M103 running warm on freeway, water pump?
 

So it hit 110F yesterday and i almost feel like cooling is slightly worse than last year.

Fan clutch was new last year and locks up/roars as it’s supposed to
Radiator is 2 years old, condenser 2 years old.
Water pump now has 120k on it...thermostat is a couple years old
Coolant level is good, reservoir cap is good holds pressure (2 years old as well)
Coolant mix leans 70/30 water G05

On the freeway at 3pm at the hottest part of the day at 75mph it’s still running at ~96C...slowing down it hits 108C (30-40mph). I know this environment is the extreme.

The fact that it still runs at 96C at 75mph tells me:
A) radiator is blocked, but that can’t be true because it’s new (no leafs/debris all clean no bent fins)
B) coolant flow is low so the heat isn’t being circulated fast enough, which would be pump related. I’m leaning replacing the pump, but I don’t know if I have no rust in system that I’m condeming pump for no reason.

Anything under 100F and ZERO issues, cools fine.
Any thoughts?

did you get a behr radiator? i've had higher temps with other brands. not as efficient. water pump would leak before i'd replace it. the impellers USUALLY don't slip like you're thinking. at least, haven't seen it yet. good luck, chuck.

Yes radiator is Behr. No signs of any leaks from the weep hole in the pump

Check the radiator for cool spots indicating a blockage which is not likely due to it's age and then try a new quality thermostat.

Water pumps rarely cause overheating unless the impeller is corroded. Did this pump ever run normal temps?

Good luck!!!

M103 cars have undersized radiators to me, I just do not think they can keep up in your temps. When it is really hot and humid here, I run similar temps.

79 or 87 stat in yours? I am running the 87

FWIW...
I just replaced my radiator 2 weeks ago with a Nissens from *******. Original cracked at lower right corner. Thermostat last year. Everyday for the last 2 weeks has been a heat index of 103+. Car still runs at normal temps with AC on in city driving and that's down here in the Texas Gulf Coast. Only issue is no AC through the center vents!

Out of curiosity do you have R134a or R12?

Here's a test I ran on the way home from work today; first pic is AC ON, second pic AC OFF. You can see how much the condenser adds to the heat load...I wonder if R134a in this environment is too much.

http://w124-zone.com/downloads/photos/300TE/ac/acon.jpg

http://w124-zone.com/downloads/photo...E/ac/acoff.jpg

Sorry for the late reply. Using R134. Interestingly, this winter, such as it was, I thought my WP was on its way out as well. With the heat on, and at idle the air was lukewarm. Once I got under way the heat was at normal temp. Then the weather got warm again and didn't need the heat. Also, the car was not getting up to temp so I replaced the thermostat which appeared to be stuck open. New one works great as the car gets to normal temp and stays there.

The higher he glycol percentage, the lower the heat capacity, and 50 percent provides good corrosion protection, so it might make a difference if you drop the glycol to about 50 percent.

The aux. electric fan should engage at 105C. Is that happening? On the very rare occasions when the dual aux. fans on my 190E 2.6 engage I can literally see the temp gage moving down.

Duke

A common cause of running hot at speed is a soft lower radiator hose. At higher engine RPM's, it can partially collapse due to pump suction.

The cooling system on inline 6 w124s and w201s is marginal. The radiator and viscous fan is undersized and the aux fans kick in at much too high a temperature. There are several things you can do to improve the situation. Run a smaller fan pulley, increase the water to coolant ratio, run a colder aux fan switch or add a manual switch in the dash for the aux fans. As much as some people hate to hear it, this is a design flaw that only becomes apparent in hot climates. All the inline 6 w124s suffer from it. There isn't enough room for a properly sized radiator and viscous clutch fan.

Hey! Someone agrees with me on this one. I been saying this for years and years.

I checked all the fans I had around, BMW M30 ones. 603. 606...all have wrong pitch blades. Even considered a V8 radiator in the 300SEL and figuring out some sort of radiator hoses to work. Closest I found I recall was an SDL radiator and one of the hoses matched close, but one was crazy out. :(

The best solution I've found for my om603 is electric puller fans behind the radiator in place of the viscous fan and eliminate the pusher aux fan to expose more of the condenser and radiator to airflow. The problem is most Efans are too thickto fit between the radiator and engine. Right now I'm using a pair of puller fans from a first gen Prius. They're the right size and shape and very powerful. I trigger them with a 91c temp switch in the thermostat housing through a relay. My temp gauge never exceeds 90c.
https://i.imgur.com/RMcg7l9.jpg?2

https://i.imgur.com/a6SbxyS.jpg?1

https://i.imgur.com/21ZIitK.jpg?1

What is the width of them?

