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Discussion Starter #1 (Edited)
Having trouble finding a seal kit (p.n. 60777065) for the original hydraulic detensioner (V-6 12v engine)?

Don't despair (and don't pay $90!!), here's a pdf with the secrets of each seal revealed, and another with an overview of the detensioner.
 

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Very interesting, thanks.
I just paid about US$75 to get the kit from Italian Autos in Auckland, NZ.

This is the third time I've rebuilt a hydraulic tensioner and I find I always have three O-rings left over. That document identifies one as being for the backing plate (the short fat one fits in a hole, I don't know where the large, thin one goes). The other two are apparently for the bearing mounting stud but although the replacements seem to be the right size, I've never removed any O-rings from there, and fitting an O-ring means the bearing centre won't sit flush under the bolt and washer and won't pivot easily... Doesn't seem right!

On the latest rebuild I also found the bearing mounting bushes had picked-up on the mounting stud and seized. I cleaned the stud with emery and greased it well. I suspect that perhaps a later revision incorporated the O-rings to seal out water and dirt.

Since the usual failure mode seems to be oil dripping out of the bottom and running down the bellows, I suspect that the only seal that really requires replacement is the piston shaft seal, which can be installed with silicone sealant to fill the gap around it as Jason suggests, to give a more peace-of-mind result. Otherwise the seal just floats around, which is unconvincing.


-Alex
 

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Great work Steve! I posted your link to this info over on my maintenance sticky for future reference.
 

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Discussion Starter #4
Thank you Alex and Steve. Alex, regarding the three o-rings that you had left over, you are absolutely right, not all detensioners use the pair of o-rings on the bearing mounting stud, and the brown viton o-ring for the base of the hollow stud is (apparently)—not used on all units. I did this job almost 10 years ago and I just did it to another car a few hours ago, and had exactly the same three o-rings left over. The oem kit 60777065 obviously is meant for a broader market, perhaps some of the older 2.5 liter V6 engines require the extra seals. I will make a note of this in the "detensioner repair kit" pdf.
 

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Discussion Starter #5
I'm bumping this thread because of the recent new interest in the oil-fed detensioner and a new-found source for the rod u-cup seal. Details can be downloaded from post #1.
 

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Discussion Starter #6
bellow

I just did a routine TB & detensioner service and am pleased to have finally found a good workaround for the dust bellows.

Pictures below show it mounted on the Busso detensioner, recoiled and extended. It's a MotionVac MB25-NBR "multi-bellows suction cup" available online at

ANVER style B2.5 replacement suction cups

for $4.00 plus shipping. The diagram below shows where you must cut it in order to make it fit.

The pdf "repair kit" in the first post of this thread has been updated with this effective dust boot.
 

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Steven - Nice find. I just installed one on a spare hydraulic tensioner I have. Cutting the top makes for a nice snug fit around the square seal carrier.

On the bottom part on the shaft, I don't see a need to use the OEM metal cups/spacers. Seems the uncut bottom of the bellows makes a nice tight seal at the groove that the circlip would fit into.

Am I missing something important that those metal spacer cups function as? Maybe keep the piston from striking the oil pot cap when pressurized? That wouldn't seem to be a problem. though. What's shown here is also without the internal spring.

UPDATED NOTE: Read post #12 below. Bellows does have to be cut at the bottom.
 

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That's good news. More than one way to skin an Alfa, so to speak.
 

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Discussion Starter #9
Going without the metal cups and flat square cut o-ring is probably safe. I guess if the original design has a function it's to "seal" the shaft from the outside when it's recessed (= engine running), but it's hard to image that a flat square-cut oil ring would have much sealing power. Anyway I'm glad you gents like the repurposing of the suction cup! They make them in other materials as well but standard NBR seems like it will handle the job. I'll be watching mine, already installed on the car.
 

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I tried fitting it without removing the top collar, but the rubber was too fat to go into the small groove on the square shaft seal carrier. Cutting the collar off still leaves plenty of grab . . . at least when the rubber is at ambient temp. Time will tell how durable it is. Regardless, it's easily replaced in-situ should the need arise. And with the tight fit at the bottom and top keeping the piston shaft clean, maybe the square shaft seal will see longer more reliable life.

