260e 124 series, overheating

[optimusprime]

Eminec did you check out the post from Krimat2005 about the heater pump ?. He as given you the answer to the question you wanted to know on how the pump gets its 12 volt power from.

 

[emimec]

Update.
Covered 100 round trip last Wednesday, no problems with temperature, steady 85c, no water loss. Next day, battery flat !
Water temperature good all week, no loss until today, when evident from overflow. Seems the problem relates to stop start short runs, which today was.
I followed info about auxiliary pump, still doesn't do as advised. Changed the controls with a new one i have, this is the bit with the two rotary controls and the circuit board in. Point of interest here, original had pin 4 missing and also one transistor, when compared to the new one, but both had same part numbers. Made no difference, auxiliary pump still not working as when instructions are followed.
Yet to get compression test done.
Bob

 

[emimec]

Forgot to say, auxiliary pump does have a 12v supply, it's the switching of the earth that seems not to work

 

[emimec]

update

Managed to get to a friend's garage today, who specialises in mercedes, and has done plenty of work help me in past, and it was them that did my head gasket time ago.
Anyway, they gave my car what was called, I think, a sniffer test, albeit the test was a green liquid in a special contraption that sat in the header cap orifice. The liquid did not change to yellow as apparently it would if gases present. The mechanic said it's usually better with a cold engine, and mine was hot, but seemed confident the head gasket is ok.

I guess I'll just carry on monitoring it, especially as summer looks like it might have finally arrived, and warmer air temp, so see how she performs the next week or two.

 

[grober]

Can you confirm you have a viscous engine fan and not an electromagnetic coupled one? [[ this is the one on the engine not the one in front of the radiator if you have aircon.]

 

[emimec]

I have the viscous fan on the engine, and as you rightly pointed, a thermostatic (which is a bit noisy) for the air con mounted on the radiator.

 

[emimec]

stumped now !

Friday afternoon the car continued to lose water from the overflow after a short local trip.
To 're cap, head gasket was done time ago, and the test using a green liquid performed by my local mercedes independent was to prove negative.
I changed the filler cap, no difference. Tightened all hose clips, plus there is a new radiator in place. No visible leaks, only thing I can think now is that the water pump impeller is shot, if indeed this happens on this car. Other than that, I am well and truly stumped as to why the car runs at average temperature of 85, or near 100, when In traffic, this happens. Bob

 

[carat 3.6]

The water pump being faulty is a possibility, albeit a rare one

If you remove the thermostat from the water pump you can just about get a view down at the impeller, though the only real way to be sure is to replace the pump.

The sniffer test confirmed there is no exhaust gases in the coolant, but that doesn't mean the gasket is ok. You need to do a compression test on each cylinder, if one is reading noticeably lower than the rest you've found the problem.

 

[GadgetBoy]

Neither the historical head gasket repair nor the sniff test are absolute proof the head gasket is ok.

The rest of the evidence still strongly suggests the head gasket is suspect.

 

[emimec]

I think your right, deep down i think it's the gasket. I also noticed a while back the idle is not as smooth as it used to be, you can see the bonnet vibrate by the windscreen sometimes, yet more evidence i guess. I'll get local lad to do compression test in the week

 

[emimec]

cylinder leak test

Those in the know tell me a cylinder leak test is my next option. I still can't make sense of this problem, the water only escapes through the overflow when I stop. Happened again tonight, did 18 mile each way trip, first half, all ok, second half after some London traffic delay, pulled into petrol station, and there it was, running out of overflow. Temperature in traffic went up to about 95.
Having removed the water pump from a spare engine i have, couldn't help notice how clogged the pump was where it mates to the block, wonder if this could be my problem.

 

[gbjeppm]

Was the filler cap that you swapped over new, I still lean towards that?
I had exactly the same issue on a 190e, overflowing from the expansion tank, brand new filler cap fixed it. Or asking the question a different way, is the expansion tank holding pressure? Damaged entrance? Bad seal?

 

[219]

The aux coolant pump has nothing to do with coolant temp/engine overheating. It's a 'booster' pump for the heater. I'm not sure exactly how it's used i.e. whether it's simply on or off and switched by the heater or a variable speed/pulsed deal according to heater settings etc. http://www.w124performance.com/service/w124CD1/Program/Climate/83-630.pdf doesn't exactly go into much detail but suggests to me (possibly wrongly) that it'll only run flat out when the heater is 'working hard' hence setting to defrost and feeling the pump?

If the aux pump isn't working i'd expect the heater output to be poor when the engine is idling and/or heat demand is high due to temp setting. Especially if the heater fan is set highish for demisting/defrosting. It'll be listed on the fusebox cheat sheet (both in your owners handbook and in the lid of the fusebox) somewhere, it's supplied by fuse #7 on mine along with duo valves and various other aux fans, HVAC bits and pieces and the reversing lamp

If the engine is running hot then you need to look elsewhere... tired/knackered radiator and/or main waterpump, dead viscous fan, dodgy thermostat etc. A better description of how the car overheats may help us narrow things down

Agree with the bits in bold . I'd start with the basics and look for a blocked up radiator or cooling system : have a feel across the surface of the radiator for cold/hot patches which can indicate blockages ( taking care of your fingers wrt the fans ) .

Giving the system a good flush then refill with fresh coolant and make sure it is properly bled .

Failing that , as above I'd suspect the water pump ; either do it at the same time or recover your fresh coolant before swapping it .

 

[emimec]

No, It was the one I kept after replacing it with a new mercedes bought one, it was ok But the time, but noticed the edge of the rubber starting to split.

 

[emimec]

Thanks, it has a new radiator and thermostat. It runs generally at 82, Rising to 90 -95 in London traffic, can be ok, no overflow. Long runs are ok, it's when you either stop or get in traffic, then temp rises to the 95, but not always, then with the engine off after getting petrol or something, you see water from the overflow. I would think if it was a gasket, I would lose more on a run. Seems like residual heat or pressure builds up when engine off.