Engine problem - bent valves

A few months ago I finally found the persistent coolant leak on my car, it was a loose hose clamps that I could not find until I used a coolant system pressure tester. Then I had it back on the road for a few days. Seemed to be running fine, no unusual noises and good power. I was out one afternoon and stopped by Advance Auto to ge something for another vehicle. I was there for 10 minutes or so and when I came out the engine would not turn over. Seems to be a dead battery. Tried a booster they had, a jump start and another battery but it did not seemed to turn over. Finally I got it to turn over and almost start but it was making a ticking/ knocking noise so I stopped and called my roadside assistance and had the car flat bedded to my house. When we got there I tried the key one more time and it started but had the knocking noise so I turned it off after only 5-10 seconds. We were busy getting our house ready for sales so I left it parked for a month or two. Oil and coolant were clean, no contamination. finally a week or so ago I had some time so I removed the serpentine belt and turned the engine over by hand with a ratchet. It would revolve 360 degrees but would catch at the same angle every rotation. With a little more pressure it would click and then rotate another 360 degrees and catch again. Thinking it was something in the valve train I decided to drop the engine to determine what it was. I removed the transmission and put it on my engine stand (after removing the pressure plate and flywheel. It still caught at the same position of rotation. First I removed the cam cover, cams, lifter and lifter tray on both sides. From the exterior the valves looked fine. I tried the boroscope that I bought but could not really see much. So yesterday I removed the 4-6 head and discovered that all the valves were bent. There was slight marking o. The tops of the pistons but no scratched bores, broken valves or other visible damage. Today I removed the 1-3 head and everything on that side looked good. With the heads removed the crankshaft seems to turn fine. So now I am trying to figure out what caused this? This is a five chain engine. The 1-3 cams are driven off the IMS end of the half shaft which also has the sprocket/chain fro. The crankshaft to the IMS. It would seems that the 1-3 cams where rotating properly and not out of sync as the was no damage on the 1-3 side, which also indicates that the IMS/crankshaft chains sprockets were intact. I have read about how they are a pressure fit on the IMS and these sprockets can loosen. now I am thinking about the sprocket on the oil pump end of the IMS. Is this also a interference fit on the shaft? If so could this sprocket had come loose and the 4-6 cams stopped rotating letting the valves hit the pistons (note that all the exhaust and intake valves on 4-6 have come into contact with the pistons and are bent)?. This seems to be the only thing that I can think of that would have caused all the bent valves. Or could the timing have slipped enough that in a few rotations all the valves would have hit the pistons and bent the valves? Unfortunately you can�t see much on the oil pump end of the IMS, nor really on the IMSB end and the only real way to see what happened is to split the cases which mean almost a full rebuild of the engine to repair the IMS by pinning the sprockets if that is the problem. So I am looking for any insight that others may have on this problem. For those of you that may have followed my threads I the past you may remember that in 2008 I had a cracked head with extensive intermix. I had the head repaired and have gotten another 12 years and 50,000 mile out of the car when at that time I was told that the engine had to be replaced.

Hi Doug, it sounds like your IMS sprockets have indeed slipped. Check the bank 2 scavenge pump, and timing chain, if a piece of timing chain roller comes off and lodges in the scavenge pump, it will exert tremendous force in the IMS sprockets. A certain engineer here has claimed the scavenge pump drive snout was designed to break off to eliminate stress on other parts, but that is not the truth.....

Both the bank 1 and bank 2 scavenger pumps seem fine and I have not found any debris or visible damage I. Either bank other than the bent valves. I am thinking that the only way to determine is the oil pump end sprockets slipped is to split the cases. In theory I could fix the 4-6 head and reassemble what I have disassemble setting the timing. But if the sprocket has slipped it is bound to happen again. Ironically I have a 1-3 head that is new, never installed, but the damage to the valves is on the 4-6 side.

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Did you disassemble the bank 2 scavenge pump and check it closely?

No as it turns freely but I will disassemble it to check.

Sorry to hear of your trouble, I agree with Porshetech 3, my first impression when I read your post was a slipped IMS sprocket. Also agree with your assessment that repairing the bent valves would not address the slipping IMS sprocket issue, and you would probably find yourself in the same predicament after all the work is done. Pinning the sprockets would appear to be the only solution. Amazing how many "gotcha"s these engines have. Best of Luck.

Wow... bummer! Look at it this way - you're 50k miles ahead of the game! I think it's time for a rebuild (if you've got to split the case halves, why not go all the way?). If the cylinders are in good shape, there's nothing saying you have to go the full "Nickies" route, but it's definitely worth consideration... Good Luck

I hate to hear you're having trouble, Doug. Hopefully, you'll get it sorted out quickly.

By the way, the front bumper looks outstanding! I'm glad we could make that happen.

We had a boxster with a new engine once that had this happen twice but not as bad...first time we though it skipped a tooth. No damage though....then it happened again but out of warrantee. Since the first one happened during warranty, the shop sent it back to builder to pin gears. No cost. Anyway, you have done so much for us here on this thread, I have two 3.4 heads you can have, just pay shipping. They are off my engine that lost a rod bearing and broke the case but the valves look fine. Where are you located?

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Wow, you gotta love the community support with guys like this on the forum!!!

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Yep, I believe you are hitting the nail on the head! Mike

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here are some pics

I am truly impressed by lowpue's offer to Dharn55 and salute his generosity! Both of these members have offered this board loads of sage advice through the years and we're lucky to have individuals of this caliber on whom to rely when things go sideways. Well done!

