by Bammo on Mon Nov 20, 2017 12:45 pm
Well I cleaned out the inlet manifold last weekend and put a new gasket / seal set through the engine - manifold, throttle body, injectors etc.
Gave it a good long blast yesterday on the highway and have exactly the same symptom as you Iain - clearly sounds like high pressure air escaping under heavy boost. I found a residue patch of oil on the top of the throttle body where the 2" air hose comes up from the intercoolers. The Jubilee (hose) clamp wasn't completely tight there and the rubber hose was compressed in the wrong spot (you have to get that clamp back in exactly the same spot as before or they don't seal properly).
I tightened it up and the oil spray stopped but sadly the noise didn't and the power level feels down - as if the boost is lower than normal which seems to fit with a leak on the turbo output path. I also noticed the rubber hose coming out of the turbo that heads into the intercooler was half hanging down - hard to describe except to say it just didn't look securely attached to the turbo and the jubilee clip on that one looked aftermarket and quite different to the others in the engine which is a bit weird. I tightened that up too (although hadn't previously touched it) and still no change to the noise.
I'm thinking perhaps I need to replace the hoses and the clamps on both side of the intercooler - I reckon its still a simple issue of the clamps not properly sealing the hoses as the hoses are too deformed.