just changed the belts -- bit-o-whine too tight? suspect balance shaft

[kenny]

The proceedure for the timing belt was very good and the recent purchase of the $$$ tool seemed to work OK. However, the tention on the balance shaft belt was also supposed to be 4.0 (same as new timing belt setting). The problem is this belt is thicker and the tool doesn't seem to work right. We kind of did a 'similar' feel to the timing belt type tensioning but were never able to get the thing to work right on the balance shaft belt and the proceedure in the manual just wasn't cutting it.

After we put it all back together (also new cap and rotor) it was a little hesitant first few minutes but seemed to smooth out and runs strong. There is a little whining going on and I've heard some people talk about their belts being too tight causing the rollers to 'complain'. I suspect the balance shaft because of the reasons listed above -- thoughts from you regular wrench turners? Thanks

[Scott R]

Yes, I had the same problem. I think the old specs that the 9201 tool used have changed over the years with newer belts. Back it off a bit and it should be fine.

[kenny]

Scott,
That could be. I guess my main point was that the balance shaft belt is double sided and way thicker than the timing belt -- it just doesn't seem to fit/work like the timing belt; so, I'm confused about the proceedure for the balance shaft belt (as opposed to the timing belt which seemed to work OK).

[todwic]

The specs have changed. Firstly, they have a different belt than the original, and secondly the tension recomended has changed several times over the years.

[kenny]

...and the new spec/method is....?

[Scott R]

I wish Clark Fletchers site was still up his procedure covered this well from the garage tech perspective.

[kenny]

So... after all the belt posts -- got to be the number one topic! no one knows the actual procedure for tensioning the balance shaft belt?
Hey! at this point I'd go for a good rule of thumb or something. Also if the timing belt has really changed that much, is the reading on the tensioning tool changed. I can't find anything in the manuals or subsequent addendums that indicate as such. Additionally, the balance shaft belt procedure is a no-show!

[singpilot]

I just did the timing and balance belts. They whined until they were broken in. My mech says they do that. Took about 3oo miles. I had the tension checked again at that point... was still right on. If you don't get a better answer, see if it still does it after the shiny newness wears off of the belts.

Just did the chains and Carrera tensioner update on the 911. They were noisier (sounds like a turbine) until they had a few miles on them as well. Everyone thinks it's the fan that makes that noise.

My $.02

Michael Krebs
'83 944
'80 911SC

[kenny]

thanks singpilot. I've noticed that the whining has started to diminish as well. I just find it a little weird that after all that's been said on the topic, there is still a pretty big hole in it. I don't think I have a problem (at least now I don't after things have started to settle down a bit) but I was just looking for enlightenment.

[dan10101]

Heres the timing belt tension procedure from Clarks Garage -
------------------------------------------------------------------------------
Procedure

Initial Tensioning on Belt Installation (1983 -1986 Model Cars Without Spring Tensioner)


Pre-tension the camshaft belt by turning the tensioning roller eccentric nut (thin 24 mm or thin 27 mm open end wrench) counter-clockwise until the belt can be twisted 90° using the thumb and forefinger. This should be checked at the midpoint between the cam sprocket and the crankshaft sprocket. Tighten the tensioning roller locknut to 45 Nm (33 ft-lbs). Apply counter-torque to the tensioning roller eccentric nut while tightening locknut to prevent altering the belt tension.
Note: Originally, this was the only method of tensioning used on 928s and 924s. I know of several shops that have never purchase Special Tool 9201 and use this method on 944s as well. However, it is very risky and I strongly recommend checking the belt with the factory tensioning gage.


Belt Tensioning (1987 Model and Newer Cars With Spring Tensioner)

Release the spring tensioner by loosening the locking nut and locking bolt near the spring end of the tensioner.
Tighten the locking bolt and locknut to 20 Nm (15 ft-lbs).
Checking and Adjusting Cam Belt Tension (All Cars)

Yes, all cars. While some people contend that the tension does not need to be checked on cars with spring tensioners, I would disagree. From experience, I've found that spring tensioners vary from car to car and will not apply the same tension consistently when the spring is released. The spring tensioners seem to get close enough to the 2.7 ±0.3 spec for a used belt to be of little concern. However, the spring tensioner WILL NOT tension a new belt to within the tolerance for a new belt (4.0 ±0.3) unless the spring is released, the engine is rolled a degree or two, and then the tensioner is tightened down. The problem is that since spring tensioners tend to vary, you don't know exactly how many degrees to roll the engine. That's why it's important to check the tension using Special Tool 9201.

Procedure


After the camshaft belt has been pre-tensioned, remove the flywheel lock if installed.

NOTE
Do not install starter until crankshaft bolt is installed and torqued as the flywheel lock will need to be installed again.