The damned M103 radiator core is right around 20" x 20"

23.5", perfect fit on the 603 radiator.

Unfortunately my coolant ratio is 70:30 water to G05 and in 110F the clutch is engaged all the time and temps still stay there. No collapsing radiator hoses either.

How did the car run last summer? Did it have the same problems in the same kind of weather?

I recently chased overheating problems in my SL. Not a W124 and not a M103, but perhaps some of the same things apply here.

To make a long story very short, my issues were 2-fold:

1: Still had the original thermostat in it, MB logoed and everything. Unbelievable it made it 35 years, but it did. Original thermostat was still working, but would not open fully and would cause overheating (>100˚ temps) on a warm day, anything over 90˚F outside.

2: After replacing thermostat, car ran significantly cooler when moving but would still have temps creeping up in traffic or when idling in gear. Fan clutch passed the "shred a newspaper" test, but was replaced anyway as being suspect. With new clutch, heating problems disappeared immediately. It also makes a noticeable noise when the clutch engages and the engine is revved. I only bring it up because it may seem like the clutch is working properly but could still be slipping enough to reduce cooling capacity.

110F ambient is a challenging heat load. Could you use an infrared thermometer and shoot the temperature at the radiator inlet and outlet, then post back? I'm curious how much heat rejection you're getting under those conditions. It could well be that you're simply beyond the design point of the cooling system.

The viscous fan clutch should cut out at around 30 kilometer per hour.
After that speed the airflow through the radiator overcomes the clutch flow.

Last time I had your problem it was the water pump.
I put a erzatz non oem Behr pump (PRC knockoff) in the car - didn't get any better. Changed pump again for a Graf and all overheat problems disappeared. Car ran at 87 - 90 constantly even in very high ambient temperatures.
Fleebay knockoff cheap pumps don't cut the mustard - it's just one of those occasions you have to bite the bullet and get the real item

If you have a minute leak anywhere, the pressure cannot be maintained - the symptoms you describe can also become evident.

It’s completely normal.

The needle is not like American cars which basically don’t move unless you are overheating. You are totally within the operating spec of the car, despite extreme ambient temperatures.

If you simply can’t let it go, change your coolant mixture so that it’s mostly water, and remove your thermostat.

I'm not familiar with the M103, but if it's anything like the Mercedes V8's and diesels then removing the thermostat is a BAD THING. The thermostat does 2 things:

1: Allows circulation from the radiator

and

2: Closes the bypass port

If the thermostat is removed, the bypass port is always open and will be recirculating coolant through the block instead of through the radiator like you want it.

I thought you were running the r152a? My temps just recently were high like that on the freeway with a/c on with my electric fan set up (http://www.peachparts.com/shopforum/3746181-post28.html). I just recently went back to the viscous fan and my temps remain low ~85. What you can try doing is swapping out your thermostat for this one: [79°C Thermostat (MB p/n 1102000615)]
Even when idling and the a/c on (using r152a) the temp will creep up to about 105, then the aux fans kick on and the engine will stabilize at about 90 - 95 until I start moving again, then it drops back down to about ~85. Also, my aux water pump is still wired in to cut on at 91C, which may or may not help or make much difference while the car is on, but when the car is shut off after being at about 100+C, even for 5 - 10 mins, the temp is back down in the 80C range vs it being at about 115C when starting back up without it.

Because I'm running a 79C thermostat its hard to say if my temps would be similar to yours. Many many will agree that this is normal, even the mb engineers maybe, but we all know heat kills and I'd rather be running a little on the cooler side than hotter side. If you can, try to order a 79C thermostat and see if it makes a difference. I do not think there is any other issue with your cooling system as you seem to be pretty meticulous in making sure your parts are replaced.