I am a believer in you have to give to get....And just to be clear, I am happy to give to contributors to the forum who make it a very positive experience. Darn55 is definitely one of those. So I am just paying forward for another 10 years of knowlegde he shares... Assuming of course he wants my stuff. Thanks for the kind words though.

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I am in the Chicago area. Really only need the 4-6 head as I have a new 1-3 head that has been sitting in my workroom for years. I would be happy to pay the shipping!!

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PM me and let's close this out.

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You are so close you should just Drive your IMS over to LN's shop.

So an update on the problem with my engine, an answer on what stopped the cams on the 4-6 head from turning resulting in the bent valves and I am sure caused the sprocket on the IMS to slip. I had already removed the heads and yesterday I did a little more disassembly preparing to split the cases m(by the way I bought the DVD's by Raby on assembling an M96 engine in prep for doing all the work that will need to be done) including removing the paddles for the IMS to cam chains and found this! The remains of a green cam plug was stuck on the IMS sprocket jamming the chain! So I can now see what caused the problem but am mystified on how this happened. A little background on the car. I bought it in August of 2000 with 4,000 miles on it, it was originally sold in February of 2000. I never had any major work on the engines by the dealer or a shop. Then in fall of 2008 I had a major intermix, parked the car until spring of 2009 when I dropped the engine to see what had happened I started with the 1-3 head, taking off the cam covers and removing the cams, lifters and lifter tray. That is when I say the crack in the head and sent it to a shop in California for repair. When I reassembled the engine and started it up I had one of the expansion plugs in the end of the intake cam on the 1-3 side pop, I think it had been deformed by the homemade too I was using to secure the cams in place. Having the expansion plugs pop out is one of the modes of failure that FSI has found and I could not find a replacement expansion plug so I took off al the cams on the engine, both the 1-3 side and the 4-6 side which involved removing the cam cover on the 4-6 side, and having the ends of each cam threaded for threaded plugs. I put everything back together including new green plugs at the cam covers. I had never removed the 4-6 head prior to the last few weeks. I never lost a green cam plug, always removing them from the exterior of the engine. I then set the timing and then put in new green plugs. Since that time it has been 11 years and 50,000 miles and I never had a problem. Then I did not drive the car much from the fall of 2019 until last summer due to a persistent cooling leak that took me a while to find. Found the leak with a coolant system pressure tester, it was a loose hose clamp in an area you could not readily see, fixed that and was back on the road for a few days and it was running fine and then suddenly the engine was not turning over with the starter and had a clicking noise when turned over by hand.so I parked it for a couple of months until I had tie to drop the engine again. And as noted earlier that is when I found the bent valves on the 4-6 side. So here is the mystery to me. The last time I had any green cam plugs out was 11 years ago and 50,000 miles ago. And as I said i don't remember losing any green cam plugs and I would certainly have noticed if one was forced into the cam cover.. And if you have worked on one of these engines you would know that if a green can plug was pushed into the cam area there is really not much room for it to go farther in. But lets say my memory is faulty, or somehow a green cap was "lost" in the engine at the factory, it still would have been in there for either 11 years and 50,000 miles or 20 years and 100,000 miles before this happened. So and am truly mystified! Looking forward to your comments though. In any case I am going to split the cases with everything that involves to see the IMS, look at the sprocket for damage, see if it is slipping, etc. I think I will use the other IMS that I have, have LN pin the gears and start reassembly. What a trip.

That defies all reason, the only answer // "Porsche Gods"

Truly amazing! As you mentioned, little to no room between the plug and the end of the cam. I would agree with your hypothesis of a rogue plug lost during factory assembly that had been there all the while and finally found its ultimate repose. Far fetched indeed, but how else to explain it?

I actually pushed one of the green cam cover plugs in too far (The engine was in the car and I was reaching up from underneath, trying to make sure it was properly seated and I got a little ham fisted and pushed it in... Oh S*IT! It took me a couple hrs to fish it back out (I was amazed that I got it out) but I was finally able to get a hooked pick on it - right through the center hole - and pull it back out... There's not really a lot of room for it to go anywhere, but I suppose if it bounced and sloshed around long enough it could make it's way between a cam chain and a cam lifter and cause some havoc.

In this case it was not chain between the two cams or these sprockets. It was the chain between the exhaust cam and the IMS. There is a little more room under the cam plug but if this cap was pushed in you could try to retrieve it by removing the scavenger pump. But I know that I would not have ignored it if I had pushed one in. I think the source of this cap is going to remain a mystery And between the time and gasket sets head bolts etc etc it will cost $1,000-$2,000 and that doesn't include the time as I am working for free🤪

So is this another thing to add to the list of catastrophic engine failures? lol. That seems like such an odd thing to happen but I don't know enough about these engines.

I have seen them pop out, but not go in like that.

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i should be be clear that all 6 of the plugs were in place when I dropped the engine so the one caught in the chain/sprocket was inside the engine. And as I said the last time I had the engine apart was 11 years and 50,000 miles ago.

So are you able to use the heads i sent you?

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i havent got that far yet yet but I am sure I will, and the IMS too. Hoping to find the time to finish the disassembly this month but we are in the middle of moving so between that and work time has been short. Thanks once again for your generosity!

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No problem....its win-win...you get a big break on cost to fix and i unclutter my garage....now if i can just get rid of my extra sets of 996 and 991 wheels, wife will be happy.

The human factor caused this green plug to enter the engine. Someone needs better component control. I’ve found all sorts of stuff inside of virgin engines.. Extra wrist pin clips, extra oil crankshaft thrust shims, and O rings. In every case the wrong guy had been there.