[WJH]

Okay, got ready to slip my balance belt on. The manual says the balance belt has a painted tooth and to put that side out. I don't see that mark on my Gates belt. Am I missing something?

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[Scott Collins]

I have always used the Gates belt and just took it out of the box the way it was and mounted it. I have never heard about the painted tooth, just about lining up the balance shafts the proper way.

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[JWahlsten]

Never seen a painted tooth. Just ensure you've got all the marks lined up correctly then go back in after 1500 miles and retension...

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[WJH]

Thanks guys, perhaps that is for a Porsche belt? I checked my manual for the 944 Turbo (my son has one) and it doesn't make reference to the painted tooth. Now I've learned another new thing!

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[ds968]

If anyone has the manual handy, what's the recommended re-tension interval ( time , not just mileage ) AFTER the first re-tension ?

I was talking to flash and the manual indicates every 15k miles but apparently makes no reference to a time period. One could assume 15k mi implies roughly one year, but could not find a mention of the " and/or " corresponding time for that . Same problem in the manual with timing belts : it tells you to replace every 60k miles, but no mention of the and/or how many years. We all know from many posts on this forum what the safe timeline and mileage is for timing belts, which is considerable less than what Porsche suggests, but curious if there is anything written by Porsche about balance belt re-tensioning years schedule ??

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[WJH]

Okay, another question. On my 944 everyone says to set the balance belt idler roller so that the top belt run doesn't touch the idler roller. In the 968 manual they talk about using the idler roller to preload the belt by 0-1mm, so it touches. Do you let it touch? I've read that can contribute to belt noise. Oh well, I'll guess I'll start it up and find out.

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[WJH]

Just a follow up. I let it touch and deflect and it was somewhat whiny. I went back and set the bottom at .5 and the top at somewhat less. I can barely see daylight between the belt and idler pulley. It seems to be quieter this way. That's my story and I'm sticking to it!

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[DaveN]

If it's the adjustment I'm thinking of my mechanic uses a piece of paperboard (cereal box) for the gap. That's like 1 mm?

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[Cloud9...68]

I set mine so there was just under a mm of pre-load between the belt and the idler below it, using one of the dial indicators I bought for the cam timing:



   



Even with this gauge, it was a very time-consuming task to set this pre-load, and the gap between the idler and the belt below, as moving in the right direction for one always seemed to move the other one farther away.

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[ds968]

Looking at the photo I can't help but think that the balance belt has no place to go no matter how loose it gets, and the ONLY risk is if it breaks due to age, etc.. and takes out the timing belt, so what are the risks of a really loose , not properly tensioned balance belt ? Noise ? Vibration ? Both noise and vibration ?

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[WJH]

[quote name='ds968' timestamp='1333252191' post='124256']

Looking at the photo I can't help but think that the balance belt has no place to go no matter how loose it gets, and the ONLY risk is if it breaks due to age, etc.. and takes out the timing belt, so what are the risks of a really loose , not properly tensioned balance belt ? Noise ? Vibration ? Both noise and vibration ?

[/quote]

If it's real loose it can flop around and hit the cover or the water pump pulley. It's surprising that it doesn't flop around more. Where I noticed the most vibration is between the upper balance shaft and the crank when you raise the RPM. I determined it's not exactly and exact thing.



The good thing is she is buttoned up and running smooooooth - and hopefully leak free.

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[Chris Vais]

If the balance shaft belt gets too loose you might end up with it skipping a tooth or two on the balance shaft cog, putting the engine out of balance. I had that happen on my 968.

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[vliegwielolaf1234]

[quote name='Chris Vais' timestamp='1333260229' post='124263']

If the balance shaft belt gets too loose you might end up with it skipping a tooth or two on the balance shaft cog, putting the engine out of balance. I had that happen on my 968.

[/quote]

For that to happen you also risk breaking the belt , the only way it would be able to skip a thooth is for it to run on top of the pully wich would put a lot off stress on the belt .

So get right , not to tight not to loose .

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[RS Barn]

I've seen several balance belts that jumped off and were tangled in timing belt. If you smell something funny for awhile, it could be the timing belt cutting through a bunched up balance belt.

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[flash]

mine got cut longitudinally. no idea how that could have happened, other than walking off the edge.



so, clearly we should get the tension right, and we should be following the owner's manual and re-tension after 2400miles after changing, and again re-tensioning every 15k (which is what porsche equates to 1 year of driving)

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[Cloud9...68]

As far as the re-tensioning, could we have a show of hands as to how many people have successfully done it it? By that I mean, how many people, after replacing their belts and setting the tension, went back in after the prescribed interval, checked the tension, confirmed that the belts had loosened, and successfully re-tensioned them?



I'm not asking this to be cynical. The reason I'm asking is that, as I've mentioned before, after my first belt change several years ago, I set my BS belt a little too tight, such that it whined for a few minutes of driving after having sat long enough to cool completely. Thinking that it would loosen up over time, I drove it several thousand miles, expecting the noise to diminish, but it didn't, not even in the slightest. So I went back in, loosened the belt a bit, and the noise went away. I'm interpreting this to mean that at least in my case, the belt didn't really loosen after the initial installation.



The other concern I have is that unless you have a P9201 tool, setting the belt tension is very subjective, plus setting the belt preload and belt-to-idler clearance is a very tedious and tricky task. A generous member here lent me his P9201 tool, and wow, what a difference. No guesswork, and a result that's virtually guaranteed to be perfect. I finally got the pre-load and clearance right, too, but it took a lot of patience.



My concern is that I'm not completely convinced that re-tensioning the belt isn't likely to do more harm than good. Now, if you have a P9201 tool, I would say that sways the decision in the direction of doing it.



So, I'm looking for some hard evidence that re-tensioning the belt makes a difference, as I wonder if, akin to the discussion in another thread on lubricants, the recommendation that was made by Porsche 20 years ago was correct at the time, but as the quality of belts has improved, is it possible that re-tensioning is no long necessary, and may even be counter-productive?

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[flash]

hand up here. neglected to do it once, and paid the price. with the mileage on the belts only at 25k, and it was merely age beyond the 3 year limit (5 years), i have to think that if it walks like a duck...................



that being said, i don't use the tensioning tool. i felt what the tension was supposed to be like once, and can now duplicate that with ease.

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[RS Barn]

Once you set with tool you can use another way to duplicate by feel. Without a proper starting point it's very difficult to estimate tension

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[MB968]

[quote name='WJH' timestamp='1333167478' post='124182']

Okay, got ready to slip my balance belt on. The manual says the balance belt has a painted tooth and to put that side out. I don't see that mark on my Gates belt. Am I missing something?

[/quote]



Looked at the Gates belt purchased a couple of weeks ago, not yet installed. It does have a painted tooth, which also happens to be on the same side as the factory numbers that are on the belt. That makes sense to me as the normal outside of a belt is the side with the factory numbers. In the absence of a painted tooth I'd use the side with the factory numbers as the outside.

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[Cloud9...68]

My belt is also like MB's, and I agree with his advice.

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