87TDT drinks coolant - PeachParts Mercedes-Benz Forum

punkinfair · #1 10-29-2007, 10:55 AM

My 87 is drinking coolant. sipping maybe is a better word.

i have spent a few hours searching a reading the forum. my car has no apparent symptoms of a cracked cylinder head. there is no oil contamination in the expansion tank, the car has never come close to overheating in the 2+ years i have owned it. it doesn't seem to have residual pressure in the upper coolant hose, however it is not clear to me what a "hard" hose should feel like, exactly. there is fluid in the upper coolant hose when the car is cold, but when you squeeze the hose the fluid just moves around. it doesn't feel like the hose is pressurized.

the car does not emit any white smoke. there are no odd smells or anything else i can identify as significant to the loss of coolant. i replaced the water pump last summer and there were very small traces of leakage (stains on the oil sump) from the pump, but those traces are now gone and there was never even a drop of coolant on the ground. the only sign is that the coolant disappears. it seems to be accelerating - i think it used to be maybe 2-3 months and i would need to top up the tank. recently i topped up the expansion tank and it was nearly empty in 10 days. the car is well maintained, MB coolant, and has been a perfect trouble-free vehicle for about 2 years. it still runs perfectly, but the vanishing coolant is worrisome. i did a cooling system pressure test in the spring and it held pressure fine.

the only thing i can think of is that the heater core may have a slight leak. if the climate control is left on when you shut off the car, then you start the car the next day or a few hours later, the windshield gets fogged up and the air smells a bit funky. this clears up quickly. the car has done this pretty much since we've owned it so i haven't been too concerned. but it makes me think there is a leak in the core because the moisture has to be coming from somewhere.

anyhow, thanks to anyone for some ideas on what to do next. i am a mechanic but the vehicles i work on have no radiators! i am slightly lost when it comes to watercooled cars...

TX76513 · #2 10-29-2007, 11:06 AM

Look under the A/C drain vents after using the AC - are there traces of coolant? Don't do the taste test but the smell test.
This may be a prudent time to do an engine oil analysis to see if it's "making oil".

Brian Carlton · #3 10-29-2007, 12:16 PM

Pressurize the cooling system with a suitable pressure tester and search for the leak.

If you fail to determine any leak, then you may begin to suspect the engine is consuming the fluid. During the next oil change, send a sample for testing and specifically note any Glycol contamination. It will show up in the oil well before any other symptoms are present.

The cracked head on the SD had no symptoms other than constant consumption of coolant.

If the test confirms glycol, you'll need to pull the head. The problem could be a bad head gasket or a cracked head..........impossible to tell without pulling the head and having it pressure checked.

punkinfair · #4 10-29-2007, 04:40 PM

Quote:

Originally Posted by Brian Carlton

The cracked head on the SD had no symptoms other than constant consumption of coolant.

ok, that is interesting to know. i will look into an oil analysis. thanks.

Hatterasguy · #5 10-29-2007, 10:09 PM

It may not be the head, these cars do blow head gaskets. My brokers SDL blew its head gasket a few years ago, similer symptoms.

The headgaskets were redesigned a number of times, and much weaker than the heads.

I wouldn't bother doing the oil test, because you know what its going to tell you.

Brian Carlton · #6 10-29-2007, 10:11 PM

Quote:

Originally Posted by Hatterasguy

I wouldn't bother doing the oil test, because you know what its going to tell you.

We have a name for people who have the answer before they do any testing..............

punkinfair · #7 10-30-2007, 12:12 PM

i did replace the expansion tank cap last year and the hoses are all in good condition and tight. but it won't hurt to look again at all the connections. i did have most of it pulled apart last year when i did the water pump and belt tensioner. in the meantime i made a little hatch mark on the reservoir yesterday to track the fluid level. i do check the transmission fluid regularly. if there was leak of coolant into the transmission via the cooler, how would that exhibit itself?

i'm going to send the oil to get tested at blackstone labs, unless someone from ontario has a lab contact close to me here in toronto.

TX76513 · #8 10-30-2007, 08:16 AM

.......and aside from checking to see if there is coolant in the oil. Oil sample testing is just good business with these older cars. Quite a bit of information can be gathered from a sample.