W126 running hot after intake work
 

Replaced intake gaskets. Not she runs dang near 115. Never more than that. I did several burping attempts, even unscrewed the sensors to free any trapped air. Still runs hot.

T-stat is newer Gates. Pump certainly works. Top of radiator gets plenty warm. Aux fans do kick in, so I don't think its a sensor issues unless two go bad at once.

Did some searching, but is there anything special I need to do? System should be self bleeding from what I understand.

I always remove top hose from radiator and fill it that way.After I fill block and rad.

+1

Been there, done that with filling upper hose at radiator. Burped this thing several times today. The temp is certainly related to engine RPM. At 70mph she gets to 115c. At 55, 105c. Slower, about 100c. Very consistent temps at these speeds. If I turn on defrost she drops 5c pretty quick then will slowly drop another 5c.

Its like she just can not cool. My first thought was AF mixture. But she is running nice and since I got rid of any air leaks (if any), she would actually be running richer.

I did cool burps, hot burps. Disconnected hoses. Pumped the upper hose so all I could fee was water in it.

It just weird, I have changed the t-stat before and never had this issue. Also I will note the viscus fan clutch (BEHR) was replaced last week. No issues before intake work with that fan so pretty sure its good. It certainly feels tighter when spinning by hand and I can certainly here the dang thing spool up.

I think I may try a t-stat swap. Other than that, the only thing I can think would be that the water pump somehow went bad during this work, but that would be one heck of a coincidence. I guess before I do that, I will pull the upper head plugs in the back and see if any air comes out.

Is it possible that anything like a parer towel or rag could have worked its way into the cooling system when you were doing all this work? It has been known to happen. Ask me how I know.

I doubt it. I am really careful about those things. But I suppose, anything must be possible until proven not the case. I sure hope not. Maybe a good dose of citrus powder would dissolve anything. I only use shop towels and the car only has distilled water in it right now anyway, so no waste of coolant if I do.

I could not wait and the engine was already warm. So I loosened the head cap things at the back. Both bleed water just fine. Did the dash temp sensor too again, same. It really seems like the coolant is flowing. Just either not fast enough (blockage as suggested) or t-stat is holding back. The upper hose gets plenty hot, top of radiator is too hot to touch. I put a gallon of washer fluid in today - well that all steamed off already (stupid heated fluid idea).

Frustrating for sure. I even thought maybe I reversed the intake gaskets! Well, not possible. Car would not even run right if I did. And the coolant passages are the same for both sides.

Well I guess I am starting to rule out air pockets and move onto blockages and flow issues.

Can you tell if you are losing any coolant? How old is the radiator cap?

Expansion cap is about a year old, original MB part. Not loosing any coolant at all.

Presuming the 560 has low speed electric fans, are they operating?

" and the car only has distilled water in it right now anyway, so no waste of coolant if I do."

I'm thinking that might have something to do with it. Your normal 50/50 mix has a different boiling point. My very limited experience with MB tells me they are very sensitive to having the exact fluids in use.

Good point.

No, that does not matter. After all, I have been running distilled water for months now due to the coolant leak at the intake gasket. If anything, the system is now under slightly higher pressure further increasing the boiling point. Not to mention, in some areas many run just water (Arizona, etc).

edit: under pressure, the boiling point of water is 125c, which is the upper limit and red zone of the gauge. Adding mix at 50/50 only increases the boiling pint 6 degrees Celsius.

No, only hight speed. Viscus fan and the aux fans kick in with AC (which I do not have) or at 110-ish Celsius. Which is what they are indeed doing. Its probably the reason I do not go into full on over-heat.

If they were not such a pain to acquire (shipping, waiting, etc) I would toss in another viscus clutch just to rule it out. Quick to change. But again, its new and BEHR, not URO crap, so I am pretty dang sure its good. Feels pretty tight when hot.

Out here in Tucson, I've always run a low coolant ratio (25%) and it works very well; but I've never run straight water. Maybe you could try getting two quarts of anti-freeze in there just to rule out the possibility that it's not the lack of coolant.

You mentioned you replaced the fan last week. Is it possible that you just didn't notice the temp running higher back then, or could the ambient temperature be higher this week?

Just a quick thought. On my 500, and I believe your 560, there is a ground wire that runs from a small bracket behind the P/S pump to the left finderwell. It is the main ground for the body. If it didn't get hooked back up or didn't make a good connection then it can cause all sorts of strange problems with the gauges and other sensors.

Paul

Replaced t-stat, same results. She actually drives a couple miles holding temps just fine. Then, is seems, after all of the coolant is warmed up it starts to climb slowly. This is from a overnight cool down.

Figured I had the part, worth a shot.

