Hello.

As some of you may remember, my engine was rebuilt last year after IMS sprocket problem. One of sprockets driving the cam-shaft chain went loose and had to be replaced along with the woodruff key (sprocket locking mechanism). Actually, it was the $2 worth woodruff thing that caused all the trouble, so we had to tear entire engine apart. The mechanic who did it for me is my friend, he has about 15 years of experience with 911's, however, he only worked on 964/993 engines before.

So, once the engine was back in the car, the IMS sprocket noise was completely gone and I was happy. However, the typical 996tt chain rattle appeared. Like we know, some turbos have it, some don't, thing is, mine was the one that never had it and I was sort of proud of it.

Now, I have this chain noise, but it's much louder than on most cars. I can hear it once sunroof is open. It sort of disappears when I rev the engine, but it's hard to tell because it's loud anyway when revved. The sound is not present when engine is cold, but it starts to appear "cyclically" once it heats up and then becomes permanent.

I believe somehow it does relate to engine rebuild (because it was never there before), but we have no idea why. He listened with a stetoscope, the sound is clearly coming from the left part of the engine, esp. from the oil pump on the left. So, we removed some parts from the engine to get to the left chain tensioner. We removed it, disassembled it, it looks perfect. We even pulled the spring by about 5mm longer.

Then we replaced the oil (put Castrol 10w60 instead of Motul 300V that was there after rebuild) and started the engine... The noise was NOT gone at all, it was absolutely the same.

We are sort of clueless and pissed... He says, it *might* be the oil pump too, but he's not sure.

Does anyone have any idea what's happening? Ideas, please?

 

Hey, There are no woodruff key ways on the cams on a 996 turbo engine. What you should look at is the cam chain tensioners. One maybe installed upside down. oil can not feed it so the chain rattles around.

 

Hi,

Woodruff keys are on the IMS, not the cams. They hold the sprockets.
We'll check the tensioner, but I don't thing the mechanic put it in the wrong way...

 

video/sound clip from the noise?

 

[
Hi - greetings from the uk.

I had a snapped timing chain and consequently an engine rebuild.

I have the same symptoms as you described, and wondered if you resolved your tt? What was the issue in the end?

Many thanks

GER

 

Hello.

Nope, I haven't resolved it. But it's been 2 years and the engine's been running fine. I don't know how to resolve it and so far I haven't figured out the cause. The sound is clearly on the left, however.

 

Thanks for the reply.

I didn't appreciate it's been 2 years!

So the noise hasn't got any louder then. Perhaps I will just live with it. My car is currently with the garage still so perhaps they may find something. Interestingly, the chain tensioner had been installed upside down. They were fairly confident in the noise diminishing given them turning round the right way. Like yours though - it had no effect!
Baffled.

 

I had my engine rebuilt under Porsche warranty over 12 months ago due to oil leaks.
Mine was also a very quiet engine but after the rebuild to my disappointment had the dreaded rattle.
I had it inspected by a different P dealership as well as an independent and both told me it was fine and nothing to worry about.
But the thing that gets to me is it wasn't there before. I have been paying attention to oil usage, cutting open oil filter and oil tests...pleased to say the engine has not missed a beat.

 

Well, mine is not getting any significantly louder, but it's a bit louder up to every oil change, and quieter after oil change.

And it does worry me a lot. Plus, I think, it would be pretty hard to sell the car like that, because no regular buyer would believe this sound is normal. The tech guy said we could do a test in: in his repair shop temporarily replace the tensioner with a threaded bolt (the kind they use when setting camshaft phase) and see if we could make the sound go away. But we never actually got to do it. He also said when he removed one of the oil pumps, he could hear it produce excess noise and that it might also be responsible. He also said he was wondering if the chain pulleys vertical alignment might be the problem.

But we got 2 more cars after rebuild with the same problem here, hm.

I really do appreciate if someone with the same problem keeps us updated on the progress if any. Please!

 

I know IMS noise and chain noise get talked about quite frequently with these cars, but has anybody considered lifters or variocam? Lifters and variocam are both directly effected by oil. So is the chain tensioner IIRC. So if the noise changes when oil is older than that means it is likely an oil pressure sensitive part. That would also cause it to be noisy on startup because lifters, tensioners and variocam are both low on oil pressure until things circulate or inflate.

 

I would look into noisy oil pump mentioned to owner by mechanic.

 

My rattle is always there, it doesn't seem to change whether its cold, warm, hot or even just before oil change.
The independent technicians located the sound with a stethoscope and said it was normal.

 

I cant remember the last tt Ive heard that DIDNT have that rattle

 

yup. 996 and 997 both.

 

Hello to all Porsche fans!

it's been 2 years after engine rebuild and driving with the darn rattle.

I was driving my car about a week ago and suddenly the PSM light went on, then the CEL, then the engine shut down. I tried to restart it, it would rev, but wouldn't start. I had the car towed to my place, after that tried to start the engine several times again, and finally, it stopped turning, like it was stuck. I hooked up a Durametrics cable and it shows signal below limit, implausible signal on camshaft 1.

I took the car to the shop and the diagnosis is: the timing chain on bank 1 (that's on the left), broke, TADAaaa!!

And while the engine is being worked on now, I found some gruesome stories on the net of valves bent, chain being wrapped around the IMS, IMS breaking in half, crankshaft breaking and finally, engine case cracked!

I guess I won't get much sleep for a couple of days before the tech gets the engine completely torn apart...