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I have a 1999 996 C2 6 speed, My car has been sitting for about three months due to my broken left foot, I have started it about 3 times and let it run for a bit to keep the battery charged and the seals wet. As a note my car has 89K on it and is a weeked car, In 4 1/2 years I have put 18K on it. This past weekend I started it an could instantley here a rattle or more of a clack - clack - clack, I shut the engine off right away. I have always changed the oil every 3K . I have read the write up in Excellence magazine on the IMS failures and it sound like this could be the issue. I have read the write ups on Pelican Parts and the L & N engineering sites and I am trying to understand if I can do the IMS retro fit or if the engine is done. I sounds the same as before other than the rattle, the idle is as smoothe as before

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I have a 1999 996 C2 6 speed, My car has been sitting for about three months due to my broken left foot, I have started it about 3 times and let it run for a bit to keep the battery charged and the seals wet. As a note my car has 89K on it and is a weeked car, In 4 1/2 years I have put 18K on it. This past weekend I started it an could instantley here a rattle or more of a clack - clack - clack, I shut the engine off right away. I have always changed the oil every 3K . I have read the write up in Excellence magazine on the IMS failures and it sound like this could be the issue. I have read the write ups on Pelican Parts and the L & N engineering sites and I am trying to understand if I can do the IMS retro fit or if the engine is done. I sounds the same as before other than the rattle, the idle is as smoothe as before

May be a good idea as first steps to remove the oil filter at this point and cut it open to inspect for metal particles, and also to see if you are getting any oil drips or leak from the area between the engine and the tranny.

I hope it's only a lack of oil getting up there on startup that is causing the clack-clack-clack.

Regards, Maurice.

Edited by 1schoir

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Could be a chain tensioner that drained down and the chain is rattling. This is not uncommon, many 996's have a little chain rattle when they first start up, until the tensioners get enough oil. Some say to replace the tensioners if you hear a chain rattle. It could also be the IMS bearing. The problem with checking the oil filter is that the OEM bearing is sealed, so you will not see any particles unless the bearing is far enough gone to push out the shields.

If you shut the engine off right away you probably have not done much damage and the IMS bearing upgrade, along with new/updated tensioners is the way to go.

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Noise then oil...most likely cause is the IMS bearing. Even though you shut it down right away if the bearing failed

metal will be threw out the engine and a tear down is needed.I have done two this year so far none of them jumped time and they ran fine

but metal was everywere.

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I hear so many bangs, clacks, dinks, bongs, whirrs on my 2003 C4 cab, particularly with the top down, all of the symptoms in this forum cause me an ulcer - it's hilarious.

Is there an encyclopedia or index of noises a 996 engine makes?

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My '99 with 50k miles makes a rattling noise when started cold every time. I counted, it lasts 2 seconds. It's quieter since I switched to 20W50 Mobile 1.

I read that Porsche was aware of a noisy IMS during cold starts in the 1999 and 2000's then corrected it in the '01 when they changed the IMS bearing design. Am I correct?

Edited by azrob

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azrob - The noisy start up really has nothing to do with the IMS bearing,it is the chains and the tensioners. Porsche did redesign the type of chain in 2000 and the tensioners later. I think this may have helped on the start up noise. But you can't update the chains without a new crank, IMS, etc. You can install new/updated tensioners, and the tensioners will wear and stick. Replacing the tensioners is a recommended part of upgrading the IMS bearing.

Edited by Dharn55

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Not sure I agree with the metal everywhere in a failing/failed bearing. Lots of cars are being "saved" with failing bearings these days, look at the Flat 6 and LN sites, along with posts on the misc blogs. The first thing I would do is to take off the oil filter, cut it open and roll it out to look for metal fragments. Then I would drain the oil and drop the pan to look for fragments. If you find much this might indicate/validate a bearing problem (although you will find some if the pan has never been dropped since new). And even if the bearing is throwing off some fragments that are getting beyond the seals on the bearing, they should be pretty much filtered/caught by the screens in the oil intake and the oil filter.

I would go ahead and drop the engine and look at the bearing, this is the real confirmation, and has to be done whether the engine is toast or not.

Edited by Dharn55

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I hear so many bangs, clacks, dinks, bongs, whirrs on my 2003 C4 cab, particularly with the top down, all of the symptoms in this forum cause me an ulcer - it's hilarious.

Is there an encyclopedia or index of noises a 996 engine makes?

This describes my feeling very well! I was once told that Porsche engines sound like a sewing machine. My wife and daughter recently had their sewing maching out and I can't say I agree with that observation; I think the sewing machine was more quiet.

  • Upvote 1

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I have a 1999 C2, Cab, 6 speed, w/ 58k miles and get the rattle on cold start if the car has been sitting for several days. I guessed it was the chain tensioners since the noise goes away after a second or so on cold start. I gave it a start this morning and no rattle, since I drove it yesterday. My clutch is a little grabby, so when I do the clutch I will do the tensioners, rails, IMS bearing etc.

