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[Entwood]

I would agree with everything doz says... if the header tank had bubbles coming from it when running with the cap off....   

The pressure from a cylinder is way above the pressure of an uncapped coolant system, even when not firing it is way above 2 bar ...  think compression test.... so I would expect gas transfer to be even easier .. that gas would have to escape somehow, so would bubble through the header tank.

 

[doz]

I think that will cause the car to boil. Which this one isn't or at least the gauge is telling us it isn't

[PAULCDX]

When I ran the car without the cap on I didn't notice or see and bubbles in the header tank........ I put my finger in the bottle and felt the water was warm but no bubbles....... Only when I put the cap back on did I see the water level rise and then escape I'm assuming under pressure.

[Elite_L0ver]

thinking about it does this engine have a pressure realease valve on them for cooling pipes to bleed air out of the system 

like this



i know they got them on veccy engines i cant see why not 

run engine
release the bleed nipple with cap on and leave it open until no more air can be heard  and pure coolant comes out be on hand with a BIG bottle of water to keep topping up   

[Elite_L0ver]

there could be and air lock somewear

[adey2]

im watching this with intrest as mine has a problem where whilst moving all is well then min you stop it gets hot quite quickly, but min move cools right down again, and yes the fans do cut in

[Elite_L0ver]

im watching this with intrest as mine has a problem where whilst moving all is well then min you stop it gets hot quite quickly, but min move cools right down again, and yes the fans do cut in

sounds like your stat 

[PAULCDX]

ummm don't know lol but lets hope there is and it's not a HG issue 

Car will stay off the road now until I can get it looked at 

[Elite_L0ver]

ummm don't know lol but lets hope there is and it's not a HG issue 

Car will stay off the road now until I can get it looked at 

prob good idea have a look tomoz maybe 

[adey2]

i may change it when do rocker gaskets now it warming up outside

[PAULCDX]

Let's hope it is the stat even though it was replaced only 6 weeks ago........ My car is fine when driving but once stood still temp gauge soon rises and water spills out after it reached 100c, temp gauge goes back down when moving.......

[doz]

If it's spilling out at 100 change the expansion bottle cap

[PAULCDX]

I did wonder if I should change the tank or the cap or both and see how that goes......... Are things still pointing towards stat fault?

Cheers for all the help 

[Entwood]

Its hard to say Paul .... the cap will increase the pressure in the system and therefore raise the boiling point .... but under no pressure yours is not reaching boiling point, so, in theory, the cap should make little difference.

The "thermal siphon" within an engine works best at zero pressure, and yours seems to be doing just that .. controlling nicely with the cap off.

It is when you put the cap ON that problems start ....

So ... a small increase in pressure is leading to a large increase in pressure sufficient to cause changes in water level and pressure leakage ..

possibilities to my mind ....

Stat stuck shut, small pressure rise causes thermal siphon to cease, leading to localized "boiling" at the engine block, resulting in steam causing a large pressure rise and water displacement, as well as the block temperature rise you see.

perhaps all those could also be caused by the waterpump not moving water within the system ??

Not sure TBH

[PAULCDX]

Yes mate it would appear I see the problems when the cap is on..........

I am having a cambelt and water pump change done soon so hopefully that will sort out any water pump issues that may be there.