Today I'm going to get some stuff and fabricate a bench tester to leak test rebuilt hydraulic de-tensioners before installation. Basically an adapter with a 10mm x 1.25 threaded hole for the feed stud and an airhose quick disconnect. Put in a little engine oil to lubricate the seals, then pressurize to 80 psi and lower into a pan of water and look for bubbles. See any fault in that approach?

UPDATE: Tester fabricated. See: http://www.alfabb.com/bb/forums/164-168-1991-1995/426897-hydraulic-de-tensioner-test-rig.html
 

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Discussion Starter #11
Your approach sounds fine and I would be interesting to watch but I'd do it without the water dunking, just watch for oil. Frankly I don't know where most of the leaking usually occurs as my cars with Busso detensioners have been trouble free, BUT I have serviced them at 5 year/12k intervals, finding them virtually dry. I'm very pleased with the fit of the K22-008 u-cup (a special order), and the quartet of o-rings -218, -012, -011, -110, all easily purchased at a hardware store. I have never used an o-ring at the base of the hollow stud. When installing I think it's very important to slip on the detensioner over the hollow tube—not too fast—so you don't accidentally cut or injure the -012 and -011.
 

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I'm going to have to retract my opinion that the metal cup isn't necessary. With one of the spares I have, I put the bellows on and pressurized it. The piston goes way too far up to have that lower nub on the bellows.

Soooo, we're going to have to cut it off and use the metal cup and square ring or even just a washer and circlip. Even then it collapses the bellows fully. Compared to the OEM bellows the substitute is much thicker material.

Here's pictures of the de-tensioner pressurized and not.
 

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Thanks for posting this. It will be very useful when I do the next timing belt soon. The info on the bellows is especially useful because I borrowed a new one from a kit a friend had for the tensioner on my son's car recently and I owe him a replacement. I will see if any of those bits can be sourced here in Adelaide.
 

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Discussion Starter #14 (Edited)
John, one metal u-cup and the flat square-cut o-ring should be inside of the bellows and the direction of the outer metal u-cup should be reversed from what is shown in your last post. The way you have it the outer metal will cut through the bellows. It should be oriented this way...

--- circlip ] W [ | W --- body of detensioner

--- = shaft
W = bellows
] or [ = metal u-cup
| = flat square-cut o-ring

On my installation I cut the complete shank of the suction cup (there is still a little meat inside) so that the bellows didn't impede the full movement of the shaft.
 

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Discussion Starter #15
...I will see if any of those bits can be sourced here in Adelaide.
You should be able to source one in Australia, the key measurement is the cup dimension, in this case 25mm (with small part of bellows being 10mm). If you need assistance from me to get the US one, let me know.
 

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The diagram in the factory manual shows the bellows, square-cut o-ring, then the metal cup, then the circlip. The parts manual picture is not very clear and is even missing one of the metal cups.

Anyway, I think either way will work fine. I did put a very small hole in the top of the bellows (paperclip heated to red hot) like the OEM bellows, to allow the bellows to extend because of the airtight seal at the top and bottom. Regardless, as long as it keeps the piston clean from abrading the square seal in the seal carrier, it should be good.
 

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Discussion Starter #17
I think the order does matter. I'm not sure what diagram you mean from the "factory manual" but here is a detail from the schematic that used to come with the rebuild kit, showing the order, from top to bottom...

square-cut o-ring
metal u-cup ⊔
bellows
metal u-cup ⊓
circlip
(naturally the top two items fits inside the bellows)


I know for a fact that if the edges of the lower metal u-cup faces the bellows, it will eventually cut the bellows like like a cookie cutter.
 

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Interesting. Here's the pic from the factory manual rebuild instructions, which are pretty poor . . . to be generous. I'm reading the "grommet" to be the square o-ring and the washer as the metal cup.

Although, I suspect that the pic is wrong and you're correct about the order of the cups and square seals.
 

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Discussion Starter #19 (Edited)
Well that is definitely incorrect. Incidentally the eper catalogue corroborates the diagram provided in post #17, with part #10 called "ring" and #9 called "cup". #13 (bellows) is called "shield" and #7 is called "lockring".
 

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What is the prefered sealing method at base of the oil feed stud? I know that the brown viton 17.17mm x 20.62mm x 1.78mm oring is recommended - does that sandwhich between plate and engine? Between plate and tensioner? Or is it supposed to fit inside the plate hole as the oil return o-ring does?
 
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