Bkresse

After replacing the alternator I began to hear this engine chatter. You will hear an example at 00:01, 00:05, 00:18, 00:25, and 00:30 in the video clip.


Brief history: I was driving the car when the bearings in a remanufactured Bosch alternator went bad. Before I shut the motor down, the alternator fan briefly interacted with the alternator fan housing. I observed an area on the inside housing wall where the fan slightly scraped the paint away and maybe the smallest amount of metal. The affected area was roughly the size of a dime. As expected, I also found some fan shroud paint and a sight scratch on three of the fan blades.

After hearing the noise, I disassembled, rechecked everything, and reinstalled the assembly. The fan rotates smoothly in the housing. Everything seems aligned and sound. Additionally, I was concerned about the fan belt tension, so I ran the engine with a fan belt tension of .5 inch and then .25 inch slack. The noise was evident in both scenarios.

Any Ideas? Could the Fan and/or housing be damaged to the point of causing this noise?

Thanks for any help you can provide.

masterdave

sounds like the fan rubbing up against the housing to me, I have been having the same issue, I will be getting around to fixing it one of these days.

Bkresse

Thanks masterdave... If it's just barely rubbing, then it may not be that serious? You're still driving your car with the noise?

This just occurred to me... could this be engine knock. Fuel related and just coincidental to the alternator issues? I use Costco Premium 93 octane?

It kind of has a dull chatter similar to the sound of a diesel truck makes, but much less pronounced. It's not sharp or specific. Nor does it appear in a consistent pattern.

Also, the damage in the pictures happened when the alternator failed. I painted and marked the spot on the housing to monitor any new damage. I have not seen any evidence of new damage or interaction between the housing and the fan... yet.

masterdave

It may not be a serious issue but it can be, 2 of my fan blades are chiped in the corners. People have warned me that becasue the fan is a ballenced impelor the more it gets out of wack the worse the problem can be. I have been driving mine in this state but not for long and intend on fixing it this winter. Keep playing around with the fan belt tension, if you got new alt bearings they may just be settling in to place.

I can say if its engine knock, the thing about gas is that it almost dosent matter where you get it from in my opinion. If a place says there gas is 93 octane then its 93 octane. Some people can be picky where they get there gas from, I typicaly am not. I usualy go Hess, Mobil, Shell or Exon. Never had any issues or noticed a difference.

Ed Hughes

I'd pull the fan an check for scraping evidence. Some light sanding on the blade edges may help. Did you paint it recently? Often, the tolerance is close enough that a coat of paint on the shroud and one on the fan causes interference. Don't run it this way.

rusnak

You really need to listen to the engine while it's warm, and check the fan blade clearance with a feeler gauge.

Bkresse

Ed, maybe you're on to something... Again. I did paint the housing when I had it taken apart. I wouldn't have thought of this because the newly painted housing didn't appear to touch the fan. However, there is so little tolerance between the housing and the fan maybe the paint thickness is creating some unusual flutter that's facilitating this darn noise.

Im going to check this out ASAP.

Thanks!

Bkresse

Rusnak, great idea. Any idea about the required clearance for the gauge?

ron mcatee

Did you remove the spacer behind the fan or leave it on? It needs to be on the shaft prior to putting the fan on the shaft.

Bkresse

Fortunately, I decided to install the fan with it on in the first go round.

I asked the question about needing it or not based on the fact that the broken alt that I took off didn't have it. Also, I found no direct reference to leave it on. But, I kind of thought it through and decided to install it with it on. To my good fortune I was correct as supported by all the feedback. Unfortunalty, I was hoping that if the alt didn't need the washer and I had installed it, that it may have been the source of my new chatter noise. It wasn't.

rusnak

The fan makes more of a squeal when it scrapes. That low frequency knock could be either the fan hitting the alt (poor belt fit), or something else like a rocker or some such.

TroyN

Maybe a stethoscope would help id the source of the noise.

Bkresse

TroyN, I never used one, I'll give it a try. Funny, I just looked at one at Northern Tool this past weekend.

ivangene

you can substitute a long screwdriver to your ear pressed firmly

or short broom handle or any number of other objects...just make sure the end at the ear doesnt fit into the hole

Bkresse

I went out and bought the scope at Northern Tool, $3.99. Amazing what you can hear with that thing.

I'm convinced that the sound is isolated to the fan area. So I think I'll remove some paint from the housing and cross my fingers. I can't imagine this noise would be caused by another faulty Bosch alt.

I'll let you know. Thanks everyone.