I have a 2006 Jaguar 3.0 S Type

I have air entering the cooling system, pressurizing the system resulting in a false coolant level low alarm and following approximately 2 hours driving the engine will overheat. Checking the coolant level after the vehicle has sat over night the level is checked and no coolant lost, level normal. Testing for leaking head gasket with combustion leak detector (Picture attached). There was bubbling present during the test but no indication of carbon.

Observation

With Combustion Leak Detect installed, it was observed if the cabin heater temperature was raised to maxim (27C) the bubbling would stop. If the cabin heater temperature was lowered (18C) the bubbling would reappear. This test was carried out numerous times with the same result. Cabin heater temperature selected to high no bubbling; lower temperature bubbling would reappear.

The following tests were carried out to determine if there was a head gasket leak or air trapped in system.

· Cooling system was vented as per Jaguar bleeding procedure numerous times.

· Compression tests carried out on all cylinder. All cylinder reading within spec.

· Pressure test carried out on cooling system for 1hr. Pressure maintained. No leaks observed.

· Cooling system drained, vacuum pulled and filled with coolant system using vacuum filler.

· Combustion leak detector used to confirm no head gasket leak (no combustion gases in cooling system).



I am thoroughly out of ideas any comments would be appreciated any comments

Keith

2006 Jaguar 3.0 S type

 

Hi Keith, i just changed my thermostat and the fan is coming on all the time, i guess i have an airlock too. the only bleed screw i can find is next to the cooland cap, and it just squirts water . Im gonna have to undo a hose to coax it out i guess. somebody said theres a bleed screw above the 'stat, but i aint got it, just a flat lid. Dont spose this helps unless you actually let air in .

 

The Duratec 3.0 litre unit is very robust, but is sensitive to component failures. Has anyone bothered to replace the thermostat and bleed the system per the Workshop Manual?

 

maybe naively, but i didnt expect there to be a proper method , with the stat just under the tank. I thought it would bleed itself, with the tank being high.