hi, i have a blobeye STI which was tuned in the following stages -

333 bhp - no leaking on standard cap
400ish bhp- standard cap leaking so replaced with STI 1.3 bar cap and problem solved.
450ish bhp - problems back

its a genuine cap that cost £45 not long ago at all. Do i need a 1.5 bar one like Cosworth ?

Thanks

 

I'm running 490 on mine standard cap they 1.3bar caps are a waste of time and only pressurise the system more than it needs.

Could be a problem somewhere causing excess pressure id be tempted to get a sniff test done to rule out a hg on way out.

 

Thanks for the reply. I thought about the headgasket's but the car is so bang on that I don't think it's that. No water in the oil etc. I will get a test done. I find it strange how it's only doing it now. Was only mapped last week see

 

Is it over flowing out of the overflow bottle?

 

No mate

 

stick bike pump on top expansion pipe of rad on left side from front, plug pipe you have took off, pressure system with bike pump and leave for a few days longer the better. Take plugs out disable fuel pump and crank engine with tissue paper/blotting paper over plug holes. Make sure no water gets onto paper=no hg problem into bores. I find the stand up pumps with gauge like out of lidl or aldi are good. Dont think you can get borescope in plug holes for visual check. This process should work on scooby