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[Doctor Gollum]

The water pump only pumps when it's running. There's not much water in the head to leak down without pressure from the pump. 

[oregad]

Got to find another cap for the expansiontank, going to put in a bicycle-valve in it, low budget pressure-tester. Then pull the plenum off, have my doubts it's the HG, but you never know, to be continued... baw

[Doctor Gollum]

MarkDTM did a pretty detailed post regarding the V6 HG failure.

Basically, when it fails on the Omega it does so in such a way that coolant leaks out of the gasket rather than mixing with oil. When the HG failure gets worse, the failure point allows water into the #6 cylinder but not the oil passages because where the gasket fails first is between the water passage and the back of the engine and, then secondly, between the water passage and the cyinder. This means that it leaks coolant externally as the mode of failure and in to the cylinder only when the engine is running and at no point do the water and oil passages become connected.

This is in contrast to the oil cooler fail which sees the oil pump force oil into the cooler without allowing coolant into the oil, even though this is often misdiagnosed as HG failure.

Once the head comes off, the point of failure will be immediately obvious, at on the back left corner.

[oregad]

MarkDTM did a pretty detailed post regarding the V6 HG failure.

Basically, when it fails on the Omega it does so in such a way that coolant leaks out of the gasket rather than mixing with oil. When the HG failure gets worse, the failure point allows water into the #6 cylinder but not the oil passages because where the gasket fails first is between the water passage and the back of the engine and, then secondly, between the water passage and the cyinder. This means that it leaks coolant externally as the mode of failure and in to the cylinder only when the engine is running and at no point do the water and oil passages become connected.

This is in contrast to the oil cooler fail which sees the oil pump force oil into the cooler without allowing coolant into the oil, even though this is often misdiagnosed as HG failure.

Once the head comes off, the point of failure will be immediately obvious, at on the back left corner.

You're a champ for the recap, thank you very much. Dreading to pull it apart in a parking lot though, but what can one do...

[Doctor Gollum]

It's only 30ish bolts and the cambelt

[Nick W]

It's only 30ish bolts and the cambelt

Head gaskets aren't difficult, but there's a lot of stuff to remove first that's at least half the job time.


And you do need to seriously consider the while you're in there parts: thermostat is easy with the belt-cover backing plate off. and I bet the engine end of the top hose is in a state; it's not worth putting suspect coil/leads back; how good is your oil cooler; if you're considering upgrading to the later manifolds do it now(they're really not worth the grief of fitting them any other way); V6s are always covered in oil and other crap so there's a lot of cleaning to, if only so you don't look as if you fell down a coal mine; etc etc

[Marks DTM Calib]

Its pretty much impossible for oil to get into the water via a failed headgasket, its usually the other way round (water in the oil) or water in the bores, or just water leaking.

The basics are that a headgasket has only one high pressure area for oil (to feed oil to the cam bearings and followers) and its very well protected by integrated rings and seals, to get oil into the water jacket would require this high pressure oil feed area to fail and get into the above atmospheric pressure coolant (which it is most of the time).

The one place oil can get into the coolant is the oil cooler 

[TheBoy]

Its fairly well known that Omega V6's never suffer HG failures.  Except mine. Twice


(For clarity, some early 1998 model year (so mid 1997 manufacturer) do suffer an issue where coolant leaks out the back of the 2/4/6 bank.  All others are near bulletproof).  As DTM and others say, on the Omega, the only way to get oil in the coolant is due to an oil cooler failure.

[oregad]

Allready changed thermostat, hbv, coils and dis-pack what else woild there be to consider changing?
Genuine VX-dealer gasket or £300 full set for rocker, head, intake with NN brand?

Its pretty much impossible for oil to get into the water via a failed headgasket, its usually the other way round (water in the oil) or water in the bores, or just water leaking.

The basics are that a headgasket has only one high pressure area for oil (to feed oil to the cam bearings and followers) and its very well protected by integrated rings and seals, to get oil into the water jacket would require this high pressure oil feed area to fail and get into the above atmospheric pressure coolant (which it is most of the time).

The one place oil can get into the coolant is the oil cooler 

Awesome answer. So there might be a chance in hell I'm on the wrong track and just need to seal the oil cooker.

Engine (usually) run great, recently it misses a sparks at idle quite random, as said, no watery oil.
Smokey exhaust (humidity 77% & 1°C outside, lovely weather), was way worse when 1st cyl was dead due to DIS-pack died cause corrosion.
Smokey oilcap when hot, dipstick. Not excessive or pressurising. Might be smelly, no idea.
Yeah, and ... draining water quicker than a drunk.

Makes me think of HG, but might just be valve-related and oil cooler being bust, riiight...

Would I be able to spot the leak on HG through pressure-test?

[Doctor Gollum]

Oh yes

[oregad]

Oh yes

excellent, enough hope to start the process and find out the false hypostasis is a way to go.

[Marks DTM Calib]

Either way, oil in coolant is NOT head gasket 

[Migv6 le Frog Fan]

You need to find the source of the coolant leak. A mirror on a tick so you can see the rear of the engine can be helpful. Or pressurise with compressed air is even better.
After that, you definitely need a new oil cooler. And then lots and lots of flushing of the cooling system to get rid of the oil from it.

[oregad]

You need to find the source of the coolant leak. A mirror on a tick so you can see the rear of the engine can be helpful. Or pressurise with compressed air is even better.
After that, you definitely need a new oil cooler. And then lots and lots of flushing of the cooling system to get rid of the oil from it.

Yes, my plan is to take the plenum+DIS-pack off (to see what's happening), then pressurise, let us pray.

[Doctor Gollum]

You need to find the source of the coolant leak. A mirror on a tick so you can see the rear of the engine can be helpful. Or pressurise with compressed air is even better.
After that, you definitely need a new oil cooler. And then lots and lots of flushing of the cooling system to get rid of the oil from it.

Yes, my plan is to take the plenum+DIS-pack off (to see what's happening), then pressurise, let us pray.

Praying won't help.

If you have oil in the coolant AND a coolant leak where you describe, these are two separate problems.

Your best case is that the oil cooler has failed and the oil cooler cover plate is perforated.

A more productive list of parts to remove for proper inspection is the plenum, upper and lower intakes. That way you'll be able to see if the coolant is coming from the oil cooler cover plate or thermostat and draining out over the bellhousing.