Have been experimenting with my 300TE regarding it running what I consider abnormally hot. I know some are saying this is typical, but I don't buy it. I have NEVER owned another vehicle that ran in excess of 110C at any time unless it had a serious cooling system problem. The cooling system is either totally inadequate by design, or we are having some type of issue from an aftermarket part or other problem. When I was young and stupid, I had an old Datsun 240Z that the water pump locked up and wrung the fan off of. I put it back together without a fan and drove it that way in town for about a year. It was not much more different than this 300TE in terms of trying to keep it from overheating. That is NOT a good thing.

Here is what I discovered today. I believe the issue is with insufficient coolant circulation, as opposed to radiator efficiency or fan circulation. The radiator in the 300TE is nearly identical in size to the radiator in my Volvo 960 wagon, a 2.9L four valve, twin cam inline 6. The Volvo never runs more than 5 degrees above the thermostat temp, no matter the ambient temp, with or without AC running. That tells me the radiator should be adequate.

When I stopped today in a parking lot with it running at about 100C, I hopped out to do some other checks without turning the engine off. Just as I jumped out, the electric fans hit high speed, so I know the two speed fans are working. I used a rag and the fan clutch was delivering plenty of pull to the fan. I could not stop the fan. That says that the air circulation is as designed.

When I left the parking lot, it was raining pretty good. Temp was right at 100C by the time I got on the interstate a half mile or so later and ran in to a good heavy rain. I even got behind a semi to get a good spray on the radiator. The temp hardly changed, coming down to only 90-95C, at best. That cold water spray and drop to 75F in ambient temp should have dropped the coolant temp like a rock. Lack of it says to me the radiator and fan is not the issue. That obviously means that the cool water in the radiator is not getting properly circulated through the engine.

As I was getting off the interstate, I did one of my no fan tricks in the old Datsun and downshifted and coasted a half mile or so to the exit ramp. Temp dropped drastically. Closed throttle means no fuel being provided to the cylinders via the injection, so the engine is essentially air cooling internally. Same result going down a long hill a short time later. Again, saying the coolant has stagnated in the engine.

I really think there is a restriction of some kind in the system that is causing the water pump to fail to sufficiently circulate the coolant. Maybe the thermostat doesn't open enough and is restricting the flow. Maybe the water pump design is flawed and doesn't meet the needs in terms of flow and pressure to circulate the coolant.

I'm going to start with a different thermostat and see if it has any effect. Maybe the OEM thermostat has a larger opening than a typical aftermarket thermostat that meets the size and temp requirements? I am currently running a Stant thermostat I put in it about Feb, so it is new for all purposes. Does anybody know what the OEM Mercedes brand is? If not, I'll order a genuine Mercedes, but would rather not pay $50 for a $12 thermostat if I can avoid it.

On the om603 and om606 you can get a smaller water pump pulley to spin it faster. Maybe one is also available for the m103.

Just did a search and realized that you posted this same issue 3 years prior (http://www.peachparts.com/shopforum/tech-help/369583-smaller-water-pump-pulley-m103.html). I would think that unless you can remember a time when you had similar ambient temps and your car never made it past the 85-90°C mark while driving similar speeds then the issue may not be the cooling. You may want to check the tension on the belt, make sure you aren't running lean, and maybe even check to make sure there isn't rust. There must be something that's being missed. We've both had similar issues with cooling and I've also done several mods to the engine to help run it cool.

Psy2cho has a wagon which punches a much bigger hole through the air than the sedan. The cooling system is clearly undersized for his car in his climate.

Hoping my parts car has a MB thermostat, if so, will change this evening and report back.

Hell, I knew the 603s did...never crossed my mind to check the M103. :eek:

'A1042050210' is the PN from the EPC! Going to find myself one ASAP. More coolant flow and more airflow over that puny radiator is always welcome.

BMW did this with their M30 I6s. Went from a 144mm pulley to a 130mm pulley, about 0.5" smaller. It was optional for the Afrika Korps destined vehicles :D but became standard around 1989.



Like you, I still agree the radiators are too small in these climates. I remember another shop owner here telling me something similar about my W116 280S. The radiator was too small, even with the oil cooler. He preferred to remove the oil cooler and go with the larger radiator.

I think 1042050210 is just the updated part number, I don't think the size is any different than stock. I've ordered two as replacements, I don't remember them being smaller.

