Disco 300tdi pressurizing

Does anyone have any ideas why my 97 300tdi disco is pressurizing the header tank?

things already done in the last 2 weeks :- head gasket
New head
Removed thermostat

Is it overheating too? water pump maybe?

have you checked radiator is hot all over surface,tis the most common cause of over heating and head gasket failure

Removing the thermostat won't do it any good, it puts too much pressure on the head and is more likely to blow head gasket, check water pump as mentioned and also ejector valve (little black disc in the line under the header tank with 3 pipes to it. These often fail and cause problems.

@OP: sure, you should put back the thermostat or install a new one

@bigrichsri: by the way, how do you test the ejector valve ?

first suspect would be head gasket / head.
decent gasket used ? elring or payen, if its a britpart one be dubious.
defective new head? overheated new head? (warping / cracking) what make was it?
brand new head or second hand new head?

other stuff but less possibilty would be a cracked liner.

put the stat back in as its a 3 port valve. coolant continually circulated round head when stat shut, when open introduces rad into system.
removing stat allows pump to shift water from rad bottom to pump to rad top......
leaves block and head coolant static........

ejector valve is just a tee peice.

edit.
oh jyhelle, posten on your thread too.

300 tdis dont get cracked liners as they dont have them ,wether its got stat in or not doesnt matter apart from warm up time on engine check rad ,check system is full properly with bungs removed

jamesmartin said:

300 tdis dont get cracked liners as they dont have them ,wether its got stat in or not doesnt matter apart from warm up time on engine check rad ,check system is full properly with bungs removed

Click to expand...

didnt know they were linerless!
would still replace stat tho.