earossi

Over the years, I have had opportunities to replace and adjust the tension on the balance shaft belts in my two 968's. I don't own the P5201 tensioning tool (to costly). However, I did purchase the Arnx tool for tentioning of timing belts (944's) and for tentioning the balance shaft belts on both 944 and 968 cars.

Though the tool is easy and straight forward to use, I find that my balance belts are always tentioned too tightly. I know this because they "whine". I end up having to reduce the tension until the "whining" goes away at which point the balance belts are really loose.

Anyone have an idea of what I may be doing wrong?

Grandpa#3

The Balance Belt is only tensioned at 28 ft lbs, so it will feel really loose compaired to the Cam Belt at 40 ft lbs.

Cheers,
Larry

future

I just use a gentle 90 degree twist of my index finger and thumb, works for me every time ... maybe I have the magic touch

Whining equals as you state, too much tension or your rollers need replacing – best policy is to replace all at the same time then you know for sure.

I've seen idiots put there rollers in a parts washer before installing a new B-S-belt ... the Whining turns into a scream

earossi

I did replace all rollers less than 10 hours of use ago. Using the 90 degree twist sounds interesting. I assume that you do this midspan between the upper balance shaft and the tensioning roller, right? My question is how you define "gentle" twist? Does that mean that you use very little effort to twist the belt through the 90 degrees? You would know if it was too tight, due to the whine. But, how do you know if the belt is too loose? I would hate to find that it was too loose by having the belt come off the rollers!

earossi

I am assuming that the screaming sound applies to the rollers that have their own bearings and seals, right? You are not referring to the rollers that mount on the balance shafts. Though I have not put any bearing containing parts in parts cleaner, I am just curious as to the reason for your statement. Does the parts cleaner take out the lubed bearing integral to the roller? Just curious.

future

Yes twist in that point and yes a very gental twist ... it should firm up at about 95 Degrees then run engine and listen if all sounds normal :-)

FRporscheman

The whining is good, you want that. Generally speaking, the belt tension doesn't have to be EXACT for it to work, but it might void warrantees / etc. If the belt is tightened to spec, it will whine. If you run it a little looser, you can lessen the whine, but if the whine is completely gone, the belt is too loose and is liable to wear out and snap.

Cheers

john durdin

IF ITS TENSIONED RIGHT IT WILL WHINE A BIT , ITS THE NATURE OF THE BEAST . JOHN

FRporscheman

Putting the rollers into a parts cleaner, or spraying them directly with something like brake cleaner can/will wash out the grease sealed which lubricates the ball bearings.

I have used brake cleaner on a rag to wipe the roller surfaces though. It's safe to use on the plastic and metal rollers.

You can use a stethoscope (or long screwdriver) and stick it to the mounting bolt/nut of the roller while the engine is running to track down a noise, if you think it might be coming from the rollers. You can only do this to the rollers whose mounting bolt/nut is fixed (i.e. not spinning)(duh).

earossi

So, having some time on my hands yesterday morning, I decided to "experiment" with the tightness on the balance shaft belt. I stripped off the belt cover and then, without really looking closely, reset the belt tention using the 90 degree twist procedure mentioned earlier in this thread. Left the cover off and took the car for a ride. Still a lot of whine. So, back into the garage for a closer look. At first thought, I was just going to loosen the belt a little bit further.

However, I got down really close to the belt to visually see the 90 degree twist, and rapidly noticed belt debris everywhere. Sure enough, the BS was coming apart on the front side of the belt (facing the front of the car). As I looked further, I then noticed that the upper balance shaft (the one that I had removed and reinstalled) appeared to have moved forward about 1/4 inch compared to the BS tensioner pulley. In fact, the BS is forward just enough so that the BS roller nut is contacting the backside of the plastic belt cover.

Obviously, I have to now replace the belt; but, the bigger question is how could the balance shaft have moved forward? The shaft is held in place by the front housing which is firmly bolted to the motor. Is there a possibility that the roller was not completely installed onto the BS when I torqued down the retaining nut? I have never heard of such a failure in the past.

Any ideas of what I may have done incorrectly or what I should look for as I tear the thing down again? I'm assuming that I have to remove the balance shaft cover and front housing in order to figure out what was done incorrectly.

I never really paid much attention to the positioning of the BS when I installed it since there does not appear to be any way to adjust location of the shaft.

Ideas?

earossi

Bump

earossi

Well, I took a hit to my dignity and it also cost me a new balance shaft belt and the time and energy to install it, but I found the cause for the apparent "forward" movement of the balance shaft that put the belt into misalignment which lead to its grinding failure.

As it turns out, the balance shaft itself was fine. What had occurred was that when I slid the balance shaft gear into place, the woodruff key did not stay square in its half moon shaft groove. The key was pushed backwards by the gear as I slid it into place on the shaft. As the key moved backwards, it slid upwards out of its groove. Not completely; but, just enough to wedge itself between the back side of the bs gear and the shoulder on the shaft. The result was that as I tightened down the attachment bolt for the gear, the key was able to hold the gear about 1/8" outboard of where it should have bottomed out. That produced the misalignment that lead to the belt rubbing on the gear sides.

Lesson learned is to make absolutely sure that the gear slips on easilly and that the woodruff key remains where it should have. Second lesson learned is that I should have inspected my work before moving on. That's the hit to my dignity.

Hopefully, this little confession will help someone else not make the same mistake.

Lastly, I would like to thank Raj who contacted me to discuss the problem. In that discussion, he was the one that mentioned the woodruff key issue. Thanks Raj. It is guys like you that make this forum such a wonderful tool for not only our cars but for the friendships that form. Without help from guys like Raj, there are many things that I would have never attempted before.

RajDatta

My pleasure. Glad it turned out to be something simple.
Is the lower BS spinning freely now?
Regards.
Raj

earossi

Raj,

Yes, the lower BS spins as easily as the upper BS which I had not touched. I must have just had some Loctite 574 run into one of the bearing races for the lower shaft and as soon as the motor kicked over, I am fairly confident it corrected itself. Have a new BS belt on the way and should bolt her back together tomorrow sometime.

Then it is time to pull the oil pan to replace the gasket. Hopefully, this takes care of 99.9% of the leaks on the motor! I know the front of the motor does not leak a drop since I replaced every seal in that area.

Thanks again for the confidence and help.

Ernie

jacbabbitt

Hi Earossi
When you replaced the oil pan gasket did you have to raise the engine or anything, or did the oil pan come out fairly easy? I fighting leaks too?
Thanks
Jack