losing small amount of coolant

[lgb240]

I've got a '91 318is, has about 250K km (150k miles). I'm chasing a small coolant leak ... I constantly lose about a quart of coolant from the rad reserviour. I've had the car for 6 years, about 30K miles and have had no overheating or coolant issues to speak of (until now)

Here's what I've done recently:
- t-stat and gaskets
-plastic pipe / o ring under manifold (inspected other coolant hoses under there - they are fine)
-heater control valve - all seems fine under the dash, no wet carpet or heater core issues
- a few years ago, new rad, water pump, t-stat - no visible leaks currently

There doesn't appear to be any coolant in the oil, no white smoke, no sludge / mocha looking stuff on the dip stick. The car runs very well, pulls strong, idles great, the temperature will rise slightly if I'm idling for a while and haven't checked the coolant level in a while - never to the point of over heating, just raising the needle slightly on the guage.

I've searched and read countless posts on profile gaskets / head gasket issues. I don't suspect the head gasket or cracked head because of the condition of the oil and how well the car runs. How do you diagnose a profile gasket issue (without actually pulling the head?)

Where else could the coolant be going? Any ideas / help would be appreciated.

Thanks

[Dj Buttchug]

you can r&r a profile gasket with out pulling the head. It is a complete bitch tho. Ive done it.

If it were me id mash the car till you start having a serious issue then overhaul the engine.

If your loosing coolant and its not leaking on your driveway then you probably have a small leak internally. drive it and enjoy for now. it will only get worse.

[lgb240]

Thanks DJ - that's what I've been doing - just driving and adding coolant

[jlevie]

I'd recommend having a cooling system pressure test run. You could have a small leak that only occurs when the car is being driven, like a leaking water pump seal. That sort of a problem will get worse, and can cause a sudden cooling system failure. That would be really bad for the engine.

In the absence of cooling system leaks, the loss of coolant could be from a small head gasket leak that is pumping air into the cooling system. At some point (usually while driving) the pressure will rise to the point that the cap lifts, which will vent some coolant. One way to find out if that is happening is to chalk the inside of the vent tube. If the chalk gets washed of, coolant is being vented. Oh yeah, a bad cap can also cause this.

[KenC]

Do you know if the profile gasket was ever replaced under the recall?

It's easier to just pull the head and replace it. It'll eventually destroy your head/block and lower timing case.

[3bvert]

had one with a small crack in the exsaust "channel" of the head. on the ex manifold side past the seat. did not show on a leak down or pressure test, oil looked good, no steam in exsaust as it was a small leak and evaporated before reaching the tail pipe.

[lgb240]

Do you know if the profile gasket was ever replaced under the recall?

It's easier to just pull the head and replace it. It'll eventually destroy your head/block and lower timing case.

I have a bit of history from the previous owner, but nothing before him, so I'm not sure if the profile gasket was ever done.

I'll probably end up pulling the head before the snow flies (this is my winter car) just not looking forward to this PITA.

Thanks,

[Stevie30]

I had a similar problem on my M42. I replaced the radiator with a new one and problem went away.
I found a crack in the tank at the air vent screw. My theory is that the coolant was leaking slowly and boiling away undetected.