When I bought my XJ8 I fully expected to do all Tensioners Chains and Guides so the car sat until I was ready to get it in my Garage.

When I started the car it idled rough, so I let it warm up and took it for a short drive. By the time I got to the street, it was throwing fault codes and the lights came on. I turned around and drove it directly into the garage and shut it off.

Remembering posts that described the symptoms of failed Tensioners, I decided to pull the passenger side Valve Cover to have a look at the Tensioner. I fully expected to see a failed Plastic Tensioner.

On closer inspection, the tensioner looks as if it's completely collapsed.

Has anyone seen this?

 

There is no picture on you post, but I expect the exhaust camchain tensioner has completely fallen to bits and gone into the chain chest. The plastic body cracks up from the heat. You may be lucky if you have not lost the valve timing, otherwise it is a heads off job, in which case you might as well do all the tensioners top and bottom, plus chain guides

 

I don't know why you can't see the pics....


The tensioner is completely intact. It's the new style aluminum body one. The problem is the hydraulic plunger is completely collapsed.

 

Cant see pics either, and when using new style tensioner you have to use shorter bolts. I have seen people use the longer ones and they seat but dont tighten the tensioner body down and you have a nice internal engine oil leak that keeps oil from pressurizing the tensioner. Then again, you just may have a failed part, just cause its a new style doesnt meen it cannot fail too. Although i have never seen that, yet.

 

Thanks Brutal.

I'll make sure to check the bolts and make sure they will not bottom out in the head.

BTW, do you know the thickness of the "T" Shaped tool that gets wedged in between the primary tensioners and the guides during reassembly? I dont have one but have lots of stuff to make one out of.

Thanks!

Ken

 

The tensioner looks OK to me. No signs of breaking up. Perhaps the tensioner needs oil pressure for the piston to extend? My new tensioners have a slack chain riding over the top shoe. The chain at the bottom is tight though.
Plus, will bad tensioners trigger codes? I don't think so.

 

No i dont use that tool, i think ours grew legs years ago. Really the bare minimun you have to have are the cam locking tools. You can eyeball the crank hole(unless youre crosseyed), and when tightening the sprocket make sure you release the plunger to put the slack on the correct side
dan the slack goes on the plunger side not over the top shoe. Its the top shoe on 1 side and bottom shoe on the other side. That maybe what you ment, but for those here that take things exactly theyll end of with cam off a few degrees if they get the slack on the wrong side and have a rough idle.
Another point Ill make too is I like to turn the engine over before I put the cam covers back on too build oil pressure in the tensioner and not have any chain whip starting on dry tensioners. this is why most tensioner failures happen when people go to start their cars instead of when driving down the road. oil pressure drops when sitting overnight in tensioners when the plastic bodies crack, and then you get chain whip from the slack that takes off shoes and destroys tensioner bodies. if you ever have tensioner shoe that goes between the chain and sprocket, ( leaves teeth marks in the pieces), replace the upper chains since this type failure streatches the chain and will cause it to snap later and this is never good

 

FWIW,

I checked with my buds at the Ford Dealer and they said to put a zip tie around the stationary tensioner and the moveable one and zip it tight. That takes the tension out just like the Tensioner would.

 

Dan,

All of the other tensioners and chains are tight. This is the only one that is not pumped up.

Yes, slack chains on the exhaust side will cause the valves to open late thus making the car run rough. When they run rough, codes likely get triggered.

I should have mentioned that prior to this incident the car ran perfectly.

 

Aren't the new, metal secondary tensioners supposed to be spring assisted to keep some tension even if they lose oil pressure? They come with a pin inserted, to hold them in the compressed positon against the spring during install, don't they? If I'm correct, it looks like the spring may have failed on this one.

Sinister: What does the other bank's tensioner look like?

 

The other Secondary Tensioner was fine.

Once I got this one out, I fiddled with it for a second or to and it popped right back into the position it should. Must have been "stuck". I could not get it to stick in the compressed position again.

I was doing the whole Tensioner job anyhow so I tossed that one and the other one for good measure.

 

The reason why the chain was so loose in the picture, is that the valve springs are pushing the exhaust camshaft clockwise in that particular position, and on that side the piston of the tensioner is below. The top is fixed and that is what you can see in the picture.

Not sure if there was anything wrong with the tensioner when you say you could not get the piston to move. The spring is relativly weak, and it is the oil pressure that truly pushes it out.

 

well now at home I can see your pics, so in the future I would do your pics as attachments cause alot of us viewat work and pics like yours that are not attachments are blocked by company firewalls.
I agree with Avos and your last post, you dont have a problem

 

Hmmm that engine doesnt look well maintained at all. Perhaps th eoil cahenls are filled with oilsludge..

Do an oilflush on the engine this might help. And yes check to see if the correct bolts have been used

 

Actually for 133,000 miles I was really impressed when I opened her up. No sludge that I found anywhere. I even took the oil pan off looking for tensioner bits. No sludge there or on the pickup screen either.

The dirtiest part of the whole motor was the Timing Cover.

 

I fished the Tensioner out of the trash. I'll continue to play with it to see if I can get it to stick again.

 

Regarding the sludge or brownish look on the camshafts, etc I agree with Jaggachafen. I am not a mechanic, but I recently replaced all tensioners, chains and guides on my XJR. When I opened my car up, there was no brown colour coating the parts. I had been running Mobil 1 synthetic oil for several years and have heard that could be the difference. Jaggachafen, regarding the suggestion of running an oil flush, is there a product you recommend? I put half a can of Seafoam in my crankcase just before changing the oil the last time, and half a can in the gas tank. If there is a product and procedure that is recommended, Sinister may want to consider it, because the look of his engine compared to mine is a bit concerning. Also, I am about to repair my daughter's Ford Escape... plugged cat converters. Her car was not well maintained and would definitely benefit from an internal clean-up. Will running synthetic oil help clean things up over time?

JWT

 

I have never held one of these tensioners in my hand, so could I ask a question ? The tensioner for the lower chain on the old XK engine had a ratchet device to stop the piston from being pressed in too far when the engine was started and no oil pressure was available. Do the V8 tensioners not have something similar ?

 

No they dont, they just have pin hole to slip a pin in to hold them in for assembly onto the engine. Then you pull the pins to release the plungers and tighten the sprockets. Why his stuck in who knows, does the refrigerator light really go out when you close the door

 

The secondary tensioners have spring tension only with the engine not running, but the new style primary tensioners that I recently installed did have a ratchet mechanism to stop them from retracting. There is a small tab that you can push to release the ratchet. These metal bodied primary tensioners were much nicer than the plastic ones I took out. The plastic primary tensioners still looked fine, but there were a few cracks in the straight guide. I think that is quite common from what I have read on the forum. I guess maybe they don't bother with a ratchet on the secondaries since the chain is quite short, but it might haver been nice of they were the same as the primaries.

Anyone got a good product recommendation for the oil flush?