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Not the tensioners! I replaced the tensioners and still have the rattle, I also dissected the oil filter and it is perfectly clean not debris at all with about 2500 mile on the oil - filter. could this be the IMS with no debris? or ???

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In general, if your IMS is on the way out, there should be evidence of it in the oil filter as a specific type of debris. On the M96, there are multiple chain tensioners that can go off, causing the "rattle" type of complaints; and in some cases, the tensioner issue can be resolved by switching to an oil with better film strength (e.g.: get rid of the 0W-40 Mobil 1). There are also several chain guide "paddles" (number dependant upon if the engine is a pre '03 five chain motor rather than the later three chain version) that wear and can also lead to a similar sound. If the guides are gone, replacing them is the solution; different oil is not going to help.

Edited by JFP in PA

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Because of how, and where, the chain guide paddles are located (they are what the tensioners are pushing against), this requires some significant effort and specilized tooling (cam allocation related). Not a "backyard DIY" type of project, which is why most try different oils first.................

billettensionerblade.jpg

Edited by JFP in PA

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If not M1 OW40 then what oil / weight would I want to use?

Considering that 10W-X oils were until recently recommended for use in the arctic, I have never understood the need for 0W-anything, particularly in temperate climates. First, based upon years of UoA’s, I have no faith in Mobil 1 products. It has been all downhill since Exxon took over.

I would suggest looking at Castrol Syntec 10W-40, it is what we use.

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Because of how, and where, the chain guide paddles are located (they are what the tensioners are pushing against), this requires some significant effort and specilized tooling (cam allocation related). Not a "backyard DIY" type of project, which is why most try different oils first.................

billettensionerblade.jpg

More to the point -- you have to crack the case to get to these parts.

The real tricky part is assembling the 4-6 pistons and doing the blind wrist pin spring lock.

My partner manufactured his own tool -- but its not for the feint of heart. If the spring lock

doesn't take it will require taking the block halves apart -- finding the spring lock -- and

starting all over.

mike

Edited by txhokie4life

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If not M1 OW40 then what oil / weight would I want to use?

Considering that 10W-X oils were until recently recommended for use in the arctic, I have never understood the need for 0W-anything, particularly in temperate climates. First, based upon years of UoA's, I have no faith in Mobil 1 products. It has been all downhill since Exxon took over.

I would suggest looking at Castrol Syntec 10W-40, it is what we use.

redline 15/40. oil wars heating up again?

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Because of how, and where, the chain guide paddles are located (they are what the tensioners are pushing against), this requires some significant effort and specilized tooling (cam allocation related). Not a "backyard DIY" type of project, which is why most try different oils first.................

billettensionerblade.jpg

More to the point -- you have to crack the case to get to these parts.

The real tricky part is assembling the 4-6 pistons and doing the blind wrist pin spring lock.

My partner manufactured his own tool -- but its not for the feint of heart. If the spring lock

doesn't take it will require taking the block halves apart -- finding the spring lock -- and

starting all over.

mike

Not sure that is correct (splitting the case) From all the info I can read you simply need to lock everything in place, remove the head covers and cams and then you have access to the cam chain saddle guides. The chain ramps chain be replaced by removing the bolts on the front of the engine block. However, you better be a darn good mechanic as everything will need to be retimed on assembly and you will need a few special tools. Pelican has a great tech article with tons of photo's that show this clearly.

Tom

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I believe that the IMS to cam paddles can be changed without splitting the cases, but the IMS to crank paddle does require the splitting of the cases.

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I believe that the IMS to cam paddles can be changed without splitting the cases, but the IMS to crank paddle does require the splitting of the cases.

You are correct.

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I removed the tensioners, flywheel, IMS flange and IMS bearing c -clip in order to replace the IMS bearing, then discovered it couldn't be done on my engine which was a factory re-man with later IMS bearing.

 

After putting it back together, refilling with oil and trying a test run, I got a rattle a few seconds after startup. I immediately shut down the motor to prevent possible damage. Is this anything to worry about, or will this awful noise go after the tensioners fill with oil? I was more concerned because the motor started to vibrate a lot more when the noise started.

 

https://www.youtube.com/watch?v=iQxTScPNPjQ

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I removed the tensioners, flywheel, IMS flange and IMS bearing c -clip in order to replace the IMS bearing, then discovered it couldn't be done on my engine which was a factory re-man with later IMS bearing.

 

After putting it back together, refilling with oil and trying a test run, I got a rattle a few seconds after startup. I immediately shut down the motor to prevent possible damage. Is this anything to worry about, or will this awful noise go after the tensioners fill with oil? I was more concerned because the motor started to vibrate a lot more when the noise started.

 

https://www.youtube.com/watch?v=iQxTScPNPjQ

 

It is the tensioners, it would have been a good idea to pre fill them by pumping them up in a container of oil before reinstalling them, but they will pump up in the engine after it runs for a bit.  Just don't drive the car or rev the engine until it settles down.

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