ALFAGTV6.COM

[mcandiago]

Hi all,

I just wanted to report back on my hydraulic tensioner/detensioner rebuild.

Over 1000 km now and no leaks.

Now some information:

1. I used the latest Alfa Romeo rebuild kit for the tensioner/detensioner.

2. I was meticulous about cleaning the tensioner/detensioner, in particular, the vertical shaft contected to the detensioning piston, which is responsible for the detensioning.

3. On the hollow oil shaft which screws into the engine block and which allows the flow of oil to the detensioning piston, before I installed the new O-rings, I put teflon tape around the O-ring grooves to provide a better seal between the O-rings seated on the hollow shaft. I also unscrewed the hollow shaft and put teflon tape around the threads of the hollow shaft.

4. With some tooth paste and a cotton dremel pollishing bit I polished the inside of the hollow cylinder which fits over the hollow oil tube. (Make sure you clean the detensioner well after this)

3. I lubed all parts liberally before assembly

Frankly I don't know if all these steps are necessary, but teflon tape has always been a good friend of mine.

So far so good. The motor is high and dry and touch wood I have no leaks and no bloody smell of burning oil.

As a note, I have come to understand that generally the leak of the detensioner usually occurs because of a weak vertical shaft seal (The shaft that actually detensions). The rebuid kit has not addressed the problem of providing a more robust spring type seal(the kind of seal where there is a compression spring around the circumference of the U-profile seal), typical of seals of this nature because it at the dimensional limit of being able to do so.

Perhaps also, the quality of material in the rebuild kits is better???

Will keep you posted.

Marco

[David]

Marco,

I haven't had any problems with leaking detensioners so far. I agree the shaft seal is the weak point provided the piston shaft is not scored or worn. A couple of the rebuild kits I have used previously, had the seal with the small spring but I believe the main problem is the outer seal not sealing properly in the retaining groove. Do they then actually leak when there is no oil pressure to keep the outer seal against the groove, ie engine stopped?

The last kit I used on the latest 3.0L project had an all rubber shaft seal a bit like a small master cyclinder seal with a lip on the outer edge of the seal to seal it properly in the retaining groove. With the previous seals I filled the retaining groove with engine gasket silicone, put the seal in place and cleaned up the excess silicone that was squeezed out. Once set, the seal could not then move in the retaining groove.

The quality of the rubber in the shaft dust seal has been poor and they tend to fall apart fairly quickly.

David

[Daniel]

When I did the 3.0 conversion on my Dad's GTV, I rebuilt the tensioner using the propper kit. Bloody thing leaked from the first time it was started.
I decided to machine a new piston out of 316 Stainless and use a different lip seal which I machined a carrier to take.
It has never leaked since

[mcandiago]

Daniel,

that is some beautiful work.

An excellent solution to the limitations of the current shaft seal.

Bravo!

Marco

[mcandiago]

David,

my understanding of the nature of seals is at best limited, however, what you said seems to make sense.

If there is tolerenece on the outer sealing portion of the seal at low oil pressures, then it will indeed leak around the seal. This is why I think the teflon is good in these cases. In some cases where the tolerence is borderline it can really help fill in that extra tolerance.

Your solution appears to be equally adequate for shaft seals which have play in them.

The shaft seal in my rebuild kit was a good tight fit. I was more concerned with the O-ring seals.

We'll see how long she lasts.

Daniels solution is a killer and frankly I think it is a true and long-term solution to those who would like to switch back to the hydraulic tensioner.

Now all Daniel has to do is provide his own rebuild kits.

He could call them Ricambi Alfa: Tensioner Rebuild kit (Supplemental)

[Daniel]

Hey thanks Marco.
I'd hate to think of what it really would have cost to make those bits if I'd paid for the materials and machining - I used scrap 316SS and aluminium bronze from work and machined them up myself.
The seal was cheap - less than $5.
I do have drawings though, so more could be made.

[mcandiago]

Good stuff Daniel,

I'll know who to contact then if/when mine fails.

Out of curiosity, how is the new seal held in place?

Marco

[DaveH]

Great Job Daniel.

Y'know: the cost of machining a batch of those wouldn't be so bad if you can find some HMC/CNC Lathe time. And a machinist who will run the parts. The couple of hours you may have spent on proto #1 could translate into 15mins/part for a batch of 20 (rough est only).

Just a thought.

[mcandiago]

Just a quick update as promissed WRT to the tensioner rebuild.

5K now with no problems. A little sweating, but entirely acceptable in my opinion.

Will report back at 10K.

Marco