Strange noise on 1987 L98 TPI Corvette engine - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-20-2008, 06:55 PM
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Strange noise on 1987 L98 TPI Corvette engine

Hi guys !
i've been facing a strange problem with my L98 !
A rare noise coming from the center area (i guess)
its driving me mad.-
Sometimes i try to start it and its stuck,starter won't turn.
"Shhck " "Shhck " ...i wait a bit, and it starts
has a real horrible noise on idle only...and when the normal operating temp its reached ...sounds like a dry belt,like a bird singing,only on idle,past 1000 rpm
it goes away,and like it wakes up ! and acts normal again...
It sounds like a bad bearing on a pulley but i removed the belt
and the sound its still there !
the only thing that makes me doubt its that i swear the noise comes from the intake ..
its definetely a rotating part...i think its too loud to be injector
but not sure ...
NO BELT INSTALLED :
http://www.youtube.com/watch?v=9TBSsb0TD0U
CLOSE UP TO THE NOISE:
http://www.youtube.com/watch?v=T5Ta13ztleI

i think the stuck starter or hard start and this noise are related...
Both problems came up the same day ...
i hope its nothing internal
thanks

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Old 07-20-2008, 07:07 PM
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The noise sounds nasty, it sounds like a roller tappet thats lost it`s roller but not really sure, but I am thinking your going to have to pull it down to find the source of the noise, it could also be a burned up rocker arm. I think the hard starting is lack of grounds. My brother has a corvette much like that one, when we did the rebuild the grounds were loose and it had the same problem, since it`s a fiberglass body car, it relies on the block for the grounds, and all the grounds run to this source, I would check them and clean them.
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Old 07-20-2008, 07:09 PM
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Nope no grounds,its getting stuck
im pretty sure both problems are related,the noise and the stuck start
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Old 07-20-2008, 11:35 PM
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any ideas ?
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Old 07-21-2008, 02:08 AM
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That sounds like a serpentine belt idler squeak, or at least an accessory drive noise to me. Maybe an emission 'air' pump?

The hard start problem could be a ground cable problem- (battery to engine) or a weak starter and/or battery.
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Old 07-21-2008, 02:15 AM
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Not a serpentine belt noise,i removed the serpentine belt and the noise was still there !!! that's why the video title says NO BELT .-
i had a problem with the alt before and i've been there.
the noise its i guess coming from the injector area,intake...yes pretty strange...maybe the EGR ? but i swear its a rotating noise ...


he hard start problem could be a ground cable problem- (battery to engine) or a weak starter and/or battery.
Nope,the contact its OK,the starter its trying ...if i keep the key on the start position the starter will smoke,cause it happened once while testing...
battery and grounds are excellent

The engine sounds healthy to me
yes it was rebuilt 3 months ago and runs pretty cool.-
but the issues started at the same time
hard start...and the squeak !
thanks !


im suspecting something with the flywheel / starter.....
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Old 07-21-2008, 02:31 AM
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Quote:
Originally Posted by DoubleVision
The noise sounds nasty, it sounds like a roller tappet thats lost it`s roller but not really sure, but I am thinking your going to have to pull it down to find the source of the noise, it could also be a burned up rocker arm. I think the hard starting is lack of grounds. My brother has a corvette much like that one, when we did the rebuild the grounds were loose and it had the same problem, since it`s a fiberglass body car, it relies on the block for the grounds, and all the grounds run to this source, I would check them and clean them.
Ok, I've listened to the sounds again and again. I do hear what DoubleVision hears somewhat. It's a squeak and a chirp combined. WEIRD. If there was a failing roller lifter, the hardened steel rubbing on each other could equate to that noise...

Do an oil change and really get serious about inspecting the oil that came from this engine. Use a magnet, microscope, whatever. Cut the oil filter apart, inspect the pleats of the filter media.

The extra friction could be the cause of the hard start. Once the starter struggles to get past that point, it kind of gets a running start for the next revolution, and finally starts.

Crazy noise. It has OIL PRESSURE, right?
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Old 07-21-2008, 02:36 AM
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Yes the oil pressure its ok
yes it can be a lifter too
The extra friction could be the cause of the hard start. Once the starter struggles to get past that point, it kind of gets a running start for the next revolution, and finally starts.
Yes could be ...strange thing that this noise dissapears at 1000-1200 rpm
then came back at idle only
and it starts when the engine reach normal operating temp
before that..it runs OK
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Old 07-21-2008, 06:07 PM
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i will have to get under the car to see if the noise its actually coming from the starter or flywheel
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Old 07-21-2008, 08:45 PM
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My first thought was a dry rocker. Possibly a hole in the pressure regulator diaphragm.

One other idea was to unplug the brake booster vacuum line while the engine is running, if the noise goes away check for leaks. I have an 87 vette and replacing all my vacuum lines got rid of a lot of noises I thought were normal.

how many miles are on the car?
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Old 07-21-2008, 08:46 PM
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127.000 miles
but i've just rebuild the engine.-
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Old 07-21-2008, 09:04 PM
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were the heads or deck milled? same rockers and lifters or chinese craftmanship?
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Old 07-21-2008, 09:07 PM
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my bet is a lifter not pumping or a too tight rocker. Did you set the lifter preload within spec?
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Old 07-21-2008, 09:09 PM
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all american products
all brand new rockers and lifters
engine rebuilt 2 months ago,runs real fine
but now the problem appeared...
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Old 07-21-2008, 09:15 PM
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if the heads or deck were milled and you set your lash to factory specs you will have to much preload on the lifters which equals to much pressure on your valvetrain, therefore binding something up and getting the metal on metal squeaking. Another thing to think about if the heads or deck were milled was your manifold milled to match? Even a slight angle between the manifold and heads could create your whistling noise. JMHO
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