patanga

My S2 is on the road again but I am still dealing with what I presume to be a noisey balance shaft belt. I've made a couple of videos showing where things are right now. The first vid demonstrates the noise itself. Assuming that the noise is typical of the balance shaft belt then I guess it must be too tight. The second vid will show the tension to which I have set the belt.

The problem that I am trying to overcome is that I have just about run out of idler pulley adjustment that allows the pulley clearances to remain within recommended specs. As I understand it the lower idlers should maintain a gap of 0.5mm and the belt to upper idler clearance should be close to 0.1mm. You will see from the second vid that the belt already looks quite loose. Is there anything obvious that I might do to overcome this?

Vid 1

Vid 2

patanga

I've held a metal ended screw driver against the water pump housing, timing belt top idler and the balance shaft idler pully's as a stethescope and the most audible noise comes from the balance shaft belt idlers. That might indicate that the noise is caused by the belt teeth running against the idler surface and maybe the tension is still be a little too tight. Looking at the second vid though I am about out of adjustment in terms of backing it off and it is already very loose. Keeping in mind that both idlers are new does anyone have any more ideas?

william_b_noble

definitely a belt is too tight. remove balance shaft belt and see if noise persists. if yes, cam belt is too tight - loosen lock bolt, let the spring set again and tighten (your car is an 87 or later from the looks of the engine and has the self tensioning timing belt. there should be just a little whine from the belts. I sometimes set the belt tension with the engine running (my car does not have the auto tensioner) and I set it to where it is just barely starting to whine).

Grandpa#3

The Cam Belt is set at 40 ft lbs and the Balance Belt at 28 ft lbs., so the Balance Shaft Belt will feel real loose. It does not sound all that bad and the belts will stretch. The belts should be re-tensioned at 1,500 miles. We always tension all the belts with our P9201 tool. The video below is in 3 parts for a Water Pump and Belt change out, but shows how to tell if the Balance Shaft Belt is adjusted about right.


Cheers,
Larry

patanga

Thanks for your feedback gentlemen. Much appreciated.

Larry: It was your video # 3 that I actually used as a reference. Thanks for taking the time to post it.

I had another go at the adjustment today and I can confirm that .5mm clearance (credit card thickness) is at the lower idlers and the top balance shaft idler is just clear of the belt when the engine is not running. Referring again to your video, I set the lower adjuster so that the belt is just at the flattened setting (i.e. natural curvature removed) without starting to apply further tension. Both of the balance shaft belt idler pulleys are new and the orientation of the 27mm eccentric nuts are also similar to that shown in your video. Yet for some reason the noise remains.?? By the way: When you say "The Cam Belt is set at 40 ft lbs and the Balance Belt at 28 ft lbs." Do you mean those are the gauge readings on the P9201 tool, or that is what you set the idler mounting nut torque when tightening?

Of note is that the noise was not there previously, i.e. when the old & worn idlers were still on the motor. That said the new idlers feel perfectly smooth, as they should, when rotated by hand. I have held a stethescope against all of the idlers and water pump and with the motor running the noise is definately coming from the balance belt idler area. The upper balance belt idler moreso than the lowest adjuster.

I've also tried setting the belt adjustment a little tighter and then more loose to see if there might be a sweet spot but as yet have not been able to achieve quiet operation. Is there anything else you can suggest that I could have overlooked or could try to get rid of the noise?

Cheers & thanks in advance.

mike77

My S2 had this noise so I increased the gap between the balance belt idler roller and the belt and it went away. I found if the roller was always in contact with the belt and spinning quickly when the engine is running then it made noise. I set the idler gap slightly above spec, it only touches the belt if the belt flaps a little. The idler now only makes the occasional half turn or so when the belt comes into contact and no noise.

Since I'm saying set the gap beyond spec, do this at your own risk. My car has run like this for 2 years with no problem.

patanga

Thanks Mike77. Where things are at now is that I have set the tension of the belt so that the idler clearance is around 2 mm when the top balance shaft sprocket it rotated clockwise so that the belt slack is removed. With the engine running the idler wheel still spins, but I can at least now stop it with a little pressure from my finger. So far I've managed to keep all of them attached to my hand. There is now quite a bit of clearance when the engine is switched off. I will give this setting a go and see how things work out. The noise is still audible so time will tell if the setting is good. My local Porsche specialist has also confirmed that the model was renouned for this condition.

mytrplseven

Some of us acquire the tensioning tools and some of "back yard" mechanics (old School) set the timing belt just tight enough so the W/P barely moves when turned by hand. The balance belt should be able to be turned just past 90 degrees and looks overly loose but since it's double toothed, it's not a problem. I've done mine that way (1987) and a little whine is apparent but it's not loud and I'm not worried. I rechecked at 2000 miles and after all the teeth had seated and settled in, I re-tensioned and the belts had slackened slightly but now they're good to go.