Hey guys. My car makes this knocking sound on a cold start when the car has sat for several days/weeks. Only does it for a few seconds and then gone. Looking at the oil pressure gauge, it will sit at 0 for those couple of seconds g that the knocking is going on and then shoot up to 4bar and the sound goes away immediately so obviously oil related. I talked to my mechanic and he said it is no big deal and that when the car sits for awhile the oil drains away from the lifters and it takes a couple seconds to repressurize the system. This diagnosis makes sense to me, but figured I get some other perspectives. Is this bad for the engine? Do any of your cars do this? I took a video of it so you can hear the sound it makes. Thanks for the help.

http://www.youtube.com/watch?v=i5e3uja3Rx0

 

your mechanic is correct...they all do it...worse the longer they sit...plus the motor is cold so all the clearances are larger...if you heard it on a restart when the engine was warm or the car was recently driven it would be a different story

 

+1 and spot on.

 

Thanks for the relieving comments. I just wanted some reassurance since no other car I've owned has done that. I guess it's just because these engines are such raw beasts. I never noticed the noise for a couple months because I was driving it more frequently when I first bought it but now that it tends to sit for longer periods of time, it's become noticable. It has never made that noise when warm so guess I won't worry about it.

 

Yep..I'll record mine on sunday, starting her after a week, and you'll hear the same sound..

 

Many people seems to have this problem including myself.... There was a TSB from Porsche #1728 mentioning the replacement of the check valve at the bottom of the oil reservoir to fix this lack of oil pressure on start. (See picture) I did the replacement of this valve and got the same problem after. See http://forums.rennlist.com/ /turbo /996 turbo and do a search for "Brief clatter at start up" from timf. I explain the complete installation of this valve on Rennlist. My next attempt is going to be another type of oil. I am using Mobil 0w40 and will switch to Castrol Syntec 5w40 also approved by Porsche.....

 

I think even with a properly working check valve the oil will drain off the lifters anyway causing the noise...A more viscous oil will probably last longer in the lifters.

 

What I do is remove the fuel pump fuse (C4 by the drivers left foot), and crank the motor over a few times to get the oil circulating. Don't let the starter crank and crank, just some 5-10 second bursts with a cooldown time in between. Then put the fuse back in and start 'er up. I personally think that without combustion, there is much less wear by circulating the oil this way instead of by just starting the motor.

 

I would guess since these cars are between 5 and 10 years old now, that if the noise were causing serious problems that there would have been a lot of talk on how to fix it. My thought is that hearing that type of noise means extra wear on engine components which is something to be avioided, but since nobody seems to be worried about it, and there are plenty of cars that have plenty of miles and approaching a decade old without documented problems with the lifters indicates it's probably not an issue.

A fix for the issue could be to do like race cars do and add a compressor to pressurize the oiling system prior to engine start. Just a thought

 

A fix for the issue could be to do like race cars do and add a compressor to pressurize the oiling system prior to engine start. Just a thought[/quote]

or....drive it every day

 

Or at least once a week man! Get out and have some fun!

 

You are worrying to much!

 

maybe I'll just try and drive it more. It is really just a weekend car for me. I guess I just won't worry about it. I took it on a good cruise this weekend and it ran great!