RE: Engine died at 70MPH, won't start

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RE: Engine died at 70MPH, won't start

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RE: Engine died at 70MPH, won't start - 3/15/2008 12:58:59 PM

FactoryJaguarTech

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Joined: 1/6/2008
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I do one of those kind of jobs at least once a month. People dont realize how much work it is to get things torn down like that. I enjoy it most of the time, but I prefer nice clean electrical work....lol

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RE: Engine died at 70MPH, won't start - 3/15/2008 2:57:03 PM

JagtechOhio

Posts: 487
Joined: 3/12/2008
Status: online

Hiioooh, Silver

Thank you for posting the photos, and sorry for your misfortune.

That failure is hopefully an anomaly. I'm going to have a look at some 4.0 heads to see if it could have been caused by a blocked oil passage, but I don't know for sure if the 4.2 heads are the same. Otherwise, either the cam bearing caps had been incorrectly interchanged...or the cam journal saddles were not properly line bored when the head was originally machined.

The latter is what happened with Series III 4.2 blocks, I built dozens that burned up rear main bearings because the saddle diameter was too small. With that failure, the problem only became obvious when the seal burned up and leaked...often times that took a while before enough damage was done.

Point being, if your head was improperly line bored, there will be others. Anybody have another explanation of silver's siezed camshaft? Hard to figure that this engine is just a lone ranger.

Fight them to the death for a factory rebuilt motor...even if you have to wear the mask when you do it.

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RE: Engine died at 70MPH, won't start - 3/15/2008 3:01:42 PM

FactoryJaguarTech

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Blocked oil passage possibly. My money is on the bore diameter. Friday car LOL

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RE: Engine died at 70MPH, won't start - 3/15/2008 3:46:56 PM

JagtechOhio

Posts: 487
Joined: 3/12/2008
Status: online

Greetings Factory,

I'd bet on the tight clearance too. Let's just hope it was only one Friday! It's a little bit amazing to me that one of those morse chains could break, they look stronger than snot. Even the 4.0 primary chains never break. What with the cam being hollow, I'd have guessed it would have twisted off at the front journal. Great to see the pics, though I'd love to see the numbers on the cam caps...

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RE: Engine died at 70MPH, won't start - 3/15/2008 4:10:01 PM

FactoryJaguarTech

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Yeah I know what you mean, however with that damage, would be impossible to get accurate measurements.
No matter how strong the chain, that gear is unbelievably resilient to damage. How many 4.0 have you seen secondary chain snap and never damage the exhaust cam gear? I had one last week that actually blew out the top of the cam cover, snapped the coil cover on the way, and jammed up in the exhaust cam gear. Not even a chipped tooth.
I wish the chains were the same length, I would put them on my VDP.
We have had 3 4.2 X350 in 6 months roughly that the secondary tensioners fell apart on, but never saw the chain come apart like that. Makes me want to vomit....lol

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RE: Engine died at 70MPH, won't start - 3/15/2008 4:18:16 PM

JagtechOhio

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Joined: 3/12/2008
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Thanks FJT, I was wondering if gen 3 secondary tensioners would eventually start showing up as "destructable". I was still thinking of using 50K miles as a recommended replacement interval. Overkill, or prudent insurance?

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RE: Engine died at 70MPH, won't start - 3/15/2008 4:23:33 PM

FactoryJaguarTech

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I would say if the customer is planning on keeping the car, do the tensioners and probably the secondary chain too. However, this car had its own issues different from the average cat.
We will see.....we are a big dealer and I think total we have seen 5 tensioner failures and 3 4.2 engine failures. Pretty good going considering 4.2 has been out now 5 years.

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RE: Engine died at 70MPH, won't start - 3/15/2008 4:34:45 PM

JagtechOhio

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Joined: 3/12/2008
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Thanks for that, I can't get that sort of up to date information anywhere else. Sometimes I start to feel like Gilligan, stranded on "Independant's Island".

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RE: Engine died at 70MPH, won't start - 3/15/2008 4:45:16 PM

FactoryJaguarTech

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LOL. I help out the independant guys down here alot. One day they will be able to help me with something I am sure. We are all in the same game, just paid by a different company.

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RE: Engine died at 70MPH, won't start - 3/16/2008 7:28:44 AM

jag_genius

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Joined: 6/30/2007
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i miss a good old tear down like that.. still havent had a 4.2 tensioner failure up here. there running gggggreat

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