Hi,

I have been experiencing a ssshhhing or hissing noise from the engine bay over the past week. This only happens between 1500 - 3200 rpm the just sudenly stops. I initially thought it was the turbo spooling up. but i am now thinking is there a split pipe somewhere..

I have looked around the engine bay with engine running on idle but there is noise at all, if it is reved a bit there is no noise.

So after a 2 tests

Test 1 - drive normally upto 3k revs for warm up no hard acceleration there seems to be a constant hiss there seems to increase with revs and reduce with the change of gear.

Test 2 - keep in second gear and accelerate off roundabout not hard but making reasonable progress 2000rpm - hissing, 3000rpm - louder hissing, 3200/3300 rpm hissing just stops. take to 5500rpm change to 3rd hear dump valve eject air rapidly and hissing stops until the car is driven gently and comeback again.

I do not think i have a leaking/split pipe anywhere, but i am thinking is the dump valve sticking open slightly or is the boost actuator sticking occasionally and overboosting hence the reasonfor the hissing (dump valve releasing the presure to atmosphere)??

Car is a 04 Plate WRX (40k miles) completely standard engine but prodrive exhaust CAT back including centre decat pipe. Car is under warrenty but if its a simple case of wd40 on a sticking part then i will do it myself but if its requires to be dismantled then i will take it back to the dealer.


Thanks

Steve

 

I had a Seat turbo with the same (but intermittent) problem a few years back, I changed the dump valve & it cured it for a while but it came back, it turned out being the boost solenoid playing up.

 

Steve - did you find the problem?

I've got the same symptoms!

Chris

 

sounds like your dump valve to me m8