996 cold start rattle

Hi, I've got this rattle on cold start. It sounds much worse in the video than it actually does in reality! 3.4 engine. I'm thinking it's timing chain related, but would be interested in your views. It doesn't use any oil, doesn't smoke, the tailpipes are clean and the engine sounds lovely after few seconds once the rattle clears. The oil was clean on the last change, the filter clear of debris other than two or three tiny pieces of dark plastic material (possibly chain guide material?) Has anyone had a similar rattle? What do you think? Cheers. https://www.youtube.com/watch?v=u9RT2k236Lk

It's always hard to diagnose a problem through a sound clip but to me it sounds more like a tapping than a rattle, and sounds a little like the tappets pumping up? I have had chain rattle before on a V8 Audi S4 and that was definitely more of a rattle sound? If it is chain rattle your tensioners may be losing pressure and once pumped up are re-tentioning the chain?

As Chris says it sounds too heavy to be cam-chain rattle. That's usually a 'brraaapp" sound for a second or two at cold start. Sounds more like a sticky tappet/lifter but it's not consistent in its timing so I'd guess maybe not. Is it only at cold start? Those engines do sometimes make a sound like piston slap at cold start but the engine usually starts perfectly with no noise then after a few seconds the knocking comes on gradually, fading in and out for a minute or so before disappearing. I say sounds like piston slap as I don't think it actually is. Even my mates Hartech rebuilt car does this so it's nothing to worry about. Again though it's not as pronounced as your noise. The only way to get a definite answer is to get it to a decent Porsche mechanic unfortunately. Good luck. :thumb:

I've had my enginer rebuilt with new tappets ~10 000km ago and it sometimes does the same thing. If you keep the revs up at ~1200 there's no noise, and it also disappears within 2-3 seconds. If the engine is warmed up at all, there's no noise either. I talked to the shop who did my rebuild and they said it's normal. Just happens on some engines.

Mine makes exactly the same noise on a cold start. After 10 seconds or so at idle it disappears and won't show up at all if I drive off straight away. Won't show up again until the car is stone cold. No smoke, no oil consumption etc. Got a little more frequent when I moved to a thicker oil - Millers 10W50 - and during winter. Doesn't really do it much in summer. I guessed it was tappets, rather than something more sinister, and my mechanic agreed after he'd heard it himself. Don't think it's anything to worry about.

Yes, mine started making the exact same noise last year and i made similar recordings. I did take it to my local indie who said it was lifters, but I'm not 100% convinced as it makes that non-regular noise. Anyway i decided to block the noise out of my head, and now I'm not focussing on it as a sign of impending doom it seems quieter

a porsche specialist told me to try nanotech or nano drive as its good for the noisier engine. Worth a shot

Thanks for all of your replies, it's much appreciated. It's the not knowing what it is that's the biggest worry! I don't want to spend time and money replacing the wrong things! I'll keep an eye/ear on things for a while and see if it gets any worse, or maybe just buy a louder exhaust!

Hi IMHO I agree it is not a chain. Tappet is favourite for sure. You could run an engine flush through the engine, but read about it first. Best of luck. Berni

At timing 0.4 seconds its a single tappet , from about 0.6 seconds the noise alters and i would suggest its another tappet .. both are sticking a bit . As to whether any work is required .. i would say just monitor it for now or if you haven't already done so and are concerned then get your local garage to have it over night and a listen from cold .

Thanks everyone. My first post on here, so it's great to have had lots of helpful replies!