For various reasons I've got the engine out of the car and I'm taking the heads off. (The main reason it is out is because the transmission was acting up - long story, OT for this thread.)

Time to pull the cam gears and timing chain and I'm playing with the Jag V12 chain tensioner for the first time and it's as big a treat as I expected it to be.

I've read Kirby's book, Bernard Embden's site, some stuff at Jag Lover's and a few threads on here. I can see it all pretty well since I've got the engine out of the car and I think I know what I'm trying to accomplish and how it is supposed to happen.

I can do is rock the tensioner latch back and forth and it moves the way I'd expect it to. I can hook on to the foot of the tensioner and I can move it - it takes quite a bit of force to pull it upwards but it does move.

What doesn't seem to happen is the rod sliding back through the latch. I am turning it CCWise and it moves about as far as I'd expect it would need to in order to let the rod move. I might not be turning it far enough CCW, but to go more than I have been will require quite a bit of force and I'm trying not to break it.

I don't get the latch to the point that it goes a far enough to lock. When I pull the latch itself is moving up and I can't keep a tool in it so it stays CCW. I think the whole tensioner is moving, which may mean it is already broken, although it looks intact...

I'd been pulling stuff off of the engine most of the afternoon and was headed in. I figure I'd see if anyone has any input.

Here's what I'm considering... I'm thinking that since I'm pulling the heads anyway and am going to replace both crankshaft seals that I should take the studs out of the front of the heads and remove the whole crankshaft cover. My other option is to keep mucking with the tensioner and applying greater force to it until it either locks open or breaks.

I'm not sure if I care if the tensioner breaks - I kind of think I should replace it whether it is broken or not. I don't want to have to do this again soon and so I'm renewing anything that makes sense. On the other hand, the stupid thing is really expensive and it may have been replaced before. I just don't know the history of the engine.

So for those of you that have actual experience with the tensioner and have done this before, what do you think? Pull the cover before removing the heads? Maybe loosen the tensioner / chain as much as I can and take the gears off? I can get it to loosen up but whenever I turn the engine it clicks back tight again, which I think just means it isn't properly latched open.

 

If I were in that far, I'd change it. Regrets are hard to live with. Money spent you may not need to? Well, you do have a Jag....

 

FWIW, I am rebuilding a perfectly running 6.0 before I put it back in, just because its such a pain to remove anyway. May spend a thousand or so in a basic refresh, but hope to drive it a very long time, and at least I'll know....

 

Yeah, exactly.

My engine doesn't really need a rebuild but the transmission was getting wonky so it was coming out. While I was at it... I'm thinking about like you are. Quite a bit like you are, actually, since I'm thinking that a busted slushbox means that it is time for a manual transmission conversion.

How hard can that be?

 

I hate to see, "so then what happened?!?" threads so here's the outcome of this part of the story.

I think I got the latch to release, lock, and stay locked. I decided to stop worrying too much about damaging the mechanism but still tried to follow the many recommendations I've read.

I found that the amount of force it takes to pull the latch up is more than "substantial", at least in my case. What I wound up doing was to make a hook out of a long threaded rod (didn't have a battery hold down to grind up but as suggested in the book is probably just about perfect).

I chained it up to my shop crane and used that to apply upward pressure while working the latch back and forth. I wasn't putting engine lifting force on it but it was pulling pretty good. Finally I could feel the latch give and let me rock it a bit farther CCW and when I released the lift on the crane it stayed in place. I could then turn the engine with the timing chain "slack" and the latch stayed put.

I had to do this a few times before I was able to get it to work its way loose - I expect that my latch is actually damaged in there but can't see it yet. I also think I'll replace it despite the cost.

Despite having done this myself I would not say that it is an easily repeated performance. I did learn a bit more from the "doing" than I understood from the "book learning" but not all that much. Maybe once I get the front cover off it will become more clear... but I doubt it.

The timing gears are now off and I'm proceeding with head removal. I expect all I'll get done for the rest of the day is to remove the nuts (and really, did there really have to be FOUR DIFFERENT SIZES!?!?) and start fabricating the plates to pull them up.

Anyway, that's the way the story of the timing chain tensioner stands now. With excessive force it released and locked.

 

How hard could that be.....indeed..... And getting those heads off? What a challenge. I am attempting that now on a spare V12. The plates mentioned in "The Book", only appears to bend the cam bearing studs in my case. So.....I am now having a set made that bolt onto four cam bearing studs instead of the two.