Air Hissing Turbo Noise from Mk7

[simont2010]

Hi! I've a 2007 Mk7 transit with 243,000 km's on the clock (it's an ex rental motorhome). Anyway, I'm stuck in central Australia, and with no mechanics open today I thought I'd try and do some diagnostics to work out what might be going on.

What happened: we were driving along the highway yesterday, when a loud compressed air type hissing noise suddenly started. Initially thought it was air leaking out of a tyre, but soon realised that the noise was rev and load dependent. It kicks in a little after the turbo kicks in, and as mentioned is load dependent - fairly loud when driving along the hwy, but can barely hear it if you just rev the engine when stationary. This makes it hard to identify the source. Power is down significantly - most noticeable at the higher revs obviously. No other signs of problems - no smoke or oil or anything. One other little thing - when idling, the engine used to give a little jump in revs every now and then (for 1 second every 30 kind of rate). I presumed this was a normal (but don't really know), but now it doesn't do that when idling - just sits at constant revs.

I've had a look over the hoses between the turbo and the inlet manifold, and can't see any obvious holes or cracks. Been reading a bit and read stuff about EGR's, and someone who had a crack in the manifold. Not sure what to do next. Any suggestions? We are supposed to be meeting friends at Ayers Rock in a couple days!

[Plumbtek280]

Had this problem on a mk6. There was a hole in the pipe going from the manifold to the egr valve. This got bigger over time and eventually sounded like the exhaust was blowing, but only under load. it also lost loads of power.
Replaced the egr pipe and blanked the egr off. sounds and runs like a new van now!!

[ake]

You need to check all the pipes and connections from turbo to inlet manifold, it may even be a cracked manifold

[simont2010]

cheers guys. Thought I'd better report back that yes, it was a split in the hose between the turbo and the intercooler. Thanks for your help.