etc). I'm going to check her out again at lunchtime with a short drive to see how she acts.At least she didn't have a crap load of coolant on the ground like yesterday. I'm thinking of changing out the thermostat, and also getting her a leakdown test for the compression, etc sometime soon. Anything else?

Haven't changed the thermostat yet??? It could be sticking causing the problem. I know it is not recommended - but for a test I would do it - take the thermostat out and see how the car performs. If the problem disappears---------. Fast easy and doesn't cost anything. Worth a try.

Yea I'll probably end up changing the thermostat out anyway...My worry is that with all of the up and down of the temps, I will end up blowing a gasket (although the trusty MB dealership techs keep saying that its made to withstand 120+ temps with no problem until it surges way past the redline!). I don't care what they say, just because it MAY be able to withstand it, why even put it thru that constantly? Can't understand it myself but it was like they wanted me to just drive the hell out of her without even paying attention to the temps because it can ''TAKE IT'' so to speak. I know these are superbly crafted automobiles, but I like to pamper my baby as much as possible to sustain a long (er) lifespan. :) Anyone besides Mike and I feel that the 560 runs normally at a steady 80-85 degrees tops or are there other 560 owners that run at 100+ constantly?

Alan

I'm always at 80-84 now, ran hotter before reconnecting the overflow hose which for some reason seemed complete the pressurized system. Ran 85-100 prior.

I talked to Mercedes Canada Technical Help last month and they guy told me that as long as the temp DOES NOT EXCEED 120C gaskets and head should be fine. He said you definately do not want it to climb to 125C or serious damage could result. Hey Earl - what exactly did you do with the overflow hose that reduced the temp?

I'm interested in what you did also...Moe, what temp is your 560 running most of the time? I'm convinced that they should'nt be above 100 degrees but even with the thermostat not even supposed to open until it hits like 87, its kinda crazy that it was reading 80-82. Go figure...I wonder what you did to the hose because I'm going to my MB parts supplier to pick up a new expansion tank at lunchtime since he's just 15 min away and has it in stock and may pick up another hose to boot. I figure if it doesn't work, I'll take it back but what the heck.

With all my overheat problems, I am down two last resorts- coolant temp. sensor or Freon pressure sensor. Our temps up here are only about 60-70F right now so my 560 runs OK at about 85-90C all the time. Have not had to use AC yet. When temp goes up to 80-90F then I will see if it still climbs to 110C and will use IR non-contact thermometer on the block to verify actual temp. Be patient - I will solve my problem - or die trying. Hey Greenacres2 - still waiting to hear what you did with your overflow hose - don't forget us!! ;) ;)
PS - the old 1930 Chevy has a huge Rad and NO thermostat(were not invented then)and runs well -also no oil filter - just a splash system like a lawnmower! Technology - go figure!

Just got back from picking up my new expansion tank and of course she ran at 82 steady on the way there but on the way back, she shot up past 100 again (which the aux fan kicked in at that point) and when I parked, I saw coolant again coming from the cap area...One guy from another supply center says I need a kit to install it but the guy I got it from says otherwise.I will have to take my sensor out and put it into the new tank though. I guess this will be an ongoing problem until I can pinpoint what the deal is with this coolant temp issue.

Overflow hose
 

Runs from expansion tank to overfow reservior in right fender well. Was broken off (old, brittle) at expansion tank. Removed right front tire and cowling from wheel well to expose overflow reservior. Replaced hose with one from FastLane. There was no sign of leakage prior, and I only did it to clean up the engine bay but the operating temp has not gone above 84 since, and we've had weather up to 90f a few times. Did the hose in early march and that's the only thing I did at that time or since to the cooling system. I replaced the thermostat in December, and I'm pretty sure it's an 80c t-stat.

It doesn't look like the overflow would come into play unless the coolant gets too hot, but I would idle at up to 100c prior. Only thing I can figure is that the overflow helps with pressurizing the system and closes the loop. Half hour job tops, and that's for a novice DIYer.

Looks like I'll be trying to switch out my level sensor to go into the new expansion tank.Does anyone know how difficult this is? I heard from the guy I bought it from that I'll probably break it trying to get it out but its possible. I wanted to just get a new one with it but he had none in stock. Also, how difficult/how much time does it take (approx) to change out the thermostat and water pump? I'm thinking of doing the water pump soon for the heck of it too.

