Winterreise

Ok, I have made another very short video in which you can hear a little of the knocking sound. The engine recorded here, is not completely cold but you can still hear the sound I am wondering about.

Thanks to all,

Bob

Winterreise

One last video with the car much warmer. Sound is greatly reduced and insignificant to me. Just wanted some thoughts...

Ahsai

Ok, so based on your testing the noise is not generated by any of the pulleys. It's unlikely the cats (like others have commented) but you can use a long screwdriver to verify when the noise occurs. Just touch the cat with the screwdriver and put your ear against the screwdriver. If it's the cat, it will be very obvious. Also, have you checked if all the spark plugs are tight?

Macster

The initial noise could very well be a loose converter brick.

If an engine ticks cold with thick oil that even though cold flows very quickly -- in just a moment -- throughout the engine at cold engine start generally it will tick with the engine hot and the oil pressure -- at idle at least -- down to may be less than 2 bars.

Not sure I'd advise you use a rubber mallet, unless you are gentle with it. Use your fist to thump the exhaust system listening for a loose brick, or anything loose, really.

The converter brick is rather delicate and if a brick isn't loose now it may be after you go at the exhaust with a mallet, even a rubber one.

My Boxster had a deep knocking noise that I attributed to a crankshaft with excessive end play. Figured with over 280K miles on the engine things were wearing out.

But the deep knocking noise would go away as the engine (and exhaust) warmed up. Once fully hot the car buzzed like it had a loose heat shield but there was no knocking.

I had the car in for something else and I asked the tech to ID the noise and fix the loose shields. Frankly I had my doubts the buzzing noise was really shields, but I wanted the tech to tell me that.

And he did.

So while he still had the car I picked up a pair of used exhaust manifolds at a salvage business. Before handing over my AMEX card I gave them the shake test and both were quiet. I held on to them too after I gave them the shake test cause sometimes people treat these rather rough.

The tech installed the used manifolds and the buzzing noise was gone, but so too was the knocking noise. Cold the brick knocked about then when hot I guess there was less clearance so all it could do was buzz.

I suspected the brick was the culprit for some time as every once in a while the CEL would come on -- sometimes I'd go months and months with no CEL -- and the error code (P0430) indicated something was amiss with one converter. However, the engine and its converters still passed its emission testing every 2 years.

But I sure enjoy the peace and quiet of the "new" converters.

essjayarr

I also have a '99 and listened to your video. My car does the exact same thing for a few seconds only on the initial start of the day. My car has 71k miles. Rennwerk in NY did an IMSB, clutch, aos and looked the car over at about 67k miles.
I'm not stressing about it, but will keep an ear on it.

FirestarterTR

Hello all;
I am hearing same noise just for 3-4 seconds @ cold start.
It occurred after new tensioners inserted.
We could not be sure because here are no authorized dealer or service.
So we ordered chain tensioners with Engine type, not VIN or Engine No.

Could anyone help me in this forum can tell me exact tensioner part number for my engine?
And also place of that tensioner?

My car is 99 - 996 Carrera2 3.4