are my tensioners toast?

[Baby]

Apologies for being too dense to answer this question myself after having read so many threads on it.

I've had these later tensioners on my '83. They had been sitting in a plastic bag in a box for a couple years as I slowly get the motor together. One of them has so little tension I can compress it 90% by putting the piston on the bench and pushing down on the body. The other compresses possibly a mm at most with this same process. It's just a click I can feel. Then it doesn't budge.

I could be mistaken, but I believe these cannot be rebuilt and must be replaced when they fail.

I assume the one is shot. Is there a reason to think getting oil into the chamber and bleeding will restore pressure? Or does it need to be replaced?

If you did replace one, would you replace the other as well?

[Trackrash]

If the oil ran out they will be soft. If bled they MAY be OK.

Show a picture of the top. IF the ball valve is missing from the top you may as well buy new ones.

[targa72e]

There are no seals or rubber parts to wear on these other than sealing o-ring on front. The piston to body is metal on metal with oil retained by the small clearance. There are two spring and ball bearing seals that can leak when stored but would not likely cause problems when re-pressurized in running engine. One area that is not obvious that can cause problems is that there is a air bleed built into the upper part of the tensioner. The cap on the top of the cylinder has threads cut into the shaft. It is then pressed into the piston body. These threaded passages are very small, if they get clogged they can not bleed air and will always be soft. You can remove these and clean the threads to restore the built in air blead function. I have done several of these with success.

john

[dannobee]

You can pull them apart after removing the C-clip near the hole for the grenade pin. After that you can clean them up and fill them with oil before reinstalling.

Also, look into the Jerry Woods mod, just in case. FWIW, two of the washers stacked for the banjo fittings that go on the cam carrier usually space up the tensioner just the right amount.

[ahh911]

I tried the suggested priming method in a container, terrible way. Read this, syringe with tubes etc.. what you can scrounge around till it fits snug into the oil hole, inject till the air/oil pops out the top, then try it.
Phil

[Walt Fricke]

Air compresses, oil doesn't. Air is also "thinner" than oil. So you would suppose if the compression chamber has no oil, the spring loaded piston, with no seals or rings, would compress under just spring pressure. With oil in that chamber the piston can't easily move.

I didn't know you could easily remove the hardened cap of the tensioner piston - I recall a picture posted on Pelican with the tip removed, and the tip itself, showing how the pressurized oil can slowly ooze out below the tip part, as one notices when recompressing a used tensioner in a vice preparatory to inserting the pin and installing on the engine. Is it threaded so a vice grip will twist it out and back in? Good to know this can be done, and that clogging might happen (really dirty oil? engine blew up?).

[Baby]

Thanks for all the replies! And the extra effort Phil made to illustrate a syringe!

It looks like the ball valves are in place. (See pic.) Considering the motor blew because of some as of yet to be identified issue around the driver side timing chain, and that one of these could have been the culprit, it sounds like I should take these apart as much as I can and inspect and clean them up before charging them with oil and testing them to hold pressure.

@dannobee, for disassembly, are you referring to the c-clip that holds the piston in?

It's curious that one has air and one has oil--I wouldn't think that they'd leak. But maybe it's because they were oriented differently in storage or something.

[trond]

how i prime tensioners

[Baby]

Nice setup, trond. Looking forward to trying something like that instead of the bath, which I agree is a pain and a mess.

In case anyone cares, here is a pic of the tensioner disassembled as well as one of the mod dannobee mentioned. From this thread: Shops that don't recommend Carrera Tensioner Update?

Someone said the c-clips are much easier to remove when the piston is compressed.

pics by aigel.

[boyt911sc]

Priming or feeding oil into the hydraulic tensioner/s is critical. In the past, submerging a hydraulic tensioner in a bath of oil achieved sufficient oil priming. However, I had three (3) NEW sets of Carrera hydraulic tensioners from our host failed the tests. Further investigation revealed that the 3 sets that failed the compression test were actually GOOD.

Some pictures to share:
After priming a used hydraulic tensioner and doing a compression test, the tensioner collapsed under load (single socket).


A different hydraulic tensioner after priming and under compression test. With additional load, you could see that the tensioner did not collapse.


Some of the hydraulic tensioners that were used in the investigation. I used 3 used sets and 3 brand new sets purchased from our host. Pelicanparts graciously accepted the 2 brand new sets of tensioners when I sent them back.


The oil priming method suggested by John W. was implemented and the test results showed that the new generation hydraulic tensioner seems to fail using the immersion method but passed the test with the hand pump method.


Tony

[Walt Fricke]

I got my '77 in December, 84. The first thing I did for the engine was to change to the 11 blade fan. Then came Turbo/3.0 exhaust valve covers. The next upgrade was Carrera tensioners, done with the engine in the car. Not knowing of any need to do more, I installed them out of the kit they came in (better idlers either in kit or bought separately). No priming. And no problem - I supposed they promptly expelled the air inside - after all, they are pressure fed.

