Air in cooling system

[Victoria2]

Air in cooling system

I have and issue with my 2006 Jaguar S type 3.0L with air entering the cooling system, resulting is a false coolant level alarm. The coolant level does rise in the reservoir but none is lost and returns to normal level once cool. I have vented the cooling system through the bleed screw several times . There appears to be air entering the cooling system from somewhere. Suspecting a failed head gasket I have carried out a compression test on all cylinders and all within spec. I carried out a cylinder pressure test with air and does not appear to be any leakage. Also there is not a smell of combustion gases from the coolant reservoir.

Would appreciate any comments

[Mark Five]

If you're not losing coolant and you're not having to keep topping up the cooling system I'd try this next: https://www.instructables.com/id/How-to-Burp-your-cars-cooling-system/ and if that doesn't work I'd look at the connections to (or replacing) the coolant level sensor.

Good luck

[JustBadly]

There is a refill process in that you turn on the heater and unscrew the bleed hose while the engine is running, while topping up the coolant. A warning light will also trigger if the coolant is too high. If a head gasket goes it is quite violent with smoke, coolant blowing out, misfires. No way that has happened there, I think it has not been refilled properly and there is still air in the system but that is all.

[JustBadly]

One more thing is the reservoir filler cap. The coolant system operates at 20psi and if the cap is old it won't hold pressure. Once up to temperature the water will evaporate thru the filter cap and it looks as if there is coolant loss. This is a really easy fix but if no good I want more info and don't open the filler cap when the engine is hot.