I just replaced the timing belt on my 91 Accord and I'm hearing a high-pitched ringing sound from the engine bay. I loosened the accessory belts because I thought it was a bearing but the noise is still there. It fades in and out.

Here's a vid:

[youtube]XXmMFhhCC2o[/youtube]

 

Any ideas?

It seems to keep ringing for a bit after I shut off the engine. Until after the intake makes its whooshing/vacuum sound.

 

Does the sound change tone with engine speed?
Did you replace the tensioner idler pulleys and waterpump as well?
Did you tighten the timing belt per the instructions or did you pull it a bit tighter? Kinda sounded like a bad bearing in one of the idler pulleys. Had one go bad in a Mazda, first made a high pitched tinny sound then became a howl that changed pitch with engine speed.

 

Who did your belt? Sounds like it might be overtightened.

 

I did the TB job and didn't replace the pulleys because they spun fine. I did replace the water pump. Tensioned according to the Helms. Did it again yesterday and the noise is still there.

I took off the lower cover yesterday and I don't think it's a tensioner pulley. Sounds like its coming from behind the engine near the fuel rail. Saw a vid on youtube of a leaking intake manifold gasket making the same sound so I think that mite be it.

Mike did your idler pulley sound as high-pitched as the sound in my vid? Did it grind or make noise when you took it off and spun it?

 

Somewhat of a high tinny sound. It progressively got worse and would howl. When I pulled the idler it spun freely without slop and didn't make any grinding or death sounds. I picked up a new one, SKF, and it would not spin freely. It was smooth to turn, but it would not freewheel like the old idler.
With the Mazda I was trying to be a cheap ***, just bought a belt and forgo the idler bearing as I thought it was fine. Nope, with the new belt it made all sorts of noises. Replaced the idler and back to sewing machine quiet.

Considering its a sealed bearing, that regularly spins to 4500+rpm and its only lubrication is whatever grease was packed into it when it was made, and has no external lubrication or cooling(outside of whatever air is blown about by the belt under the cover) it's fair enough to replace it when time for a new belt.

When I redid the TB on the '95 EX 2.2 I picked up a complete kit with timing belt, balance belt, and both idler bearings for less than two belts separate. The kit was Gates brand.

I don't believe its your intake as you said the noise started only after belt replacement. From what I recall on replacing the belt, I did not touch anything on or near the intake that would cause such a problem.

BTW with the new WP did you bleed the air out of the system via the nipple on the intake? It looks like a big brake bleeder screw.

 

If you suspect an intake manifold leak get some carb cleaner and spray it around that area, and if it changes the idle in any spot you spray it you probably have a vacuum leak.

 

Remove all belts and see if it still there (sound)