hissing from muffler then gone again after engine re-start

[Long]

Hi,

i have a 2.5 turbo diesel bongo 1997. I was driving normally when suddenly i had a loss of power and then there was this hissing coming from the rear passenger side. i went to check it out it was coming from it was near the muffler on the far back. not sure exactly where.. at first i thought it was a transmission slipping problem, but it didn't have any power even in park. i turn off the engine and then turn it back on. the bongo runs perfectly normal again with no signs of problems for weeks. then it happens again 100% randomly. same thing once i turn off the engine and turn it on again it runs perfectly normally again.

does anyone have any idea? fuel filter clogged? fuel injectors? i am thinking of using a diesel fuel injector cleaner.

the weird thing is the van runs perfectly after i re-start the engine. it only happens very randomly? limp mode? i am confused. i even brought it to a mechanic and they tried to re-create the problem on a dyno and wasn't able to do so. from their diagnostic there was nothing wrong. and their test drives didn't show any transmission slipping.

does anyone have any idea or experience this symptoms before?

any help is very much appreciated

[mikeonb4c]

Don't think a 97 Bongo has a 'limp' mode and i think also its too early a machine for diagnostics to work either so puzzled about that. Odd sounding symptoms. Where are ypu based as a Bongo specialist could be your best bet though even for them intermittent symptoms may make it hard to diagnose. I wonder if it could be turbo related.

[wonkanoby]

might be some thing blocking the exhaust internally

[Gasy]

Is it a winter pack bongo and the exhaust valve is operating