Cooling system not pressurising

Hi All,

Finished my Head gasket replacement with the SAIC model, pain in the arse job that was, especially when numpty boy here forgot to put the oil pickup back in the sump...

Anyway, since then the cooling system will no pressurise, it's acting as normal, circulating coolant and the block is definitely not overheating. I'm wondering if I've just got too high a concentration of coolant in to make it actually pressurise.

I'm pretty sure it's not airlocked - the radiator top hose gets burning hot to the touch and the cooling fan kicks in and out while it's sat ticking over.

No kettling noises when it shuts down, which I'd expect if it was partially airlocked.

I may have accidentally stacked it with a 60+% OAT coolant mix while not paying attention, or there may be an airlock hiding somewhere, but I'd expect it to overheat and/or the cooling fans not kick in. I did something similar with a bmw years ago, too much coolant and the system just wouldn't pressurise.

Thoughts?

I don't think a 60/40 mix of OAT coolant to water would have any effect on pressurisation. Have a look at the coolant bottle as they can craze and crack around the beck area. Is the coolant cap in good order? Thermostat in and in good order?

The pressure builds up when it's hot. Coolant/water expands slightly when hot. Air in the reservoir expands more, putting pressure in the system. Pressure is good. It stops the coolant boiling. Water starts to boil in a kettle around 92 degrees for eggample. Too much pressure should vent oft via the reservoir cap if it's working correctly.

Does the coolant level drop?
What engine is it?

Coolant reservoir and cap brand new, though it could be the new cap as it's a ****part one I guess.

Thermostat is definitely working, rad bottom hose gets hot when sat ticking over.

Bit of a headscratcher, going to try putting the old cap on as I blast to work this morning and see what happens.

Did you take the sall pipi off the header tank and blow into it to release the jiggle valve all done with the engine running,failure to release the jiggle valve will mean no water in the head although when the head was off you could have taken it out, hope this helps

teddywood1 said:

Did you take the sall pipi off the header tank and blow into it to release the jiggle valve all done with the engine running,failure to release the jiggle valve will mean no water in the head although when the head was off you could have taken it out, hope this helps

Click to expand...

It's not quite as simple on the TF manifold, as it's inside the alloy casting!

However, I'm pretty sure the jiggle valve is working - pulled the hose off and water flows out of it really slowly.

Going to pressure test it tonight with my bodged setup...

Hey look, turned out it was the ****parts brand new coolant cap.

Dismantled it and there was a massive crack right through the centre of the pressure relief valve. Should have ordered the genuine one for £3 extra.

Oh well, live and learn to avoid britparts.

some times you have to live a while to learn never go for the cheapest if you can a ford the best.