Sloth

I have noticed that when the car has sat for a few days w/o being run it makes a rattle sound when first started. The sound only lasts a few seconds and oil pressure reads normal upon startup and everything else seems normal. My own thoughts is that it might be the hydraulic valves pumping up, but would be curious to know if anybody else has this. My GT3 has done this since new.

I have been out of town getting hitched and on my honeymoon, hence my 3 week absence. So needless to say the GT3 has not been run since 9/15 and I know the sound will occur when I start her up. Any thoughts would be appreciated.

Ed Newman

My 996 rattles sometimes, mechanic thinks it may be the cat.

Steve in FL

Sloth: Well I'm still waiting for my GT3 but my Boxster does what you describe. My understanding it's the hydraulic lifters/cam followers/whatchamacallits. Supposedly one reason Porsche now uses multi-viscosity oil with 0W on the low end of the scale is so that they quiet down faster.

Viken

As Steve stated, it's the hydraulic lifters and this is normal in any car after it had been sitting for quite some time. The lifters rattle until oil pressure is built around them.

Sloth

Thats what I thought. Thanks for the assurance guys.

TNGT3

Yes, normal sound. However, my exhaust sounds pretty wicked if I have not driven it for 5 days or more. Actually, I kind of like it. It is very raw sounding until it warms up. Has anyone experienced this?

rockitman

Mine rattles too Sloth. Glad you asked the question and that it is normal. I was wondering about it myself and I thought it was the cold cats rattling...

Mr. C4

Sloth,

My Gen. 1 GT3 CS makes a hell of a lot of noises also after it's warmed up but that's just GT3.

On start up, after sitting for a few days, there is a 4-5 second rattle/thumping/grinding/purring noise which I actually suspected (still suspecting) being the starter motor bendix gear not dis-engaging from the flywheel. Now, when I hear of all other Gen 2 GT3's making a start-up noise, I do no longer know what to believe. The car has been in at the dealers and the ignition barrel is being changed after the starter was found to be OK, they suspected that a short in the ignition barrel could be causing the bendix gear not dis-engaging. I'm confused!

Ciao,

Johannes E.

RR

Sloth I know exactly what you are talking about.
The exhaust sounds wicked until it warms up and then, like a switch it quiets itself down.
I wonder why this is?

Viken

When you start a car cold, the fuel mixture is richer to allow the engine to heat-up quickly. After a few minutes, the mixture stabilizes itself and the engine gets a little quieter.

clord

I have 2K miles on my GT3 and have the same audible experiences as noted above. During warm-up, the fuel mixture is richer, as Viken says, the idle RPM is raised slightly and an auxilliary air pump is activated to help heat the cats. I speculate that all that rich burning and extra air is popping/burbling in the exhaust/cats and making that sound. As noted above, it quits completely when the air pump stops and the idle drops to normal. Transient hydraulic lifter clatter after a long period of inactivity is different, but entirely possible on a flat engine too.

colin.plastow

It could be the cam chains. My 99 C2 consistently makes a noise when started after sitting for a few hours. I asked the dealer to check out the noise when it was in for it's recent 96K (KM's) service. They sort of off handed said that all they could hear was the chains. I said "that's probably it what's the fix" their comment was that they had a bunch of 996's in the shop that made way more noise than mine and that it wans't unusual. Sure enough the comment on the worksheet from the mechanic was "chain noise, quite common". I guess the hydraulic tensioners bleed down after a while but pump up pretty quickly as the oil pressure builds. Looking at the parts on PET it looks for all the world like there may be an adjustment of sorts but I'm assuming not if they didn't suggest/ do it. I really wish I had service manuals at times like this. I guess it's just one more of those little idiosyncrasies that we put up with on a Porsche that probably wouldn't be tolerated on something more mundane.

blake

I wanted to resurrect this thread as my GT3's "clatter" has gotten louder. A local shop that services GT3 Cups was concerned, and had me take it to the Porsche dealer. They looked at it today and think its the lifters, but want to do further diagnostics tomorrow to see if it is a real problem... I have less than 30 days remaining on my warranty....

I'll keep you guys posted. Wish me luck.

-Blake

Martin Bishop

I complained about the same rattle as mine was going out of warranty in April as well. They removed the cats and found them destroyed. The material could almost be poured out. The Master Tech said he found it quite common on cars that were run at higher RPMs such as tracked cars.

I have yet to get a very cold start on the new cats yet, plus the LWFW makes it's own noise but have high hopes

1999Porsche911

It is not normal and does not happen to all GT3's. Your valvetrain should not "rattle"; EVER. Depending on how long the car has sat and what oil you are using, you may, occasionally, get a light "ticking" of the valves until they get pumped up, but nothing at all that will even remotely be confused with a rattle coming from the valves.

There are many parts of the car, external from the engine that can cause a quick rattle or vibration sound at startup. They inlcude the license plate vibrating agianst the body, cats, mufflers, etc. The air pump can also vibrate at startup.

A test you can perfrom that may help you identify whether it is oil related and internal to the engine, is to pull the fuel pump fuse and crank the engine for several seconds. This will pump up the valves as well as lube the chains which are also suspect in startup engine rattle. Reinstall fuse and start the car. Is there a change in the noise you are experiencing? If there is no change, suspect something external.