hi all, would a blocked thermostat make enough back pressure in the water to split the header tanks, thanks phil.

 

i think it might be head gasket related ...I am having the same probs , but my header tank is alloy so it will not split ....be blowing the radiator caps off though

 

i have already done the head gaskets and a new header tank has split again, compression test shows ok also, so im a bit stuck, thats why i thought it may be the thermostat, thanks phil.

 

so where do you think the "pressure" is from then !!

, same here had compression test do and evrything seems ok but losing coolant when on boost ., and i have a forged engine with ARP studs running 1.7 bar boost

 

i really havent got a clue now, i cant even check if i think i have solved it, because i need another header tank, i think ill get an alloy one like yours, saves splitting them again and again, what are you going to look at next.

 

me !! no chance ......I let the Subaru specialist worry about it
all I do is get the cash out !!

 

best way, if you have it, im a bit tight though, if you get it sorted before i do, you will have to let me know what yours was so i can try that, all the best, phil.

 

will do m8

 

A blocked thermostat would certainly pressurize the system, but it would also cause overheating, and your temperature gauge would be off the scale. If you have ruled out the head gaskets for certain, you could have a cracked head or liner. Either would normally be indicative by water mixing with the oil in the sump, but not always. It could be cracked in a place where the coolant is pressurized by compression into the exhaust system, this would show up as heavy vapour/steam from the exhaust.

Either way, a dye test would show if there is an internal crack somewhere. It is simply a dye that is added to the cooling system, with the engine running, the dye will change colour if there is a crack.

 

i see, i might just take it out again and check it everywhere, it will only take me an hour and half to whip out, as i have got it down to a tee now, dam thing.

 

Not always the case , as i had that test done and it show negative, but still losing coolant , you will not notice its in eveyday driving .
only when at high speed (on boost 80-90 plus)run for around 6-8 mile .......it will lose about 1-1 1/2 Litre of coolants, i manage to drive it for 100mile before the temp when to 100c!!