M62TU burning coolant?

[Spetz9]

Hi everyone,

I have a 2001 540i, 110K miles, pristine condition and religiously serviced.
I get a "check coolant level" message every few hundred miles and I top up with coolant.

The car runs fine, no coolant leaks, no "milkshake" in the oil, there is no white smoke/vapour from the exhaust...
I did drain the coolant to do timing chain guides, so perhaps there are air bubbles? I would have topped up coolant 3-4 times since then.

I have not owned the car long enough to know if the coolant issue was there before this.


What test should I be performing to check for possible head gasket failure?
Compression? Leakdown? Test the coolant for C02?

[jeanpxrk]

I had an isssue with coolant leak for a while. I did a leak/pressure test and found i was leaking coolant from the gaskets located in the valley pan. I had no other sign of coolant leaks. That may be your issue. I say just get a pressure tester and see.


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[Spetz9]

I would not assume head gaskets, not a common problem unless extremely overheated.
Pressure test it and check for weeping radiator or coolant tank, water pump.
But my guess is block (coolant) valley pan.
Heat cycles fatigue the seal at about that point.

I replaced they valley pan as well as everything else there while doing the timing chains. I have a borescope camera so I will try looking into this further.

I have pressure tested the system. The pressure tester was faulty so I could not check to see if there is pressure loss, but no coolant leaked out from anywhere during the test.

[jicaino]

Have you replaced or refurbished your heater valve?

[Spetz9]

Have you replaced or refurbished your heater valve?

I have not. Are these a common failure point?

[jicaino]

Until I refurbished mine it drank about a cup a week. Yes, it's a fairly common failure point, especially on low mileage vehicles IME.

[Spetz9]

Until I refurbished mine it drank about a cup a week. Yes, it's a fairly common failure point, especially on low mileage vehicles IME.

Where would the coolant be going?
I am reading up on the symptoms, and the car isn't really exhibiting any of these (heater works, outside temp works, etc)

[jicaino]

Where would the coolant be going?
I am reading up on the symptoms, and the car isn't really exhibiting any of these (heater works, outside temp works, etc)

I'd the seals are toast, they act as a pinhole leak, gradually and slowly evaporating what's missing. Since the solenoids themselves are sealed (coils are watertight) if the upper seal it's gone it isn't a major leak and until the plungers rust out and freeze you'll have normal HVAC operation

[philly98540]

Check under the bellhousing for any coolant/residue. A faulty job on the valley pan or a bad rear coolant cover plate (have to take off trans to access this plate) will typically show up under the bellhousing. If you cannot see anything anywhere under the car then maybe try to add some coolant leak detector dye to the system and check in a few drives. I think most use a UV light so you need that too.