Mysterious coolant disappearance. Help!

[drrty byl]

My '96 ti is mysteriously losing coolant. I don't have the lifetime cooling fluid in my system and have been flushing it regularly about once a year for the three years I've owned the car.

The radiator reservoir drops several inches below the "KALT/COLD" mark a few hours after topping off the coolant. Every time the level droops I pour in a little more fluid to bring it back up to the line.

I placed newsprint under the radiator/engine area: no drop/leak marks anywhere, whatsoever. There are no visible cracks in any of the radiator hoses. The car never overheats when driving either. Someone told me the head gasket might have gone bad and to check the color of the oil beneath the engine cap -- that it would be a crusty yellow color if coolant had been seeping into the engine. No such symptom.

Could it be that somehow this marker is incorrect and that the car is boiling off excess fluid? Is this something to worry about?

[aceyx]

Can I assume you bleed the system after flushing it?

If yes, it might be time to try UV tracing fluid. Does it the engine bay smell weird? Burning coolant has a particular smell.


And once a year is a bit much. Drain & change every two, and full flush every other change.

[drrty byl]

Yes, bleed the system after flushing. The engine bay smells very ordinary - nothing weird..

[Tyler]

Pull your dipstick out and check it a couple times. See if it's way over the fill lines and if it is then the coolant could be in there. I know you said you checked where the oil's put in but check that if you haven't already.

[m3outtanowhere]

i have a 94 318is with the same problem. the coolant level will drop but never goes empty. Fill it up and drive it 30 min. later same low level. I never found out what it was. I also have never had a cooling issue. But...sometimes when i really push the 318is hard, and at night time, i will take the rpms to 6500 and shift from 3rd to 4th i can see a plume of smoke in the cars headlights behind me. But i cant see it ever during the day. This make me think that the plume is clear???? so weird but never hurt the car yet and it has 140kmiles.

[andyman7931]

has this always happened or is it something new with this coolant change?

I'm getting coolant in my spark plug hole which is causing a misfire... so far it's either a headgasket or cracked head. I'm not looking forward to either of those.

[m3outtanowhere]

it has always happened. I know that my car burns oil (1/2 qt a month) but i like my muffler bearings lubricated. j/k oil consumption on the 318is is because of calce guides.

[m3outtanowhere]

Originally Posted by andyman7931

has this always happened or is it something new with this coolant change?

I'm getting coolant in my spark plug hole which is causing a misfire... so far it's either a headgasket or cracked head. I'm not looking forward to either of those.

and i just went through a head gasket too. sorry to hear that. it was a 2000 dollar total when i was done.

[drrty byl]

Just noticed it happening in the past 2 months or so, last coolant change was about 4-5 months ago.

Strange that happens to you m3outtanowhere -- do you typically refill the reservoir or leave it alone? Have you ever had to replace your radiator? My ti has about 132k on it.

[m3outtanowhere]

leave it alone, it never hurt mine.

[fly2thesun]

I just found the same problem in mine.

Coolant just disappears without trace. Not in the oil or on the floor. And the level doesn't go lower after some point. The car runs just fine, but does overheat a little bit under a long idling. ( Overheating goes away when I turn on the A/C, as the auxiliary fan comes on. ) It seems that the auxiliary fan temp sensor is not in contact with the coolant because of the low level..

It's quite mysterious.. and interesting that nobody seems to know why...

[aceyx]

At what rate are you losing coolant? (How much do you add, how often)

[drrty byl]

Originally Posted by fly2thesun

Coolant just disappears without trace. Not in the oil or on the floor. And the level doesn't go lower after some point.

I'm pretty sure my car was having this problem due to ~100 degree weather -- coolant may have been evaporating somewhere along the system? It stopped vanishing at the end of the summer. Replacing hoses didn't fix the problem either.

Originally Posted by fly2thesun

does overheat a little bit under a long idling. ( Overheating goes away when I turn on the A/C, as the auxiliary fan comes on. ) It seems that the auxiliary fan temp sensor is not in contact with the coolant because of the low level..

My engine is in good shape and never overheated, nor did the expansion tank really seem to lose that much coolant. It sounds like you could be losing quite a bit of liquid?

[fly2thesun]

Maybe it is not that mysterious

Here's a little more detail..
I had the thermostat (it was stuck open) replaced 4 months ago by a mechanic.. Since then, the car seemed just fine.. except slight overheating under a long idling (first found in late February).. It was only a few days ago that I suspected coolant loss. I checked it, and the water level was really low, literally at the bottom of the expansion tank. I topped it off, but it dropped just as low in just 2~3 days. Couldn't find any leak mark though. Maybe all the leakage had already dried off when I checked.

And yesterday I topped it off again.. This morning, the water dropped by about 1.5 inches, and I finally found a wet spot, where the bottom of the expansion tank meets the radiator. ( Part #3 in the picture is supposed to seal this place. ) But this evening, no additional loss is found since the morning.. 1.5-inch drop in the first 12 hours, but no drop in the next 12 hours?.. Strange, I thought.

It seemed equally strange that the amounts of loss for the first 2~3 days and for 4 months seemed roughly the same. It leaks really quickly for the first few days and then stops leaking completely?

But, more probably, there was a lot of air in the radiator after 4 months of slow coolant leakage, and it just equilibriated in a few days after I topped it off... 'cause I didn't bleed it.. ( I'm sorry for skipping the obvious.. but I'm a novice.. ) I'll do it properly from now on..

On the other hand, what can be done to the leak at the bottom of the expansion tank? Just the gasket (#3) might be enough if I'm lucky? BTW, does this gasket seal by the pressure from the cover (#5) and the screws(#6)? I don't see anything else to press it hard for good sealing.

Thank you so much for reading and advising..

[pdxmotorhead]

Your describing a steam leak. Only leaks at operating temp, often it can be in a hose, sometimes its a porous spot in aluminum, like the thermostat hosing or a radiator. UV is the best way to find these, also can use a fitting to put 15lbs of pressure in the system with a hand pump (I really don't reccomend a compressor for this test!!!!

Dave