HGF on my V6

[kaiser]

I have no stream of water from that little pipe either.
I think it is one of those issues you should take with a pinch of salt.

[SD1too]

Originally Posted by archermav

... I think I'm calling it fixed ...

So what did you do to "fix" it?

Simon

[T-Cut]

Originally Posted by kaiser

I have no stream of water from that little pipe either. I think it is one of those issues you should take with a pinch of salt.

I agree. The small bore pipe from the head to the tank filler neck is there to facilitate head bleeding. This may be either air or super-heated coolant. Air comes out when the head's being filled as part of the coolant refilling process. That can only happen when the pressure cap is not fitted. A small amount of coolant may flow out by squeezing a large hose or when the engine's running because of pressure drop from the pump. However that flow will stop when the pressure cap is refitted. When the hot engine is turned off, the head contents may super-heat, increasing hydraulic pressure in the head. This pressure exists in the small bore pipe and this will lift the relief valve in the cap if necessary. It's a strategy to avoid over-pressurising the full system.

When the pressure cap's in place it's physically impossible for anything to flow through the pipe.

TC

[archermav]

Originally Posted by SD1too

So what did you do to "fix" it?

Simon

Nothing really, I tightened the bleed screw as there was a small leak from that. Coolant just stopped leaking from the expansion cap, perhaps it was as simple as I hadn't tightened it

I was afraid to tighten it too much as the first new cap hasd broken, the top came off leaving the body of it still in the expansion tank. Now it's tight

[T-Cut]

Originally Posted by archermav

I was afraid to tighten it too much as the first new cap hasd broken, the top came off leaving the body of it still in the expansion tank. Now it's tight

Over-tightening is a killer of pressure caps. They only require a light nip on the rubber washer. The more they're tightened, the more the two o-rings are squashed and deformed. Eventually they're worn too much and it requires even more tightening. Put a smear of silicone grease on the rubber seals and washer then give it half a turn after enaging the thread. If that leaks, give it a quarter turn more until you've got the correct compression. Remember the amount of turn needed. Don't make the tighter the better mistake. If it's so tight that the body locks in the neck, buy a new cap or replace the rubber bits.

TC