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Discussion summary
YOUR RESEARCH996 Startup Rattle
Leading reported evidence
Replace ims
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Performed · outcome unconfirmed
IMS was replaced 15k miles ago along with the clutch, RMS and air injection pump by the previous owner at a very reputable indy.
Leading evidence: 'Replace ims' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Clean engine oil' (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
In 2001 Porsche changed the IMS drive chain tensioner to a new design with a preload spring to reduce noise from chain slap.
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Performed · outcome unconfirmed
I added a can of Liqui-Moly this afternoon and ran the engine at idle til it warmed up.
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Suggestion
This is the tensioner next to the oil filter & is very easy to replace, be sure to pump up the new tensioner with clean engine oil before install.
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Suggestion
If you still have simular rattles you probably have 1 or more clogged tensioners & or lifters that need to be removed & inspected for wear & purged of debris & dirty oil or replaced.
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Suggestion
If you still have simular rattles you probably have 1 or more clogged tensioners & or lifters that need to be removed & inspected for wear & purged of debris & dirty oil or replaced.
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Pelican Parts: 1 discussions
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Generation: 20261026T130754Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Has anyone experienced any kind of engine "rattle" sound on first startup?
This is a 99 model with only 50k miles. The "rattle" only occurs after sitting overnight or longer.
The noise goes away immediately, and never occurs again the same day.
I was told this is a characteristic of the first generation of the Variocam system and is not something to be concerned about.
Any comments or documentation available to confirm or deny this?
Len
My 99 C2 does the same thing. It goes away in a few seconds. A 996 guru on another forum says "It is normal." I think it might have to do with the light
0W-40 oil too.
The rattle you describe is very common & often caused by a chain tensioner leaking oil overnight or clogged with debris. In 2001 Porsche changed the IMS drive chain tensioner to a new design with a preload spring to reduce noise from chain slap. This is the tensioner next to the oil filter & is very easy to replace, be sure to pump up the new tensioner with clean engine oil before install. This usually reduces the startup noise considerablly not to mention the excessive wear it causes. If you still have simular rattles you probably have 1 or more clogged tensioners & or lifters that need to be removed & inspected for wear & purged of debris & dirty oil or replaced. Changing to 5w- or 10w- viscosity oil helps minimize overnight leakdown also.
The chain tensioners have been replaced w new, but I don't know if they are of the latest design. They were purchased from our local Porsche dealer.
Do you know the PN of the new design?
The rattle is still there, and still only at morning startup. Any time during the day there is no rattle.
We have also tried different viscosity oils, from 0W-40 Mobil 1 to 15W-50 Mobil 1. Same noise only at morning startup.
Len
Common for lifters to bleed down causing noise on 1st cold start.
Also there is an air injection pump that only runs on first cold start, for 10-30 seconds, but that is usually a "squeal" or "Vacuum cleaner" noise. The pump lives near your left knee when you are looking into the engine bay. Have someone cold start it while you look, feel, listen to the pump.
Using a stethoscope, the noise is definately coming from the chain area. With new tensioners giving the same result, we are tearing what little hair we have out of our heads.
What has Porsche done to upgrade the tensioners and variocam sprockets since 1999?
Wayne, can you suggest anything we can check?
Len
Bumping this to find out a solution.
I have an early 99 C2 that has developed a loud rattle at startup, sounds like it is coming from the left bank, and it remains but quieter at idle, but disappears when revved a bit, only to return at idle again.
IMS was replaced 15k miles ago along with the clutch, RMS and air injection pump by the previous owner at a very reputable indy.
No CEL or running issues otherwise, just that noise that scares the H@LL out of my checkbook
I added a can of Liqui-Moly this afternoon and ran the engine at idle til it warmed up. Shut it down and let sit for a few hrs and started back up much quieter. I did look underneath and there is seep oil on the main tensioner (32mm nut) and one drip on the driveway from it.
Planning to change the tensioner, oil and filter, and do a compression test this weekend.
I had the IMS done, new chain guides and tensioners, the works...and there is still a slight rattle at start up after sitting overnight. Some noise is pretty normal. It's hard to judge when loud is too loud.
