Loud Rattling from Alternator/Power Steering belt.

Hello All,

My wife and I bought her father 95' Riviera SC last year and yesterday it started a bad rattle immediately after starting it. The car has only 32,000 and was garage kept during her fathers time as owner. Today i removed the Alternator/Power steering belt and it does not make the noise, so I do not believe it is the Supercharger. I recorded a couple videos that I posted below. I took the alternator in to Autozone and they tested it, and it ran fine. I also checked the bearings on both the idler and tensioner which seem normal. The only thing weird I noticed was that when I unhook the alternator wires the noise is quieter. Please let me know what you think. Any help is appreciated. I feel like it's the alternator, but they are non-refundable and I hate to buy one and not be able to take it back.

Video 1 - No Alternator belt.
https://www.youtube.com/watch?v=Tsr-7vOsvec&feature=share&list=ULTsr-7vOsvec

Video 2 - Alternator belt on but no wiring attached
https://www.youtube.com/watch?v=c1u9RWRtcaE&feature=share&list=ULc1u9RWRtcaE

Video 3 - Alternator belt and wiring on.
https://www.youtube.com/watch?v=rSa2eaLe-ok&feature=share&list=ULrSa2eaLe-ok

Nice job documenting the noise with the video recordings.

It seems obvious from the video with the belt off it's a mechanical problem with the alternator (bearing). I could see how it would pass an electrical test, but find it hard to believe the alternator pulley feels smooth and tight when spun by hand. However it's possible.

Based on the evidence so far, I would take one of two paths:

1) Purchase a new alternator and replace. This will probably fix the noise, but I understand wanting to be 100% sure before spending the money. You can return a unit that is defective. There is a high rate of DOA rebuilt alternators being sold (most are rebuilt in China). I'd guess 25-33% from local parts stores are bad units.

2) Purchase a mechanics stethoscope for $20 and listen more carefully for the source of the noise. Then you can be 100% sure, and will have a new tool in the box.

Best of luck!

PS - does the alternator feel hotter than other parts of the engine? A mechanical bearing failure can sometimes be diagnosed by touch.

Okay so I went and bought a stethoscope today and could not hear the noise coming from anything I touched. However I crawled under the car and put the scope to the oil pan and could hear it well. I also took pressure off the alternator/Power steering tensioner while it was running and the noise got worse. I really can't get the scope to the harmonic balancer but would assume that the noise would run through the oil pan since they are next to each other?

You wouldn't be the first with a bad harmonic balancer. The rubber insulator dries out and cracks, then the outer ring of the balancer can get very noisy.

Here goes nothing.....just bought the Harmonic Balancer. I did notice it had a slight wobble, not big but enough to see it was not spinning smoothly.

Inspect the HB you take off the engine. It will have a casting number on it. Make sure it corresponds to your new one. The other thing you can do is look for its opposite key weight and make sure they match in size between the old and new. The 95 SC riv had either the 1st design HB or the second design and you have no way of telling what one you have until you take the old one off. You don't want the wrong weight one running on your engine.

2nd Design, 2-1/2 inch Weight (Large) Opposite Keyway replace with ACDELCO Part # 88960264
1st Design, 1-Inch Weight (Small) Opposite Keyway replace with ACDELCO Part # 88960265

1st design will have Casting #24502174 marked on it somewhere.

Okay, I confirmed that I had the second design and the replacement was the second design as well. The noise is totally gone now and clearly the rubber was cracked all the way around the HB. One little issue though, the car seems to run ruff now.

Assuming plugs and wires are all good, maybe clean the MAF? (Pull it out, and VERY gently run a q-tip soaked in rubbing alcohol along the wires inside.)

It has to be the balancer I would think....It ran smooth this morning even while making all kinds of racket. Now the noise is gone but the motor has a vibration in it.

thewashman wrote:

Okay, I confirmed that I had the second design and the replacement was the second design as well. The noise is totally gone now and clearly the rubber was cracked all the way around the HB. One little issue though, the car seems to run ruff now.

running rough is a different problem...

With the car idling in park (or neutral with brake set), on a level surface, watch the tachometer.

While idling, no load, the tach should be rock-steady. Yeah that's right, no perceptible movement. If it is fluttering or "hunting" (revs increase then decrease, then increase, then decrease, etc. over the course of a minute or so) then you are overdue for servicing the idle air control (IAC) and / or the throttle body (TB) if nothing else (the coil pack, the fuel pressure regulator, the fuel pump) is wrong.

What to do: pull the throttle body and clean it... don't bother using a spray-in cleaner. Make sure you use a cleaner that is "coating safe" whether a spray or a liquid. You want to clean off the tar and leave the golden coating behind. GM dealers sell a liquid cleaner that is quite good. Most auto parts stores sell a CRC cleaner that is good enough.

Do a search on this editboard, you'll find instructions for removing/cleaning the throttle body, cleaning out the IAC passages and resetting the IAC. If you have over 100,000 miles you may find it simpler to replace the IAC, they are not free and not a kings ransom either.

The reason to pull the throttle body -- if you don't then all that happens in a cleaning is you float the accumulated tar into the air intake, where it does not help you there either.

