22 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH996 C2 Rattle on Cold Start
Leading reported evidence
Replace oil
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Discussions that performed work without a confirmed outcome
1
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Leading evidence: 'Replace oil' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check accessory drives and idler/tensioner roller bearings' (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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Check accessory drives and idler/tensioner roller bearings
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Discussions that contain suggestions
1
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Suggestion
With the belt off you can check all accessory drives and idler/tensioner roller bearings for any looseness.
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Suggestion · Original poster
I had it looked into and was advised to change my chain and cam tensioners, expensive!
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Suggestion
Last oil change I went to Red Line 5-40 and the rattle is much better, probably 80% less.
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Unsuccessful attempt
As I noted earlier in this thread, I replaced my tensioners with new ones due to the rattling on a cold start up after my car wasn't driven for a week or more. It made no difference.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
22 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Generation: 20261026T163944Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
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.
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.
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 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.
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
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.
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.
I recently had a similar experience with redline oil.
As I noted earlier in this thread, I replaced my tensioners with new ones due to the rattling on a cold start up after my car wasn't driven for a week or more. It made no difference.
A couple of weeks ago I did an oil/filter change with Redline 20-50. I started it for the first time since the change this morning. No rattling. In fact the motor is very quiet with hardly any mechanical noise at all compared to before.
I was using Mobil1 5-40 before the Redline change.
I also sent an oil sample drawn from my oil filter housing to Blackstone for analysis. They said it looked great, but thought it was a 5-30 weight oil. I have heard the warnings about pulling the sample from the housing, but I would rather hear what the worst case scenario was, which there wasn't one.
Your car may run hotter in stop and go traffic with that 20 weight oil. Keep an eye on the temp gauge. I can only use 0W40 in my '99 or the car turns into an inferno. I'm in Arizona where it's as hot as hell.
I know 20-50 is a heavier weight than recommended. But part of the problem is, manufacturers specify low viscosity oils to increase their fleet fuel economy numbers, to their knowing detriment of engine life or performance. I don't own this car for its fuel economy. In fact I was heavy footed on my last tank and only got 11mpg!
My car has never had any issues with running hot in the past, but I will keep my eye on it with summer around the corner.
Is your cold start rattle still gone after the change in oil type/brand? My C2 rattles when cold for about 60 seconds at idle or not at all when driven immediately. I've run Mobil 1 0-40 and 5-50 with similar results (rattle is present).
My '99 C2 has a completely rebuilt engine with the best of everything. It made the very same noise under the same conditions before the build and still after the build.
From what I understand it comes from the exhaust lifters which leak down because they hang somewhat upside down.
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