So on the several rebuilds, and rebuilds, of this and other air cooled 911s, I never worried about the tensioners. They always were full of oil, and hard as can be to get compressed so they could be installed. So it is a mystery to me as to why one new one, once the pin was pulled, compressed with basically only spring pressure, and another presumably required a vice, with a little oil coming out under the tip.

But next time I have to install a tensioner, I'll for sure be careful not to ignore one I can compress basically with my hands. And rig up a way of squirting oil in, as so nicely illustrated here.

Archimedes would have been proud of Tony's methods. I'm impressed, as I usually am.

[boyt911sc]

Originally Posted by Walt Fricke

I got my '77 in December, 84. The first thing I did for the engine was to change to the 11 blade fan. Then came Turbo/3.0 exhaust valve covers. The next upgrade was Carrera tensioners, done with the engine in the car. Not knowing of any need to do more, I installed them out of the kit they came in (better idlers either in kit or bought separately). No priming. And no problem - I supposed they promptly expelled the air inside - after all, they are pressure fed.

So on the several rebuilds, and rebuilds, of this and other air cooled 911s, I never worried about the tensioners. They always were full of oil, and hard as can be to get compressed so they could be installed. So it is a mystery to me as to why one new one, once the pin was pulled, compressed with basically only spring pressure, and another presumably required a vice, with a little oil coming out under the tip.

But next time I have to install a tensioner, I'll for sure be careful not to ignore one I can compress basically with my hands. And rig up a way of squirting oil in, as so nicely illustrated here.

Archimedes would have been proud of Tony's methods. I'm impressed, as I usually am.

Walt,

I had very similar experience like you had in the past. Upgraded to Carrera hydraulic tensioner with motor installed. Tensioners primed using immersion method and had done a few with no problem.

Then came this motor from Maryland and with a rattling noise. The tensioner was initially diagnosed as good and working but produced an abnormally loud noise when engine was running. Fred Apgar was invited to take a look at the motor and came to a conclusion that I had a collapsed tensioner after using a long screw driver.

Ordered a new set of hydraulic tensioners from our host. Primed the tensioners (set #1) using immersion method and installed in the car. The tensioners produced the same loud rattling noise. Ordered another set of tensioners (#2) and had the same result. Ordered another set (#3) and using an oil hand pump for priming as suggested by JW. It worked and the motor was turned over to the owner. Then set up a test rig to evaluate newly primed hydraulic tensioners using the hand pump method with different load as shown in previous photos.

Our host accepted the two (2) sets of hydraulic tensioners and got credited for them. For whatever reason, the new batch of Carrera hydraulic tensioners is not being fully primed using the immersion method that have been used earlier. And the oil hand pump procedure does a better job.

SUMMARY:
The hydraulic tensioners (brand new) that were primed using the immersion method failed or collapsed during tests. While the same tensioners (new) that failed using the immersion method passed the tests after undergoing an oil hand pump priming. The oil hand method is the recommended procedure for these new generation of hydraulic tensioners.

[targa72e]

As mentioned earlier the cap on the piston has to be able to bleed as well. The hardened cap on the top has a shaft with threads and is pressed into the piston. The picture below shows the bleed hole that allows and air trapped at the top of the piston out.



If only the ball valves bleed oil and not the top of the piston you cant get all the air out. I have used a long punch to remove the caps. Then clean the treads and press back in.

john

[Baby]

Good stuff!

[ahh911]

Found my "tool" to inject the oil under pressure. Self explanatory, self sealing as you hold the syringe tight against the tensioner. Minor leaks if any. Worked flawlessy several times. The conical end is simply an aquarium airstone fitting. The green aquarium tubing was to fit snug in the tensioner. simple.
Phil

[strictly]

Some fantastics replies, just to say, i have used all of the above info (from this forum!!!) before to give me the confidence to take apart the tensioners, clean them (including those cap "air escape" threads), then "pressure" bleed them using the hand gun method.

I was so happy with the results, I since bought used tensioners (always a bargain) for other cars and followed the above....

Add the jerry wood mod, and a safety wire over the relief valve that can pop off (to hold it in - carefully drill near the top of the tensioner)....and you have a BULLET PROOF tensioner!

All from the PP forum! =P =)

[dtxscott]

Great thread. Curious as to the behavior of a failed tensioner when installed.

Why I ask.... On my recent top-end rebuild, i kept the tensioners submerged in oil and installed. Post-rebuild the engine runs great except I have a vibration at 1600 rpm when cold and goes away after a few mins.

My thinking is one of the tensioners is losing pressure and pumps up after running for a minute.

Other than tracking down exhaust leaks and injector wonkines, could the tensioner be a potential source of this transient vibration?

[Baby]

Finally decided to take this one apart and inspect/clean. I removed the circlip. How do you remove the piston? I figured it would slide right out, but no such luck.

[dannobee]

Once you remove the circlip, there is nothing else holding in the piston. The oil film is likely keeping it in. Maybe hold the end of the piston in a vice and pull on the body.

[Baby]

Aha! Thank you, dan, that did the trick. Some tenacious suction, for sure.