Alan

Figure on 3 hours for the water pump - unless you have a leak and have to do it over again. When I changed mine the gasket weeped - took it out again and applied a LIGHT coating of silicone to gasket and re-installed - no problem

I lightly went though the multitude of replies.

I put my money on an air bubble in the system that can't be purged. There is a plug on top of the block back by the firewall used for filling the coolant passages in the block. Take the plug off and slowly fill with coolant. If there is air back there, you will not get coolant flow, even with the water pump turning. Check this before you replace the pump.

Have only had my 560SEL for a short time but done lots of highway driving and temps for me remain steady at 80-85 degrees. This of course has change in heavy stop and go traffic in this hot Mississippi weather and then went up to 100 or so and immediately back down when back at normal highway driving. In town, remains 80-85 even on very hot days.

560 coolant issue
 

The coolant level sensor is easy if you have the right pliers. The ones that push clips apart.

My brothers 560 kept fluctuating on the temperature. We thought it was a bubble, but one of the hoses had a pinhole in it. We have a coolant pressurizer, and we pumped up the system and coolant shot out and we found the hose.

If the coolant tank, cap, radiator, and viscous coupling on the fan are new/working properly, then I would look at the thermostat. Since you have been through six gallons of coolant, I dont think that you have air bubbles in the system.

See if all your connections on the coolant tank are secure.

Try the thermostat next.

Good luck,

Austin

Could still have the bubble and go through gallons of coolant if it boils off because it is not circulating. It's the same as if the pump is shot.

Tell me if I'm wrong.

Well, another day of the off again,on again thing with this coolant....Last night she ran fine all the way home (for about a 45 min commute in light traffic) but as soon as I pulled up she shot back up to 110+ and coolant leaked from the overflow and cap area. I topped her off and left her alone all night because of other commitments that prevented me from getting back to her.

This morning I topped her off again with the heater and car
running until the heater was blowing hot in which I added more coolant to the max level and took her out for our drive into work. On the way in she was at 82 as usual until I got about a block from the job. She went up to 100 steady and I noticed a smell of coolant and when I turned the heater on it was blowing very luke warm instead of hot.Sure enough, I parked and coolant is all over the ground again and bubbling around the cap (this time I did notice that the cap was not on tight as I was going to keep it off at first because it would run cooler longer with the cap off when I was just trying to get her to burp--tried it again this morning so...)

I just read about the block access and I'm wondering if that is for the 560 engine (because I've never had to use it before) and where exactly is the "accessable to fill" (so I can run out and see if I can find it) with coolant? I wonder if I should try one of those "flush and refill" places that have the systems to check the pressure, etc later on today after I exchange the expansion tank.What do you guys think? How long has it taken anyone here to change out their thermostat? It looks to be just as easy as the others I've replaced but looks time consuming (not that I won't take the time necessary to get my baby back in shape). Thanks again for the replies guys. Any others are welcome too at this point and could use all the help I can get.

Alan

Sorry, the access plug is on the head. I think it is in the same spot on most or all of MB heads. At the very rear of the head, on the intake side. Now of course this is for inline engines.

I'm not sure about V-8's. But I would look anyway. When you fill from a low spot like the expansion take, coolant will not fill certain passages. The air cannot escape. It's kind of like priming the pump.

FORGET THE AIR BUBBLES - THAT AIN'T IT! Think about what you wrote "Last night she ran fine all the way home (for about a 45 min commute in light traffic) " There ain't no way in that hot spot down below that would allow an air pocket to sit there not cooling for 45 minutes then BOOM cause the car to overheat. If it was an air pocket - it would act up as soon as you hit operating temperature. I would suspect three things in the following order based on the facts you give that as soon as you came off the freeway and arrived at home the thing overheats.
1) Since it runs fine on the highway where there is a lot of air going through the rad to cool it - I still suspect the viscous fan - if it does not draw enough air through the rad - you will have the problem you see. If the problem is intermittent - so could the fan be intermittently acting up - getting ready for total failure.
2) if the thermostat was sticking it should be acting up from cold going to warm as it tries to open - to have the car run for 45 minutes with normal temp then overheat - then when you cool the engine it acts normal for awhile makes me doubt that it is the thermostat - but what the hay - cheap to try. I would still run the car for a couple of days without a thermostat and see if it still overheats - if it does - go back to suggestion #1
3) Since you say the aux fans do work the only other thing that I can think of is a head gasket -
ARE YOU REALLY SURE THE VISCOUS FAN IS LOCKING WHEN THE ENGINE IS HOT???? If the fan is not locking when the engine is hot - the car will work good when you have enough airflow from faster speeds - but will climb in temp. when you go slower if the viscous fan does not pull enough air past the rad.
Since I cannot see you car - I am using the same common sense logic I use when I diagnose my cars. Hope you can see my logic.

