Coolant loss

[Mr. BILL]

Hey guys,

Some of you may remember, I did a new head, heater core, water pump, T-stat, and radiator in September.

The car is runniing fine, but I'm getting a fairly steady coolant loss. Maybe a pint a week.

So far, I have checked: no cross contamination of oil or coolant, (no milkshake) No visable signs of leaks, no white smoke from exhaust, no fogging windows or pancake syrup smell with heater on. There is a slight of smell coolant from outside of car. I checked and tightened all hose clamps.

The only thing I didn't repace was the radiator cap itself, but it shows no signs of coolant loss.

BTW, this is a '90 525 M20 engine. Any ideas?

Thanks

[Hector]

leaks coming from around the head gasket, and if everything else you said checks out, then my guess would be that maybe somewhere the water in the coolant is evaporating thus giving you a loss in the H2O/coolant mixture.

*This is a long shot and may not have anything to do with the problem at hand but check that the bleeder valve is tight.

*After you have driven the car and allowed it to cool down, if you open the radiator cap do you hear a hissing sound from pressure relief, and does the coolant level drop or does it rise after the pressure has been relieved?

[Mr. BILL]

leaks coming from around the head gasket, and if everything else you said checks out, then my guess would be that maybe somewhere the water in the coolant is evaporating thus giving you a loss in the H2O/coolant mixture.

*This is a long shot and may not have anything to do with the problem at hand but check that the bleeder valve is tight.

*After you have driven the car and allowed it to cool down, if you open the radiator cap do you hear a hissing sound from pressure relief, and does the coolant level drop or does it rise after the pressure has been relieved?

Hector,

The bleeder screw is tight, so is the cap.

When you open the cap, the coolant level rises when the engine is at operating temp. When it's cool and you open it, not much happens. No hissing and the coolant level stays the same

Thanks for the reply.

[Derek A.]

Pull your plugs and take a look. If you are consuming coolant through the combustion chamber your plug(s) will generally have a whiteish coating on them. A compression test might also reveal a breach in the head gasket.

[Alan_525i]

I went through this exact fact pattern these past few months. Loss started slow, but enough that I was topping it up frequently. My mechanic checked all "external" sources of leaks and found nothing. We guessed head gasket but there was no mixing. Loss accelerated gradually and finally we started to see it mixing in the oil. So we yanked the head. Head gasket was not failed. The head was cracked. Supposedly a series of M20 heads had a casting flaw that allows them to crack even with normal use. So my car is in the shop now for lots of work...

Hopefully this isn't the case for you but it sounds just like my situation.

EDIT: Oops! I just read you did a new head. So i guess this isn't it. But I'll leave my post up in case it helps someone else. Let us know what you find.

[PABLO]

Any solutions yet??

[Scott C]

Hey guys,

Some of you may remember, I did a new head, heater core, water pump, T-stat, and radiator in September.


Thanks

Well Bill,
I will fess up to not having tightened my hose clamps sufficiently and suffering with a slight leak for a period of time ;). I had to really look (dry outside, level floor and fresh white paper underneath the car) to see the leak since it was caught mostly on the metal support below the radiator.

Also, check the temp and level sensor on the radiator?

Good luck
Scott (95 525i M50)

[632 Regal]

didn't want to over tighten them when I replaced them all.

[Mr. BILL]

Any solutions yet??


The leak got worse, so I took it to my Indi buddy. Turned out that the little housing on the throttle body that has two nipples on it was leaking. To be more specific, the gasket was shot.

They replaced the gasket and pressure tested it. Now it's OK.

Thanks to those who replied.

[winfred]

those things suck, i am impressed that it wasn't corroded into nothing as is usually the case, i just bypass it with a piece of heater hose fron the bottom of the thermostat housing to the block above the starter and be done with it


The leak got worse, so I took it to my Indi buddy. Turned out that the little housing on the throttle body that has two nipples on it was leaking. To be more specific, the gasket was shot.

They replaced the gasket and pressure tested it. Now it's OK.

Thanks to those who replied.