I just went through this. M104 wagon black on black in Tucson. Replaced the entire cooling/hvac system; Nissens radiator/condenser, Graf water pump, hoses, 82c thermostat, mb water switches, Denso compressor and drier+switches, evap, new spal aux fans, zerex 50/50. Everything. @110F my temps still went to 105f. What worked for me was replacing the new Behr fan clutch with the upated Sachs one.

Now even with super high ambients my temperatures never go above 95f even with the a/c running at idle. Incidentally I’m running r154a as well and getting 44f at idle and 36f freeway which I think is also helping as far as condenser heat dissipation.

Might want to check into the updating fan clutch or go the Spal electric puller way.

ps2cho, if you want, I still have my Spal electric puller you can try out and see if it works for you still pretty new, only had it for a year. If it works for you then you can buy it from me. Although, I did remove it because I didn't think it was keeping my temps low enough. I am using the viscous fan, which has done better.

Also, why is the Sachs clutch better or updated? There are only 2 things that I can think of what would make the Sachs better or updated, and that is either sooner flexing of the bimetallic strip....which would not mean anything unless the thermostat had opened up allowing the coolant into the radiator, or the viscosity of the silicone fluid has a higher weight. The latter would seem more likely as I have drained out a clutch and filled it with 30k silicone and when the clutch was locked, it was spinning at 100% of speed vs 80% with no slippage.

Not sure entirely but several people on the “other” forums have said the cut in temp is lower for the Sachs unit. I have also read the Behr clutches are quite flakey. For my situation and high ambient temps the lower therm and Sachs clutch is what ultimately worked.

Ok, so then the bimetallic strip flexes sooner allowing the clutch to lock up sooner. I wonder what the cut in temp is because if it is still before thermostat releases coolant to the radiator, I don't see how it would make much of a difference. On the other hand, running a 79C thermostat would most likely yield great results with the Sachs clutch.

The fan clutch for M103 doesn't engage until 95 C and even then it's not doing much when car is standing still in traffic.

Although I've never tried it, the fan clutch for 400E/E420 engages at a lower temp (around 82 C). If it fits the M103 motor it may be worth a try.

The easiest fix is to solder a 1K ohm resistor onto the coolant temp sensor. This way the signal to the auxilliary fan(s) is sent at around 90 C and not at 105 C.

Got a little news, guys... I can't swear to it until after I run it into town tomorrow evening, but a test run this evening with the thermostat from the 104 out of my 93 300E parts car seems to show a drastic improvement. I drove several miles at 60mph and then stopped. Temp yesterday shot above 100C in seconds. Barely touched 100 this time, and then after idling for a timed 4mins with the AC running at 72F setting when I immediately pulled off the highway to simulate a long traffic light. Less than a mile of 35-40mph brought the temp back to around 90C.

It has never come back down that quickly or crept up so slowly since the serious heat set in here in Alabama. I have been forced to shut off the AC at any traffic light to keep it under 110C and it was rare it dropped below 95C when I started movung again.

I didn't think to measure and compare the fine details of the two thermostats, but they were slightly different. The one I took out has "BTT/BTO Made in Germany" around the top of the body. The bypass plunger has "2.466 87 L6" stamped on the bottom. The plunger that closes the bypass port is 1.694" in diam and measures 1.125" from the bottom of the flange to the sealing surface of the plunger. The bypass port is 1.300" below the flange, so the plunger only moves 1.175" to close the bypass. The spring on the bypass plunger is VERY stiff. I think the thermostat is opening until the plunger seats on the bypass and then can't compress that spring enough to open further, restricting flow from the engine into the radiator.

The thermostat from the 93 had a noticeably smaller diameter plunger and it seemed shorter, so perhaps lets the thermostat open further when hot.

It will be wonderful if the solution is this simple. Will report back soon.

Typo above, the bypass plunger only moves .175", not 1.175".

Please do! I just looked on my maintenance doc and I am currently running a Behr 87C from 2014, so its 4 years old and has 50k on it. I am tempted to go buy a new thermostat, but I may hold out until you report back before purchasing to see if a later thermostat works better.

We can eliminate the fan clutch because if the cluthc was the issue, as soon as it engages and "roars", temps would drop fast, but on my 300TE it does not. It just stops it rising further, but never cools it down enough.

