occasional scary clattering sound

[jhugh]

It has now happened twice, the appearance of the scary and mysterious clattering sound.

A month & half ago I had new rear tires put on my '84 911 at Wheel Works in San Francisco. I've rebuilt the engine myself, have about 10K on the rebuild. C2 cams, ti springs & retainers, heads built by Ted Robinson, fabspeed premuffler, Dansk dual outlet muffler, dastek piggyback computer. As soon as I got in my car and drove off, I noticed a LOUD clattering sound coming from the engine. The sound modulated with the engine speed. It sounded like a valve train nightmare. After a couple blocks I pulled over and stopped the car, opened the decklid and saw nothing, smelled nothing. I started it up again and returned to the engine.. still sounded horrible. The clatter seemed to be coming from the the center or passenger side of the engine, intake side. Figuring the guys at the tire shop had taken my baby on an unauthorized cold engine fun run & trip to the redline, I called them up immediately and began to chew them out. They were incredulous, insisting they had not driven my car.

Luckily I was also but one block from an independent Porsche shop, The Stable, on California Street. I pulled into their driveway and stopped the car. The friendly but busy mechanic dude walked up and I explained the sitch to him. He asked me to open the decklid and start the car, which I did. No clatter, man. Gone. He listened to the engine, poked around. He said it had a slight valve noise, but nothing out of the ordinary. In fact it sounded very healthy and was probably in near perfect adjustment. Hmmm. He must have thought I was insane.

Fast-forward to last weekend. I'd spent an hour or so messing with my pedal cluster and throttle linkage, with the car held up on the driver's side only... on a jackstand by the torsion bar cover. When I was done, I started it - same horrible sound! I stopped the motor immediately, opened the decklid and restarted the engine. Again, the sound. Again it seemed to be coming from the center or passenger side of the engine, intake side. I stopped the motor and swore floridly. Went inside for a few minutes, returned to the car and started it again. No sound. And to this day, no sound.

So WTF??? I'm thinking some intermittent valvetrain issue? Maybe an alternator or fan issue? Cam chains? Could it have had something to do with my car sitting canted for a while? Any knowledge or recommendations would be greatly appreciated.

Thanks in advance!

[3.2 CAB]

Hi Hugh, I had a similar noise that would come and has gone, I thought it was the right side tensioner failing, so I took the chain covers off and ran the engine to actually see what was making the noise. When I started it up, ran fine, no noise at all from the possible failed tensioner, no chain jumping around, no other noises. The motor oil that I had dumped from it had about 1600 miles on it. I did see a copious amount of oil coming from the right tensioner, I have been told on the 911 forum that this is coming from the check valve, or safety valve, or whatever this valve is, and that the tensioner is indeed bad. The only reason I can think why mine did not make the noises when I started it up to test it, was the 12 new quarts of castrol 20-50 was still thick enough to keep the tensioner pumped up, even with the oil flow out of the valve. So here I was, wanting to see the chain making the noise, but it would not do it. The only thing I have to go on is the oil flow out of the tensioner, to determine that it is probably bad and will have to be replaced. I hope you can find out what is wrong with yours. My right side tensioner was really flowing oil out of the thing circled in the picture, if you revved the engine, oil would squirt 6-8 inches out of it. Good luck.

[jhugh]

Thanks for your reply! This could be the ticket. I do happen to have a very slow but noticeable oil leak from the other (driver) side of the engine, from the chain cover. I've been meaning to open it up to see what's going on. But that's the other side of the engine from where it seems the noise is coming. Bottom line: I better look at my tensioners pronto.

A question: if I have a failed or failing tensioner, is it a big BIG problem, like I shouldn't drive the car? Or do you think it's only failing to tension the chain when I hear that sound? I ask because the 911 is my daily driver and I won't get a chance to dig into it until this weekend.

Cheers

[3.2 CAB]

Hugh, I parked mine due to the thrashing noise, I have several other rides to choose from. I searched the old threads and such, and from what I found, everybody seems to act like it is a bomb waiting to go off, I did not want to take a chance on the chain slipping just one tooth and crapping out the engine. That picture is actually one I found from someones previous posting that showed a tensioner, it is the left side tensioner on a pre 84 engine. What really got me was it would not make the noise when I was wanting it to, I looked at the ramps, and all around the case but I could not see anywhere the chain had been dragging. It will sit till I get the tensioner kit, and replace both sides, if it actually needs them. I am waiting for more info to come to determine if for sure the tensioner is faulty. I would not like to have to depend on one of these cars for a daily driver.

[NevenM]

Hi

Is there a rebuild kit available for Carrera Tensioners?

TIA

Neven

[3.2 CAB]

Not that I am aware of. I am going to call Jerry Woods and find out more about mine.