Coolant not circulating

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Originally Posted by Epic_Dragon

There is no water in the expansion tank when it happens.

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I would suggest that if there is ever any time that your coolant tank is empty, you have a big air lock in the engine. Where do you think the coolant goes? It compresses the air pocket in the head. Release the cap, the air expands, coolant reappears in the tank. Meanwhile, the air pocket is risking your engine. Water is to all intents and purposes not compressible. Air does not cool your cylinder head.

I had a P38 in here a week ago, the bleed pipe from the engine to the coolant tank was completely blocked with red gunge. A new hose was fitted and now there's little chance of an air lock forming.

Ill check bleed pipes and bleed it again and see if water is gushing. I will test the fan as well. The red coolant sucks for making that crusty stuff! Airlock is one of my suspicions because I know water is not compressible. Is the bleed pipe on these the one with the bleed screw or the small one that comes from radiator to expansion tank?
Is definitely not head gasket pedro :) its not doing the same thing that it did when head gasket was gone. It is not over pressuring either. And metal dowels were used, plus head checked. It's also not overheated or had any issues till now. Only issue ive had recently is trans. Professionals told me mine was terminal without even pulling pan off :/ a simple trans filter change and oil change and it is wonderful again. No metal in there at all. Was sludge! Hopefully fix this current problem very soon. My horse is at the breakers and i need to get up to see him. My car is very much in the dog house right now haha. It has impeccable timing!

The one with the bleed screw is the top hose, the thin one from radiator to tank is the return pipe... did you lift the tank above the bleed hole when you filled the system?

Have bled coolant system several times since ive owned it :) thats what i knew them as, top hose and return pipe but wasnt sure if one was also known as a bleed hose/pipe. I do raise the expansion tank when bleed the system. Im not sure how an airlock would form though all of a sudden if that is the cause. Unless is indeed a blockage somewhere caused by the red coolant crusty stuff.

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Originally Posted by Mick_Marsh

That only happens to yours.

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it would seem not,,,:p

misery loves company:D

Sounds similar to what i was getting, tiny leak through the head gasket made it seem like there was a constant air lock.

Not saying it is the headgasket (and im definitley no expert), but just because it was done recently and the symptoms are different doesnt mean you should rule it out in my opinion.

I believe it is the thermostat not opening. Because just rebled system and not really any air bubbles. The heater is blowing cold even when it got to temp.

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Originally Posted by Epic_Dragon

The heater is blowing cold even when it got to temp.

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that could just be air in the heater matrix

take out thermostat, put it in hot water, see if it opens

If the heater is blowing cold it can't be the thermostat not opening cos the system is conceived so as to keep the flow through the matrix in the first place with closed thermostat exactly for heating reasons then only when the coolant gets to the operating temp the stat opens to let the coolant through the rad as to be cooled.... is the coolant gushing out hard from the bleed hole above 1500 rpm?

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Originally Posted by Epic_Dragon

I believe it is the thermostat not opening. Because just rebled system and not really any air bubbles. The heater is blowing cold even when it got to temp.

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Is it a genuine thermostat?
I had a Britpart thermostat stay shut from new. Caused all sorts of dramas.
Never again, genuine only.