98 V70 does this TB path have wobble? [ Gates wobble, replaced Conti, no wobble]

Post by **erikv11** » 21 Dec 2015, 10:13

I did a much-needed timing belt job yesterday morning, but wonder about the amount of belt wander on the new mechanical tensioner and the idler pulley. There isn't much but there is some; any thoughts?

New idler pulley is blue box Volvo, new tensioner is INA from I forget where (!), water pump I did not touch it is Volvo branded.

Post by **kahl** » 21 Dec 2015, 11:34

When I did my nephews 2000 V70 I saw the same movement. I drove the car for about 50 miles and the belt settled down. When I did the 98 V70 I saw no movement at all. Both cars had their water pump,tensioners and pulleys replaced with the TB.

Did you notice and wobble on the water pump pulley before you put the TB on?

Post by **erikv11** » 21 Dec 2015, 13:58

I did check the WP pulley, it had a good feel and no apparent wobble. Good idea to pull the cover again in a few miles, I will do that and get a look at my other P80's too.

Post by **Ozark Lee** » 21 Dec 2015, 15:37

I'm trying to figure out from the frequency of the wobble what the diameter of the offending roller is. It appears to be smaller than the cam sprockets but the rest of the rollers and sprockets are all about the same diameter.

It doesn't look like it is wobbling much but that fact that it is wobbling is a bit unsettling.

...Lee

Post by **cn90** » 21 Dec 2015, 20:48

I wonder if this is "normal" for a timing belt.
I have a 2005 XC90 with 2.5T engine (mechanical tensioner), one of these days I can take a look with engine running and tell you what it is like.

However, a different video from a Volvo with hydraulic tensioner shows very stable TB...

Post by **mecheng** » 22 Dec 2015, 07:26

Did you check it when the car was cold or hot?
Did the tension arm move out of the correct 'window'. I had to readjust mine.

If you want I can take a video over the holidays.

Post by **cn90** » 22 Dec 2015, 09:04

I took some random photos from Volvo 850 and Volvo XC90 2.5T engines to show the concept of "Axial" movement, i.e., movement along the axis of rotation.

- The WP has a "inner flange" that prevents the TB from "walking inward", touching the engine.
- The Crank Pulley (harmonic balancer removed for better visibility) has an "outer flange" to prevent the TB from "walking outward".
Within this "confine", the TB can only move so much from side to side.

So, let's say the TB width is 24mm, and the "confine" is 24.5mm, then the TB can walk 0.5mm from side to side.
Probably within spec (I may be wrong though).

Of course, there are other factors too:
- Any play in WP bearing?
- Are Cam sprockets "straight" (no wobble)?
- Any play in mechanical tensioner pulley?
- Any play in Idler Pulley?
- The Crank Pulley: is it straight and true?
- Is the TB nice and straight from factory? BTW, Gates TB is kn own to walk from side to side, simply b/c Gates TB is not as straight as Conti.

Just some of my thought process. Anyway, the photo to show the "confine", see RED arrows...

Post by **cn90** » 22 Dec 2015, 09:09

Re Gates TB, below is a youtube video showing Gates TB issue, which is solved by switching to Continental TB.

The youtube video owner said:

tjani8 wrote:...Why brand new Goodyear belt not go straight? I put old belt back and it goes straight. Bad belt?
Update 9.11.12
I bought a new Contitech belt and now has worked well for four months...

Post by **erikv11** » 22 Dec 2015, 17:01

Thanks all for the helpful posts.

If anyone has some video of a mechanical tensioner in action I would love to see it. All of my other P80 cars have hydraulic tensioners.

The idea that it is a crooked belt had not occurred to me, I am leaning in that direction and may just get another Conti to be sure. But ha, that video of the Goodyear belt makes me feel like I got a gem!

Here is another video now that the car has seen 30 miles of driving, the wandering looks about the same. I did readjust the tensioner because it was slightly off, it sits at a better spot now but another reason I post this video is to show the calibration lever, does its movement raise any eyebrows?

And finally: I will drive the car a lot in the next couple weeks. So I am thinking it is a minor wandering, probably OK short term but should fix it soon. Maybe next week, or after the holiday if I feel better about it, but certainly no later than that. I will keep checking it every couple days, make sure it doesn't get worse. Maybe it will get better, maybe the belt will stretch into round/true. Sound reasonable?

Post by **rspi** » 22 Dec 2015, 19:13

I wouldn't take another look. I believe it's fine. I see that slight movement a lot.