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Hissing noise but no boost leak

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Hello everyone,

I'm having a problem with my Defender 2006 TD5 and I thought you can help me. 

I've been noticing some black smoke when hard accelerating. black smoke is more before the turbo kicks in. Thought it might be a boost leak in the pipes, but after testing each part one by one, no luck finding any leak on the intake. it's holding up the pressure nicely. (from turbo to intake manifold) Then I decided to put pressure (5psi) on the whole system including the engine.

there is a noticeable hissing sound, seemingly originating from the rocker cover. To confirm this, I removed the oil cap and the sound became more apparent, I removed the rocker cover and I found the hissing sound coming from the 4th or 5th pistons (maybe both). 

Worth to mention:
There are no signs of oil and water mixing, and no blue or white smoke. The oil and water remain clean.
I have blanked the EGR to eliminate any related potential issues. 

I have attached a video, you can see it is louder around 4th and 5th.

Does anyone have any idea about where the problem is, and potential solutions?




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The hissing sound observed is most likely air escaping through partially open intake valves - nothing to worry about & not related to your issue.

I had a similar issue which turned out to be one of the induction hoses having delaminated.  When there was enough intake vacuum, the hose was collapsing (on the inside, nothing visible on the outside), restricting the air intake resulting in black smoke.  When the turbo started producing pressure, the hose re-inflated, opening up and the black smoke cleared.

There were no holes in the tube - and it looked perfect on the outside.

It took some finding & figuring out - but once I found the hose, it was obvious.  I could see the inside of the tube had de-laminated.

At that point, I renewed all the induction hoses.  This was on a 2003 Td5.

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