Even though I am certain my old viscus fan is bad, I am going to reinstall. Upon closer inspection, I dont feel there is enough resistance in the fan. Is there a good way to test it? I did notice that if I hold high RPM in park the fan quiets down. Not sure how long, maybe 30 seconds? It actually sound like the cars RPM is dropping (but clearly its not) - if that makes sense. But I can move it by hand when cool - tighter than the old one. But when hot, there is no noticeable change in resistance.

Well new viscus fan was not change. So I removed the temp bell housing, lower and upper hoses and took the shop vac to it. Sucked whatever could have been in there, if anything, out. Made the the vac did not sounded restricted. With the t-stat it was, I could tell. Pulling the lower hose before it and it flowed fine. Basically a reverse flush :) I would love to actually flush her, but that may be a last effort. I got her up to temp to where the t-stat opened with expansion cap off and now I am letting it cool back down (still with cap off).

If this did not help, I will be pulling the water pump next weekend. I dont have another on hand right now and if I am going to pull it, I may as well replace it anyway.

On a good note, all the water is coming out crystal clear.

Well hope and dreams crushed again, can only think maybe water pump now for whatever reason.

So guess I will be driving it running hot until I replace the pump or she dies. Guess its a good reason to finish the 750il and finally put the Benz down.

Sorry it's not working. Thanks for the updates. Good luck and let us know what it finally turns out to be.

Are all your belts there and are they tight?

Yup. In fact, with the water pump there are two belts. Both also assist in power steering. So if they went out or slipped then power steering would be affected.

Today I cleaned the condenser and radiator. Tested 2 t-stats. Purged it twice more, once from dead cold to warm up.

At this time, I can only lean towards water pump. T-stat(s) certainly open. Viscus fan clutch is new, even old viscus clutch yields same results.

So thinking water pump. Its probably original anyway. So if it does not solve the issue I dont feel I am wasting money.

There should be a thermostat to stop heated water from flowing through the washer tank.

My SL does not get driven in winter so I bypassed the heated washer and heated base of windshield.

Given you are running straight water, dump in a bit of antifreeze to color the water. It gets difficult to find leaks with straight water. Straight water has the best heat transfer rate but needs elevated pressure to prevent boiling.

I'he been looking at maybe getting an extra overflow cap and rigging up a vac line to it. Supposedly pulling a vacuum will get any air out as well as act as a leak detector. If it can't hold vacuum you have a leak.

I thought there was suppose to be one. Guess mine is not working, never has as long as I owned the car. Not a top item on the list right now though! But I will look into it.

I dumped some stuff that shows up under black light. Pretty sure there is no leak, the upper hose remains "inflated" for a long time when the car is off. Under pressure, I should be good to 125 degrees celsius. Without pressure, no more than 100c. Antifreeze at 50/50 mix only adds a few degrees to boiling point.

Pretty sure no leak. If there is one, it would have to be pretty tiny and thus not significant. I can certainly try the vacuum test.
When off, the car maintains pressure in the cooling system for a long time. At least an hour if not more. Never really checked longer than that.

Forgot to add. I just pressurized the cooling system with a garden hose and tap water. I really, really got sick of buying up the local inventory of distilled water - even if its cheap.

I pulled temp sensors and the plug on the back of the intake. Also pulled the air vent hose on top the radiator.

I did this for two reason. One, I descaled the system with corrosive acid that needed to be flushed out. And two, this way I could almost guarantee no air in the system. I wont go through details, but yes I made sure no air was pre t-stat too. In short, engine running and water coming out everywhere. Good times. Still runs hot...

Water pump ordered. :)

Have you actually used an infrared thermometer and checked the engine's temps in various places (top of radiator...water pump housing....upper hose....intake area...sensor area) to see if its actually running at those temps?

The engine fan should be ROARING above about 85C.......the one on my 420 fully engages over about 84-85C and moves a TON of air, my front aux fan also comes on low around 85C With the A/C on.....

I just did the intake job on my 420 a few weeks ago and did not burp anything, I filled the coolant just by filling the expansion tank and running the engine...0 issues, runs at 82-85C, even sitting idling with A/C on a hot day it never even hits 90C. I am running about a 45% mb coolant to 55% water mix in mine right now.

No. But to some degree, I trust the gauge. Only because the aux fans kick in right around 110, and the dash gauge reads that. So two sensors agree on temps at 110 at least.

My new viscus clutch grabs much better, so I can hear the fan now really well. The fan is roaring when I start the car. After a bit, it disengages, as it should. Its a short jump to the highway for me where the car will now reach operating temps. And yes, at 85-ish I can hear the viscus fan spool up. I can verify with a rev (especially if I drop into neutral). But temps still slowly climb. The only thing that seems to save her form overheating is the aux fans.

And I believe that, hence my frustration! I have replaced the t-stat before and other operations that resulted in major water drainage during work. Always filled it back up, squeezed the upper hose and never had an issue.