You may need to get the throttle body gasket via internet. Last time I did this job I found that only one parts store within 30 miles of me carried the gasket (and the mechanics seemed to know who it was but were not saying, I had to call around). It was easier the prior time (and cheaper) to just order the thing - I got it off Amazon.com or rockauto.com not sure which.

An issue with the coil pack or an issue with the wiring could lead to running rough as well - but you have to eliminate the causes one by one, can't just test around or guess. Reason is that the PCM (engine computer) compensates for air/fuel mixture, for instance, by measuring and metering. Well, if the measurements are off it will richen up the mixture and at some point the car will get rich enough to run rough, it detects that and backs off, then things look too lean and it richens up, et cetera.

In order to break the cycle you have to catch up on maintenance that's peculiar to old and high mileage cars, but is not detailed in the maintenance instructions. Maintenance instructions say stuff like "check emissions system" not "look for tar in the throttle body and IAC." As a result, the average owner - call him Donald (or Donna) Driver, gets told by their independent mechanic "if there was a problem your emissions light will come on... and it's not on..." and as a result conditions like this (rough idle) get slowly, slowly worse. Donna gets frustrated and sells or trades the car; If a trade, the used car seller fixes things just enough to give the novice purchaser Donald a good test drive, and Donald buys the car and when the temporary fixes are exhausted the old problems show up with a vengeance. This also happens to owners who want to keep their car but are not familiar with what needs to be done at advanced age/higher mileage. Things like the idle quality will get a little worse day by day as deposits accumulate, but the PCM is so good at hiding the problems that it takes a pretty long time for things to get so far out of adjustment that any problem is apparent -- at which point there is a lot to do to get things right.

You were really fortunate to properly diagnose the bad HB - so now be assertive and patient, uncover the other problems as best you can. Eventually you'll get the state of the car's maintenance to a good level. Just don't be angry about that it takes a while.

Albertj


If you are going to keep the car the only way "out" is to fix the problems as you can find them, and it will take a while.

Another thing to keep in mind, is the 95 didn't have as fancy a knock detection system as the others and can't pick up on the frequency of the knocking being real or something else. So if the HB was rattling around enough to hear, the knock sensor would for sure have been hearing it and interperting it as knock. What the PCM would do is tune your fuel trims and timing for whatever pattern of knock it could come up with. Now with no rattle it might take some start and run cycles and miles for it to realize that everything is ok again. Just a thought. Though you should consider and try everything Albertj mentioned. Hes a smart cookie.

@ Karma - if he resets the Mac and cleans the MAD the PCT will reset in a drive. It willact wayward at first, the telltale is the idle will go to 2000 rpm and sit there for a couple minutes... then if everything else is OK it will settle and purr like a happy kitten.

After this TB jazz the next thing to check is motor mounts. I bet the rear transmission mount is sacked.

I begin checking all that thanks for the input, but remember this car only has 32,000 original miles and was garage kept until this last year.

The tach is steady as can be, I can clearly see the motor vibrating when i look at it.

I can't recall if the 95 can get a case learn, or if anything needs to be done to the CPS after something like this. The crankshaft position sensor is driven off the HB and works in conjunction with the camshaft position sensor to determine timing. I am wondering if something's up with the timing of those sensors.

Also did you check all spark plug wires?

thewashman wrote:

The tach is steady as can be, I can clearly see the motor vibrating when i look at it.

check engine mounts
check sparkplug firing order
check your work on mounting the HB


My only other thought is was transmission line pressure set too high - you'll get a strident vibration at idle.

Well thanks for the input guys, turns out they had sold me the wrong HB. Mine uses the 96' model and not the 95' it should. All the auto parts sites tell me it's a Dorman Part# 594-161, but it turns out mine uses the Dorman 594-122 which showed in their computer for the 96 model. So I am guessing I have a series II engine and not a series I? I'll post some pic's of it as soon as I get it cleaned up. Thanks again for the help guys. Will be sure to keep up with the site.

If its 95 and supercharged its not a series 2. period. And if so you DO NOT want to put on a 96 one.

The Dorman 594161 is a 1st design. What is your original casting number?
As far as I know, Dorman ONLY makes a 1st design replacement.

If yours is the 2nd design you want ATP Part # 102109, or ACDELCO Part # 88960264. Anything else will take apart your engine.

Again:
1st Design, 1-Inch Weight (Small) Opposite Keyway
2nd Design, 2-1/2 inch Weight (Large) Opposite Keyway

I was wondering when you mentioned removing the Alt belt about it being a series 2. Can you take a pic of the motor?

Edit - hmm just watched the video, that is definitely not a series 2.

Good possibility Dorman has listed the 2nd design as a '96 part accidentily or out of ignorance. Good resaon that it would seem Dorman only made 1st design. If the 594-122 is an identical match to your original then I would safely consider this to be the case. As Karma said, the balance weights are very important to be a match, as you now know after feeling the vibration with the wrong one installed. Also be sure the clock position of the keyway is correct to your original HB.

Here was my HB adventure. Sounds like you might be fighting the same issue:
https://rivperformance.editboard.com/t9037-95-sc-harmonic-balancer
Also, after running that balancer, I'd suggest replacing the seal when you change.