87TDT drinks coolant
 

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...

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".

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.

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

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.

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

Well where else is the coolant going.


Bet you a pizza that they flag it for coolant, ya on?:D

I don't usually guess the answer. I let the data tell me the issue.

Maybe the coolant is leaking?

Do you honestly suggest that this fellow remove the head without a shred of data to confirm a problem with the gasket or the head.........because you say so?

Its always good to test, but the coolant is going somewhere.

Testing the engine oil is a wise start. Coolant loss can be explained by all the aforementioned plus faulty cap for expansion tank and leak into the transmission cooler (checked your transmission fluid level lately?).

If engine oil and transmission oil show no sign of contamination, get a new cap for the expansion tank.

.......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.

Mine has a small break in the reservoir, where the hose is clamped, that is causing this same problem. Another round-tuit project.

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.

If the heater core is leaking, the sweet smell of of the coolant is unmistakable. I don't think this is your problem.

Does your car have the optional coolant loop through the windshield washer reservoir? This can leak coolant into the reservoir.

Get an engine oil analysis done quickly, and act quickly if it shows any sign of coolant in the oil. If you need to replace either the head or the gasket, earlier is better to prevent much deeper damage to the bottom end of the engine.

tranny fluid mix would exibit a pinkish fluid on the stick. also the level would rise...

this is an old post but i thought it would be good to update. one day a few months ago (still wondering why the car was running perfectly yet sipping coolant) i removed the coolant tank. it turns out the coolant was leaking from a crack on the back of the tank. the coolant was leaking slowly enough that it never hit the ground or made much of a mess. it didn't leak until the car was hot and then the hot coolant mostly evaporated before it hit the ground.

once i found out what was happening i removed the wires for the sensor and just left to coolant level low in the tank below the crack and it stayed there. i finally got around to replacing the bottle and all is well.

Thanks for the update you must be relieved!

Found a similar problem on Rudolph. At first I thought it was due to someone having put on the wrong pressure radiator cap - 13 psi instead of 20 psi. But upon startup with the proper pressure cap installed, once warmed up I noticed air/coolant bubbling up from the seam where the metal radiator cap fitting joined the plastic tank. Some JB Weld putty took care of it for the time being until I get around to putting in a new tank.

Another culorit I found a while back on the now-wrecked '87 was the ancient rotted braided hose going from the surge tank down to the recovery tank in the fender well. PITA to replace - had to pull the battery and the fender well liner.

I always tee in a pressure bottle to the lines and pump to 15 or so psi. see if it holds. All these stupid leaks are easy to find with engine at ambient, in the quiet garage with engine off. I dont know how many leaks Ive found this way. Glad it wasnt more serious, and I'll check my coolant bottle, that thing is a relic.

oh yeah, somebody owes somebody a pizza. ;)

Yes, Hattie owes Brian a pizza. Good thing he didn't pull the head.;)

Excellent outcome. Glad the head didn't need to come off.


Oh Chris........where's my pizza........???;)

It's a good idea to replace that tank, even if it isn't cracked. The new ones come with a silicone pack that helps to protect the cooling system.

He diagnosed it wrong! It was leaking not being burned!:D

Who diagnosed it wrong???

The OP, he said it was burning coolant. I'm not responsible if he can't see a leak!:D;)

.......'scuse me.....:

I'll have pepperoni on that, please.:D

When will you be in town?:D

Tuesday.:):)

With the BMW?:D

Depends........I'm still struggling with a CEL and a leaking backplate........it might be back at the M/B dealer. If so, then it will be the '87.........which you also have not yet seen.

The Mercedes dealer does BMW's?

I know a good pizza place too, right down the street from 40.

The mechanic does them on the side.........but, he's not too good at it.:mad:

Excellent.:D

See you switch manufactures and your stuck.:D

Unfortunately........

How's the HVAC? The variable-assist steering? The ... nevermind.

At the moment, everything is fine with the exception of the backplate. It's leaking air and the cold idle is poor. The CEL will light up after the test mileage sequence is performed.

I do love the way it drives.........

... and looks.

coolant don't burn...

i know i'm a newbie, but...

Concentrated Ethylene-Glycol is flammable so yes, coolant does burn.

I just replaced my Coolant Tank pressure relief cap. I put on a 16# cap. Cap made by Stant. $6 at Walmarts. It fit very well and went on Tighter than the old original cap came off. I think my old one was shot. Not sure never saw any coolant leak.

The old Cap said 120 on it. I guess this is 120 degrees C. Boiling pressure for 120C is about 15-16 pounds. So I think I'm ok.

Anybody else use Stants caps on these cars?

They fit nice plus it has the Trigger in the middle to release pressure which I like.

Did I do anything wrong that I may regret later? Figured I'd ask here.

TY

120 on the cap is 1.2 atmospheres=17.6 psi.

The 16 psi cap will be fine.

Your SD has an OM617 engine, right? The OM617 engine in my '85 300D-T has a 120 cap on the expansion tank and that is the factory cap so you are OK.

Jeremy