Inlet Manifold gasket leak??

[ricster]

On my tours around Moz last week I seem to have developed an air leak somewhere on the motor. When the motor idles all is fine, but from about 2000 rpm when the turbo is boosting I can hear a psssssssssssst from somewhere on the motor. When I take my foot slightly off the accelerator the pitch of the psssssssst changes slightly, and when I floor it one can hear the pitch change again.

So, I assume it to be either a tiny leak on the manifold gasket where connecting to the block, or at the flange where the IC pipe connects to the Manifold. If this is the case, the flange gasket connecting the IC to the Minifold can be easily changed, but the intake manifold gasket will be a more challenging task!! Can I reuse the existing gasket? Would I need to use some gasket maker goo ( I think its normally red in colour ) with the old gasket, or is it better to get a new gasket ( unfortunately I assume this would be a Nissan only part ).

The other thing I thought it could be was at the flange on the back of the turbo. When on full boost, the waste gate will start to open up a little to balance the boost to the 0.5 bar. The waste gasses then blow out into the exhaust. The stud on the flange from the back of the turbo connecting the start of the exhaust broke a while back and I removed the broken stud and replaced it with a bolt I had ( I didn't have a stud and nut that size and depth) and forgot to go to the bolt shop to get new studs, as I'm planning on building a new stainless 3" straight through exhaust with an unrestricted 5" resonator box ( purely for that wild diesel truck sound ). The flanges don't have any gaskets in and don't have any "gungum" gasket stuff in either. So if there is a small leak there could this cause the pssssssssst i'm hearing.

My EGT's are behaving like normal, and I'm not noticing any loss in power either..... any ideas or comments

[Michael]

Cedric

It sounds like a boost leak to me and it is actually very easy to find it. You basically have pressurize the system from the inlet side of the turbo.

I have done this test on my wife's 2.0TDI Passat and it works like a bomb. All I did was disconnect the pipe between the turbo and the air cleaner and build a "adapter" that fits onto the turbo and has a coupling where you can connect a compressor hose or even a bicycle pump to. All you then do is give it some pressure and find the leak.

Check out these two youtube links




I think if it was a exhaust gas leak you should very quickly see the black carbon deposits where the leak is

[firessafari]

Take a piece of tissue paper ,hold it at one corner and move it slowly over all the joints . With the engine running . When you reach the leak it will start fluttering. you cant reuse any gaskets. replace them dry. no gasket maker. Johan.

[ricster]

Yeah I'm going to lay under the Iron maiden and search for soot marks first. I need to replace the silicone IC pipes anyway as they looked a little rough when I rebuilt the motor 4 years ago.... just never got around to changing them. Maybe a good time to take a spanner to all the bolts to make sure all is still tight and in place anyway.

Johan, the problem with doing that is that my viscous is locked solid, so it gets a bit windy to start with