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YOUR RESEARCH03 C4S engine failure - update with cause
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Run poorly (and cam codes)before you heard the big pop
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Suggestion
With both cams on bank 2 being out of time, and the engine running poorly (and cam codes)before you heard the big pop, it clearly indicates the gears slipped on the intermediate shaft.
Leading evidence: 'Run poorly (and cam codes)before you heard the big pop' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Run poorly (and cam codes)before you heard the big pop' (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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Run poorly (and cam codes)before you heard the big pop
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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
With both cams on bank 2 being out of time, and the engine running poorly (and cam codes)before you heard the big pop, it clearly indicates the gears slipped on the intermediate shaft.
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.
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All,
Sorry for not extending older thread. It was getting long and difficult to manage.
I took the Bank 2 cam cover off today and the scavenge pump has ingested what looks to be a steel washer of some sort.
This led to the pump seizing and shearing the pump drive off the end of the exhaust cam sprocket.
While on the face of things this is a good thing I have two issues.
1. Where did the washer come from and are there more parts
2. Where is the shrapnel from from the oil pump and cam sprocket.
On the upside it does look as if we did NOT lose the timing chain but recall this whole issue started with intake cam over retarded and poor idle.
It may yet take a complete engine disassemble to find the true root cause.
I will update as I find more,
David
Debris. Suspected Variocam lifter retention ring.
Debris
Case of pump blown out.
Drive key sheared off
You can just see debris at top of lobe.
Cam sprocket oil pump drive sheared off.
With both cams on bank 2 being out of time, and the engine running poorly (and cam codes)before you heard the big pop, it clearly indicates the gears slipped on the intermediate shaft.
The big pop you heard while starting the next time was the scavenge pump/exhaust cam drive breaking, due to pump trying to lock up.
There are no washers inside the m96 engine that I can recall, I usually see a piece of chain roller shell, or a piece of valve spring that gets sucked up in the scavenge pump to lock them up.Pics would be helpful here..
The debris/shrapnel from the broken drive, if not laying in the cam chain housing, has been washed down to the crankcase area near the IMS, but will probably be too large to drain through the small holes back to the sump (these drain holes really need to enlarged ). So disassembly will be required to remove them.
With only 20k miles, pinning the IMS, disassembly to remove shrapnel, a bank 2 scavenge pump, and probably a new bank 2 chain, and some bank 2 valves, cleaning and careful assembly should net you a nice low mileage engine.
It really looks like this piece.
Washer is bad description. I think it is top of valve lifter.
I agree however until we find all debris we can take no chances.
Thanks for information
David
Happy sleuthing! It looks like you may have averted full engine catastrophe!!! The downside is that you've got to totally tear the engine down. The upside, as PT3 said is that with a few parts and some careful reconstruction work you can come out the other side with a nice low mileage motor. The big question becomes ; How much upgrading do you want to do while you're in there?
Forgot to add. You can see from exhaust cam sprocket that timing intact as bolts still in center of slots and not witness marks from where they were originally tightened.
I have investigated Nickies and a 3.8 upgrade. However that adds $5k plus.
Slippery slope.
David
Can't think of what that washer is inside the engine. I think what happened was the timing chain got stretched by the the scavenge pump when it got seized.Will be interesting to compare the timing chain length with the one on the other bank.
See my updates above. I think it�s the retention ring from one of the lifters. I do think chain stretched. I also think the timing variations I saw were parts of the ring getting stuck in the chain.
David
