2003 996 C4S ENGINE LOST COMPRESSION

On Friday after Thanksgiving I was heading out to go up to Newcombs on ACH and my C4S gave up on me. I was getting on the freeway (curved entrance) getting some speed, going up the gears. Running the revs to kissing the redline, and at 4th gear the engine lost power, the dash lit up like a Christmas tree so I pulled off. When I stopped the engine died. I let it sit for a minute then tried to restart. No codes, but engine was turning without compression. The car was up to running temp when this happened. I would never run that hard out of the garage. Engine has 43K miles, IMS was done in 2011. Car was well cared for with regular oil changes prior to my ownership. Water pump was done like 500 miles ago. Shop thinks the engine is done. Possibly a broken cam or chain. Obviously I am shocked.

what IMS replacement was performed? Most IMS replacements have a replacement interval of less than 13 years unless it is one of the pressure fed bearings. I would do a leak down test and turn the engine by hand. If it has zero compression on all cylinders, that would probably be due to the engine timing being off and bending the valves. There is probably not a simple solution to this problem. DO NOT spin the motor with the starter until you check it out further. Sounds like it will require an engine tear down.

Ims gear slipped on the shaft?

Quotes source post: 19780124

That's a really good guess and would account for loss of compression across the board. Unfortunately requires a complete tear down of the engine. Reason why FSI/LN pin the IMS gear to the IMS shaft.

This is the repair done from the records I received.

Dont think the bearing itself had anything to do with that repair. When an imsb goes it has very different symptoms then what u have going on. Gonna take some forensics.

Just a few preliminary guesses based on the circumstance you provided about the entrance ramp and high revs... 1. oil starvation/thermal runaway...First thing is check the oil filter and sump for metallic debris 2. dropped exhaust valve seat..common on this year model especially if overheating......Pull spark plugs and scope for piston damage 3. Scavenge pump locked from small debris that will cause chain reaction of broken timing chain and/or IMS gear to slip on the shaft.......Remove scavenge pumps and inspect for damage and free rotation... Any and all of these are bad news...sorry ...

Sounds like it might be time to build a 4.0! Thanks for the pointers. Will be working with a shop to help diagnose. Will update when we have more to share.

43k? That is astronomically insane. There�s something going on with these cars, I�m telling you. op assuming you have taken care of it, I can�t believe this just happened out of nowhere. really sorry to hear this. Hope you get it back on the road sooner than later� you didn�t money shift the old girl did you? �we won�t bite.

Definitely no money shift. Kind wish I did. At least that would explain it. I have only had the car for a few months. Had it inspected and didn�t find anything to indicate deeper issues. Prior owner had solid records. Just could not drive it anymore due to age/health issues.

You have to rip it to the bones to find out why.

Seems with what he explained and what folks are posting, he should have heard some loud noises coming from the motor. Was that the case? If he dropped a valve or spun the timing (piston/valve contact) which all could have occurred, he would have heard it. Also, if he truly has no compression, I would think it's catastrophic...like a hole in the motor or something bad allowing it to spin so freely? Just a thought.

How do we know there is no compression? Did you do a compression test? Any smoke? Surely there would be smoke. Was it a long, right turn? IIRC long right turns do these cars in on track days. very curious!

The only confirmation of no compression is that the engine is turning without any resistance (compression). Shop suspects #3 & 4 - will confirm with scope and comp test. The music was on kind of loud when I was driving. I felt the loss of power then turned down the sterio as I was pulling off the road. If there was a loud noise, I didnt hear it when it happened. Length of the turn was just a short entrance ramp. Maybe 4-5 seconds tops.

That's where I'm confused. Car should still fire even if one or two cylinders has low compression. I guess no compression at all is what is throwing the red flag for me. It does sound like it is.....very bad. Sorry this happened to you again. I feel for you.

Yep, experienced Mechanics can hear an engine spin over with 0 compression and tell.....there are actually test equipment that test "dynamic compression' by analyzing battery amperage draw during cranking to determine compression, and with ignition input can pinpoint individual cylinders with low compression just by the amperage/sequence.... That said, anything that causes a total lose of compression at high RPM will have a cascading chain reaction what will require a full tear down to asses any/all collateral damage.... so sorry... but the forensics are always interesting ..please share...

