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'87 560 SEL smoke silver/chocolate
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Discussion Starter · #1 ·
Working with a friend and we have an overheating problem at idle, the problem is that as the overfill tank fills we have to remove some of the coolant, it refuses to return to the radiator. I'm thinking thermostat, but wonder if anyone has had similar troubles with the 500E. (1985)
Thanks
Mark M.

I hate a disobedient inanimate object.
 

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Smoke Silver '87 560SEC, Black Pearl '87 560SEL
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sounds to me like a head gasket problem. Do a compression check.
 

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'87 560 SEL smoke silver/chocolate
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Discussion Starter · #4 ·
Alright, but just for discussion sake, what leads you to say head leak, I'm only asking from not understanding, not to be argumentative. By the way, the coolant is clean as we remove it and no other apparent leaks around the engine we can see.
Mark
 

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Smoke Silver '87 560SEC, Black Pearl '87 560SEL
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Something is pushing water into the overflow tank. Either you have a thermostat that isn't allowing any flow (major overheat) or a water pump that isn't (major overheat) or something else is pressurizing the system - compression leak via a head gasket.

Is the engine really getting that hot or is it likely close to a normal temperature, but a full overflow tank. One quick test is to have a emissions testing station take their tailpipe emissions measuring "wand" and let it sniff the overflow tank air - if it measures any hydrocarbons or NO, head gasket leak.
 

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'87 560 SEL smoke silver/chocolate
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Discussion Starter · #6 ·
Thanks for the explanation. It does make sense. A compression test is on the way.
Mark M.
 

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1984 280SEL AMG
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You could also have a pin hole leak in the cooling system... Do a presure test on the cooling system... That will tell you where/and if you have a leak anywhere... Also look to see if you have water in the oil, or oil in the coolant... Those are a sure sign of a head leak... Pull the thermostat and check the temp raiting, then toss it into a pot of boiling water, that'll tell you if it's good or not... The water pump... Pull the thermostat. start car, if water flows free, it's good.


Good Luck
Rich
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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Cannot a weak spring on the pressure cap cause reduced system pressure, resulting in higher temperatures with coolant being expelled? In a worst case scenario with a head gasket leak, any small drops on the dipstick?
 

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'87 560 SEL smoke silver/chocolate
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Discussion Starter · #9 ·
Thanks for all the input gentlemen, I have a question about why the coolant doesn't return to the engine. I plan to replace the cap but low pressure don't seem to answer an overflow problem. By the way, no coolant was found in the oil.
After some more discussion about the symptoms with the owner, I think we have a bigger problem than just a slight overheating, it seems he noticed the trouble and came home and hasn't run the car much since. Afraid of getting stranded I suppose.
Mark M.
 
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