Help me diagnose this noise - Chain rattle?

[ianc]

Hi folks,

I need some help on this one. I haven't actually broken out the stethoscope on this yet, but I think I'm convinced I need to do tensioners. Please give me your thoughts.

As background, the car has made this noise since I bought it. I recently did a top end on the car, but that seemed to make no difference in the noise at all (although it sure runs a lot better!). It now has ~133K on it.

When I first start the car from cold, it does not make the noise, but after I drive for a few blocks or let it idle for a few minutes, it starts. As soon as the car warms up, the noise goes away. I thought about driving the car over to S-Car-Go (5-10 min away) to have Rob King listen to it, but the noise will be gone by the time I get there. The noise is not the steady tick-tick noise of a valve or rocker arm, but more of an irregular scrapey kind of noise and is definitely coming from the right side of the engine.

One thing that is really making me think I need to do tensioners is that I remember when doing the Carrera tensioners on my SC 10 years ago, the old tensioners were so stiff I could barely compress them with channel locks. When I was compressing these while doing the top end to get the pins in prior to removing them, they compressed very easily.

Take a listen to this video and see what you think. This was taken in the morning about 3 blocks from my house. You can really only hear the noise for about the first 1-2, and last 3-4 seconds of the video when the camera is over the right chain box.

http://video.google.com/videoplay?docid=-7846998326776584774&hl=en

What's the verdict? Thanks for your .02,

ianc

P.S. YES, I know I screwed up and put the cruise control cable under the heater duct. Since fixed...

[A Quiet Boom]

Subscribing, I've heard a similar noise on mine under similar circumstances. Help us out guys.

[rusnak]

Hi Ian, I was just gonna say that you should plug that little hole in the heater elbow from the cruise control delete, lol.

When my 914-6 chain tensioner was in mid-collapse, I heard a VERY loud noise like a chain being pulled out of a trash can. This is not like that (metal on metal grinding). The sound in the last few seconds is troubling, but not as severe. It almost sounds like cylinder knocking. I'd probably take a metal coathanger, straighten it out, and use it as a stethoscope by holding one end against parts of the engine, and the other against your closed ear. You can cushion it with a piece of cloth or a cotton ball. This will allow you to pinpoint the source of the noise.

Good luck!
Russ

[ianc]

Thanks for the input Russ.

Remember, the car was making the same noise before I did the top end. All of the pistons and cylinders were carefully inspected, measured and found to be fine, and the heads were done as well. Don't think it's to do with a cylinder...

I did borrow a stethoscope and will leave for work a little early tomorrow to try to pinpoint it a little better. Just looking for some seat of the pants feelings. I know the vid could be a lot better and it's kind of hard to hear...

ianc

[rusnak]

I agree, it's not due to a piston hitting a cylinder. That would mean excessive wear or bad rings. What is strange is how the noise comes and goes. I'll take a listen on mine with my stethescope.

My guess is it could be the tensioners are worn (the spring part that is), then they tighten up with pressure when the oil heats up and more oil flows through them, and then relax with lower oil flow. If the tensioners are going, you'll get more noise at start up, and then it'll go away when the engine is hot. You said the noise comes back though....

[ianc]

You said the noise comes back though....

No, it doesn't come back until the engine is started from cold again...

ianc

[Scott R]

I just went through this a while back, same noise, almost the same conditions except when hot my noise was fairly consistent. At any rate the tensioner was failing and the chain started to chew through the ramp, the ramp disintegrated and the chain started to chew on the ramp pins.

The end result is two chewed up ramp pins, and a cut like a chainsaw cut in the back of the case due to the ramp being in pieces. After tearing it all down I was surprised in how well all of this stuff is constructed. I was able to drop new hydraulic tensioners in and new ramps and I was on my way. Of course now I'm in the middle of a full rebuild and I'm replacing the passenger side chain box for good measure.

I still have the old chain box if anyone wants to see a pic of what happens when the tensioner fails.

[slodave]

Originally posted by Scott R
I still have the old chain box if anyone wants to see a pic of what happens when the tensioner fails.

I'd like to see what happens. Thanks!



Dave

[Giantman]

I had a very similar sound in my SC. I thought tensioners but it turned out to be the air (smog) pump falling apart internally. I guess however that the 3.2 is devoid of such a device correct?

Simon.

[WERK I]

ianc,
In your case, I hope it is a tensioner going. The noise you describe is exactly the noise I experienced on my 930. When it started, it sounded beautiful, 1/2 hour later a noise that sounded like a very bad piston on the right side. The problem with the piston theory is that piston slap is worse at startup, not after warmup.
I put a stethoscope on the valve cover(s), upper and lower. The sound was slightly louder as I got closer to #6, so I removed the valve covers. My worst fears, #6 intake lobe damaged along with the corresponding rocker arm. It appears the spray bar hole clogged for that lobe.
I was wondering what would keep me busy over the winter!

[rusnak]

Dave, I concurr.

Ian, I put a stethoscope on mine this morning. My gut says most likely the tensioners, since I know you checked out the top end thoroughly.

If you do end up changing the tensioners, could you post a thread so we could see how it's done? I hope all turns out well!

Russ

[ianc]

Hey Russ,

Yeah, I tried to listen again with a stethoscope this AM, but it wasn't really conclusive. I could hear a kind of scrapey noise coming from the right chain box, but the noise wasn't that loud this AM. By the time I got out and had actually listened to it for a minute or two, it had disappeared... I think I'll do them anyway, and I'll post pics. Thanks,

ianc

[Scott R]

Here are the pics I mentioned earlier, I had to re-charge my camera.

[jstobo]

I assume this is on your 80 targa not the 87. Tyhe 87 already has carrera tensioners. If you can push down on the tensioner plungers and compress them easily-they are gone. Replace immediately. New tensioners usually take a vise to slowly compress them.(In other words do not pull pin on new tensioners until installed. I know I know but all of us do stupid things once in a while). Of course the Carrera tensioners are different if you upgrade to them as you obviously know. Good Luck

[ianc]

I assume this is on your 80 targa not the 87

Nope, it's on the 87. Video should show this I think...

ianc

[A Quiet Boom]

EDIT, wrong thread

[rusnak]

Ian, too bad you live so far away. I dropped by my mechanic's house today to say Hi and ask if he could help me put a new catalytic converter on the car. It was like going to the Degobah System and visiting Yoda. He's the real deal, dyed in the wool Porsche mechanic from the old school. He had a 356 rear end on a stand, and a few more 911s in various states of work in his driveway. He would be the perfect guy to take something like this to, and you'd be amazed at how fast and cheaply he can fix Porsches.

[ianc]

Hey Russ,

I don't really mind shelling for the parts or doing the work (not that much anyway ).

I just wish I was 100% certain it would fix it...

ianc

[LARRY SHARP]

it could be that the chains are stretched out to the limits of what the tensioning systen can handle.

[ianc]

it could be that the chains are stretched out to the limits of what the tensioning systen can handle.

A possibility I had considered, but I sure hope not. That would suck.

ianc