993 TT timing chain rattle

[markzb]

Hi everyone

I have a 1997 twin turbo 993. I have a problem during startup of which I hope someone may offer some advice.

When the car is started up in the morning, or after sitting for a few hours, it sounds like a flapping timing chain based on the sound I hear.

It last for litteraly 0.5 seconds and then it is silent. For then on, and under all driving conditions, there is no more noise. I gather that as soon as oil pressure builds up, then the rails are tensioned and all is well.

But as of late.....there are some starts ( say 1 in 5) where the rattle now lasts for about 1 second...and that is a very worrying and painfully long 1 second!

The car has done I would estimate 35K miles. I say estimate because when I got it, the mileage meter wasnt working.

So.....how do I determine if I my problem is with the tensioners or the being chains too long, or worn rails?

Is there some sort of measurment in terms of rail position with regards to timing chain case that enables us to determine if the chain is worn?

Anyway to test the tensioners?

Appreciate any insights at all.....

Many many thanks

mark

[WERK I]

Have you used a stethoscope to isolate it to the chains? I was wondering if maybe it isn't the hydraulic lifters not building up pressure to take the lash out of the rocker/valve clearance. Collapsed lifters make the same noisy mechanical noise when cold and the oil is not flowing through them as it should.

[Wayne 962]

What type of oil are you using? Is it coming from one side or another?

-Wayne

[markzb]

Hi Guys

I thought the 993 did not have hydraulic lifters. I am using Mobil 1 engine oil. I am not too sure which side/s its coming from as I havent had anyone else start it!

My suspicion is that I have a faulty timing chain tensioner. Does anyone know how I can test then? Do they ever fail, this style tensioner?

Thanks guys!

[WERK I]

Yep, the 993's were the first to utilize hydraulic "dampers" in the rocker arms. The 993's do not use the Carrera style hydraulic chain tensioners. They use a spring loaded ramp to maintain chain tension. That's why it doesn't make sense that the noise is coming from the tensioners only on startup. The 993's tensioners would always be noisey since they are not dependent on any type of oil pressure.

[Bill Verburg]

I agree the most likely culprit is 1 or more hydraulic lifters, John Dunkle posted some pics on Rennlist when he replaced his
993 lifter repair Sounds more like a metallic rap(IMHO) though

The 993's do not use the Carrera style hydraulic chain tensioners. They use a spring loaded ramp to maintain chain tension.

While not Carrera style they are hydraulicly tensioned.

[WERK I]

Originally posted by Bill Verburg
Sounds more like a ra(IMHO) though

While not Carrera style they are hydraulicly tensioned.

Excellent, Bill. I stand corrected. I just pulled out Bruce Anderson's description on the tensioner and missed the sentence on the oil feed for them.