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Matt, Mechanical Engineer
Category: Jaguar
Satisfied Customers: 22741
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Hi, I have a s3 v12 e type in the workshop suffering from an

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Hi, I have a s3 v12 e type in the workshop suffering from an excess of pressure in the cooling system.
The cooling system has been drained and refilled using a vacuum refill tool in order to eliminate any air lock.
Both thermostat s are opening at 82○c and there is even heat distribution throughout the radiator.
A cylinder leakage test shows nothing and neither does a test for combustion gases in coolant.
With a pressure gauge on the cooling system, warming the engine from cold, by the time the thermostat s are fully open ( 92°c) the pressure is showing 17 psi.
Any thoughts.

Regards Andy.
Hello Andy

if you haven't already then I'd replace the header tank filler cap as these are supposed to vent off at 14-15 psi

I' d also check that the small bore hoses that run back to the header tank are free flowing and not blocked
Customer: replied 3 years ago.

Cap has already been replaced and pipes are clear.

Hello Andy

in that case air must be pulled in somehow as the coolant circulates

usually the chief culprit is a faulty water pump seal that will allow air in but not water out

I'd also double check all the hose clips before fitting a new pump though

Matt and other Jaguar Specialists are ready to help you
Customer: replied 3 years ago.

Hi mat

I replaced water pump and all hoses.

Problem solved. Thanks


Glad you got it sorted