Engine knocking noise...need help identifying
 

Please help me identify this engine noise. It started after some hard driving.

There is no knocking noise at idle, but it starts as soon as I accelerate.

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Any clues will be appreciated.

Max.

I'm not sure but my first thought is timing chain noise? It sounds like the chain slapping in it's housing. It looks like you have a 3.2L engine so I'm guessing you have the pressure fed tensioners. I thought these were less prone to failure so a collapsed tensioner is less probable. Anyone else have an idea?

Thanks Rich, in fact its a 3.2 engine, my car is a 1985 3.2L 911.

Place the metal end of a large screwdriver on the chain box and the other end in your ear and rev the engine a little. If it is the chain / tensioners you will know.

Sounds like a valve not getting back out of the way fast enough, look for a broken valve spring.
Bruce

This is a good suggestion that I'd like to take a step further. Choose the longest, thinnest screwdriver in your tool box, and place the screw end against the chain box cover. Put your ear against the end of the handle. Move the screwdriver around gently, side to side, along the raised, horizontal "seam" (sorry, probably not the right word), on the chain cover, you'll find the problem. One side will be noticeably louder than the other.

The correct tool for your investigation.......
 

If you could borrow a mechanic's stethoscope, this would give you a better sense where the noise is coming from inside the running engine. Even with my bad hearing, the sound/noise it picks up is so sensitive and clear.

http://forums.pelicanparts.com/uploa...1304652144.jpg

Tony

Very strong possibility of failed tensioner

I had a failed tensioner on my 88 3.2. The noise went away at about 2000 rpm. I changed both.
They can be changed with the engine in the car.

Wow, that is the classic "chain drug over a metal trash can" sound of a failed tensioner. You don't want to be driving around until you fix that.

Thanks everybody for your answers.

Looks like that the main suspect is a failed tensioner...in fact, when I tried to identify where the noise was coming from, it seemed to be coming from the center rather from one of the sides (i.e. valve trains).

As suggested by Pete and Tony I'll do the "screwdriver listening test" (or stethoscope if I get hold of one) this afternoon.

I'll post my findings.

Max H.

Stethoscope at Autozone for about $12. Good luck, my guess, flat6pac, valve. Steve

I gotta say +1 to that.....

Valves, and valve springs will be 2nd thing I'll be looking at.

Steve - $3.99 at HFT but maxhofer is in Chile. Screwdriver (without a necktie) in the short term.

Mechanic's Stethoscope.

I have never heard the chain over the garbage can noise. This tapping noise is very distinct and very uniform. I am leaning towards valve as well.

I had a rather noisy valve at one time, simply re-adjusting cured that. It didn't sound anything like this, though. A broken spring can make that kind of racket? Listening, I'm reminded of one of Scrooge's ghosts walking around dragging his chains.....sounds like one whole side is rattling itself to death. Just $0.02.

Looking forward to maxhofer's feedback. I though for sure youtube would have a video of a bad tensioner on a running engine but nothing.

Speaking from never hearing the rattle noise I am thinking the tapping noise would be a little less uniform if tensioners but that is simply the layman speaking.

Mine , got it fixed ASAP with upgrade kit from PP

YouTube - failing tensioner

Nasty noise!

Yep - thanks for finding that video for me. It does have a uniform noise.

What kind of oil are you using or used?

Draco, I'm using Liqui-Moly 20W-50 non-synthetic.

re. mechanics stethoscope, I've read and tried using a wooden dowel. For some reason(s) it seemed to filter out the unwanted noise. Just put one end on the engine spot of interest and hold it against your ear.

I'm picking one up this p.m. Due to mother's day I couldn't work on the car during the weekend, but i'll jump on it today.

Tazzieman's noise sounds very much like mine.

The reason I asked, I had the "Rumbling/Rattling Metal Trash Can" noise 2 years ago.

Drove on the freeway at moderate speed enjoying a drive to the beach then all of a sudden, the rumble noise occurred.:eek:

Limped home and took both fans off, used a stehtescope and verified the noise was coming from the driverside chain cover. I was ready to take her in the next day but the noise disappeared. Weird.

About a year ago, it came back for a day then went away again. Strange.

2 years ago, I started to use different brand of oil (not liqui-moly) but Mobil 1 synth to Dino/Synth mix. I thought to me is was to too much of a coincedense. Now I use straight Dino, have not heard the Rumble of the Trash Can yet. If it does, then I guess it will be time to tear her apart to take a peak inside.

if its not the chain tensioner I would guess intermediate shaft bearings.

UPDATE:

Ok, here's what I've found so far. I went for the chain tensioners first.

