Question. Com V6

[gordon]

Hi guys anyone know whats going on with these V6 ( iron ) motors with engine oil in the cooling systm - oily residue in the radiator cap and overflow bottle ,

[Mick]

head gasket, head or inlet manifold are all fairly common

[MeFB]

head gasket, head or inlet manifold are all fairly common

What Mick said.

Not sure if the welsh plugs are a problem area, but also might be worth checking if you can get to them. I think welsh plugs normally lead to water in the oil, rather than oil in the water (but not 100% sure on that one).

Maybe do the easy stuff like replace the inlet manifold gaskets and see if that stops it? After that things start to get a bit more complicated.

[gordon]

head gasket, head or inlet manifold are all fairly common

Yes have heard that , but theres no leakeage from cyl heads / gaskets into the cooling systm , Eng oil is clean , no
moisture in it , is Manual trans

[Craig Allardyce]

I've had the same problem with V6 in a VT Commodore. To my disbelief replacing the manifold gasket cured the oil contamination in the cooling system . I would have thought the coolant water presssure in the manifold would have been higher than crankcase pressure in that area of the engine, and therefore coolant would have migrated into the oil system before it went the other way. I'm still not sure how it happens, maybe through the cooling system when it cools down it draws oil in through area of leakage in the manifold gasket. I have known of some systems that will not leak under pressure but will under a vacuum. Maybe this is the case with the type of gasket used on the manifold. Distortion of the manifold thru expansion and contraction at different temps could also be the case.
Anyway, I heard it was a solution to the problem and thought what the hell, its easier than pulling heads so I gave it a go!!

[MeFB]

what the hell, its easier than pulling heads so I gave it a go!!

Exactly. Smart thing to do.

[gordon]

Craig, Very scientific approach there, to balance up the plumbbobs & vacuums levels to the problem
But it seems to be if it works thats the go !

Yes Alan thats what we want to hear !

[MeFB]

This is from the Just Commodores forum:

Oil can also leak directly into the valley of the motor once the engine is shut down. The cooling system is still under about 120kpa pressure and the crankcase is at atmospheric pressure.

As the engine cools, the cooling system pressure falls. The pressure eventually goes slightly below atmospheric (when the vacuum valve in the radiator cap opens) so it will draw in some oil through the faulty manifold gasket.

When I did mine there was oily residue under the radiator cap and inside the coolant overflow bottle.

I kinda had the same question in my mind as Craig and had to find out the answer because it was bugging me silly.

Seems plumbobs and vacuums might be the culprit after all

[Mick]

me to had a VT with oil in the water was worried at first it was head gaskets but have mates with a worshop and straight away without realy even looking they said inlet manifold gasket, replaced them problem solved
not guaranteeing this is yor problem but sounds like ours and reasonably easy and cheap to do

[gordon]

Thanks guys for your input , will do that and fingers crossed !

But about Manifold gaskets , the Manifold gasket for along the side of cyl head for Red & Grey motors , the ones available with the Silvery metallic on one side are rubbish and break up after a while , are there any better the original
GMH used to last forever ...