Unknown strange engine noise

[DarkAngel]

Hello,

Ive made videos this week-end about a strange engine noise that i cannot identify :(

It appears when the engine is running and also when it stop, it makes a metalic noise like "rattle"
on the third video, we can hear it a little but usually it makes much more noise

The belt tensioner does not seem to move excessively and ive checked that the alternator and climate pump is tight correctly

If someone has an idea from where it can come from ...

Thanks for your help :)

1) http://youtu.be/OpJT7LIqf9M
2) http://youtu.be/Mc3TUkZx-zA
3) http://youtu.be/QFJsKHduLTo

[geezer]

Sounds like belt tensioner/ bearing. Easily available on the internet.
IMHO

[scottfab]

1. Remove the belt and inspect it for a bad spot.
2. Belt ok? then spin each, water pump, A/C, alternator, idler pulley and tensioner pulley as well as the PS pump. Listen and feel for any grinding.

[DarkAngel]

thanks for your answers, i will try to check this

regarding the belt tensioner, what is the difference between this one :
http://www.whiteracingproducts.com/index.php?main_page=product_info&cPath=1467_10_44&products_id=91

and the one from ecklers
http://www.ecklerscorvette.com/corvette-engine-belt-tensioner-1988-1991.html

there is a huge difference of price between them

[Dynomite]

Just in case you want to try something different :D
Experimental Bling (http://www.zr1.net/forum/showthread.php?p=174422)

http://i287.photobucket.com/albums/ll142/dynomite007/A%20Corvette%20LT5%2090/63e1fa11-78c9-4c58-9752-51a0f3cbb766.jpg (http://s287.photobucket.com/user/dynomite007/media/A%20Corvette%20LT5%2090/63e1fa11-78c9-4c58-9752-51a0f3cbb766.jpg.html)

[geezer]

Functionally no difference. If you isolate the problem to the tensioner pulley ( as per Scott fab suggestions) try Jerry's Gaskets for the best price on a OEM pulley.

[Blue Flame Restorations]

Dual mass??? Where is the noise coming from? Front or rear of engine?

[mike100]

thanks for your answers, i will try to check this

regarding the belt tensioner, what is the difference between this one :
http://www.whiteracingproducts.com/index.php?main_page=product_info&cPath=1467_10_44&products_id=91

and the one from ecklers
http://www.ecklerscorvette.com/corvette-engine-belt-tensioner-1988-1991.html

there is a huge difference of price between them

The cheap one does not fit the LT5. Marc Haibeck rebuilds the tensioner part if it doesn't turn out to just be the pulley bearing. i think it could also be a bad alternator bearing- removing the belt and hand spinng some of those accessories might tell you.

[DarkAngel]

Dual mass??? Where is the nokise coming from? Front or rear of engine?

it seems it comes from the front of the engine

[rkreigh]

sure sounds like the tensioner, and that pulley has a strange wobble to it too

probably the bearing is shot.

start the engine briefly without the belt

wiggle each pulley other thing that can happen is (rare) the chain guide can fail and make a racket - hope it's not that!!

[Dynomite]

sure sounds like the tensioner, and that pulley has a strange wobble to it too

probably the bearing is shot.

start the engine briefly without the belt

wiggle each pulley other thing that can happen is (rare) the chain guide can fail and make a racket - hope it's not that!!

Yes.....in one of the video clips there was a belt tensioner pulley wobble during the first part of the video. Just replace the pulley the rest of the tensioner is probably OK.

And concur....just remove the belt which will eliminate all pulley noise :thumbsup:

[-=Jeff=-]

Yes.....in one of the video clips there was a belt tensioner pulley wobble during the first part of the video. Just replace the pulley the rest of the tensioner is probably OK.

And concur....just remove the belt which will eliminate all pulley noise :thumbsup:

only pulley I saw in that video with wobble was the Alternator

[GOLDCYLON]

only pulley I saw in that video with wobble was the Alternator


My thoughts as well -=JEFF=-

[Racinfan83]

only pulley I saw in that video with wobble was the Alternator

Me too. And that would be the FIRST thing I checked. No way should that wobble that much on a 7000 rpm engine at idle. And it looked like it wasn't always consistent wobble which would tell me the bearings are bad in the Alt...

[Dynomite]

only pulley I saw in that video with wobble was the Alternator

Yep....that is correct.....I got excited......it is the Alternator pulley :handshak:

[scottfab]

only pulley I saw in that video with wobble was the Alternator

There ya go do'n that "paying attention" stuff again.:)

[DarkAngel]

thanks everyone for ur answers
i will check alternator and pulley asap

to change it, i guess i have to take out the throttle body to have access ?

[Dynomite]

thanks everyone for ur answers
i will check alternator and pulley asap

to change it, i guess i have to take out the throttle body to have access ?

If it were the belt tensioner pulley...then just the pulley bearing.

