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996 C2 Rattle on Cold Start

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Old 03-22-2013, 12:08 PM
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Z4k26
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Default 996 C2 Rattle on Cold Start

Hi,

I have a 992 C2 cab and have been getting a horrible rattling noise from the right side of the engine on cold start up. Rattling lasts about 3 seconds then goes. I had it looked into and was advised to change my chain and cam tensioners, expensive! But I did it! Although slightly improved on the noise it is still there!!! I am now confused as to what the cause could be and how to resolve. Many thanks in advance if anyone can help Z
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Old 03-22-2013, 12:13 PM
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Originally Posted by Z4k26 View Post
Hi,

I have a 992 C2 cab and have been getting a horrible rattling noise from the right side of the engine on cold start up. Rattling lasts about 3 seconds then goes. I had it looked into and was advised to change my chain and cam tensioners, expensive! But I did it! Although slightly improved on the noise it is still there!!! I am now confused as to what the cause could be and how to resolve. Many thanks in advance if anyone can help Z
Remove the serpentine belt and start and idle the cold engine just long enough to confirm the noise is present or absent.

What you hear or don't hear determines what you do next.
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Old 03-22-2013, 12:42 PM
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Thanks Macster. I will give this a try. May I ask, how is this potentially linked to the noise? what are the likely outcomes?
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Old 03-22-2013, 04:31 PM
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Good to know

Last edited by M3BimmerBilly; 06-03-2013 at 09:58 AM.
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Old 03-22-2013, 05:51 PM
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Chain tensioner, keep the oil level up to the top line on the dip stick. My '99 makes the same noise on the drivers side and it is quieter when the oil level is at the top line.
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Old 03-22-2013, 06:32 PM
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Had a rattle on the right side too...turned out my exhaust tip was loose.
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Old 03-22-2013, 07:00 PM
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Like most problems with the 996 Im just going to wait until the engine blows up.
Well thats comforting.
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Old 03-24-2013, 01:26 PM
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Many thanks guys. Going to try Mobil 1 and see if its a problem with the oil getting through. Def not the exhaust tip this time. I will report back. Thanks.
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Old 03-24-2013, 02:13 PM
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Originally Posted by Z4k26 View Post
Many thanks guys. Going to try Mobil 1 and see if its a problem with the oil getting through. Def not the exhaust tip this time. I will report back. Thanks.
What oil are you using now?
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Old 03-24-2013, 04:40 PM
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Hi Alpine003, last top up was Shell Helix 10W-40. I am not sur eif that is causing the issue? the noise was there before i topped up with this oil.
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Old 03-24-2013, 05:47 PM
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Originally Posted by Z4k26 View Post
Thanks Macster. I will give this a try. May I ask, how is this potentially linked to the noise? what are the likely outcomes?
What starting and running a cold engine sans the belt tells you if the noise at cold start is coming from a noisy accessory drive or idler/tensioner roller or coming from someplace else.

That someplace else could be inside the engine or it could be from a loose spark plug, and exhaust leak, and exhaust system rattle or a loose heat shield.

If the noise is absent when the belt is removed then the possible causes can be a noisy idler or tensioner roller. The ones on my 02 Boxster are original and have over 265K miles while my 03 Turbo developed a noisy idler roller at 45K miles. It didn't rattle though but instead made more of a well, dry bearing sound.

Or it could be a noisy water pump. The Boxster water pump died (so to speak) at 170K miles. It didn't rattle though but made a low growling noise. However, the water pump can be in varying degrees of failure and as a result they can make different noises.

With the belt off you can check all accessory drives and idler/tensioner roller bearings for any looseness. You have the water pump, alternator, A/C compressor, power steering pump and the one with any play is the suspected bad one. Most often it is the water pump.

If you take the belt off be sure you know how to put it back on and put it on so the belt runs in same direction it did before you removed it.

With the belt removed and the noise still present then you have to consider calling in a professional. To correctly pinpoint the source of the noise and thus be able to advise you what you do next.
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Old 03-25-2013, 07:24 PM
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Thanks Macster, got it. I am going to give the removal of the belt a go once i try the oil change. I will report back.
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Old 03-29-2013, 06:12 PM
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a combo of:

Changing the Cam tensioner
Chain tensioner
switching to mobil one 0/40
replacing the serp belt

has improved the rattle alot, but it still exists!!!

I am now going at the oil pump and will report back
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Old 03-29-2013, 09:05 PM
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I have heard that lifters can cause that too. I replaced all my tensioners and it made no difference on my car.

If I don't drive my car for for a couple of weeks or so mine does it too.
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Old 03-29-2013, 09:12 PM
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I had a persistent start up rattle, both hot and cold, for just a fraction of a second. I changed the bottom chain tensioners and tried oils from 0-40 to 20-50 with no change.

Last oil change I went to Red Line 5-40 and the rattle is much better, probably 80% less. Its still there from time to time but much better. I guess our motors like pure ester (group 5) oils.
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