Petrol Hi-Jet bubbling expasion tank


Hi ..... I have a Hi-Jet EFI 96 with petrol driven engine and 30k on clock. Sometimes when driving the temp gauge will creep to almost max then suddenly drop, this hasn't been happening so much lately but on almost every drive I can hear the expansion tank bubblin away but this also seems to be intermitent. A mechanic suggested I start by changing the rad cap.....any ideas.



Get a compression test on each cylinder. Sounds like the cylinder head gasket has failed. Its compressing gas into your water and escaping out the radiator. Its probably making an air lock and the engine overheats. Take a sniff into the radiator - can you smell petrol fumes?
Get it sorted before the cylinder head fractures or a hole through the cylinder head at a hot spot.
Changing the rad cap wont sort this problem but it means your mechanic can 'run away' !


Thanks for the reply Mace.......had a sniff in rad and doesn't smell of petrol. The bubbling only seems to be intermitent. Left it a good 10 minutes today just ideling with no problem, any chance it could be something else, like thermostat misbehaving. Will have a compression test done anyway.........cheers