17 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHHowdy Folks! New to me Porsche 996 owner
Leading reported evidence
Inspect .....fingers crossed
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
I will post the results after I get the car next week and have it inspected.....fingers crossed.
Leading evidence: 'Inspect .....fingers crossed' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'case' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check oil and filter' (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.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
I know, most used car buyers are supposed to do a thorough inspection before buying anything, ESPECIALLY a Porsche.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that suspect a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suspected cause · Original poster
I sent the video to a local Porsche-only shop and they are the ones that told me that was very likely the case, but of course would need a full inspection to confirm.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
I'd not start it until you check the oil and filter for glitter.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
If the cats are bad, I will probably have both replaced along with an LN engineering bushing solution kit.
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
What's encouraging to me is that my mechanic says it sounds just like a cat going bad and that he probably would have noticed movement in the RPMs if the engine was getting hung up by the IMSB (of course, this is only based on a video he saw of it running).
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
case
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that suspect a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suspected cause · Original poster
I sent the video to a local Porsche-only shop and they are the ones that told me that was very likely the case, but of course would need a full inspection to confirm.
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.
17 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T163944Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hello,
Just bought my first 911 996. I am new to Porsches and to German made cars in general. All of my collector cars have been American Muscle (63 Corvette conv, 68 Camaro conv), which I love, and my daily drivers have been Toyotas.
I've ALWAYS wanted a 911 and the 996 seemed within my price range, especially this one...
So I found a 1999 996 Carrera 2 conv with 59K miles, that appears to have cat issues. The owner sent me a video of the car and it sounds like ball bearings are banging around under the car. She thinks it is the engine tearing itself apart, which turned me away at first, but there are no warning lights on the dash, it is holding nice and steady, 1k rpms at idle, and no smoke on the exhaust. Revs perfectly. She wants nothing to do with it and pretty much sold it to me for scrap value. I know, most used car buyers are supposed to do a thorough inspection before buying anything, ESPECIALLY a Porsche. But this car has meticulous maintenance records, Carfax and Experian Autocheck show no damage history, accidents, etc. I know it's a gamble, but I am willing to roll the dice on this one. Feel free to disparage me for being a fool but I feel pretty good that it's just a bad cat (or both). I sent the video to a local Porsche-only shop and they are the ones that told me that was very likely the case, but of course would need a full inspection to confirm.
Anyway, the way I see it I will either go up in smoke or hit at least a double on it. If the cats are bad, I will probably have both replaced along with an LN engineering bushing solution kit. I'll probably have the clutch set replaced as well while it's open. Total cost will be in the 5K range I think.
I was thinking for a trouble free IMSB car, the LN mod is the best one to get, so can anyone speak to this? Also, I prefer a quieter exhaust but am all for maximizing performance, so taking recommendations on what cats/exhaust to get installed.
I will post the results after I get the car next week and have it inspected.....fingers crossed.
Thanks for reading and thanks in advance for any recommendations,
OJT
I say for scrap value I would drop the cats and see of that fixes it. If that fixed it I would run with some cat deletes or used cats for 6 months until it is shaken down and go from there.
Long stretch from dropping cats to dropping engines and doing powertrain upgrades.
The owner of the car tells you she thinks the engine is tearing itself apart (gee ya think maybe she actually knows something, or a mechanic told her that?) and you just "roll the dice" on the hope that it's the catalytic converters? The M96 idles at around 780 rpm not 1000... how long did it idle at 1000 rpm? If the engine really sounds like marbles/ball bearings in a can I wouldn't recommend running it AT ALL until you tear the motor down. If you absolutely must run it, please take a video and post it here...
It all depends on the starting point and whether you are OK with it if the diagnosis comes back as needing an engine. This is the worst case. $20K for the car + $25K for an engine is a bit much (right now) for these cars. If you got it at a 'roller' price, maybe you make out, $5K for the car + $25K for the engine, with meticulous service records. This is a pretty good deal.
I can't comment on exhaust options. I'm in California where every environmental step you take is monitored closely.
Good luck!
These cars are super fun and eminently capable. You'll be addicted very shortly.
Before you run the engine any further, first step should be to pull the oil filter. Post pictures of what you find in the filter when you cut the element apart and stretch out the material to see what's in the pleats.
On my old C4S I had a cat go out on me. I can confirm the sound of a bad cat out of nowhere is a horrifying experience. Immediately my head went to very bad places, but it was pretty easy to identify that the cat was the culprit. A set of X-pipes later and it was all good. It isn't doom and gloom every time, but def be careful.
Thanks all,
I appreciate the responses. Oh, trust me, I will pull the cats off before I ever turn the key, that's for sure. If the noise remains, she'll be headed straight for the shop on a flatbed. Even it the noise goes away, I will be driving it to the shop after swapping the cats for a full inspection and to have the bearing replaced. Any opinions on the IMS LN bushing kit or other kits? If it turns out being the cats, I will definitely keep the old ones to share my findings. I will also open up the oil filter either way as well (good advice, thanks).
What's encouraging to me is that my mechanic says it sounds just like a cat going bad and that he probably would have noticed movement in the RPMs if the engine was getting hung up by the IMSB (of course, this is only based on a video he saw of it running). He added that the gauges were solid steady with no warning or caution lights, oil pressure, temp, RPMs all perfect (looking closer, looks like they are slightly below 1K, maybe 800-900?). Also, the owner said the noise came out of nowhere, with service performed just 200 miles prior to the noise "incident". After it happened, she stopped driving it and it hasn't moved since. I've heard stories where the IMSB gives some warning noises before failing and other stories where it is instant and catastrophic with 0 warning. If anyone who has experienced an IMSB failure (or impending failure) is reading this, would you mind sharing a bit about how it happened? I'll be searching the forums to see how they typically fail.
Before I committed to purchasing, I got prices for the rebuild as well, and if the core is good/rebuildable I was quoted 13-15K to rebuild. I guess Texas prices are a bit lower than CA prices.
At 15K I think I would be slightly better than breaking even, especially with a fresh motor, clutch set, IMSB, etc. A used 3.4 is around 8-12k and a new/rebuilt long block is 15k plus install, so 20K.
Anyway, thanks again, always great to have some encouraging words, whichever way things go!
Regards,
OJT
You got some eggs on you, son. For what its worth, ball bearings rattling around in the engine isn't necessarily the IMSB. It could be you're hearing piston knock from bore scoring or something else got loose in the engine, like a timing chain issue. Either way, not that these cars are jinxed, but rarely is the problem as cheap or simple as putting new cats in. But good luck, I hope it is!
Not sure if I'm an outlier here, but I've never heard cats, even those going/gone bad, sound like jumbling ball bearings. Sure there's rattling if the honeycomb falls apart, but from my experience it's never been that aggressive.
Could you share the sound clip by chance?
The ***** in a coffee can sound can also come from the chains hitting bare metal due to tensioner pads being worn, a scavenger pump disaster, or any number of things.
All of this is speculation. Any metallic sound in the engine is simply not good. If it�s cats, that�s called �your lucky day.�
59K miles and the cats are bad? I'd not start it until you check the oil and filter for glitter.
What you describe is the exact sound the motor makes when eating itself.
