timing cahin dampers cracked!!!!

[carlv12]

Hello,

4 years ago my 5.3 V12 engine was completely restored, with new psitons and liners, heads repaired, new valves, timing chain + tensioner + guides etc... = ALL done. But now happened an incredible problem: the upper and lower timing damper C29635 and C29636 cracked = the plastic/nylon surface on the metal went down!!!!! All this after only around 1500 miles.

Do you know or did you hear from similar problems with cracked upper and lower timing dampers (they are all the same for E-Type V12, XJ-S V12, even 5.3 AND 6.0)??? Did other customers complain about this problem? Could the reason be just bad quality of the material o is there another reason for this failure? Too much tension of the timing chain or other ideas? I just want to avoid that this happens again...

I have received feedback from experts that told me things like:

1) The damper problem is a real issue with Jaguar! Many even tried law suits against them but failed!
They made them all wrong!
You need to replace them.
I believe they are now correct but good, used ones will be better.
I think the problem is now solved. /i]

2) I am aware that Jaguar did have a problem supplying these about 2 years ago but I have not had any comments about quality within the last year

3) There was a spate of defective timing chain guides, and somehow, as I purchase these in quantity, I avoided the bad batch. The problem seems to be behind us and there is nothing to blame but faulty guides. It is indeed unfortunate as these guides require major engine disassembly to replace.

Thank you once more and best regards from Valencia

Carlos

[PeterCrespin]

Never heard of it and the comments sound like the known V8 97-2001 problem. The V12 dampers are rubber faces not plastic, although the lower tensioner is nylon.

My guess is that because correct setup requires a large and heavy special tool (a massive jig bolted to the front of the block) whoever did the engine may not have had the tool if they didn't build lots of V12s.

In the absence of correct setting due to no jig, the engine will run but either the dampers will wear (too tight) or possibly fail from the adjacent chain thrashing (too loose). Unlike the XK engine there is one long chain and setting it up is critical. I would blame the builder before the parts whereas for an AJV8 I would blame the plastic tensioners.

The jig is certainly available for loan (4 of them in fact) in the USA and I assume in UK via JEC.

Pete

[christopher storey]

your " expert " unquestionably was thinking of the early AJ V8 engines, which have nothing in common with the V12s at all

[carlv12]

Hello again,

please see the attached pics. There you can see for example that on C29636 the complete rubber surface is removed from the metal base. A new C29636 is above.

Another interesting detail as that the above new C29636 from 2012 has a changed design of the angle of the rubber surface. The wedge-shaped on both sides is different to my 2010 fitted C29636.

The other rubber pieces of the other timing chain guides are also removed, but they were destroyed or damaged by the pinions or gears.

I am dissapointed, because the worst of all this is that I cannot trust in new parts from Jaguar: will the new timing chain dampers again be faulty in 3-4 years or earlier?

Regards

Carlos

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[PeterCrespin]

OK, plastic = rubber so that part is solved.

As previously stated, setting the chain dampers correctly on a V12 requires a large, heavy and fairly complex jig tool that is expensive, not used for any other engine and not easy to make in a workshop. It also requires a small tool on the jack shaft sprocket and a few simpler ones for the cam drives. So unless your rebuilder does a lot of V12s I would be very surprised if he had all these tools.

Without the tools it would be easy to mess up this task. The rubber facing fragment shown on the right appears to have deep grooves in it from the chain sideplates rubbing. This is either a sign of gross over-tight rubbing in such a short mileage (there should only be light kissing contact) or possible thrashing irregular contact from a loose chain due to other parts disintegrating first or the chain tensioner not being released after fitting.

There is a special technique for setting the tensioner that could be mistakenly forgotten. The fact that two normally robust steel/rubber dampers that should hardly touch the chain have failed, whereas the more fragile nylon curved spring blade over which the chain is supposed to tun for a large part of its length has not suffered, makes me more suspicious of the rebuilder than the parts.

This is only a guess, however. If your mechanic has a workshop fully equipped to repair V12s and has done them successfully you could try again. If he can't show you the big plate and pins that comprise the damper setting jig, use someone else who has it. Human nature says the mechanic will always blame the parts before themselves and the opposite for the parts sellers.

Pete

[carlv12]

Hi Pete,


but then what is the reason why the whole rubber/plastic surface went down from the metal base? I mean it's not broken, I had "luck" that no pinion destroyed it. Even if the chain had too much tension, the rubber/plastik could show signs of the chain, but how could it be removed totally from the surface???

This only makes sense if the parts were faulty = the rubber/plastic was not fixed correctly on the metal base during production.

I have seen timing chain dampers on other cars after 200.000 miles and more that were worn out, but the plastic was still in place!!!!

Any ideas???

Thank you and best regards

Carlos

[MarekH]

Dear Carlos,

You can always ask suppliers such as SNGB whether there has ever been a problem with these parts for the v12 in the past. Given that four or five traders will account for the majority of sales, one of them ought to know for sure whether bad parts were in the supply chain.

Experience with the v8 engine has no bearing on this whatsoever.

kind regards
Marek