The Car:

1999 V70 T5 SE
3" catback exhaust
Boost guage
forge motorsport dumpvalve (BOV)

car runs fine untill boost is called for, a very loud hiss audiable from engine bay while inside car when boosting, usualy 10psi but will only run to 5 now have tried standstill rev while listening for the leak but it appears to be recurculating through the air intake(?) have checked all visable hoses and vaccum hoses, the dump valve spring seems fine.

Any help on good ways to diagnose boost leak? or other problems this could be.

any help much appreciated.

thanks

 

Check all vaccum lines. I mean ALL vaccum lines. Because you might not have found one that was cracked. Also did you check all the turbo hoses as well?

You have the Upper Intercooler hose. Lower Intercooler hose, Upper Intercooler pipe to turbo hose and then the Upper Intercooler pipe to lower Intercooler pipe hose.

I know you said you checked all visible hoses. I want you to check them again. Also you don't have to but it is a good idea to replace all your vaccum lines and turbo hoses with Silicone replacement versions.

1. Silicone turbo hoses can be had from SAMCO and StylinMotors Inc. SAMCO's can be bought from Viva Performance and the StylinMotors Inc. can be bought from http://www.stylinmotors.com/

2. The Silicone vaccum lines can be had from http://www.stylinmotors.com/