Well, I drove her around town during lunchtime for about 30 or so minutes stop and go (85 degrees outside) and she's stayed at 80-85 so she's acted right since I added the coolant from this morning. I called an indy MB shop buddy who says that sometimes they have just had to keep driving the 560's with the heater on to get them to act right after they flush and fill em for customers...He also says that the air pocket is more than likely right at the thermostat (what they've found) I'm taking it by there now and will be having her checked for head gasket,etc if by the time I do everything it still acts up.He says to just keep filling it and change out the tank because it is leaking allowing the pressure to act up. Anyway, on my way outta here to try to take out the thermostat to test as suggested and will update you guys soon as I know what's up. Wish us luck!

Alan

I'm kinda with moedip here -
Another thing to keep in mind is that when you pull off of the freeway (where the engine has been loaded up) the cooling system is trying to dissipate the heat from the higher rpm/load and it does not sound like it is able to do it.

Wanna know why I am emphatic about the viscous fan?? Two years ago I went to Indiana to see my sister and every time I let the car idle for a while it started to overheat - started driving and the temp went down. The viscous fan was still turning pretty fast but I called my mechanic friend long distance and he said to change it and sent one overnight to me at my sister's. Changed it in about an hour the next morning. The new one locked up real nice when the engine was hot - you could hear the air rushing when you revved the motor. Solved the problem. It's hard to tell if the fan is actually at engine RPM when it is supposed to be locked from heat - His symptoms are so much like mine (but a lot worse) - that's why I think the fan is slipping when it should not.Time will tell if I have egg on my face!:eek: :p

What milage did you change it moedip?

155,000 miles approx.

Sorry. Didn't read the last post.

If you can run for so long within good temp and then shoot up when you reach your destination (clue- now going slow, stop and go), then your circulation is probably good. The problem in in heat transfer (ie. radiator) when going slow and while stopped. The things that help heat transfer are a good pump and a good fan.

I agree... check the fan.

Good morning guys! So, this is all starting from Friday...went to buddy's shop and of course when I got there all we could see wrong was the neck on the expansion tank leaking in which I just filled up again and planned on just changing it out and taking it back to the shop today for them to check her out (I didn't want to keep him there late because they had a load of "paying" customers and the weekend rush hour,etc). After letting her sit for a while as we chatted, I was able to top her up a little bit (mind you it did NOT overheat but probably went up to about 89-90 in 95 degree weather in stop and go traffic).

He gave me four containers of water (just in case) and I took her home when the traffic died down (again, she didn't overheat per se but was higher than normal). Stopped at Pep boys and picked up some water wetter, some new hoses and headed out to change out hoses, thermostat and expansion tank. After changing out the tank, I disconnected the top radiator hose and just ran the garden hose water flowing straight into the housing near the thermostat until the water run back out of the radiator.

I then proceeded with the heater blasting to just keep the water running until it was indicative of a "flowing" system and then replaced the hose to the radiator. I pressed the hose for what seemed like an eternity to get air out of it (which my buddy says they've also had to do on occassion) until she actually made a "burping" sound and I then topped her up again and also added the water wetter to the system to see what would happen (mind you, I didn't replace the thermostat yet).

Test drove on the highway and back and she ran fine at 80-85 at midnight and 67 with NO traffic. Yesterday, I took her out again
but this time I ran her in stop and go traffic and also on the highway (and it was on the hottest day of the year so far at 100 + degrees!). She ran at a steady 82 and topped out at about 90 dropping back down to 82! So far so good but of course I've already ordered another fan clutch, and water pump just because...

I'm contemplating replacing my fan with "full time" electric fans and have been for a while. Since this last fiasco, I'm REALLY wanting to do this. Is there any particular brands of electric fans that are available for the 126? I'm also wondering if anyone has used this water wetter because it seems to be a pretty good product. SO FAR SHE "SEEMS" TO BE RUNNING FINE but of course I didn't drive her today (I have been neglecting one of my 250C's and I needed to wake her up) :)

Thanks again for coming thru fellas! I don't know if this saga is over yet because she's in the garage "resting" but will keep you abreast of my developments.