The Alternator pulley is a bit different unless it is just the bolt that has come loose on end of Alternator shaft. In that case, I modified a 15/16 box wrench to get at the nut on the alternator shaft (made sharper bend on Box end). I actually installed a different Alternator Pulley. See Item #9 Bling (Carter and Others) (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-4.html#post1581665201)


Brass Colored Alternator Pulley
Ebay Brass Colored Alternator Pulley (http://www.ebay.com/itm/230773124143?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649)
Delco CS130D Alternators 6 Groove Pulley 10476225

This pulley is identical in Outside diameter and Shaft Diameter of original Alternator Pulley. I very thin washer (3/64 inch thick) was used between the pulley and the cooling fins of alternator for exact Pulley spacing.
http://i287.photobucket.com/albums/ll142/dynomite007/Maintenance%20ZR1/2b550123-c4ed-4727-ad6d-6be083bb8afa.jpg (http://s287.photobucket.com/user/dynomite007/media/Maintenance%20ZR1/2b550123-c4ed-4727-ad6d-6be083bb8afa.jpg.html)

Alternator, Spacer, Pulley, Washer, Nut,
5/16 inch Allen, 15/16 inch Box Wrench..........................Modifications to 15/16 inch Box Wrench (sharper bend on box end)
http://i287.photobucket.com/albums/ll142/dynomite007/Maintenance%20ZR1/0db64fc7-def0-463f-ae29-c303d17c021a.jpg (http://s287.photobucket.com/user/dynomite007/media/Maintenance%20ZR1/0db64fc7-def0-463f-ae29-c303d17c021a.jpg.html)http://i287.photobucket.com/albums/ll142/dynomite007/Maintenance%20ZR1/fb56dad7-b0e7-4491-b2b6-8e1c97967ba3.jpg (http://s287.photobucket.com/user/dynomite007/media/Maintenance%20ZR1/fb56dad7-b0e7-4491-b2b6-8e1c97967ba3.jpg.html)

Now if it is the Alternator shaft bearings, it is time to rebuild the Alternator or just replace the Alternator. The Alternator has to be removed (most likely the Plenum Removed) although some have suggested you can remove the Alternator without removing the Plenum...(I have always removed the Plenum as I have TB coolant blocked).

[scottfab]

thanks everyone for ur answers
i will check alternator and pulley asap

to change it, i guess i have to take out the throttle body to have access ?

If you want to go that route here is a link.
I'd pull the plenum to do the alternator.

http://www.zr1netregistry.com/Information/TechNet/Electrical/tabid/113/articleType/ArticleView/articleId/1702/Alternator-Replacement.aspx

[DarkAngel]

hello again
i didn't change the pulley yet but when i was cleaning the engine this week-end, i've noticed that one "wings" of the alternator was broken
i guess is not big deal but just in case, i was looking for a new alternator

do you know what is the difference between the one from ecklers
http://www.ecklerscorvette.com/corvette-engine-alternator-remanufactured-zr1-1990-1995.html
and the one from rockauto
http://www.rockauto.com/catalog/moreinfo.php?pk=38487&cc=1041275
or
http://www.rockauto.com/catalog/moreinfo.php?pk=1001039&cc=1041275

there is more than 100$ difference :confused:

[A26B]

I cannot tell you what the difference is between the 3 alternators, other than price, but I can offer you some information regarding "rebuilt" components.

All rebuilt alternators are not created equal. Remy's plant is here in Edmond, OK. It's a huge place and a rather odd operation. I have been there on a couple of ocassions, to the sales dept & engineering. The do not sell direct and won't sell to me because of contracts with large parts chains which have stores locally.

I can tell you a story I was told by both an engineer and sales rep; Remy rebuilds for Autozone under their Duraguard brand and other chains, even including AC Delco. Remy has different levels of rebuild. It's not what the descriptions say, but rather what they do NOT say.

From the AC Delco alternator you linked to: Obsolete and damaged parts are replaced with OEM components or high-quality, new aftermarket parts. Plus all ACDelco Alternators and Starters are remanufactured with 100% new bearings, bushings, and brushes.

Note that the description does not mention the rectifier or regulator. Even "lifetime" warranty grades are just tested for function. If they are within spec, in the box they go, no matter how old it is. I understand that new parts can fail too, but I would prefer to at least start with new components rather than a 20 year old part, regardless of whether it carries a "lifetime" warranty. Not worth the trouble to have another failure, remove, exchange and replace.

I recommend that you try to find out exactly what has been replaced with new when the unit was rebuilt. Therein lies the difference in value.

[DarkAngel]

Finally founds out the cause of the noise

The axle of the alternator was "oval" and it breaks 2 wings of the alternator fan
http://img18.imageshack.us/img18/4269/kxw7.jpg

changed it with a new fan and the noise is gone ... but now its the belt that makes noise because the "tension" is not the same but its not big deal
i will replace it by a new one

[A26B]

:cheers: