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YOUR RESEARCH99 996 C2 88k cold start noise
Leading reported evidence
Install used manifolds and the buzzing noise was gone
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Performed · outcome unconfirmed
The tech installed the used manifolds and the buzzing noise was gone, but so too was the knocking noise.
Leading evidence: 'Install used manifolds and the buzzing noise was gone' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'culprit' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check any free play and bearing noise' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
One thing I forgot to mention in the video is that one of the chain tensioners was replaced by ROCS in NJ last year along with a new coolant reservoir and cap.
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So while he still had the car I picked up a pair of used exhaust manifolds at a salvage business.
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Suspected cause
But I hope is it's not the OPs other suspect culprit...
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Performed · outcome unconfirmed · Original poster
One thing I forgot to mention in the video is that one of the chain tensioners was replaced by ROCS in NJ last year along with a new coolant reservoir and cap.
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Suggestion
Can also unplug the SAI pump (so it won't drown out other noise) and run the cold engine with the belt off for a minute or two to see if the noise is there.
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As described in this morning's video that I made, my C2 is making a little noise for about 1 minute total when starting cold. One thing I forgot to mention in the video is that one of the chain tensioners was replaced by ROCS in NJ last year along with a new coolant reservoir and cap. Being the 5 chain engine design (M96 Mk1) I don't know which tensioner it was.
Please have a look at the youtube video and thanks so much in advance for your comments.
Bob
https://www.youtube.com/watch?v=YlG-...ature=youtu.be
That's a very nice video with the detailed intro. A few observations
- your battery voltage looks quite low at ~11.5v but the alternator looks good as the voltage jumps to 14v once the engine is running
- there seems to be a yellow warning light ON?
- the SAI pump fan noise was quite obvious but that's normal
- there is some rattling bearing noise, which sounds external. You can remove the serpentine belt and hand spin each bearing and pulley to check for any free play and bearing noise. Could very well be the water pump or one of the idle pulleys, or the aternator. Can also unplug the SAI pump (so it won't drown out other noise) and run the cold engine with the belt off for a minute or two to see if the noise is there.
I have the same year and model with almost 74000 miles on it. I do all my own DIY apart from dropping an engine or gearbox. At first as you got the camera nearer to the engine I could hear something different to what I hear. Kind of a clack/clicking sound. To me a loose pulley sound or maybe a chain slap. This I am told is normal for a cold engine. Then as mine warms up it goes away as yours does. .. Again you have the same thoughts as I do. Maybe the water pump pulley. Remove the belt and try all pulley's. I never heard or felt a loose pulley on mine. I had seen the smallest of water drip onto the floor under the pump as the car cooled down. Therefore I changed the pump and thermostat. No drip afterwards. On cold start, same noise as always which quiets when warming. I am told on rennlist this is normal. I always let the engine warm for at least 5mins. Sometime even 10/15 minutes winter and summer. I have the original IMSB double race bearing. Not that THAT matters in this case. Just saying. Lets put it this way. Mine is louder when cold than it is when warm/hot so I would not worry about yours. I also keep my eyes on my gauges and ears pricked for any changes to the normal. My answer to you in one. Don't worry. It's normal but keep those ears and eyes open anyway. Safe driving and real nice looking car.
Hello all:
So, I finally took some time to do a few diagnostic tests to see if I could isolate the source of the noise. I removed the air intake, bought a 24mm wrench and loosened the tension pulley, then removed the accessory belt. I spun all of the pulleys and all of them were smooth and quiet, including the water pump. I then started the engine (cold) with the belt still off, let it run 15 seconds before the clacking noise started as before. The car has had chain tensioners replaced in the last two years, not sure which ones but two of them had been done. The PO was probably trying to source the problem as I am. As explained earlier, the IMSB is one year old, an LN dual row. The original bearing was fine...
So, I am thinking chain slap noise until the tensioner involved fills with oil and stretches the chain taut. I have the M96-Mk 1, so there are 5 chains in this version. After one minute, the engine is quiet. The other thought is that one of my CATS is rattling. Tonight I will use a rubber mallet and tap on them both to hear if there is a different resonance between them. No CEL, no oil pressure anomaly... All normal and functioning beautifully except for the cold start noise.
All suggestions welcome and appreciated!
Bob
Didn't listen to the video but as far as a suspect cat, I don't think the rattle will go away as the engine warms up. I had a bad cat and the rattle would appear whether the engine was cold or hot.
I am aware that many 996 owners have this quirky issue with engine knocking-pinging-ticking sound when those engines are cold. The Porsche Service manager in Rochester New York, where I'm from, says that these first-generation water cooled engines make a bit of noise until the oil circulates and the oil pressure activates the tensioners. So, I'm just not sure if ignoring this is appropriate or not.
I can not longer check your video but based on my post #3 at the time, I don't think you should ignore it. Oil circulates almost instantaneously at start up, at most a couple of seconds. Your noise is way after that if I remember right.
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
996 start up noise - YouTube
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?
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.
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.
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
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