Third-Reef

I know the chain rattle on start up is somewhat common. Especially in the non Mezger 996 motors and is associated with tensioner leak down. My 99 C4 with 140K miles on the original motor did it anytime it sat for more than a day. So i was quite pleased when i got my 996TT with 45K on it and it did not do it. Well it has started now at about 65K. If i leave it for more than about 4-5 days it does the startup rattle. Just did an oil change with 5-50 and made sure to replace the o-ring on the oil filter stem (the small one) and it made no difference. The tensioners look like they are easy to get to on the Mezger motor. Is there a fix for this? Or do i just need to live with it?

fpb111

Read through this thread for some more info on this.
https://rennlist.com/forums/996-turb...ine-noise.html

Macster

My 2003 Turbo does this when I let it sit a few days. It is more likely to occur when the car is used in hot weather, which we have had recently.

I note as I let the engine idle before shutting it down the oil pressure drops some to under 2 bar which tells me the oil is plenty hot. (The oil is "fresh" with not even 2K miles on it and is 5w-50 oil.)

What I suspect is happening is with the elevated ambient temperatures (in the triple digits during the day) and with the oil very hot when the engine is shut off the oil bleed down at various areas is a bit "worse" than usual and this accounts for the noise at the next -- few days later -- start up.

If I use the car the next day the noise is not present.

Just an incentive to drive the Turbo more often is my thinking.

Third-Reef

High temps are definitely a part of this. It gets to about 120 - 130 in my garage when it is 106 outside like it has been recently and i notice that the rattle happens in a day or so rather than 4-5 when it is normal temps.

Kevinmacd

You sure its mot the hydraulic tappets?

Third-Reef

It not a tickity tapity noise. i had ticky lifters on startup my C4 with 140K on it and i am familiar with the sound. This is more rumbly slappity. Adjective factory at work here.

mffarrell

Could you post a sound clip?

Third-Reef

I will try. Its tough to not drive it.

fpb111

Really, spend a little time cruising this thread.

https://rennlist.com/forums/996-turb...ine-noise.html

Third-Reef

If you look closely you can see that I posted several times on that thread. It also is about the mezger rattle. I have that too and have come to grips with it and it's probable cause. This is a different noise.

Third-Reef

Finally got a recording of the chain rattle after the car has been sitting for a week. this is with 5-50 M1 in it with about 2K miles since oil change

996 turbo startup.mp3

jpflip

I got exactly the same noise but I think it is coming from the valve tappet. When cold start, the oil pressure needle stay down and a couple of seconds later the pressure rise and the noise stop at the same time....Is it your case?

Third-Reef

Yes my OP is down and then pops up. I think that the OP has the same effect on the chain tensioners. It does not sound like lifters to me.

"02996ttx50

i have exactly the same disconcerting and wince producing noise during startups in very hi temps, if the car has been sitting for days. it's as if the oil has all drained away and it's the sound of metal components that are temporarily unlubricated until there is proper oil pressure. thankfully, its momentary but its awful and seems to be mitigated *somewhat* by using 5/50. i think it's "normal".

agree also with third reef. this is entirely different than the typical "chain rattle".

Kevin

A quick cure to quiet down the start up lifter rattle (when the car sits for days or weeks)

Pull your fuel pump fuse and crank the start for 6 to 10 seconds..

With lifters "pumped up" >>no noise