Balance belt tension

[Guest]

Whilst doing my PS pump seals I had the airbox and auxillary belts off so I though I'd pop off the balance & cam belt cover to checkout what lurked below.

I noticed that on the balance belt there is a lot of play on the long run from the lower adjuster up to the top balance shaft pully and reading the manual they use a special tool to measure the play on that section of the belt.

As my belt was moving some 20 - 25mm I thought best just nip it up a little until I can get it checked properly so tightened the lower adjuster enough to bring the tension to a more realistic level. I also checked the idler pully clearance which should be 0.5mm. Having done this I've noticed that the idler & or the adjuster pulleys hard to tell now make a "whirring noise" is this normal or have I got something adrift, is it just the bearing within the idlers are worn and need replacing ?

Mike

 

[Guest]

I'll answer my own post then[] Just been reading on 968.net that the whirring is quite commen when the belts have been re-tensioned so I guess nothing to worry about immediately, although at some stage I want to replace all the pulleys/tensioners & front seals.


Mike[]

 

[Diver944]

Cor you really get stuck in don't you Mike, I'm very impressed [][]

Couple of weeks and we'll all be asking you questions, have you thought about a weekend job servicing and repairing the forums 968's and 944's [8D]

 

[Guest]

I've always prefered to do a lot myself as its the only way you can be assured that the jobs been done right. Also means I can save money for those important modifications later on [] Porsche on a budget is much more fun anyway how else would I get away from the screaming kids if I couldn't go and hide in the garage for a few hours here and there []

And this is just the start !

Mike

 

[Guest]

When i had the cam & balance belts changed, they found the pulley/jockey bearings were noisy and needed to be replaced. They were disapointed that they couldn't press out the old bearing and just replace that, rather than having to buy a whole new toothed pulley.

They said the bearing had been specially machined so that a standard bearing couldn't be used and that the whole pully had to be replaced from Porsche. I had all the pulleys and jockey replaced and it did whine at first but it went off after a few hundred miles.

Del

 

[Guest]

Well I've driven about 50 miles today and the engine is still in one piece so the belt can't be too far adrift, although it still whines like a sowing machine on steriods, in fact one of the guys at work asked if I'd supercharged it [] I wish !!. So anyway I've been trying to source a tension gauge with little joy except for Porsches £400+ dial gauge job.

In the end I've managed to Source a possible supplier for a Kriket tension gauge today (after posting on 968.net) The company that makes them is Gates and they kindly referred me to a UK distributer B.L.R.
Unfortunately I ran out of time today so will have to follow up this lead tomorrow, from reading elsewhere these gauges aren't as exact as the proper Porsche tool but a lot of folk seem to have had success using them apparently you need to get several consequtive & consistant readings of 28Lbs on the longest stretch of the balance belt to be on the money.

Depending on how much they are I might get a few, seems there is a profit to be made on Ebay []

Mike [8D]

 

[Diver944]

Mike, the club has one of the tensioner tools that it loans out to members (I'm assuming it's the same as a 944 one), one of the many many [] benefits of joining. Check with Steve Kevlin at club office, he's the tech contact and will know if they are one in the same.

 

[Marky Boy]

Hi Mike, I work for Gates PT in the UK. I'm not to sure about the tension gauge your talking about as we only make the belts. We make these double sided belts in our plant here so i'll speak to the technical dept tomorrow and get their take on all things tension for these belts, they designed them so should have a good idea what works and what doesn't.

 

[Guest]

I still haven't followed this up yet, but just so you know Mark the Kriket Gauge KR1 is actually designed for V belts, although a lot of the guys on 968.net have used it to good effect on their balance belts.

Mike[]

 

[Marky Boy]

I asked today regarding these belts. I was told that the qauge used is called a staeger ( or something )gauge. Seemingly they are also used by BMW and Volvo. I asked about the Ultrasonic gauges also. The measure the natural harmonic frequency of the belts vibration to determine the tension. Only probs with this is you need to know the distance between the pulleys and what the tension should be in Nm. They said with the distance however you could work out what the tension should be.

I also spoke to our QA dept regarding these belts and they said that they dont think they have ever had a customer claim from damage caused by these belts. So they think they are quite resilient and not as fragile as some people think, as long as they are not kinked during installation.

One interesting thing i did hear however was when these engines were designed porsche knew that these belts will produce a sort of whine when under tension. Rather than looking for other quieter option they kept with it saying the sounded sporty.

In general as long as these belts are in the right ball park they shouldn't present a problem. If they are to tight you'll hear it squeal, and if its to slack it'll flap about. So as long a you get as close as you can with a normal tension gauge you should be ok.

Hope this helps.

 

[Guest]

Interesting stuff, thats why I want a Kriket gauge to get it there or thereabouts, I know they are not as accurate as the proper kit. I'm also of the opinion that like most things you can virtually do it by feel which is what I've done for now, but its nice to double check.
Having done a few Rover and Ford Cambelts you tend to know whats about right, but there again their engines aren't quite so expensive to sort out if they do go pop.[&:]

Cheers for the info tho' it makes me feel a little happier with my turbo powered sewing machine, although I'll be even happier when I've had chance to listen to another one which hopefully I will Saturday at the mini meet of 968s at Oulton Park.

Mike[]