996 Turbo Engine Knock Comes and Goes

Hi Our 2003 Turbo has developed a knocking noise at idle. It's ok when cold, but when up to temperature, there is a distinct knock knock knock sound which seems to cycle. It will knock say 10 times then go quiet for a few seconds then knock again. Doesn't matter if clutch is depressed or not, and disappears with revs. Any thoughts on what it could be? Sounds to deep annoys to be a rapper I think. Thanks R

Knock or rattle? Probably heat shields past their sell by date?

Any chance of a sound clip or video? - would be useful.

Oil scavange pump almost seems random. Same with any dry sump engine. Disconcerting for someone who hasn't heard a dry sump engine before.

Thanks for your responses. It's definitely a knock. I replaced all the heat shields when I did the turbos a couple of years ago. If it is the scavenge pump, then I fear it's on its way out as it's never sounded this loud before. I will try to get a sound clip.

Can you pinpoint with a mechanics stethoscope? How many miles has it done, the timing chains can get quite rattly at idle.

So I checked the oil level which was in the middle of the read out. (Don't know why I didn't check that first!)I topped up to full and the knocking has disappeared! So looks like it could be linked to the scavenge pump not liking the level st full.

Get your oil changed and analysed. It shouldn't knock at half full, it doesn't sound good to me. Get it checked out before you put miles on thinking it's ok.

You may be on to something here. The noise returned, so have had a poke around with the mechanics stethoscope! The sound does seem to be coming from the scavenge pump on the drivers side. These seem to rarely go wrong, but the noise definitely wasn't there a while ago. I've drained the oil and pulled the filter apart. A few very tiny metalic parts in the filter which are non magnetic and a couple of small flexible brown slithers of either tensioner guide or sealant nothing out of the ordinary according to the internet. So, what's next. Are these pumps known to make this noise? Do i pull the pump and inspect for any damage? Do I refill with new oil and see how it sounds when warm? If still there then pull the pump and check filter again? Could it be a problem further down the cam/sprocket from the pump with the sound eminating from here? Loads of questions I know, but would. I'm erring on the side of pulling the pump, but I'd like to court opinions.

You need to put pics of the filter on with the particles you describe if you want any proper help dude. Equally I wouldn't take your interpretation of what the internet says as gospel - its a bit like trying to diagnose a medical condition through google... Personally I've never had any brown slithers of anything in any of my oil filters on any cars, let alone my porsche's. Edit: To spell it out: The chain guides fall apart when you dismantle the engine so they are well known to wear. The last thing you want is a disintegrating chain guide, reduced tension on the chains (which is why the noise could go under load), and then it slipping a tooth and ruining your engine.

Ok. Finally got time to take the pictures and post.

Get the oil analysed to see whats in it. Are those plastic bits hard? There quite big.

Yep they look like bits of guides to me. I wouldn't be driving that until a good indy has had a look at it fella. :thumb:

I'd say you need to perhaps consider opening that engine up, stripping it and go through each component to check its still in spec and replace anything that isn't. Horrible but far cheaper than a rebuild if its goes pop. I'd certainly not start or drive the car again until this has been done. Whilst you're at it be rude not to rebuild it with stronger rods, GT3 oil pump, forged pistons, better headstuds and better turbos. One for 9e or ES? Sport and Classic or Porsche Torque are also worth a shout if you're not bothered about upgrading it.

Yep. I've decided to drop the engine for a proper look. Had a pm conversation with Ken at 9e. Very helpful chap. Just need to break the news to the wife as it's (was) her daily!!