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Trackrash - yes, the orifice size is designed to supply the volume of oil needed to maintain a certain pressure in the chamber across the range of engine oil pressure from idle to redline. Less oil flows thru the supply orifice at idle than at redline because the main oil pressure varies from say 1 - 5 bar or so. The setting of the relief valve is designed to maintain a specific pressure in the chamber and against the plunger, that determines how many pounds of force the tensioner applies to the chains. A minimum is needed to maintain the chain tension req'd for correct valve timing. Too much pressure and the chains wear out sooner or something in the tensioner system breaks. Plug the relief valve orifice with the screw and see what happens when the plunger sees 4 or 5 bar of pressure. The "leak" from the relief valve is factored into the sizing of the main oil pump.

Draco - yes, I'd prime the tensioners with oil before installing.
Old 06-04-2016, 10:12 AM
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Old 06-04-2016, 11:01 AM
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The only way I can find to bleed all the air out of the "working chamber" is to remove the piston and re-assemble the tensioner immersed in oil.

I can find no other way to bleed out the air that is in the working chamber. One of my tensioners was spongy. It had air in the working chamber.

So if your tensioner's piston feels spongy when you depress it by hand then I would recomend removing the piston and filling it with oil while immersed in an oil bath. Note: Porsche says, in the manual, to replace it if it is not firm.

If there is another way to do it, I would like to know.

BTW, WTF is the "orifice" pointed out in the diagram? My tensioners don't have any orifice on the top of the piston, that I can detect.

Edit: I was unable to blow air through the piston and have it escape from the plug orifice. However when using a C-clamp to compress the piston, I did notice some oil escaping from the plug orifice.
Interesting that air does not enter the chamber when the piston is allowed to extend. See post #33 to see how it looks internally.
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Last edited by Trackrash; 08-05-2016 at 10:18 PM..
Old 06-04-2016, 06:34 PM
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Update, as Boosted79 suggested, I primed the tensioners before install using a cheap HF old skool oil can full of DELO 400 15W40. Yes, air and bubbles spewed out under the can's hand squeeze pressure.

Then after install I did it couple more times until all air bubbles were gone.

In retrospect, I should have fill the cam oil lines to help reduce air into the tensioners upon cranking. Oh well, no harm.

I hand cranked it several times then starter cranked with out fuel or spark 10-12 times to insure to purge the lines of oil to the tensioners. (after reading some posts, not sure if this really had enough pressure to push oil into them but it seemed to have worked or I got really lucky )

I did check the tensioners to insure the ball at the relief valve were in place, CHECK.

One thing I do want to note was I slowly pressed the tensioner to use the lock pin, after watching Nick Fulljames warned about doing it too quickly which may damage the inner seal.

Started the car and ran for 20 minutes and used stethescope to listen to the chains, QUIET, CHECK.
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Old 07-29-2016, 01:03 AM
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Quote:
Originally Posted by KTL View Post


My point is that they had a part/fix in their catalog for these tensioners to make a failsafe, along with instructions. Here's the parts & tools

It's a pretty simple mod to make Carrera tensioners failproof, look at post #43 of this thread. This is also called the Jerry Woods mod.
Shops that don't recommend Carrera Tensioner Update?

Looking at the kit you posted I'm not sure what the little shafts do, the tubing is the lock and I bet it's short (to work as a fits all kit) so the washer looking things are shims.
The tools I'm not sure but likely they are for measuring and/or installing.

The only thing about the mod is you can't use the grenade pin for install and you lose the C-clip, so care must be taken when the tensioner is removed.
You can't fully depress the tensioner for installing, so you will need a C shaped tool to hold it the together as you slip the tensioner in place.
But it does make the Carrera tensioner failproof so it's worth the hassle.
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Last edited by Mark Henry; 07-29-2016 at 07:21 AM..
Old 07-29-2016, 07:15 AM
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Quote:
Originally Posted by DRACO A5OG View Post
Update, as Boosted79 suggested, I primed the tensioners before install using a cheap HF old skool oil can full of DELO 400 15W40. Yes, air and bubbles spewed out under the can's hand squeeze pressure.

Then after install I did it couple more times until all air bubbles were gone.

In retrospect, I should have fill the cam oil lines to help reduce air into the tensioners upon cranking. Oh well, no harm.