So like I said, thinking water pump. May as well, its ordered anyway. So once I know all the components are new (viscus clutch, t-stat, pump) I will be forced to rule those out and look into other possibilities. Blockage, bad radiator (technically blockage) or even some sorta blown head or exhaust getting into coolant system. I doubt a head or exhaust issue since the radiator cap never blows over. And I see no oil or other signs related to those issues.

I've seen fins come off stamped steel water pumps before when the cooling system is run low. Water , air , vibration and the fins come off.

This car has a cross flow rad correct? I've seen cross flow rads fill with silt on the bottom and block water flow. ( had this occur on a Ford Aerostar, the rad inlet tank was tapered at the bottom making the perfect place to silt to pack. )

It is becoming time to do a leak down test. This involves removing spark plugs, turning engine to top with valves closed. Pump in compressed air ( 100 ish PSI is fine ). This tests integrity of the combustion chamber.

In your case you are looking for air bubbles in the water. If so, there is a cracked head / bad head gasket.

They are top to bottom flow radiators on the V8 W126's.

It could be a bad t-stat....they can come right out of the box bad sometimes. Maybe get one from the dealer and swap it again? I've seen one on am OM617 fail right away and had to replace it again.

You said that you replaced the intake gaskets. If it's running hot now, I would suspect a vacuum leak. thinner fuel/air mixture the hotter it burns.

Could be that valve timing is off as well.

I did run it rather rich to test that theory, same results. I wired the aux fans to be on full time, that has helped. But on extended trips, it still warms up to just over 100c, but never more than that.

Pump came today. Not to others, if you buy Laso (one of a couple OEM brands) they come with main gasket, temp housing gasket and t-stat o-ring. While those are cheap, now have three of each. lol

pull the radiator and do a reverse flush for 5 - 10 minutes. I just replaced my radiator because mine has partial blockage for a while and I never noticed it. my car would get up to 100C if it was just sitting ,, but now it it can sit for a while before the needle even moves. also check the fins on the radiator and also make sure none of the passages are pinched.

Not sure if running it rich is a legit test. I've heard of the smoke test, where you blow smoke into a vacuum line and look for some coming out somewhere.
I've also heard to test for a vacuum leak, spray ether (starting fluid) around suspected leaks and listen for an increase in RPM. But be very very careful as ether is extremely flammable.

There are only so many things that make a car run hot. From the sound of it, the car ran at proper temp before the intake gasket change, but not after.

A cooling system should not sludge up overnight to that extent. I would look over the original work, double check vacuum lines and what they hook up to.
Look at the MAS (the round thing that moves up and down as the accelerator pedal is depressed) it should be closed at idle, if it's open just a tiny bit too much air will get in.

good luck

I will check again for intake leaks. Would the car really run super smooth on such a lean mixture? I still have enough power to make some nice g-forces :) And it idles super smooth. Fuel economy, which I check with EVERY gas up and have for years now is at 18mpg. 20 on highway trips if I behave with the throttle. Again, those numbers are still the same. And I agree, it is odd things were fine before and now not. Something changed, obviously.

Nonetheless I will do a more thorough check and check the deflection plate again.

I hope to replace the pump this weekend. If anything, that will be the culprit or then ruled out.

As for back-flushing the radiator, did that when I did the last garden hose flush. All together probably ran over 100 gallons through it, if not more.

Re: Air Flow Sensor Plate ("MAS")
1) The plate is not connected mechanically to the throttle linkage or accelerator pedal, and therefore does not move mechanically with movement of the pedal.
2) The plate does move in response to changes in intake air flow. When the actual throttle (down, almost out of sight at front of engine) is opened, increasing air flow will cause the Sensor Plate to be pulled down, which in turn raises the fuel metering plunger, causing more fuel to flow.
3) If the Sensor Plate is pushed down by hand while the engine is running, the fuel metering plunger will be raised, making the mixture richer, not leaner!!

Good info. Either way the plate is fully closed as it should be at idle.

Numerous vac leak tests with starting fluid produced no results. In fact, like I said earlier, if anything they may be less leaks (if there is one now). The brake booster line to the lower manifold was not tight at all. I even now notice a difference in breaking since fixing that. Also the intake gaskets are sealed with gasket sealer. So in theory, they should be spot on sealed.

Was going to do the pump tonight, but it looks like the balancer has to come off? Did not plan on that. Anything else I should know??? :) I think the balancer is straight forward. I will mark it.

Probably Sunday, maybe tomorrow night if I have time, I will replace and report back. Honestly, I am not expecting it to resolve the issue. Gut feeling. But at least I can rule it out.

Thanks for all the input thus far.

I don't think you need to remove balancer, there might be one or two spots with indentations on the balancer where you can access the water pump bolts. But then I never worked on a 5.6. Other benz's I have seen that.

