Timing Chain stretched out
 

My 85 Carrera was making a knocking noise and was told by several mechanics (even a Porsche dealership) that I had a rod knock and would have to rebuild the engine .I bought a engine stethoscope and checked the engine to find where the noise was coming from and found nothing coming from the bottom but did find a lot of noise coming from the left timing cover. I took the cover off and found the chain very tight and the tensioner out so far that it was stuck (see pic). I think that the chain was so stretched out that it was causing the bar that the tensioner pushes against to be hitting the inside case. I think the solution is to replace both chains check/reset the cam timing. Am I making the proper diagnosis and remedy ?http://forums.pelicanparts.com/uploa...1429994129.jpg

Interested: how many miles on the chains/motor?

How do the teeth on the gears look?

The old machinist use to tell me. "If the chain is worm out, so is the engine"
Bruce

JDC911,

were you able to find a solution? Did you replace the timing chain as well (w/o splitting the block)? i have the same problem on my '85 Carrera 3.2 and your input could help a great deal.

Wajid

If the tensioner already bottomed out on the engine case then I would expect loose chain, but it says chain was very tight. Does this make sense? Also this is hydraulic tensioner and so it doesn't contract easy (under chain tension) as the old spring loaded tensioner, and so why it moved in and out hitting the case causing knocking noise?

Show more photos of the parts.

Chains mostly wear out and the sprockets wear out too, leading to the tensioner being extended too far.

Time to replace both chains and sprockets. Unfortunately that means splitting the case.

This thread is going on 4 years old, so I do not think the OP is still here. Anyway no need to split the case. Our host sells a timing chain with a master link..

OP four years ago, Wajid asked for help today.

Replacing the chain only, with the split and master link, will get you some relief.

Replacing the accessible cam and idler sprockets will get you a bigger benefit

Replacing the intermediate shaft sprockets require the case to be split. And you can then install chains without a master link. This gets you back to new.

This is preferable because using a new chain on worn out sprockets is not recommended. But as an interim solution it is probably ok.

Splitting the case also has the benefit of being able to renew the intermediate shaft bearings. My 964 engine had rod and main bearings that were still excellent at 150k, but the intermediate shaft bearings were completely worn out. I understand this isn't unusual.

While splitting the case is the ultimate solution, many among us do not and cannot do that for costs or complexity reasons. In the case, changing the chain and cam sprocket will at least give some relief until such time that the case needs to be split for a rebuild.

This might be sage advice.

I agree using a master link chain and replacing the cam and idler sprockets will gain some time.

But time is beginning to run out. And that is the unfortunate part of owning an old engine.

Wajid,

Just keep track of what is happening, and look for other signs of impending “old” issues like oil consumption and possibly head studs or general excessive leaks and decreasing performance. Worn out chains are an indication of age.

I was in a similar situation several years ago on my 1989 911 Carrera 3.2. I purchased and installed the master link replacement chains. For what it's worth, I did not replace any of the sprockets, as they looked to be in very good shape (according to 911 engine rebuilder at the time).

I video taped the entire process of me replacing the chains with the engine on my garage floor. Always meant to go and edit the footage because there is a lot of me just talking and head scratching, but not doing anything. for a first timer, it's a bit stressful as you know that if a chain gets turned over on itself and caught up inside the case, you are basically done. Have to split the case. 10X size project. If the forum felt it would be worth it, and can recommend preferred video location (youtube?), I can upload the videos. You would need patience and hand on the fast forward button to get thru them.

Mark

Changing the chains without splitting the case is easy. Cut the existing chain, attach the new chain to old chain and turn the engine over by hand to feed the new chain in and out of the engine. Attach ends of the new chain via master link. Should not have to re-time the cams if you are careful.

Chris

I had stretched chains in my 3.2 which caused a rattling sound at startup. Obviously new chains were the fix but we also noticed the ramps were worn so they needed to be replaced as well.

Now that's something I'd like to witness.

Pull the tensioner and the idler arm. Inspect the idler arm for cracks. One cracked on me, and the part the tensioner bears on moved out farther until it almost hit the housing. The crack was very obvious in my case.

Done it. Not difficult at all

Chris

Same here on my 82 SC. I replaced the ramps and sprockets also. No problem after 5 years 10,000 miles.

I have stretched chains on my high mileage 3.2. I have the master link chains but have not installed them because when I took one of the sprockets off it didn't fit well on the new chain. It had worn along with the old chains.

In the end, I took a dremel like tool and clearanced the cam chain housing so the tensioner had more room to work :-)

I believe Bruce's advice above is good, but damn my engine runs so good!

Chuck.H
'89 TurboLookTarga, 445k miles