hydraulic tensioner

[fladmark]

I need some advice from you Subaru mechanics, please. I recently had
the timing belt replaced on my 98 Outback at 105K, at the Toyota
Dealership were I bought the car used several years ago. 12 days and
850 miles later, the tensioner broke and the bolt on the idler pulley
was sheared off. The belt was still good. (I was on an interstate, in
a tunnel under the Chesapek Bay.) All eight valves were bent and the
damage was $2600.00.

The Toyota dealer says nothing his mechanic did could have caused this
failure. He says it was a coincidence that the tensioner broke at that
time. I believe too that it could have been a coincidence, but that it
is more likely that the mechanic did something wrong. Can you give me
your opinion? What could the mechanic have done to cause this failure?

Thanks for your help.

Tom

 

[johninKY]

My guess is the tensoinor bolt was overtighten when the tensoinor was
reinstalled. No way this can be proven.

 

[Jim Stewart]

I need some advice from you Subaru mechanics, please. I recently had
the timing belt replaced on my 98 Outback at 105K, at the Toyota
Dealership were I bought the car used several years ago. 12 days and
850 miles later, the tensioner broke and the bolt on the idler pulley
was sheared off. The belt was still good. (I was on an interstate, in
a tunnel under the Chesapek Bay.) All eight valves were bent and the
damage was $2600.00.

The Toyota dealer says nothing his mechanic did could have caused this
failure. He says it was a coincidence that the tensioner broke at that
time. I believe too that it could have been a coincidence, but that it
is more likely that the mechanic did something wrong. Can you give me
your opinion? What could the mechanic have done to cause this failure?

The following is cut'n'paste from the DOHC engine
manual, timing belt replacement procedure:


2. AUTOMATIC BELT TENSION ADJUSTER

1) Visually check oil seals for leaks, and rod ends
for abnormal wear or scratches. If necessary,
replace automatic belt tension adjuster assembly.

CAUTION:
Slight traces of oil at rod’s oil seal does not
indicate a problem.

2) Check that the adjuster rod does not move
when a pressure of 294 N (30 kg, 66 lb) is applied
to it. This is to check adjuster rod stiffness.

3) If the adjuster rod is not stiff and moves freely
when applying 294 N (30 kg, 66 lb), check it using
the following procedures:

(1) Slowly press the adjuster rod down to the
end surface of the cylinder. Repeat this motion
2 or 3 times.

(2) With the adjuster rod moved all the way up,
apply a pressure of 294 N (30 kg, 66 lb) to it.
Check adjuster rod stiffness.

(3) If the adjuster rod is not stiff and moves
down, replace the automatic belt tension
adjuster assembly with a new one.

CAUTION:

* Always use a vertical type pressing tool to
move the adjuster rod down.

* Do not use a lateral type vise.

* Push adjuster rod vertically.

* Press-in the push adjuster rod gradually taking
more than three minutes.

* Do not allow press pressure to exceed 9,807
N (1,000 kg, 2,205 lb).

* Press the adjuster rod as far as the end surface
of the cylinder. Do not press the adjuster
rod into the cylinder. Doing so may damage the
cylinder.

4) Measure the extension of rod beyond the body.
If it is not within specifications, replace with a new
one.

####

Just off the top of my head, I'd say that a mechanic
*could* muck up the tensioner and either the dealer
is not being truthful or doesn't know what he's talking
about.

In any case, the tensioner should have been changed
at the time the belt was changed.

 

[Edward Hayes]

I checked my tensioner per Subaru instructions and reused it. I was
VERY careful to compress the tensioner rod SLOWLY per Subaru. I took
about 10 full minutes to compress it using a vertical drill press. I
now have ~ 25,000 miles on the used tensioner without an issue. Subaru
warns people to use a certain method to test and reuse this
component. If the procedure was not followed then Yes, it could lead
to your failure but, you will never know.

 

[fladmark]

I checked my tensioner per Subaru instructions and reused it. I was
VERY careful to compress the tensioner rod SLOWLY per Subaru. I took
about 10 full minutes to compress it using a vertical drill press. I
now have ~ 25,000 miles on the used tensioner without an issue. Subaru
warns people to use a certain method to test and reuse this
component. If the procedure was not followed then Yes, it could lead
to your failure but, you will never know.