Quotes source post: 19782253

If the Ims has spun or a chain broke u may not hear anything abnormal and the car wont start. A spun ims gear or a broke chain means the cams dont move, if the cams dont move the valves dont move, if the valves dont move its possible for a bunch of the cylinders will be open. Good luck.

That�s just horrible luck. It does sound like a broken chain with no cylinders giving you any feedback. At least it�s the engine that gave up and not something with your health.

if spun ims i am going to blame unnecessary imsb replacement and blame the fear mongering (and **** everyone off in the process...again)

Sorry to hear this happened. Agreed with others, pull the filter and drop the oil pan to see what's hanging about. Cause is prolly easy from there. But happy to hear you are already planning the upgrade! These are such fun cars, and when you put the extra HP in, they get even better. Good luck with the fix/upgrade!

Quotes source post: 19782564

U really need to pull one of these motors apart and really look at them. The bearing replacent has nothing to do a press fit gear slipping on the shaft (eventhough they r located in the same spot). Its just one if the things that go wrong with these complicated motors. Its rare, more rare then a imsb failure but it happens and its something u fix by pinning when performing a rebuild.

Quotes source post: 19782974

Glad you responded to this as i was thinking the same thing . I couldn't get the connection between pressed on Sprocket on the shaft and replacement of the bearing .. unless something happens and deforms the shaft slightly as you are using the slide hammer to pull the bearing out ? I dont have one handy but is the bearing inside the hollow shaft right where the pressed on sprocket is ? and you have to pull the bearing with your slide hammer past the sprocket ? .. Worth at least thinking about for sure ..

it absolutely changes things. when u pull the stock bearing it puts stress on it. not saying that's what caused it, but if op confirms ims skipped gear u just have to wonder. the car has 43,000 miles. like, come on.

Quotes source post: 19783348

exactly.

i have said it a thousand times. no one on this board incl me obviously is a better engineer than a team of german engineers. 1% of dual row imsb's failed. 4% of single row. previous owner of op's car pulled a perfectly good bearing. edit- and again we don't even know what's wrong with the car lol so op pls keep this thread updated when u figure it out...cheers

Quotes source posts: 19783348, 19783388

If you're using a slide hammer to pull the IMS bearing, then you're using the wrong tool. No slide hammer is required for pulling an IMSB. This is all you need: https://lnengineering.com/products/t...ion-tools.html ..and a ratchet, socket, and pick.

regardless of what tool you use it puts stress on it

Quotes source post: 19783348

The bearing is on the outside of the other end of the intermediate shaft from the pressed on sprocket. My IMS with the bearing (IMS Solution) facing the camera. The small sprocket at the far end is the pressed on one that needs pinning.

Quotes source post: 19783406

Actually this one doesn't. It counter holds the shaft so the only stress is on the bearing being removed, not on the sprockets. This is similar to what's commonly used for wheel bearings.

Quotes source post: 19782304

If that was the case there would be some valves in the "open" position and some in the "closed" meaning whichever ones are open would have contact with the piston crown, so you would hear the "hit" unless I'm missing something........

Thanks for all the continued comments. Shop confirmed ZERO compression on bank 1. Pulling the engine out next. We wont have a further update until they get it out and pull it apart. Estimated to be January at this point. They have 2 engine builds a head of me. So, the parts shopping begins! 3.8 or 4.0?? hmmm

I doubt an IMSB replacement done 13 years ago would suddenly become an issue today. Anything suspect there would have shown up a long time ago.

Anyone in the market for an 76' Ice Green Metallic Coupe slick top - need some funds lol

Quotes source post: 19783930

Right, of course the IMSB replacement done 13 years ago has nothing to do with a possible broken timing chain or slipped IMS sproket... FWIW a broken timmng chain or slipped IMS sprocket is usually cased by the Scavenge pump locking due to a small piece of hard debris... The Scavenge pumps are driven by the timming chains and IMS... when a small piece of hard debris enters the Scavenge pump and locks it one of 3 things can happen....(1)The drive snout of the Scavenge pumps breaks off and the pump stops turning ( this is the best case as it causes no further collaeral damage unless you are on Track In many high G turns) (2) the timing chain beaks ( this causes bent valves or worse as broken valves/pistons)..(3) it puts excessive torque forces on the IMS gears causing them to slip ( has the same collateral damage as broken timing chain) Also this is the reason Top Engine builders of the M96 put screens on the inlet of the Scavenge ports ... Since this thread has gotten deep with a lot of false info..one more thing need to be addressed... the IMSB failure rate .... I laugh every time I see someone say the Failure Rate is "ONLY 1-8%" ....lol All large manufactures have a Six Sigma Methology in place nowadays....The Six Sigma strives for a successful Failure Rate of just 0.000034 %... Toyota Started the JIT ( Just IN Time) manufacturing process in the 1950-1960's ..and Motorola started the Six Sigma Methology in the 1980's..... Porsche incorporated the JIT and Six Sigma with the advent of the 996/986 cars with the help of Toyota.......Does some of the Porsche part meet the Six Sigma Standards of 0.000034% ? Yes they Do !!! Does the IMSB meet the Six Sigma Standard ?? Hell no !! ....The IMSB should be changed to the IMS Solution,...... if had been used during production we would not even be taking about it or spreading false info about it... Anyway I'll be very interested to see the forensics on this failure....

