I hear what sounds like a timing chain rattling on cold start for about 1 second. I don't really hear it when the engine is at operating temp. Is this likely to be a timing chain tension or guide?

 

I would check the tensioners first as this is fairly easy to do and they are not too expensive to replace. The guides are a much bigger job to replace.

The rattling is not uncommon with older tensioners which tend to leak when the engine is shut off and take a few seconds to pump back up. The fact that it only lasts a few seconds would seem to point to this. If it was the guides, or potentially an IMS problem I would not expect the noise to go away.

Do you have a Durametric which would allow you to check the timing/advance of the cams?

 

I don't have a durametric. I do have snap-on scanner

 

IMS retrofit already done. Are you referring to the tensioners from IMS to cams or crank to IMS?

 

The Snap-On scanner won't read the cam positions like the Durametric will. Given that you already have the IMS upgrade (LN i an assuming) then I world look toward the tensioners. Many times these are done with the IMS upgrade. It would be more likely the IMS to Cam tensioners if you are hearing chain rattle. If you are going to pull them to have a look remember to lock the engine at TDC. The one on the drivers side is easy to get at. The one on the passenger side takes some work to get at.

Where are you located? Maybe there is someone in the area with a Durametric.

 

Yes, I used the LN bearing for the IMS upgrade. I am located in Houston. Should I check the timing/ advance of the cams prior to changing the tensioners?

 

I don't think you have anything to worry about or look into. As I remember there is a thread concerning that "rattle" and as stated in the thread it is a "normal" occurance as the tensioner builds pressure. Someone who owned their car from day 1 even commented their car did it from day 1.

 

I have owned two 99 996s and they both did it. I had a mechanic listen to it at the local Porsche dealer and he said it is normal. That was many happy thousands of miles ago.

 

I have the same rattle... took it to Porsche they said its a normal rattle for every 996!

 

Very likely the noise you hear is normal and nothing to worry about.

The chain tensioners bleed down and upon engine start the chains have some slack and drag across the guides and make a sound like a chain being pulled over a log or large piece of finished lumber.

If the noise is present for just a moment upon a cold start, and is not present upon a hot start and there are no other signs or symptoms of something amiss the odds are very high the noise is nothing to worry about.

But if you are concerned or just want a pro's opinion take the car to pro and leave it over night and have him start the engine and report his opinion.

An oil change can reduce the amount of noise because fresh oil is more viscous (has less thinning due to unburned fuel and water comtamination). And more frequent oil/filter services can keep help keep this noise down simply because the oil gets changed before the contamination builds up to the point the noise results.

But even so if you let the car sit long enough it will rattle its chains a bit upon cold start.

Sincerely,

Macster.

 

Thanks for the feedback. I will rest easy as the noise may even be less than a second in duration on stone-cold start only. Being slightly obsessed with my new ride, any noise gets my attention. and since I am only about 120 days into my 1st 996, my learning curve is still steep. Love the process!!!

 

Don't ever go under the car while its running, it will drive you crazy! At lest it did me. You hear so many weird noises you never heard before, thats when you really start worrying.

 

You just had to tempt me.........

 

I'm a newbie to the Porsche world and I did make the mistake of crawling under the car with it running after an oil change. These engines are noisy: especially when echoing off the concrete. They weez, rattle, tick, click and some sounds I cannot describe. But from the driver's seat, it's all music!

 

j-mann, congratulations on your new to you 996. It is a gorgeous color combination and those wheels look perfect on it. Enjoy! Having never owned an aircooled 911, how does it compare?