My 1998 F150 over heats occasionally and when I release pressure at the resivior the thermostat opens and coolant flows properly and there is a bubbling sound at the rear of the motor block then truck runs fine I have replaced radiator water pump thermostat and flushed engine with lots of pressurized water still have the problem any ideas what it might be any suggestions would be helpful

 

change stat. there is a tiny hole on the lip of stat you can drill it a size bigger to help this...i drilled 3 small holes on mine and truck never over heats now

 

Thanks will tomorrow

 

i have run a few different thermostats in my 'bird...Robert Shaw, Stant, and Motorcraft....and the only one that has lasted is the motorcraft. Granted I run a 180* and am programmed accordingly........but stay OEM.