Quotes source post: 19783600

U would only hear them hit for the first couple of rotations and at a couple hundred rpm the interfearance will create new clearances and be silent. Hence by the time your brain even comprehends what has happened there will be no noise.

Quotes source post: 19783948

that's the easy way out... not sure if u have the funds but BTC is about to take off...u buy one whole btc now and it'll be around 110/115 by Christmas. That's ~$10-15k. lol I completely missed the 13 years ago part. edit- actually the car still only has 43k on it so I still stand by it being a possibility. Number of years has nothing to do with it. You should buy 2003 996 Daily driver - Rennlist - Porsche Discussion Forums and put the c4s away for a while until you figure it out.

Quotes source post: 19783981

PT3 from left field yet again! Tech Q&A - Imsb Failure Odds | The Porsche Club of America Porsche IMS bearing failure: settlement reached - Ferdinand Eisen v. Porsche Cars N. Am., Inc., Case No. 2:11-cv-09405-CAS-FFMx | Casetext Search + Citator

Quotes source post: 19784115

You Missed the whole point..again.... I know all about the Class Action Law Suit..... Would you honestly play Russian Roulette with say a 100 round revolver with 90-99 empty chambers and 1-10 live rounds? Put it to your head and pull the trigger ? I don't think you would !! ....... but that is exactly what you are doing to you engine if you leave it as factory designed............I would say you don't care about your engine ( untill it is too late) ,, or are just being naive ..

pt by now u should know I'd play russian roulette with 9 live rounds / 1 empty and still hedge a bet on it working out in my favor. we should really meet up in person, grab a beer, hash this out and play some pool. let me buy you a couple beers and shoot the ****. then u hire me as a uaos sales rep and watch me sling those things like hot cakes

An engineer and a salesman walk into a bar�

Quotes source post: 19784261

and pt tells the bartender "thanks but I don't drink"

Quotes source post: 19784258

I'll definitely take you on that !! ....I know just the bar that will let you play Russian Roulette , they won't even mind cleaning up the mess if your luck plays out.... But I could use a UAOS sales rep ....so I hope your luck holds...

Quotes source post: 19783981

The 1-4% number(of failures during warranty period) was what was quoted by Porsche during the court case. How many IMS bearings have failed since then? I'm sure the percentage is higher, much MUCH higher 10+ years later. Of course some engines failed due to broken chains, oil starvation, money shifts, hydrolocking, and bore scoring...so that helped the IMS numbers some.

Quotes source post: 19784078

Well at least this subject is not controversial at all I am fortunate enough to have a few other toys in the toy box, that this one being down isn't too rough, but don't tempt me please......haha...I have a problem.....

Quotes source post: 19783666

Whats the rough cost of a rebuild vs doing a LS swap?

I�m not sure. I know others have researched this and posted here in the past. I think I remember it being around same or a bit more to do LS all in. I could be wrong. It�s not an option for me even if it was 5k.

Quotes source post: 19783981

W. Edwards Deming is da man! I have his book on a shelf down in my 'office'. It's one boring piece lol. I've worked at corps that implemented (or attempted to anyway) all of those quality undertakings. From what I saw only Deming's original work was worth the effort, although the later stuff was in the area of software and networks and it was honestly pretty hard to get a good measure of effectiveness. But yeah, in general I agree, 1% failure within warranty period is unacceptable, and has been for decades. Sad to say that no one seems to care anymore.

