Retensioning a timing belt...

Mountainman · **Posted:** Thu Dec 24, 2015 8:05 pm

I know, they say you shouldn't, but I have two belts that have less than 10k on them, and I'm going to run them on MY personal CRD for 40-50k, and then change them. Keep in mind that the front of my engine is almost completely open, and I don't even have to go to the hassle of removing the power steering pulley to remove the serpentine tensioner, as my tensioner has been relocated. I can pull the cover in less than 10 minutes with air tools, so I'll be keeping an eye on it.

Anyhow, I figure that they don't want a belt to be retensioned because it stretches a ways (and thereby the tensioner relaxes a bit), and then reapplying full tension would actually be over-tensioning the belt.

So, that leads to my question. Has anyone noted how far the tensioner relaxes after 10k or so? The one example I have, it relaxed about a half inch, but I think it wasn't tensioned tight enough from the get go.

I'll be rechecking this belt every 10k, and I've seen how bad they can be and still run, so I'm not scared to run one that is still shiny and pliable. But, I want to get the tension close to what it should be.

Thanks for all advice and harassment :goink:

turblediesel · **Posted:** Thu Dec 24, 2015 9:32 pm

My serp. tensioner cleared the ps pulley without a problem. Maybe the new one will argue with it.

Seems like a used timing belt would have all the stretch taken out of it through use unless it took on some tight bends from storage. I'd worry about running it in the same direction and what kind of storage damage may have occurred from UV, heat, and cold. My guess is the 6 year life limit relates to rubber degredation. All belts are "new" as soon as they're handed to the customer with no indication of how long they've been living on the shelf which insinuates a 6 year installed lifetime worst case scenario. How long were your old belts installed?

:juggle:

How many rockers,
is your head off?
How many rockers,
off is your head.
:5SHOTS:

Switching topics... Is your AC pulley still in the loop on your serpentine belt reroute? I read a post that said the 2.5 euro crd has the PS pump mounted where our US AC compressor is. I'm wondering if the 2.5 and the 2.8 use the same aluminum bracket to mount the alt./fuel pump/AC or PS. It would be nice toditch the AC and move all of the power steering to the driver's side and make space on the other side. It would also be great to lose the criss-cross expensive hose clutter. Your Thoughts?

Happy Holidays!!!

geordi · **Posted:** Thu Dec 24, 2015 10:20 pm

The spring exerts nearly constant tension on the belt, so there should only be minimal risk to the belt by setting the tensioner to the correct point. The spring will flex to take up any new stretch, but if there isn't any, then the tensioner will just remain where it was placed - at the full mark.

Otherwise, I'm with you on using it again, on your personal vehicle.

Mountainman · **Posted:** Thu Dec 24, 2015 10:38 pm

You've got good points about the risks of reusing a belt. I have a bunch of belts to compare, so I'm fairly confident in using a shiny one, but maybe checking every oil change would be better.

I also read about the caution of remounting a belt in the opposite direction. This may be enough to make it not worth the risk as I probably have no way to tell unless I labeled them, which I did on one, but not the other shiny one.

Maybe the looks new is useless, and maybe they've failed looking good. But, I've seen one that had 186k miles on it, it was cracked and dry as a cracker, AND the dealer that installed it by order of a shady owner (car flipper type) retensioned it, and then it was driven for 8,000 miles, and it didn't break! I got lucky on that one... And maybe it was a super belt. I personally don't trust them past 90k miles. Maybe I'll can this whole reuse idea :lol:

As for the AC:
I gutted the AC, as I use the jeep in the mountains almost exclusively, so it wasn't needed. That really opened things up. I'm pretty sure you can keep the AC and relocate the tensioner though, but, as for relocating the PS pump. That would probably be a complete nightmare of rerouting and refabricating those lines. No thank you. Once you delete the AC and especially the viscous heater, that side is opened up nicely. Oh, and relocating the tensioner helps too.
Although, I have the slightest belt slip (squeak) at full lock, so this mod hasn't been completely refined. I think either some belt conditioner, or adding back in an upper center idler pulley with fix it. It hasn't damaged the belt, or slipped enough to be very annoying, but my belt is only making contact with one side (less than 90 degrees) of the crank pulley/balancer...

Mountainman · **Posted:** Thu Dec 24, 2015 10:46 pm

geordi wrote:

The spring exerts nearly constant tension on the belt, so there should only be minimal risk to the belt by setting the tensioner to the correct point. The spring will flex to take up any new stretch, but if there isn't any, then the tensioner will just remain where it was placed - at the full mark.

Otherwise, I'm with you on using it again, on your personal vehicle.

Cool, thanks Geordi! So, I'm guessing you've noticed on several of them that the tensioner hasn't moved much? I've had these two belts hanging on the wall for a while, and they have just been begging to be used...

geordi · **Posted:** Thu Dec 24, 2015 11:07 pm

Well, the highest usage I've seen was an original belt with 218k on the truck, and the teeth came off from the belt with just a touch.

The average are 50-90k on the belts, and don't look terrible. I have a couple that are less than 20k on them, I'd use them again on my own stuff without worrying about them. You can't really tell anything by looking at them unless they are really shredded.

The direction of travel doesn't mean anything to me however. I wouldn't worry about that.

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Mountainman · **Posted:** Thu Dec 24, 2015 11:39 pm

hmm, really makes you wonder how some fail under 100k, and then some go twice as far...

turblediesel · **Posted:** Sat Dec 26, 2015 2:50 pm

I've always heard belt conditioner is a wrong bad idea. Like transmission stop-leak and engine rebuild in a can. Just a product; not a fix.

Thought I was being smart getting after my timing belt early, 75,000 miles. Figured I'd have a fair spare for the side of the road if I ever needed it. Oh the happy innocent days when it was "just a timing belt change".

I bet Geordi could do one by the side of the road. Rockers, ARPs, and all.

geordi · **Posted:** Sat Dec 26, 2015 4:33 pm

If I was in Alaska, I'd probably spend the money to have the full set of tools just riding around in the back all the time. You guys have it rough up there sometimes, down here we aren't more than 45 minutes from a tow truck if we really really need one.

As for working on them though - I do all the work with the only requirement as "a place to park the CRD" and have done them in parallel-parking spaces on the street before... So I guess you are right. :mrgreen:

A nice shop or garage is always appreciated, but certainly not a requirement. I'm actually tearing down the timing belt on my sisters new (to her) TDI today, and potentially going to be replacing the transmission too... In the driveway. Someday I will have a shop space of my own though!

Retensioning a timing belt...

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