Lower cam chain tensioner

[ETTony]

Guys,
After removing my cam chains cover, I see that the hydraulic tensioner is completly slack.
OK I understand that it will only tension when pressured up with the oil, but I had thought that there would / should be some tension from a spring.
Whats the scoop is there a spring in there ?

Naturally I will be replacing it.

Thanks Tony

[Hugo]

Yes there is- quite a strong one. But it needs releasing. I've just been through all this with mine as I am rebuilding my engine. The tensioner comes with the spring fully retracted, and you have to remove a plug & put a tiny little allen wrench through the hole & twist it in order to release it. The book says clockwise, but I couldn't make any sense of that - anti-clock releases it on mine.
The new tensioner I got from SNGB came without this plug, which caused a bit of head-scratching. It had a red plastic tag inserted between the body and the plunger - apparently you have to remove this tag, press the plunger in & it will release by itself. I don't like this - it's too hit & miss whether it will release or not.
I ended up re-using my original body, then I found the thread for the plug had gone, so I had to go back to using the new body. In the end I just fiddled around with it and made doubly sure it had released, by pressing on the opposite side of the chain & watching to see if the plunger came out on its own when I took the pressure off.
I have my engine on a stand, of course, which makes accessibility easy.

[ETTony]

Hm, I wonder if mine was ever released, I see the hex where the Allan key engages in the piston,
I will have a fiddle tomorrow out of interest.
Aye my engine is on the stand ready for new lower chain, new crank sprocket, guides and tensioner.
No worries, my new stuff arriving tomorrow.

[Hugo]

The only confusion is which way to turn the darned thing. I read somewhere not to turn it anti-clock, but if you look at the ramps inside it, that's the only way to release the spring. Be warned, though, that little piece with the hex hole for the allen key is not properly attached to anything, & you can sometimes just turn it & it will twist inside the tube it lives in. In fact, just as I write this, I wonder if that's why they say not to turn it anti-clock, because the tube it sits in is a sort of spiral & maybe that loosens it? I had mine pop out altogether at one point & I had to shove it back in. All nice & easy if the engine's out but I would imagine it's tricky with the engine in the car.
I would suggest just fiddling with it & then checking by pushing the chain in on the other side & making sure the spring plunger pushes out when you take your finger off. Not the best design if you ask me.

[mgcjag]

Tony....have you looked at the instructions in the Jaguar service manual... Steve

[Hugo]

The instructions I have seen tell you to turn the allen key clockwise. That is a bit odd, since mine needed to turn anti-clock to release it - but the instructions tell you not to do that. It's not a very good system in my opinion - I just ended up fiddling about with it till I was satisfied it had released.

[mgcjag]

Hugo......far better to refer someone to the service manual...then if they have problems enquire here on the forum for more information ....the service manual is only relating to original parts so in some instances procedures will not be correct..........Steve

[Hugo]

What I was saying is the info in the manual appears to be incorrect. Merely telling somebody to read the manual doesn't contribute much - they can probably figure that bit out for themselves.
The manual tells you to undo a plug & turn the barrel with an allen key, which was no use at all to me, since the tensioner I just bought had neither a plug nor a socket for the allen key. I've just spent some time trying to figure out how these tensioners work. With the tensioner in your hand, you have to turn the key anti-clock to get it to release, yet the manual tells you NOT to do that, but to turn it clockwise instead. But that just winds it in further.
Reading the manual often, in my experience, just adds to the confusion.
Like my bloody camshafts, which according to the manual do not exist!

[mgcjag]

Hugo....as far as im aware you dont even have a manual....if you had looked at one you would have see that the tensioner you purchased was not an original part.....the manual gives a good understanding of how the car is put together and works.....if your ok with the poke and hope method thats great if it works for you.....but as i said reading the manual should be the first choice.......your comment of me refering someone to the manual "dosent add much" is insulting...........anyway my reply wasnt to you it was clearly posted for Tony....but as usual you do have you chip in and try to put down help that others are giving...........when replying to posts please try to give your own objective ideas and not rubbish what others are saying..... Steve

[Hugo]

All I am saying is that if you go by what the manual says you may find it misleading. I certainly wouldn't agree with you that it is 'helpful' in this instance. The reason I decided to 'chip in' was that I was the original responder to the question, and I have just been through all this with mine, so I do have a bit of experience with these tensioners, and I found the advice given in the manual to be counter-productive in this respect.
I got my tensioner from SNGB. Is there a better source for original parts somewhere? In any case, I believe the 'original' part has been modified, and that this is what they supplied, and the manual has not taken into account this development. I might be wrong about that, but that is what I found anyway.
So I stand by my comment that going by the manual may not be helpful in this particular case. I'm sorry if you don't like that.
I believe the "poke and hope" method is actually the suggested method for releasing the spring on the new tensioners, except that my version is to 'poke and hope' and then verify that it has released.
If you have a better method of dealing with these pesky tensioners I'm sure we'd all be glad to hear it ;)

[ETTony]

Last week I opened up the cam chain cover and found the tensioner slack.
Page 83 of the manual clearly shows the exploded tensioner c/w spring,
I did try releasing the spring mechanism, no joy, no bother its in the bin now.

The crank sprocket was hooked and some teeth damaged so I replaced that together with the chain.
Comparing the chains, is was stretched some 4mm.
The new improved tensioner (with no external release for the spring) is fitted satisfactorily and the guides adjusted.
Silent running now.

That job done.
Thanks for the input chaps.

[Hugo]

Hugo....as far as im aware you dont even have a manual....if you had looked at one you would have see that the tensioner you purchased was not an original part.....the manual gives a good understanding of how the car is put together and works.....if your ok with the poke and hope method thats great if it works for you.....but as i said reading the manual should be the first choice.......your comment of me refering someone to the manual "dosent add much" is insulting...........anyway my reply wasnt to you it was clearly posted for Tony....but as usual you do have you chip in and try to put down help that others are giving...........when replying to posts please try to give your own objective ideas and not rubbish what others are saying..... Steve

No, I'm afraid the manual, in this instance, does not "give a good understanding of how the car is put together and works". I found it utterly confusing and indeed contradictory. For example, it tells you to turn the allen key clockwise to retract the spring, then later it tells you to turn it clockwise to release the spring. Which is it? Indeed it cautions you NOT to turn it anti-clock, but that is exactly what you have to do in order to release the spring. And it doesn't tell you anything about what to do if you don't have a socket for an allen key, as the newer ones don't as far as I can make out. I reckon if you just followed the manual, you would have a less than fifty percent chance of getting the spring to release. I figured it all out by taking it to bits and holding it my hand and playing around with it, and then - and this is most important - verifying that the spring had actually released by pressing on the other side of the chain & making sure the spring pushed back when I let go. It doesn't tell you any of that in the manual, does it?
Does any of this matter? Probably not. I wouldn't be surprised if there are a number of cars out there where the spring is still retracted. It doesn't do much, since the oil pressure will take over and do the job a second or so after the engine is started.
I mention all this since you seem eager to impugn my motives for 'rubbishing' your suggestion as you describe it - all I am trying to do is save someone the amount of head-scratching that I went through before I figured it all out. I have no other motive than that.