kaptnknemo

Got any ideas what this noise is? It is a poor recording, listen for the clacking noise. 86S 126,000 miles. The recording is at idle about 900rpm with the hood up and the recorder is held over the center of the engine, about two feet above the main intake T.

TIA

KK

AO

Thanks for telling us where the recording came from, but where is the noise coming from? right side, left side, front, back, middle? Does it increase with engine rmp? Any perfarmance loss? It could be your valves hitting pistons and being pounded into oblivion, or it could be a leaky exhaust gasket, or a broken cam, miss-timed cams, etc. Too hard to tell from the recording. More info please.

worf928

Transaxle type?

heinrich

sounds like alternator is dragging on a bellypan or something like that. Second-best guess given the info, is a severely-failed water pump chewing into the engine block. Third guess, clutch or pressure plate falling apart and dragging. Fourth guess, thrust bearing failure.

kaptnknemo

Thanks for the help so far! The noise is comming from the valve cover area. Some guys here at work think it may just be lifter noise. There is no noticable loss of power and I just changed the oil. Oil pressure is a solid 5 (on the 86 oil pressure gage) at anything over 2K RPM and is about 3 at idle. The noise was present a little before the oil change and is now louder. It does increase in frequency with RPM. If it is lifter noise, what do I do to fix it? (I can wrench a little). The new oil is name brand stuff made for engines with over 75K miles (10W-40)

I am quite sure it isn't comming from anywhere near the transaxle, thanks worf, BTW it is a stock transaxle.

Since it drives OK and hasn't exploded in a jillion bits, I'll have put heinrich's vision of doom on the back burner for a while.

I will try to make a better recording tonite and maybe apply some filtering to remove the background engine noise.

Thanks

KK

heinrich

It is definitely not lifter noise.

heinrich

Hehe I guess it did sound a bit gloomy

AO

Probably a bad lifter (or one with lots of air). I supposed it could be a miss-timed cam. Probably best to take the belt covers off and make sure the cams are lines up and that you have'nt skipped a tooth..
If it's the lifter you might try Mystery oil, or ATF in the oil before changing the oil, but chances are you'll have to live with it until you pull the valve covers and cams. Ask BigDave if this can be done with the engine in place. Me thinks you can.

AO

Has the car sat for a long period time without running the engine?

Bill Ball

Give it a Rislone treatment and see if the noise improves.
http://www.rislone.com/engine.htm

That is one noisy lifter, if this recording was 2 feet above the engine, but if the engine runs well otherwise, that is the most likely cause of the sound.

Rislone will often unstick a lifter, but if the lifter is completely collapsed, it may not pump up and may need replacement.

heinrich

OK Guys, educate me. I've heard a thousand 928 lifters and they all click or tick. Did I download the wrong file? I hear a scouring, or scraping rotational noise

Big Dave

If you end up needing to, it IS possible to remove the valve covers with the engine in the car. The bottom bolts are difficult to reach, but possible. You should be careful not to bust any of the cam cover bolts...they are prone to failure if over-torqued. If you have the two-piece design (short bolt plus space under the covers) the spacers can snap off if you try to remove them--and you shouldn't need to.

Aside from that, I can't tell what's making that noise. When I first started my engine and the lifters needed to pump up, they didn't sound like that. Just because you haven't had a drop in power doesn't mean you shouldn't hunt down why it's making that noise. Find it soon. You may be on borrowed time. It's better to find out before anything gets worse.

Big Dave

I agree. The speed of the noise makes me wonder if something is stuck in the combustion chamber or one of the rod bearings is loose and slapping around.

AO

But if it's a rod bearing, you wouldn't hear it from the valve cover would you? That's what's puzzeling me. Could it be a busted cam lobe?

ErnestSw

Which valve cover, left or right? Front or back? The frequency of the sound is too low to be a lifter, there's much more mass involved. The resonance also makes it sound like something hitting a cover inside a space.