This is how the passenger side cover looked like before opening:

http://forums.pelicanparts.com/uploa...1305564998.jpg

As you can see cover was very dirty and with signs of oil dripping around the bottom.


This is how the driver's side cover looked before opening:

http://forums.pelicanparts.com/uploa...1305565347.jpg

http://forums.pelicanparts.com/uploa...1305565394.jpg

As you can see, the driver's side cover was very clean and with very little oil dripping from the bottom.



When I disconnected the oil tube from the passenger/right side a lot of oil came out. BUT when I disconnected the tube from the driver/left side very little oil came out.

When I opened the passenger cover a lot of oil dripped from inside also. BUT AGAIN, when I opened the driver's side very little oil came out from inside the case.

Can it be that I was getting less oil into the left side than into the right side?

A look at the inside of the cases:

Passenger/Right side Case:

http://forums.pelicanparts.com/uploa...1305566055.jpg

http://forums.pelicanparts.com/uploa...1305566076.jpg


Driver's/Left side Case:

http://forums.pelicanparts.com/uploa...1305566303.jpg

http://forums.pelicanparts.com/uploa...1305566321.jpg


On the tensioners:

I pressed on the passenger/right side chain and the tensioner's piston did not move at all. I also tried to press the piston itself, but it was hard as a rock.

BUT, when I pressed the driver's/left side chain the piston compressed inmediatelly. Here is a couple of videos of the action:

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I checked both of the oil tubes going into the cases/tensioners and they both were unclogged.


Can it be that my driver's/left tensioner wasn't getting enough oil pressure? Or is it definetely failed?

The difference in the amount of oil that came out from both of the cases makes me wonder if the problem is oil circulation.

Another find!!!:

When I removed the driver's/left cover I found a small metal piece that looks a piece of wrinkled aluminum foil (a bit thicker).
It was sticking to the inside of the cover:

http://forums.pelicanparts.com/uploa...1305568402.jpg

http://forums.pelicanparts.com/uploa...1305568436.jpg

http://forums.pelicanparts.com/uploa...1305568458.jpg


Any idea of where this piece of metal could have come from????



Again, any ideas, guesses, comments will be greatly appreciated!!!

Max.

I might consider putting it back together and testing the oil pressure on each side. I would also check the left cam for starvation. Given that hunk of metal, the left port may be clogged. But that is the least of your problems. That hunk of metal looks like part of a bearing shell. Pull the IMS cover off and see if you can detect any movement with the IMS by tugging on the chains. I'm still leaning towards defective IMS bearings.

Thanks James, I'll pull the IMS cover off and see what I find. Will post results.

I would drain the oil and see if you don't have a lot of bearing material on the magnetic plug. it could be a failed rod bearing.

Good idea, will do that too.

Question for j911brick:

James, I'm working with the engine on the car. To get to the intermediate shaft cover I guess I'll have to go on to a partial engine drop as the cover is behind the engine support bracket.

Am I right?

Max.

Right you have to remove the engine mount.

Look on top of the tensioners in the recessed hole next to the piston rod there should be a raised cap with a open hole at top, are they still there?

4sd911, here are pictures of the tensioners, am I missing the caps?:

Driver's/Left Right side tensioner:

http://forums.pelicanparts.com/uploa...1305595703.jpg


Passenger/Right side tensioner:

http://forums.pelicanparts.com/uploa...1305595793.jpg

I hate to say it but that's a rod bearing. Failed rods have a very particular noise and that's it
The piece of metal is a piece of bearing

But, can a piece of rod bearing get into the left chain case?

The caps are both in place on the tensioners.

Have you looked behind the valve covers yet?

Not yet, will do it tomorrow.

Guess I'll be looking for a broken valve spring, loose rocker or broken rocker shaft.

Yes, also look at the cam lobes if the spray bar is clogged a rocker could dig into it. The bearing failure is a possibility but is easier to inspect behind the covers first.

Metal pieces floating in the oil on the bottom of the case can make there way to the chains and end up in the chain boxes.

You don't exactly have to do a partial engine drop. You could just support the engine from the bottom and remove the muffler and engine mount. Probably easier to work with if you just drop the motor though. Either way there is a good chance the motor has to come out so prepare for that. Your probably not going to learn much under the valve cover That kind of material won't come from there. The poster that suggested rod bearings may me right. IMS bearings, which are about the thing as rod bearings, will usually have copper in them. SOunds more like a IMS bearing than a rod bearing to me. IMS bearing failure sounds like a chain tensioner failure; Rod bearing usually sounds slower and heavier. As previously suggested, best bet at the moment will be to pull the sump plate and open up the oil filter. Any flakes and you need a new motor. Sorry.