Engine Rattle

1993 PA 241K miles.

I have a non-specific engine sound that fades in and out (about 5-8 seconds of noise, then 30 seconds quiet, then 10 seconds noise, 15 seconds quiet, etc.,) Tried to use a stethoscope on PS, AC, water pump, alt, belt tensioner but can't pinpoint sound. So far I can't tell if it's only at idle in park or under load while moving as well. I can only hear it at idle in park. I will try to get someone to check it while moving.

Sound is not super loud but noticeable and is mid pitch rattle, or kind of like a muted clacking sound (if that makes sense) not real deep or not high pitched and seems to be coming from accessory belt area. Pulled belt off and ran engine, noise goes away.

Checked (wiggled) all accessories pulley bearings with belt off and all seem OK (usually bad bearings feel gritty)

Thought belt tensioner - replaced it, nope

Maybe the water pump but it's new (18 months) and no leak out the weephole and no overheating issues.

Put the belt back on, took a 2x2 and pushed up against all the pulleys while running to see if any end play problems - no

Thought maybe the harmonic balancer might be separating, but wouldn't the sound still be there with engine running and belt OFF (unless it only rattles under belt tension).

Timing chain? I know the mileage is high but engine runs great under all conditions. Just worried I'm going to blow something up.

Any ideas?
Thanks

You mentioned that you replaced the tensioner, if your car has an idler pulley I would check or replace it. Had several of these make noise even though they looked okay. Make sure that your belt is good and that it is not missing any pieces on the pulley side. Check the back side of the belt and make sure that there are no signs of heat damage or feathering. Also check for pulley alignment. Your timing chain should be fine if you do not hear noise with belt off.

Take the belt off & put both hands on the outer ring of the balancer & turn it clockwise-counterclockwise to see if you can see & feel any free movement.

You mentioned that you replaced the tensioner, if your car has an idler pulley I would check or replace it. Had several of these make noise even though they looked okay. Make sure that your belt is good and that it is not missing any pieces on the pulley side. Check the back side of the belt and make sure that there are no signs of heat damage or feathering. Also check for pulley alignment. Your timing chain should be fine if you do not hear noise with belt off.


I guess belt tensioner is kind of misleading. I only replaced the belt tensioner pulley and not the whole tensioner and pulley assembly. Not sure what you mean by idler pulley. There are no other pulleys except for the crank, accessories and tensioner. Maybe idler pulley = tensioner pulley?

Belt is fairly new with no cracks, feathering or visible wear. alignment seems good.

I will also check tensioner mounting bolts and try HotZ28 suggestion about the HB.

Thanks

Some vehicles have tensioner pulley and an idler pulley, yours sounds like you just have the tensioner. I know this is in an entirely different spot but, if you only hear the noise with engine loaded at idle, take a look at your heat shielding and motor mounts. To check your mounts, take a long pry bar, wedge it between the engine and some other tough spot like the frame and put a load on the bar and see if the noise changes or stops. You can also take some type of wood and press against any heat shield that you can find and see if that makes a change. Remeber to have the engine running and loaded the same way that you hear the noise when checking. Oh yeah, this just me struck before I hit the reply button, check your alternator. Take it off and go down to the auto parts and have it spin tested. If it is the culprit it will let you now when they get it spinning.

could it be the harmonic balancer they are known to come lose

Yes it could be your harmonic balancer. In my experiences a balancer will only make noise if it is contacting something while running. The other thing that it will do is make vibration that you are not use to at a specific rpm range. A stock harmonic balancer is usually made up of a crankshaft coupler a rubber ring and the balancing ring on the outside. The outside ring is sandwiched between a rubber oring and the crank coupler. Usually you can tell when you are either going to have a problem or you do have a problem by the look of the rubber in between the two pieces of the balancer. It should be flush with the inner and outer pieces. When it is bad it will be bulging in one place or all the way around. Don't forget to check those mounts and heat shielding.

Could it be a timing chain tensioner?

When the belts were off, the rattle was gone!

Accessory drive belts have nothing to do with engine timing belts or chains. The fact that the noise is gone when the accessory belts are off prove my point.

Checked heat shield. All OK. Also, noise is at all times, some more some less, but generally all times. Looks like its the innards of the harmonic balancer coming loose. I can see the balancer shimmy when noisy. Worried that this is going to stress out the front main bearing/seal so am going to replace the HB.

The shop manual talks about pulling flywheel cover and using a puller. Is this just to get at the engine to hold it while pulling the HB bolt? Sounds like a lot of extra trouble.

I pulled an older Buick Regal HB off years ago and I just left the belt on to provide resistance and then removed the HB bolt and tapped the HB and it came right off as the crank was tapered.

Anyone know if this is the same setup on this 93 PA? I don't see any threaded holes in the HB for a puller. Just what looks like a 3/4 or 15/16 center bolt.

Also, local salvage yard has HB for $40 as opposed to $150 new from parts store. Is there a way to check the HB? Can I assume that the magnets for the crank sensor embedded in the HB should still be good?

Thanks

It's usually balanced for each engine, like speed balanced for wheels!

15/16 to get if off, you really should get a new one here. There are some some that need a puller and some years don't, check the how to at autozone .com repair guides, register and the info is there. You will need an impact gun here or as the info says remove the flywheel cover and jam a wedge against the flywheel teeth so the crank won't turn.

HB was separating. Came right off but took three tries from local parts store to get the interrupt rings ( I guess that's what the magnet trip is called) right.

HB was separating. Came right off but took three tries from local parts store to get the interrupt rings ( I guess that's what the magnet trip is called) right.I am not sure I understand what happened here. Did the balancer come apart in two parts, or one? The "interrupt rings" (as shown below) are riveted to the inner hub and should never be removed. The new balancer should come with the inner/outer hub molded together with the two interrupt rings installed in sync with the key way location for the crankshaft. Did you, or the "parts store" use the puller (shown below) with three 6-mm, or 1/4-28 bolts, to remove the balancer from the front of the engine, or did you, or the parts store use a 3-jaw puller on the outside ring of the balancer?

http://img203.imageshack.us/img203/1236/1996balancer.gif

http://img179.imageshack.us/img179/8205/balancerpullergg0.jpg

Hotz28 that is an excellent illustration, sounds like a 3 jaw hack job to me.

Maybe I am a little lost here...

All 3800's from 91- 2009 should have 3 threaded holes for a puller as they are a press fit... They are not like the earlier years that were a slip fit...

Is this the original motor? There was a balancer and Crank sensor change from 92 to 93..

I do hope that you get this solved...


There is only one other noise that I can think of, and it could be the Balance Shaft clanking around a bit, and the sound can and will come and go... My 91 did this and I still drove it another 60k before it was totaled...

Toss in anything else you can think of or even a Video...

Sorry, Rubber was separating but did not come apart and interrupt rings were not removed. It all came off as one unit (three hole puller) . What I meant was the new HB did not fit over the crank sensor magnets properly - could not "seat" the new HB. interrupt rings were not spaced properly on new HB compared to old. Had to try again but third time was the charm. Don't know why but there must be several versions. First two were wrong but all is OK now and she is purring.

My only guess as to the noise was maybe the rubber had separated just enough to let the rings graze the sensor occasionally. I didn't see any damage or scrape marks on the rings or sensor so . . . maybe not.

UPDATE: was just tapping on the "interrupt" rings with a metal letter opener not really paying attention and wow! There's that SAME SOUND ! On closer inspection with my glasses, the leading edge of each tooth on the 18x rings does appear to be dinged. Maybe it was!

Thanks