Alan

Don't be surprised if a new fan clutch does not lower coolant temp. gauge readings. My 126 has a new radiator, head gasket, hoses, coolant exp. tank, exp. tank pressure cap, 50/50 MB coolant/H2O. Just replaced fan clutch with OEM item. Fan blade was spinning for quite awhile after shutting engine off. Blade now stops right after shutting engine off; however, my temps still go from 87C to 100C if I get stuck on the freeway if there's been an accident.

I've also experimented with 40/60 & 30/70 concentrations and have used Wetter Water. Temp. gauge readings never change.

126 owners manual indicates that rising temps are quite normal, so I'm going to put this fluctuating temp. issue to sleep.

Check and make sure the A/C condenser is clear of debris. Also, make sure the space between the A/C condenser and radiator is clear of debris.

When I took out the radiator, I couldn't believe how much gunk/junk was in between.
You should be able to see through the condenser very easily.

If you've changed to R134a and a running the SINGLE aux. fan, change it to dual pusher fans.

I would look at dual 11-inch SPAAL puller fnas (2700 CFM) if they could fit when you remove the viscous fan. You'll need to wire in a Derale relay (everything else out there is junk, IMHO), which is adjustable, and has provisions for turning on the fans when the A/C is turned on as well.

Do a search for SPAAL fan and you'll find my links. BTW- I might have spelled it "SPAl".

Good luck,
:-) neil

PS: you did install a BEHR replacement radiator. . .

Thanks Neil...yes the radiator that was replaced was a Behr (I think so anyway because I bought 2 new radiators for 2 560's-I sold the other one ) I'll look and tell you for sure when I get to her... The radiator/condenser area was pretty much clear when I checked Saturday except for a total of 2-3 bugs and the front of the radiator still looks brand spanking new...have you tried the twin fans or know of anyone that has on their/your MB?

I'll check out your thread also to read up on it...
Thanks again

Alan

I haven't tried the dual fans, only the single 16-inch puller fan for our AMG M104 wagon (2300 CFM).

She works beautiful, and keeps the temps very cool.

Satish of www.mbcoupes.com installed dual 12-inch fans (can't tell if their DUALS or two independent 12-inch fans) in his 560SEC with a M119 V8.

Check out:
http://www.mbcoupes.com/memberscars/T/satishtummala/page13.htm

http://www.mbcoupes.com/memberscars/...ectricfans.jpg

Good luck,
:-) neil
1988 360TE AMG
1993 500E

Yea I've actually seen Satish's pics of the fans and that was close to the setup I was looking at originally when I saw it.I believe that the radiator I have in her right now is a Nissens and so far it has been a good investment because when I removed the old one, the neck was surely broken although it had enough room for the PO to just slide the hose up as close as he could to salvage it and I'm thankful that it didn't blow loose before I replaced it.;)

Another $0.02 worth ...

My 350 SDL just went through a bout of running hotter than normal after I changed out the coolant pump and the viscous clutch ... both had developed a bit of wobble from shot bearings.

Normal fill with 50/50.

Immediately following this I noted the temp rising to 105C very quickly - actually running over 100C while cruising at 75 mph with AC on ... it had never done this before! So, at this point, what had changed?

1. Coolant mix - yes, but how far off do you have to get with ratio in order to account for this much change? i.e. what if you ran 100% coolant ... would it run 100C instead of 82C in same load?

2. Viscous coupling - yes, but it was new ... possible to get a bad one? Yes, but mine was still running hotter than normal at high speeds with lots of ram air.

3. Coolant pump - yes, but if it wasn't leaking, and the impellers were close to the same, it would not be likely.

Baffling. So, I put it off for two weeks - couldn't stand it any more.

This weekend I changed out the viscous coupling again and changed the tstat, too. Old tstat opened and closed when boiled on the stove - rather an ancient test that I understand is not suitable for this tstat.

Am now running the same temps as before ... at 75 mph on 98F day (it was hot today) with AC on. During high load conditions, like going up long grade or in stop and go traffic at 98F, it would predictably creep up, but never hit 100C (during last hotter than normal period prior to change of viscous and tstat it would roll right up to 105C in 70C weather with AC). Something else I noticed, but did not expect, is that following work this weekend, it now runs to 82C much faster, usually within a mile after crank up in mid-60F temps.