I never had good luck with the current generation of Behr clutches, not just MB limited. They are junk for BMWs too. Sachs set me back nearly $200 for the M103, but guess what? Works as designed. :)

Yup, I put the clutch from the 93 on my car, too. The fan cannot be stopped with a rag at idle when the engine is hot. The electric fans are operating correctly, too. It's something to do with the coolant not circulating and the thermostat is the only obvious obstruction in the system for the pump to overcome. If the thermostat isn't opening far enough, it would act exactly the way we are seeing.

Which Behr clutch have you guys used? There is a Chinese made one and a German made one. The German one is much better quality though idk if it locks up as well as the Sachs.

Just a curiosity, what kind of fuel mileage are you guys getting? I'm absolutely dead on 20mpg in the wagon no matter what.

I get 20.5-21.2mpg everywhere, city or freeway, every time. Maybe 21.8mpg in the winter w/o A/C on. Have for over a decade now. The one time it dipped to 15-16mpg was when my coil failed, so I knew something was wrong right away.

I have Genuine MB fan clutch thats only about a year old. Does not stop with newspaper. When my original clutch died, I replaced both Fan Clutch, bearing bracket and tensionr with Genuine MB pieces.
I also wonder if the 79C thermostat option would work better for us in HOT climates, because it will open earlier, and open wider the hotter it gets. It should theoretically do the same as you are trying to replicate with the other thermostat.

AFIK the m103 m104 om603 and om606 (all the 6 cyls) have the thinnest viscous fans of any W124s. Even the 5 cyl om602 runs a beefier viscous fan than the 6. I don't think a V8 fan will fit any 6.

I agree. I had the w124 fan on my 201, which has the 9 wide blades vs the 11 thin blades. However, in this case, it's not the fan that is triggering the cut in time at 95C it's the metal strip. So all that needs to be done is a simple swap of the bimetallic strip to have the viscous fan cut on at 82C vs 95C. But again, having the fan cut on at 82C means nothing unless the thermostat is also opening up sooner than the 87C. Otherwise he will just create extra drag on the engine for nothing. Even with the lower temp thermostat, if he is on the highway, the air moving through the radiator at speed would keep his temps low without modding the viscous fan, which I think was his original concern - doing highway speeds and having the temp creep up.

The wagon body makes a lot more aerodynamic drag than the sedan.what might be sufficient for a sedan might not on a wagon. I agree that at speed the viscous fan is irrelevant.

If the problem was drag related, ot would tend to get hot at high speed. That's not generally the issue. Drag increases as the square of speed, so slowing down would cool it off. That's not happening.

As for a cooler thermostat, it's not going to change the max temp, just the lower limit. I'll know later this afternoon if the thermostat change has made a significant difference. If not, I'm going to start playing with one of these thermostats to see if I can change this.

The OP is driving in 110f. Slowing down isn't going to help with the m103s inadequite cooling system.

Well if the 87C thermostat doesn’t open all the way until 105C then cooling will max out at where the thermostat allows for maximum water pump fluid change through the radiator. That’s my “tag” on theory here...
If the 79C opens 100% at lets say 95C now all of a sudden cooling performance is drastically improved. In lower ambient temps it wouldn’t matter because the engine is able to cool off enough without maximizing the water pumps ability to circulate fluid.

I think soon we can at least eliminate that theory, which is my only going idea right now to help!

Well, so much for that theory... left work and got stopped in construction on the way home (lane rural highway, 60mph to a dead stop for 3 mins). Never moved the needle. Headed to town (70mph rural 4 lane), no problem, even at stop lights. Got into town traffic and there it goes again. Never got much over 110C, but still don't like it.

Two things... it takes at least a 30 minute drive to get it to this point in 95F ambient temps. Also, it seems if it ever gets over the 100C mark, it just never can get caught back up.

Busy this weekend, but when I get some time I'm going to drill some holes in the cap of one of these thermostats and see if it makes a difference. I could live with having a summer and winter thermostat, if needed.

As for full opening temp, all the other vehicles I have ever owned never varied more than a few degrees no matter the ambient. Tells me start to full open temp is probably a range of 5-7C.

Ok, just glancing at some boiling point info... 50/50 coolant mix is good for 106C at no pressure. 15psi cap bumps that up to 125C. I guess technically we are safe at 110C, but I still don't like it. Too many folks saying their car used to hold 85C all the time and doesn't anymore.