Faulty thermo

[SD1too]

Thanks for the detailed evidence David. I can understand what you're thinking now. How did this happen? Is this car a recent purchase?

Originally Posted by Ched

... I’m at a total loss on what to do.

Unless you can think of a way of identifying which bank is at fault, it's off with both heads for a head gasket inspection. I did this many years ago with an Alfa V6. It's not as bad as it sounds.

Simon

[Ched]

I’ve had her almost 3 years Simon, apart from 2 failed crank sensors the car has never failed me and I wouldn’t of hesitated going anywhere in her, new belts about 7 months ago as well . 😟
One last thing I will check tho is the oil cooler, but I can’t see how I’d be getting coolant from a failed cooler into the combustion chamber.
At least I can try and eliminate it tho.

[T-Cut]

Originally Posted by Ched

- - - - from being left overnight, undoing the cap results in a big whoosh - - -

That's exhaust gas I'm afraid.


TC

[Lovel]

Originally Posted by T-Cut

That's exhaust gas I'm afraid.


TC

Couldn’t that also be a symptom from air trapped in the system ? If there were a crack, Surely any residual compression would also bleed off with the engine stopped, ie though piston rings or valve seats or crack in liner or piston itself? if pressure can get in it can also escape back the same way too unless it was a volume of air or gas trapped?

I would suggest the OP checks and if applicable retorques up his inlet manifolds set screws, as they do have a habit of weeping after many miles. I have came across a number of V6 manifolds that leak due to this. Coolant can leak into the cylinder from here too. The gaskets were not at fault in these examples, it was just settling in that caused the weeping. The practice of retorting is very worthwhile after some mileage runnning especially after maintenance work on the manifold. Then proceed with simple bleeding procedure again.

[Ched]

Originally Posted by T-Cut

That's exhaust gas I'm afraid.


TC

My thoughts exactly

[Ched]

Originally Posted by Lovel

Couldn’t that also be a symptom from air trapped in the system ? If there were a crack, Surely any residual compression would also bleed off with the engine stopped, ie though piston rings or valve seats or crack in liner or piston itself? if pressure can get in it can also escape back the same way too unless it was a volume of air or gas trapped?

I would suggest the OP checks and if applicable retorques up his inlet manifolds set screws, as they do have a habit of weeping after many miles. I have came across a number of V6 manifolds that leak due to this. Coolant can leak into the cylinder from here too. The gaskets were not at fault in these examples, it was just settling in that caused the weeping. The practice of retorting is very worthwhile after some mileage runnning especially after maintenance work on the manifold. Then proceed with simple bleeding procedure again.

I'll try your suggestion regarding the inlet gaskets Gary as there was gasket sealant used on the rear manifold by someone in the past, I assume it was the dealer where the car was maintained did it as there is a very comprehensive history file which came with the car.

Looking and reading about your very impressive quality of work Gary I can only say I wish I was closer to you.

[T-Cut]

Originally Posted by Lovel

Couldn’t that also be a symptom from air trapped in the system ? If there were a crack, Surely any residual compression would also bleed off with the engine stopped

In some cases yes, in others no. Read up the Bunson Valve principle, which allows one way passage of compressed gas through a fissure. Significant overpressure released when opening the cold cooling system has to be a permanent gas injected there since the cold system was last opened up. No other physical effect can cause it. (Ignore atmospheric pressure and ambient temperature differences, which have negligible effects).



TC

[Lovel]

Originally Posted by T-Cut

In some cases yes, in others no. Read up the Bunson Valve principle, which allows one way passage of compressed gas through a fissure. Significant overpressure released when opening the cold cooling system has to be a permanent gas injected there since the cold system was last opened up. No other physical effect can cause it. (Ignore atmospheric pressure and ambient temperature differences, which have negligible effects).



TC

Yes agreed the one way phenomenon could leave residual pressure, but i think we are often guilty of imagining the worst when it comes to K or KV6 engines.

[Ched]

A quick update.

Cylinder no 3 on the front bank is the culprit, I removed the plugs and that one was wet, put it back in with the others removed, filled the coolant tank right up and spun it over, bubbles galore, Just have to pull it apart and fix it now.

[T-Cut]

Thanks for the update. But unhappy news.


TC