Quotes source post: 19793302

I agree 100%.. What kills me is the people who quote the 1% ( for the dual row 99-2001 and the 6305 2006-2008) and 8% ( for the 2002-2005 6304) as being worth the risk... Having worked in Dealerships for 50 years I can say that those figures for cup holders and headlight bulbs are no big deal...they have no chain reaction collateral damage....but when speaking about the IMSB it is a HUGE failure rates due to the chain reaction and collateral damage that can wipe out 20% of the value of a new 996, and that's when engines were cheap and the car values were high...Now that the car values have depreciated, and the engine costs are much higher, a failed IMSB can wipe out 80% or more of the value of the car !! Like I said.. I have worked in Dealerships for 50 years and have seen nothing like it... Simple flaw-----huge consequences---simple fix----I don't understand why so many people don't understand this....

I seem to remember while in Lean Manufacturing training the story of when the first Kaizen expert when he walked into the engine plant at Porsche. He, allegedly, stepped in and loudly exclaimed something to the effect of: "This is a warehouse it is not a manufacturing plant..."(too many parts laying around). I bet that went over like a ton of bricks with the German workers.

Decided to sell the car as is. It�s a clean example for sure. Just needs someone willing to bring it back to life. Not me at this point. $28K w E88�s and Ohlins R/T - $20K stock suspension and twist wheels. Shop had some guys out sick so they had not gotten around to pulling the engine. Gave me time think and I am going to cut bait and move on. The extent of the damage is still unknown. Could be an LS swap candidate.

Quotes source post: 19862683

First of all, sorry to hear about the engine. I haven't read back through every comment and so please forgive me, but did you at least drop the sump plate to see if it's contaminated with metal debris? My gut tells me it will be full of metal based on your description of the events that unfolded. And I cant blame you for cutting your losses and parting with the car as-is. My advice would be to put it back to stock. You might find selling the E88 wheels alone will bring a better return instead of offering a package deal. The big challenge is getting to your price of $20K. Basically we're talking about a roller here no matter how you slice it. And, the most respected shops (e.g. Flat 6 Innovations) that rebuild the M96.03 S engines are going to cost north of $25,000. That's a hard pill to swallow on such a low miles engine. Can you imagine if this was a 986 Boxster. Those guys are in the same boat and worse when their engines go boom. Most of those guys don't even blink and just sell the cars off as parts. I've seen them marketplace all day long for under $5,000. Crazy. Thankfully, there is strong demand for the C4S and so maybe someone will offer you close to your price, but you have to be ready to make a decision to take less since so many 996 rollers are sold for under $10,000. How is the overall condition of the car? Paint, any dents?, interior? Clean CarFax??? All stock inside? Another option is have your shop install a used M96.03 engine.... OR purchase a short block from Porsche and go from there.

I really appreciate the comments. @ZuffenZeus This was was a low mile original car 43K miles. Very clean. No issues on carfax, or autocheck and clean title. Paint is amazing, no dents. Interior is very nice too. Leather is in great shape. Such a shame with the engine. I am prepared to part it out but wanted to offer a package deal to this group. We have not dropped the sump. My guy said its likely full of debris. We discussed a used engine but you really do not know what you got so it needs to be partially disassembled to ensure its a good one before you spend labor with the install. At that point why not just dig into mine. We already know it needs to be rebuilt, just not how bad the damage is. Its lots of work either way. Maybe someone has an engine and needs a chassis? Or the LS swap (eek)

I hate you have decided to throw in the towel, although in your case I don't really blame you...Its a hard pill to swallow... I was really looking forward to the forensics, but I know that even forensics costs money and take time to do properly...But being in this business for over 50 years I have seen enough forensics to know what the usual causes are ......And it is pretty common to just throw another engine in or sale "as is" and not investigate or do forensics....... IMHO 43K miles may seem very low miles to most people, ....but haven driven ultra high performance cars as daily drivers for decades and even street/track events,..... 43K miles is enough to have participated in 86 Daytona 500 events !!! .........So it really all depends on how the previous owners treated the car and maintained it ......and even the most meticulously built competition engines can fail from a $2 part ,, I have seen more failures on meticulously built competition engines from $2 parts that I can shake a stick at.........Most failures on $100K NASCAR engines during the races are due to a simple valve spring breaking and the chain reaction destroys the engine..... Good luck on selling as is and moving on and I hope you have better luck with your next car ...

I can appreciate that perspective. There is still a chance I build it if I can�t sell it at a reasonable price. There has been some interest already. So I�m hoping. Haha