M42 Hissing Noise

[sepehr]

There's a constant hiss from my engine, sounds sorta like drawing sandpaper on something. Starts at 2500rpm and sticks around till 4000+ rpm. Its more pronounced under load, but I can hear it when I rev the engine at rest.

Changed timing chain tensioner, didn't solve problem. Could the new tensioner have a problem like in this thread:

http://www.r3vlimited.com/board/showthread.php?t=51968&highlight=timing+chain

Or could it be an exhaust leak from the exhaust manifold/gasket?

Any comments would be appreciated.

[golde30]

sounds like a vaccum leak... if u smoke, run the engine and blow smoke over the engine, see if its sucking in smoke somewhere(away from air filter box)...this may work.

[sepehr]

I'm not sure its a sucking sound. Its a bit "grainier" for the lack of a better word, a bit like very high frequency clicks. But who knows. I might as well just rip them all out and replace them, they all look original.

Anyone here have a diagram of vacuum hose goes where on the m42 engine?

[jtuner]

seph, I have this same problem.. It happens at the same RPMs and seems to happen simultaniously(sp?) with my timing chain grind.. Now I haven't replaced the tensioner on mine yet, but, I'm pretty sure the sandpaper noise has nothing to do with that.. I'll be standing by to see if anyone has any ideas..

Oh my car is a 91 318is as well.. M42 powa :D

[jtuner]

bump... anyone?

[asubimmer]

if you need a diagram go to realoem.com ;)

[craig4ie]

to check if it is the tensioner, take a long screwdriver and with the handle to your ear put the other end near the tensioner. use other points around the timing chain cover as a reference. if the noise is pronounced around the tensioner then you've probably found your problem.

if not...keep lookin