I will see if there are, that would help. I did not look very close. Either way, I bet I push this project off another week. :(

Garage has a 750il parked in it and that is not moving. Temps here are over 80 and very humid. Not the best weather for car work in the open, but this has to get done.

Check the vacuum to your ignition distributor, if you have not done so yet. I suspect some misplaced vacuum hoses.

Your car not getting enough air that explains your car is running hot. Try redo the job, check the intake valve from air filter to throttle body. Check everything even the sensors.

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I dont think that is right. If I was not getting enough air I would by default getting too much fuel, and the car would run cooler.

You are full of awesome! Maybe I would have spotted them before I yanked it all apart, but I doubt it. I saw one (maybe there is only one) of those notches! That will speed things back up and make it an hour project again instead of two or more. MUCH appreciated!

As for vacuum lines. I traced them all and they are all correct. The only change I made was to pull the vacuum line at the intake for the air injection system. But that system has been disabled for years. I pulled the belt shortly after getting the car.

So I then checked vacuum at each hose. A the advance I had plenty of vacuum and when reconnected the car would surge for a half a second. So unless the advance portion itself is bad, that seems to work.

The only odd thing I found was that vacuum from the TB is very weak. But I do not know if this is normal. Via finger tip, I could not feel any vacuum at the two lines from the side of the TB. The larger hose, for purge system, has some noticeable vacuum - but again, it was weak. This was with the engine at a warm start.

The TB vacuum is ported vacuum.

The idea being to suck in fumes from the purge canister only when under load.

Take a look at the diagram below and tell me if i got the right one?

http://www.auto-parts.spb.ru/cat/cat...96abbca6a5d8ee

You now, too much vacuum to the distributor would yield to much advance, which would cause hot running.

Thats no my vacuum setup. Close, but not identical. There is no vacuum line to the distributor on my car, it goes to an advance module/coil. And some other lines do not match. This is the diagram I used.

Well so much for the notches in the harmonic balancer. Useless they would seem. I can feel the bolt I have to remove, but its closer to crank then the notches allow to get at. If the notches were maybe a half inch deeper it would work. So not sure which half-brained engineer designed this thing, but getting the water pump out is back to being a total pain.

So back together it goes for now with deep loathing for german engineers. :) I did do some more searching online too, indeed the balancer must come out on the 560.

Perhaps when faced with a major disassembly one might as well replace all the things in that area which might go soon rather than repeat. Not sure what that might be in this case.

Maybe the SLS hose. I noticed its easier to get at with the water pump out.

Well I thought this would be more of a pain than it turned out, sorta. Online indicated air tools to get the 27mm bolt at the crank out.

Well for one thing, that write-up is dead wrong. I locked the engine and got it out with a breaker bar easily. But where its wrong is that it does not need to come out. All that need to come out are the six 13mm bolts. Once those are out, the pulley assembly and then the harmonic balancer will come off. Mark them before removing.

Also the distributor is of course adjustable. Remove the adjustment screw and the pillar that it goes into does pop out. I did not know this and removed the entire distributor. No one in any write up mentions this fact. So once the screw is out, just tap that piece and it will come out. Then you can easily get to that water pump bolt. Now I have to re-time the engine a little.

Do not over-tighten the pump. I noticed a small rip/ripple in the gasket. Did not think I did, but must have.

When reinstalling the pulley assembly, be VERY careful when tightening the six bolts. The first time I had it skewed just a little and when I started to tighten it was not aligned at all. Just go slow and tighten all a little at a time to make sure it seats right. One bolt did not go in and never will. I had a heck of a time getting the last one in. Might be why I had the above issue since I backed off the other to try and get it. After several removal and reinstalls, I gave up and will have to settle for five bolts...

Update: Well she is still running hot. The more you guys mention other items, the more I had doubts it would help. But like I said a few posts back, even if it did not fix the issue I will have a new pump and can rule it out for sure. The old one is in pretty good shape. No play in it and no wear of the impeller.

Granted, I have not burped the system like crazy like I did before. But I am not giving hope to that being the issue this time. I will of course do so tomorrow anyway.

So next, another t-stat to be sure its not the issue. Takes me 10 minutes to change now after all. I am going to run an O2 test for setting mixture again, been a while. Then I will remove the radiator for closer inspection. If the radiator was not so pricey, I would toss one in for peace of mind too.

One thing is for sure, my timing may have been a touch off. All I did was set the engine to TDC and line up the marks on the distributor. That may not be the correct method, but the car had loads more power. And to think I thought it had power before. I can actually chirp the tires now on take off.

And if all else fails, the intake is coming off. That was the plan anyway. When I did it the first time, the boot did not look so well. I passed doing the donuts too because I was going back in. So in a coupe weeks it will be out for a full overhaul anyway. Maybe I will find something then if I still have the issue.