I hand cranked it several times then starter cranked with out fuel or spark 10-12 times to insure to purge the lines of oil to the tensioners. (after reading some posts, not sure if this really had enough pressure to push oil into them but it seemed to have worked or I got really lucky )

I did check the tensioners to insure the ball at the relief valve were in place, CHECK.

One thing I do want to note was I slowly pressed the tensioner to use the lock pin, after watching Nick Fulljames warned about doing it too quickly which may damage the inner seal.

Started the car and ran for 20 minutes and used stethescope to listen to the chains, QUIET, CHECK.
The problem I have with one of mine, is there is air in the working chamber. I have not been able to get the air out of the working chamber by supplying oil to the Supply chamber.

The only way I can see to get the air out of the working chamber is to remove the piston, immerse the whole unit in an oil filled container, make sure the air is out of the piston and the working chamber, then re-assemble.

When I compressed mine, oil would bleed out around the piston.

These tensioners don't have internal O rings or seals, to my knowledge.

You would think that Porsche would have, at some point, published a service bulletin on maintaining or repairing these tensioners, but I have not been able to find one.
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Old 07-29-2016, 09:10 AM
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AFAIK, there is no rebuild kit nor any repair instructions for these but then again, they weren't always this expensive. The kits are now about $400 more than when I bought mine: $1088. There's probably not enough in it for some entrepreneur to backward engineer one and come up with a rebuild kit. I would think the challenge would be to find the failure point when they go bad.
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Old 07-29-2016, 09:36 AM
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Strange, but I felt resistance like liquid pressure not mechanical like from a spring. Well in any case I took the precautions with a slow compression of them, seem to work.

Out the piston? Hmm, mine did not do that for sure, the oil came out the inlet and some from relief valve.

Could your tensioners have been replaced in the past? Mine looked pretty original and tired but no apparent leaks from the cylinder itself that I could observe.
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Old 07-29-2016, 09:43 AM
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Quote:
Originally Posted by tharbert View Post
....... I would think the challenge would be to find the failure point when they go bad.
I totally agree. Seems to me that the check valve would be the main concern.

Quote:
Originally Posted by DRACO A5OG View Post
Strange, but I felt resistance like liquid pressure not mechanical like from a spring. Well in any case I took the precautions with a slow compression of them, seem to work.

Out the piston? Hmm, mine did not do that for sure, the oil came out the inlet and some from relief valve.

Could your tensioners have been replaced in the past? Mine looked pretty original and tired but no apparent leaks from the cylinder itself that I could observe.
The tensioners I have are on a '78SC motor. So obviously not original, and I have no history on the motor. FWIW one of my tensioners is spongy. So there was air in the working chamber. I want to find out why this occurred. Problem is, no one seems to know exactly how they work.

My next step is to bleed, test, and compare to my good tensioner. I have taken it apart and see no obvious problem. The check valve seems to work, the spring is good, and I don't see any abnormal wear. (the relief valve up on top is loose, but I'm not sure that is the cause, IMO.)
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Last edited by Trackrash; 07-29-2016 at 11:28 AM..
Old 07-29-2016, 11:18 AM
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Quote:
Originally Posted by DRACO A5OG View Post
Good to know, so would it be recommended to prime with oil when re-installing as not to run it dry? on initial crank of the engine or will crank only to prime the engine good enough for us with the 3.2 tensionsers?
From this thread. Never ending problem for the 13th engine rebuild (very long post)......

Quote:
Originally Posted by VFR750 View Post
When you got the new tensioners did you prime them first? I got a new one from pelican, put it in a bowl of oil, and pulled the pin. It sucked in oil as it extended. I compressed it, installed the pin, and repeated the cycle a couple of times. Ran fine
This sounds like good advise.
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Old 07-30-2016, 02:25 PM
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I've never primed mine.

The pressure on the chain to keep the slack part fairly taught so it doesn't jump around too much is mainly from the spring inside. The oil below the piston acts like the oil in a shock absorber, dampening out the oscillations. And it self adjusts for dimensional changes due to wear and thermal effects. The older ones essentially had one way valves allowing the splash oil which gathered on their cup-like tops (very pronounced in the really early ones, but same effect on the later ones)to be drawn into the chamber below the piston as the piston rose up, which then retarded its being pushed back down. More slack, more oil and a higher piston level at which this effect began.

