996 3.6L engine failure M96.03 timing chain brokenb

[marcm]

Hi everybody,

first a picture to show you what is broken:

As there was no more movement on the 1-2-3 camshaft, I first checked the IMS. It's OK.

A look at the oil pump cover, and no chain:

The tensioner parts are separated, is there some missing element ? It fall down like this when undoing.

Any advice where to look to understand why the chain got broken ?

Thanks

Marc

996 C4 cab 3.6L M96.03, 6 speed, year 2002 sold first in Italy

Edited July 19, 2011 by marcm

[marcm]

It's a 3 chains engine. The chain is broken. I can see that the sprocket on the IMS is damaged too.

I read the advice "see if it shows signs for piston to valve contact", and I can see through the admission hole.that at least 2 valves will not close anymore.

Oil is clear, no metallic debris.

Rotating the engine is not totally easy. It rotates but is a bit harder at some point even after camshafts have been removed on the damaged chain side.

What could I check now to understand how bad it is ?

Will the contact valve/piston have damaged both or only the valve ?

I plan to first remove the head (and was stopped by one bolt allen 5..). How do I check if the piston side is damaged ?

Thanks

Marc

[logray]

If the engine had valve/piston contact you could have any number of problems from cylinder wall damage, piston damage, bent valves, guides, broken sprockets, rods, etc etc etc.

It sounds to me like you would want to at the very least crack the engine case and bearing carrier open to at least do a visual inspection of the crank house and all components and all of the pistons, rods, cylinder walls, bearings, etc.

[marcm]

I followed your advice. It took some time. I opened the crankcase and cleaned all.

It's now time for rebuilding and I will need some more advice.

damages:

-timing chain, chain tensioner, chain adjuster, guide rail

-intermediate shaft

-cylinder 1-2-3 exhaust valves and cyl 2 admission valve

-> new valves.

do I need to replace the valve stem seals ?

how do I know if the valve guides are ok ?

the car has 70000km. everything looks really good !

-> head screws and connecting rod bolts

same question can I reuse them ? maybe someone could give me the original and max acceptable length

-> timing chains: I was unable to find the procedure for a 3 chains engine

[logray]

-> new valves.

do I need to replace the valve stem seals ?

Yes, they are inexpensive.

how do I know if the valve guides are ok ?

Here is a post that might help you:

-> head screws and connecting rod bolts

same question can I reuse them ? maybe someone could give me the original and max acceptable length

You are not supposed to re-use them, they are single use stretch parts. The rod bolts are known to be a weak link on this car. If you re-use the head bolts and they fail, then your engine is ruined, same with the rod bolts. The rod bolts are very inexpensive, so not sure why you would re-use them. The head bolts are more expensive but if you have already disassembled your engine, the cost is probably not much greater than what you already have to spend on all the damages.

-> timing chains: I was unable to find the procedure for a 3 chains engine

You might try searching for a procedure to verify timing for an IMS bearing retrofit on a 3.6L, I can't find any good websites either regarding timing the 3 chain engine.

[marcm]

It's a bit strange to rebuild an almost new engine ...

the only damaged and expensive parts are the IMS and the chains

but changing all the other small parts as if they were old is hard to accept.

Pistons, rings, bearings, oil pump... all in really good shape !

[infrasilver]

Hi everyone.

I've found this thread from searching as I've had the same problem with a snapped cam chain, I've only just started breaking the engine down to find out what had happened, this what I discovered.

Marcm, what was the outcome from your engine failing, did you ever rebuild it? Would be great to know how you got on.

I'm looking to rebuild myself so all help would be appreciated.

[phillipj]

You might just want to consider buying a new (reman from Porsche) or used 3.6. They are much cheaper than the 3.4's. There a re a lot of the 3,6's out there.. Good luck

[cecollins]

Hi everyone.

I've found this thread from searching as I've had the same problem with a snapped cam chain, I've only just started breaking the engine down to find out what had happened, this what I discovered.

Marcm, what was the outcome from your engine failing, did you ever rebuild it? Would be great to know how you got on.

I'm looking to rebuild myself so all help would be appreciated.

check the scavenging oil pumps one may have locked up

[infrasilver]

Indeed it had seized the scavenger pump bank 1-3 with a piece of chain roller and this in turn snapped the chain and cracked the cam sprocket. IMS to crank pulley sheered off and 10 bent valves with 4 normal followers and 6 vario cam plus followers also required as they had dint's in them. I upgraded the IMSB and fitted loads of new parts to future proof it a little.

It took me a couple of months to rebuild the engine but its all back up and running now and I'm able to enjoy the car for the last couple of months of (UK) Summer.