Tapping sound coming from engine

BlkSCnKS

Registered User
I noticed last week that from inside my car, it sounded like it was developing an exhaust leak. Then I noticed that it was very much rpm specific noise. At exactly 2,000 rpm it seems to start and it seems like it's the worst at 2,000 rpm. Less then 2,000 rpm and there is no tapping at all. It also seems to only do it once the car warms up. It sounds to me like it's coming from the supercharger area or maybe below it. I also took the time to check the oil while I had the hood open and it was down almost a quart and a half. This means I've burnt over two quarts of oil in the last 3,000 miles. I'm almost certain the oil is leaking through the exhaust valve seals but I have no idea what could be causing the tapping noise other then valvetrain. Any ideas? Thanks, Brandon
 
I'm pretty positive that is is coming from the supercharger or the top of the engine. I'll take a look at it again tomorrow. Thanks
 
So is a noisy drivetrain pretty normal for these cars when they're cold?

BlkSCnKS said:
I'm pretty positive that is is coming from the supercharger or the top of the engine. I'll take a look at it again tomorrow. Thanks
 
I think so. I know that if I dont let my 91 warm up for like five minuts in the morning the valvetrain will tap. But of course being low on oil only makes it worse. Use a stethiscope(sp) or a long metal rod (1/2 in ratchet is good here) and place it up against the SC and put your ear at the end of the ratchet. You should here the tap if it is coming from the SC.

Shane
 
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And 1.5 - 2 quarts of oil in 3000 miles isn't excessively high. Anything under 1000 miles per quart is 'ok'. Although with the better seals and rings in most cars from mid 80s up, a quart per 2000-2500 miles is about normal. Our cars use a little more than normal from pressure induced blowby. When the SC is kicking max boost, crankcase pressue will have some oil being pushed through the PCV into the intake.
 
I had the same exact problem as you described. I also thought the same thing as you did, and progressively it got worse and now for sure it is the passenger side exhaust manifold gasket. In the process of fixing it right now.
 
Yeah, I was thinking the exhaust gasket on my drivers side has a bit of a leak, the car sounds fine otherwise, I'll be doing some exhaust work next year in addition to other maintenance, I'll just make sure to replace those gaskets too, it definately sounds like an exhaust leak to me.

birdofprey said:
I had the same exact problem as you described. I also thought the same thing as you did, and progressively it got worse and now for sure it is the passenger side exhaust manifold gasket. In the process of fixing it right now.
 
After listening to it tonight with my brother, we both agree that it is a metallic tapping and that it's coming from the passenger side of the engine. Now what? Lifters? Thanks, Brandon
 
BlkSCnKS said:
After listening to it tonight with my brother, we both agree that it is a metallic tapping and that it's coming from the passenger side of the engine. Now what? Lifters? Thanks, Brandon

It's probably something in the valvetrain like a dirty/clogged lifter that's not pumping up all the way or it could be a bent push rod or loose rocker. I would just keep driving it and see if it goes away or starts getting louder.

David
 
with my spun rod bearing it would not start making any noise until about 2K+ then under light acceleration the noise would be there, under heavy it would disappear.

If you think it is a spun rod bearing, stop driving the car right now. Since the crank can not be turned, finding one in good shape that you can afford is becoming harder and harder. The is a company in Memphis, TN that will build the crank up then turn to stock spec's, in turn making it stronger, but its about $500+.

Just some more $.02
 
Ok, I think I've narrowed it down to the valvetrain. I took my supercharger belt off yesterday and it continued to do it. So Tuesday I'm going to take the top end of the engine apart and try to track down the problem. I'm going to buy a pushrod, rocker arm, lifter, valvespring, and intake gasket kit and just return the parts I don't end up using. My fear is that the problem is not going to be readily apparent so I am wondering what to look for. What do I need to check on the lifters, etc. I can't stand it when something is wrong with my car so that's why I'm just going to go ahead and fix the problem. Thanks, Brandon
 
Just yank off the valve covers and check the lash. You will find the problem soon if it's in the top end. Might also be a bent pushrod. Did this start happening after some high revving? One time I ran my mitsu 3.0L up too high and it started tapping. When I pulled the valve cover off, there was a bent pushrod and a rocker arm cocked at a 15 degree angle.

You should check your oil for bronze just to be sure it isn't a bearing before you dig any deeper. If it is, you might be better off getting a new block than chroming whatever's worn. Put some oil in a little bottle and hold it up to the light and see if it 'glitters'.
 
The Dreaded Lifter

BlkSCnKS said:
Ok, I think I've narrowed it down to the valvetrain. I took my supercharger belt off yesterday and it continued to do it. So Tuesday I'm going to take the top end of the engine apart and try to track down the problem. I'm going to buy a pushrod, rocker arm, lifter, valvespring, and intake gasket kit and just return the parts I don't end up using. My fear is that the problem is not going to be readily apparent so I am wondering what to look for. What do I need to check on the lifters, etc. I can't stand it when something is wrong with my car so that's why I'm just going to go ahead and fix the problem. Thanks, Brandon

Brandon,

I had the same problem after rebuilding my 95, nasty tapping noise. I pulled the S/C belt, and the noise was still there. From what I gathered it, too, was valvetrain. After pulling the passenger side valve cover, it was obvious that the front cylinder's exhaust valve was loose, close to .200

I pulled the intake manifold, and the lifters, and found that was the culprit. Replaced a pair of lifters, and I'm about to put everything back together.

Good luck.
 
Thanks for the help guys. I'm going to tear it apart in about an hour and I'll let you know tonight how it went. Thanks again, Brandon
 
BlkSCnKS said:
Thanks for the help guys. I'm going to tear it apart in about an hour and I'll let you know tonight how it went. Thanks again, Brandon

If you don't already have one, get a Haynes repair manual to get the info on what crank position you need to check/set each of the lifter preloads.

David
 
If you don't want to run out and get a book, you can do it the lazy way. Put a ratchet on your crank and turn the engine till the lifter you're checking is at full lift (eyeballed). Turn it another 360* Check the clearance. If one of them is too wide, don't forget to roll the pushrod on something flat to check for a bend.

Ryan
 
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