basically, i took my car to FITP 300 mile round trip, car ran fine.
brought a GRS intercooler of my friend and we fitted it to my car. before was a pace alloy shit thing.

now the car gets to overheating temp very fast and water pours out of the header tank. and there is steam and pressure and all that jazz. there isnt any 'mayo' anywhere. and the water is circulating as far as i can tell because its coming out of the thermostat housing and back into the header tank.

i have tested for leaks and there doesnt seem to be any anywhere. also the fans come on. and i have tryed everyting in my knowledge to sort it and still it overheats.

bare in mind that on the pace alloy cooler and before we fitted the grs it worked perfectly.

help appreciated

 

sounds like your headgasket mate

 

even tho it ran pretty much the best its ever driven just 5 days ago?

 

when i had my rs and fitted a a massive front mount cooler, i had to have my fan on a switch, and soon as i started the car the fan had to go on, otherwise it would boil just like that, i also took my thermostat out to help circulation, never had probs since,

 

As already said that is classic headgasket! you only get the mayo in the cap if its water mixing with oil.