Accessory Noise

[gmtofd]

I've posted before about an intermittent noise coming from the valve cover. So convinced that it was engine related that I did not bother to check to see if the noise goes away after disconnecting the accessory drive belt, Wasted a lot of time, by not doing that in the first place. Anyway as mentioned, this coming and going tapping noise seems to originate from the front of the valve cover, but when the drive belt is removed, noise is gone. All the accessories seem to be okay, but obviously one of them has a problem. The tapping leaves when the compressor is engaged and all is quiet. The AC works fine. The water pump was changed, about two years ago. I've read where fan clutches could cause a hard to diagnose noise, so plan on removing the fan assembly this weekend.\

If anyone has any insight of this weird noise, please respond.

 

[Mooseman]

2002 and some 2003 had issues with a clicking noise caused by the original fan clutches and PCM programming. An update might fix it.

But, if the noise stops when the A/C compressor is engaged, I would suspect the clutch bearing.

 

[gmtofd]

Thanks for your help. as the compressor is so difficult to remove would like to isolate the compressor from the rest of the accessories to verify. Need the length of a shorter belt that bypasses both the compressor and idler.

If anyone has already got through this exercise of bypassing the compressor/idler, please respond. Thanks

 

[Sparky]

Can try spinning pulleys by hand to see if you can catch a sound from any of them that way. Just a clicking may be harder to identify though.

For what it is worth though, the clicking that goes away could still be from the fan clutch. Reason is, when you command AC on, it also commands a little higher duty cycle on the clutch to move more air across the condenser.

Does it click even when the engine is hot and the fan is running at a higher speed, with the AC off?

 

[gmtofd]

Ok, then before bypassing the compressor, I'll remove the fan/clutch assembly to see if the noise goes away. It actually makes a knocking noise that somehow, someway transmits to the engine, making it sound like there is something wrong with it, instead of merely an accessory problem.

With the belt disconnected, spinning the accessories does not uncover anything unusual, except from the vehicle not being used, the alternator will actually freeze up. Once with a pair of pliers, it is broken free, it spins okay.

Thanks for your help.

 

[Mooseman]

The alternator shouldn't be freezing up like that at all. I think its bearings are on their way out if it's doing that. I've seen alternators that sat for years and still spin freely.

 

[DAlastDON]

I agree, the alternator should spin with little resistance all of the time.

 

[gmtofd]

Well, the alternator bearings may be an upcoming problem, but the cause of the accessory noise, (random clacking) is a bad compressor bearing. Took 3 months to figure that out, but it was better than removing or replacing unnecessary stuff, like the entire engine. There was a time I thought the random clacking noise was coming from the valve cover, and there was a problem with the timing set and was looking at junkyard engines. The reason I was looking at engine, besides the noise, was that a compression test show only #80 in the 2nd in cylinder. What is amazing is that the motor does not idle like it has a weak cylinder?

 

[Mooseman]

You should do a wet test on that cylinder to determine if it's a valve or rings. Either way, it's a b!tch of a job. I say keep running it until it starts puking.

Or maybe the compression gauge wasn't seated all the way in? Had that happen once.

 

[gmtofd]

Or maybe the compression gauge wasn't seated all the way in? Had that happen once

Thanks for the post. Must of checked that #2 cylinder 5 times., With the intake manifold, and vc off while filling the cylinders with compressed air, and at the same time making sure the camshaft was at the heel of the lobes so that the intakes valves were closed, there was air escaping, blowing out the intake port. Going to try a chemical cleaner with the hope of de-carboning the combustion chambers, What is totally confusing is that with 2 weak cylinders, 150# for 1, #80 for #2, the motor should be idling rough, but there it idles as smooth as glass?