The pressure feds just provide a more consistent source of oil for this purpose. There is a theory that these were a solution to a problem already solved - that the early tensioners failed because the idler shaft bushing was not wide enough, which was changed somewhere before the advent of the pressure feds - first I think on the Turbos. So those engines don't need the pressure feds. But we all religiously installed the pressure feds on our engines if they didn't have them. By now, the advice is that you must upgrade the idlers while installing pressure feds on early engines.
Old 07-30-2016, 10:43 PM
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Time for a follow up.
According to the manual, if the piston moves easily, the tensioner is faulty and should be replaced.

I have added two labels to the diagram from the manual.


I have a tensioner that felt like it had some air in the working chamber. It would depress easily for the first few mm when I pressed on it with my finger before becoming firm.
To bleed the air out, I forced oil into the supply chamber with an oil can until oil came out the bleed valve.
I then used a clamp to compress the plunger while the tensioner was held upright in my vice. I noticed some oil escaping from the plug (orifice) while doing this. I repeated this a second time. The tensioner's piston was then firm the entire length of it's stroke.

As a note, I tried to bleed the tensioner upside down. This only made it worse, as more air entered the working chamber.
I also tried to compress the plunger, upside down, and release it submerged in oil. This also did not work.
In conclusion, if the supply chamber is full, and you operate the plunger with the tensioner upright, you should be good to go.

Edit: I made an edit to post #23.
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Last edited by Trackrash; 07-31-2016 at 09:03 AM..
Old 07-31-2016, 08:51 AM
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Here is what the plug (orifice) looks like removed. I pounded it out with a punch. It appears to be 7mm threads. Apparently it does allow air and some oil to escape. I had one tensioner that I could not bleed the air out of by compressing the piston repeadly. It remained spongy and could be compressed by hand.
I removed the plug and cleaned the plug's threads. Now that tensioner is solid after I bled it.
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Old 08-05-2016, 12:58 PM
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Old 08-05-2016, 06:10 PM
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Gordon - this is the first picture/diagram I have seen of this part. I supposed it was two pieces (the top looks like it is harder steel, as befits a wear surface). And that it was somehow held in.

I knew that it functioned as a slow, high pressure, bleed, because when compressing an oil filed tensioner in a vice so you can insert the pin you see oil coming out, so need a rag under the vice. Makes sense, as this would quickly bleed any air out as well.

I take it that when you pounded one of these out with a punch that damaged internal and external threads? But that on another one you found a way to unscrew it? Small pipe wrench?

Amazing that the passage way is the threads, though.
Old 08-06-2016, 02:45 PM
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Old 08-06-2016, 02:57 PM
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The plug appeared to be one piece. There were no threads in the piston. The plug is a press fit. I used a drift punch to drive it out, then I used my vice to press it back in. It is a tight fit.

The oil or air will follow the threads around the screw then out the top. So it acts like a restricter.

And...

One of my bleed valves seemed slightly loose. It functioned, but I have heard of them falling off. So I took the precaution of safety wiring it.

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Last edited by Trackrash; 08-06-2016 at 04:34 PM..
Old 08-06-2016, 04:28 PM
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What a great idea. I accidently knocked one loose once, prying around with a screw driver trying to do something. I pushed it back in, and crossed my fingers. Eventually it popped off. I got a replacement from a trashed tensioner. They are held in only with the sharp ends of the three or four "legs" of the cap shoved into the hole - not much, you'd think, but obviously enough if undisturbed. I took a little dremmel diamond coated round blade and cut a slot on the ID of the hole, so the legs had something to grip other than just a cylinder - this seems to have worked, but your idea looks simpler, and maybe more positive.
Old 08-06-2016, 06:38 PM
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Critical test........

Gordon, Walt, et al.....

After priming a Carrera hydraulic tensioner/s multiple times, would you be able to push the piston in 1/3" by hand (without mechanical device) before it becomes very stiff? I am trying to find out how to test or evaluate a good one from a failed tensioner. Since you are doing a good job in discussing the operation and function of the tensioner and its components, it would be prudent also to determine a simple test.

If we could determine what pressure or force applied to the piston (primed) that it is good or failed would be a good stepping stone. And this could be achieved by a collaborative work by several interested parties. Using adjectives to describe how hard or soft the tensioner is very subjective. If we could use an arbitrary numbers (lb. force) would be ideal. Thanks.

Tony
Old 08-11-2016, 05:12 AM
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What about just going to soloid tensioners like they sell at JB racing?
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Old 08-11-2016, 05:29 AM
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