What changed?

1. Viscous clutch - yes, but same but as before. I would liked to have waited and done this later, but once I dumped the coolant, I didn't want to waste another load of MB coolant. If it had been the viscous clutch, wouldn't the car have behaved normally with ram air flow?

2. Thermostat - yes. I believe this is what failed. Question is - why now? Was it related to having drained the coolant completely? Is there a chance something occurs to an old tstat when the coolant is left out for a few hours or days? Don't know, but this is the only rational explanation.

Good luck on the 560. I would:

1. Change the tstat and see what happens. Run water after you do it in case it isn't the problem. Don't run the water long term, but a few days likely won't hurt too bad.

2. Not change the coolant pump - pretty binary with these, I think.

Please keep us up to date - I KNOW these cases drive ya nuts!

stephenson,
thermostats tend to stick as they grow older and are slower to open and close. maybe your maintenance procedures aggravated it. my thermostat was making the temps swing from 78 - 100 (<100 only because i have the cooling mod), so i changed it. now it's pretty constant at 90 - 95 in summer heat, with A/C on and stop & go traffic.

My baby's still acting up and even after the fan clutch change, still shoots up past 110! She's just fine at highway speeds (steady 80-82) but just as soon as I take her off of the exit ramp, it shoots up and especially when I'm sitting at a light, the coolant is coming from the overflow tank and drains onto the pavement.

I've purchased MB coolant and not going to add it until this is fixed. I've been just driving with my 6 coolant jugs of water to replenish her when she cools off (the aux fan kicks in and when I shut her off, I leave the key on so it won't go off until it cools down) and I'm ready to leave for my next destination. None of the temps went up like this until AFTER I changed my coolant and have had drama ever since!

I just noticed last night that after we came off of the highway and I shut her down in the driveway, I popped the hood and saw that the hose to the expansion tank was being filled with some water that was pushed from the top of the radiator.I felt through the fan to the radiator and followed the direction of the fan with my hand on the radiator and from the right bottom of the radiator heading in a circular motion (with the fan) noticed it was cool to the touch and as I made my way to the top heading to the left it got extremely hot that I couldn't keep my hand on it. the top of the radiator was also very hot. I can't remember, but what does it mean as far as if the vents are hot/cool to the touch. should it be cool or hot after such a ride considering the ram air effect?

Although its brand new and not even been in the car a year yet, I'm now thinking it may be a radiator/circulation issue. Any opinions on this? How would I be able to check this?:confused:

Strange but true!
 

I have not yet completely diagnosed my 603 diesel overheating issue but I did learn a little something in the process so far.

If you have not yet found the exact location of your coolant leak on your 126 chassis, check out this leak that I found in my coolant system.

http://www.peachparts.com/shopforum/diesel-discussion/33244-126-windshield-defroster-heat-exchanger.html

I'm sure that any leak will prevent the system from operating at the required level of pressure so I would think you have to determine if the system will hold pressure and if not the exact location of any pressurized leaks first.

If you want to check your rad to see if it is plugged (which by your description it maybe) Remove the shroud from the rad on the fan side so the entire inside face of it is open to touch. Take off the the bottom rad hose (since your car is filled with water only already) and plug the opening on the rad with a cloth fairly tight (it will leak a little but is OK for this test. Disconnect your top rad hose and get yourself one of those plastic flower 2 gallon watering container with a spout (about $1.99). Fill the watering container with real hot water and put a piece of hose on the spout and put the other end of the hose into the top rad hole.Fill the rad with the hot water. Then run your hand over the entire surface of the rad on the fan side. The temperature should be the same all over the rad -if you feel cold spots or spots that are much cooler - you have a plugged rad - don't care if it is new or otherwise. If it is plugged you are halfway there to removing it to take to a rad shop for cleaning or recoring or to replace it. If the rad is partially plugged no amount of ram air or fan speed will stop the temp from climbing. Keep me posted.As an aside - I have worked on cars for 10 years now and have learned the hard way - just because a part is new - don't ASSUME it is not defective - have wasted a lot of troubleshooting time because I ASSUMED the new part was good. The best troubleshooting is still logic and common sense - and of course the old expert - experience - which you will have when this problem is solved! - Keep smiling - you'll get it!;)