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Austin GTV6
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Timing Belt Tensioner

Post by Austin GTV6 »

Greetings,
I plan to install a new timing belt on my recently acquired GTV6 this weekend. Previous owner had no knowledge of when it was installed nor whether it has a mechanical or hydraulic tensioner. There are no oil leaks at the front of the motor so assume it's a mechanical tensioner or a non leaking hydraulic unit but I won't know until the covers are off. My intention is just to replace the belt for peace of mind and address any tensioner issues in the near future. I'm familiar enough with cam timing and the R&R aspects of the job, but the repair manual description of adjusting the hydraulic tensioner makes no sense to me. Maybe it would be intuitive once I actually saw the tensioner, but I would prefer to have a better feel for it before I start on the job. Any advice or comments would be greatly appreciated. I've already searched the archives and am still confused.
By the way, I love this site. Had I not found it, I wouldn't have bought a GTV6.
shures
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Re: Timing Belt Tensioner

Post by shures »

Austin,

I strongly advise you to replace the tensioner. I do not have any faith in the thermal type, I know of several breaking and removed a broken one myself last summer. My advice is to research the subject thoroughly and then pull yours down and make a decision.

For my part, I prefer the original hydraulic type whether oil fed or not. I have specific info on a reversable method of plugging the oil feed if you want to PM me.

Check Mark Denovich's "Alfa Wiki" site for a drawing of a very helpful cam holding tool regardless of what you do. It can be made in about 20 minutes and will speed things up quite a bit.

[quote="Austin GTV6"]Greetings,
I plan to install a new timing belt on my recently acquired GTV6 this weekend. Previous owner had no knowledge of when it was installed nor whether it has a mechanical or hydraulic tensioner. There are no oil leaks at the front of the motor so assume it's a mechanical tensioner or a non leaking hydraulic unit but I won't know until the covers are off. My intention is just to replace the belt for peace of mind and address any tensioner issues in the near future.
Scott Shure
Ellicott City, Md
85 GTV-6
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P.Webb
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Post by P.Webb »

Here's an article from Fred DiMatteo some years ago, sent to the Alfa Digest. A few tricks to rebuilding the hydraulic tensioner. FWIW, I didn't go through all this but I did rebuild the hydraulic with the head work last month. I won't put one of those thermo-mechanical valve benders in my car...

HTH

-Peter

------------------------------------------------------------------------------------

In our original article on rebuilding the detensioner (see the March 1990 issue
of Velocissima) Fred and I mentioned a modification to the bushing or sleeve
which provides a bearing for the piston shaft of the tensioner. This sleeve is
pressed into the bottom of the cylinder of the tensioner and has an internal
groove to retain the U-shaped seal which seals the piston shaft against the
internal oil pressure. Since the original article we have had numerous inquiries
about this modification so here is a description of the procedure.

Using a press or a large vise and appropriate socket (I use an old valve guide)
push the bushing out of the cylinder. The OD of the bushing is 0.6776 and it's
an interference fit in the cylinder. Note that there is an O ring which
provides a positive seal between the bushing and the cylinder. If you have never
removed the bushing, this is the extra O ring which comes with the Alfa
rebuild kit that you could never find a place for. The standard U seal for the
shaft is 8mm ID. 14mm OD and 4mm thick. It doesn't seem to last very long and
has been one of the main sources of oil leaks. Fred found that the seal used in
the 105 series cars mechanical tachometer drive is 8mm ID and the sealing lip is
spring loaded which is not the case for the original seal. Unfortunately,
however, the tach seal is 16mm OD and 7mm thick, and the OD of the bushing is
not large enough to bore out for the new seal. A little research at the local
bearing companies showed that this is the smallest spring loaded seal available
for the 8mm shaft. So the modification we made was to chuck the bushing in a
lathe and bore it out to 0.600" diameter and 0.266" deep. Bore from top side.
Diagram in inches.

The next step is to get one of the 8X1 6X7 seals from your local bearing supply
house and make up a mandrel so you can center it up in a lathe to turn down the
OD of the seal to 0.599". 1 used a quarter inch shaft and a couple of conical
washers to center the seal. You will find that the seal has a steel body onto
which the rubber is bonded and you will just hit the steel at the desired
diameter. This leaves the bushing with about a 1/32 inch wall thickness The seal
should now be a light press fit in the bushing and a little blue locktite
ensures that it stays in with no leaks. (Be sure to place the new "O" ring under
the bushing)

For reference, here are the "O" ring dimensions (ID X cross section in mm) used
in the tensioner; Piston 31 X 3.5; oil return rear bracket 9 X 2.5; pivot
shaft-rear-9 X 1.7; pivot shaft-front 8 X 1.7; idler bearing shaft (2)14 X 1.7;
piston shaft bushing seal 17 X 1.7.

So far, we have had good luck with this mod but it is not a step that is easily
reversed; Alfa won't sell you a new bushing so it's not easy to go back to the
original configuration. The timing belt ought to be replaced by, at the most,
40,000 miles and that is the time to check the tensioner. Incidentally, we
checked the availability of the double row ball bearing used in the tensioner;
it is an SKF made in Italy, not exported to the USA. Alfa gets about $150 for
this gem! NOTE: Air tests show no leaks at 80O psi!
The true joy of an Alfa Romeo is behind the wheel.
Austin GTV6
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Post by Austin GTV6 »

Thanks for the replies. I replaced the belt and checked valve adjustment last Saturday and the engine is running fine. Actually the old belt looked pretty good and the tensioner turned out to be a hydraulic unit which is not leaking at all. I think that I'm going to stay with the hydraulic setup so I'll tear it down in a couple of months and rebuild it. Am I wrong to assume it's ok to put it off for awhile? I really want to do some suspension work next, including some poly bushings and lowering torsion bars. Improvements are more fun to do than maintenance. Happy Holidays to all!
shures
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Joined: Tue Nov 30, 2004 3:50 pm
Location: Ellicott City, MD

Post by shures »

You should be good to go if you have the hydraulic unit. I wouldn't touch it if it isn't leaking. Go for the fun stuff.
Scott Shure
Ellicott City, Md
85 GTV-6
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