Turn the engine clockwise two complete turns and align the mark on the camshaft sprocket with the alignment tab in the window on the distributor housing (TDC). Verify that the crankshaft is also at TDC by checking the "OT" mark in the window on the bell housing.
Turn the crankshaft 10° counter-clockwise. This is approximately 1.5 teeth on the camshaft sprocket.
Check the belt tension using Special Tool 9201. Pull the lock pin on the tool to release the tension roller. Align the drag needle with the gage needle. Install the tool on the section of the cam belt between the cam sprocket and the cam belt idler roller. Make sure that the tool's tensioning roller is on the toothed side of the belt.
Push the tensioning roller against the cam belt until the locking pin on the tool engages. Read the tension on the dial.

Tension specs:
New belt - 4.0 ±0.3
Used belt - 2.7 ±0.3

Adjusting tension on cars with eccentric roller tensioners:
Adjust the belt tension by loosening the tensioning roller locknut and turning the tensioning roller eccentric nut (thin 24 or thin 27 mm open end wrench) counter-clockwise and tighten locknut. Apply counter-torque to the eccentric roller when tightening locknut to prevent altering torque.
Repeat the steps above until the cam belt tension is within the specified tolerance.
Torque tensioner locknut to 45 Nm (33 ft-lbs).
Adjusting tension on cars with spring tensioners:
Loosen spring tensioner lock nut/bolt (2).
Using a pry bar or other suitable tool, manually compress or release tension on the spring as needed. While holding in position, tighten the tensioner lock nut/bolt.

NOTE
The intended tool for this purpose is the balance shaft sprocket pin spanner (P9200). The spanner pins fit into two holes on the front of the spring tensioner body.


Balance Shaft Belt Tensioning (All Cars)


Determine the amount of belt tension required for the type of belt you have.

Old style belt (15 mm wide) - 2.7 ± 0.3
New style belt (18 mm wide) - 3.5 ± 0.5

Loosen the locknut on the balance belt idler roller and move it away from the balance belt. It should not come in contact with the belt while checking the tension or during tension adjustment.
Check the belt tension using Special Tool 9201. Pull the lock pin on the tool to release the tension roller. Align the drag needle with the gage needle. Install the tool on the section of the balance belt between the lower and upper balance shaft sprockets.
Adjust and recheck the belt until the tension is within the specified limits.

NOTE
If you have someone to help you it is possible to adjust the belt tension while the tensioning gage is installed. However, the tension should be checked again after the tensioning roller locknut is torqued.


When the belt is set at the proper tension, tighten the locknut to 45 Nm (33 ft-lbs). Apply counter-torque to the tensioning roller to prevent changing the belt tension.
Adjust the balance belt idler roller such that the clearance between the roller and the belt at the lower balance shaft sprocket is 0.5 mm. This can be done with Special Tool 9207. I normally use a 0.5 mm feeler gauge. When properly adjusted, torque the locknut to 45 Nm (33 ft-lbs).

[kenny]

excellent!!

but the balance shaft belt is still much thicker than the timing belt resulting in what would appear to be high artificially high readings when measuring the balance shaft tension. Is there some adjustment then to the 9201 tool before readings are taken of the balance shaft belt? My problem is that I don't know how to use my tool (9201) on the balance shaft -- or I just stick the tool in and be happy -- with whatever reading I get.

[dan10101]

I'm not sure if this will help. On my website I have a couple of pictures. see if it clears anything up. The main thing is to get the adjuster between the cogs on the balance shaft belt.

Dan's Rennlist member web site

See the renegade archives for more information.

Renegade Archives

Hope this helps..

[kenny]

Thanks Dan, your site was very nice and I will certainly use it in the future.

As you can see from your pictures of the belts in the tool (timing and balance), it shows exactly what I've been talking about. The dial indicator is on 3 with the belt only -- no tension at all. Now if it is supposed to be set at 2.7 - 3.5 that doesn't seem like much tension after you subtract the no-tension state.

Now for $28 clams I also got the calibration tool (strip). But I'm thinking that it is for the timeing belt. With a small internal screw adjustment only, I can't imagine that there is another calibration strip just for the balance shaft as the internal mechanism would really have to be jacked a bunch to bring the dial back to zero.

That balance shaft is FAT! huh?

[Britwrench]

The calibration bar is to calibrate the GAUGE. Read the instructions.

Set the balance belt at 3.00 on the gauge. (the older style balance belt is no longer available). Always rotate the engine two turns (to bring it back to the same position) after each adjustment.

I always set the idler pulley (the one with the oblong slot) so that it only touches the belt and does not alter the straight run.

Usually these belts will whine slightly when new, if it is really noisy, you may have a faulty tensioner or roller.

[dan10101]

I was pulling on the belt during the picture to give a representation of what it would look like at 3.

Otherwise the picture would just look wierd.

DanD

[kenny]

OK but I'm guessing you didn't have '3' tension on the belt -- right?

Britwrench -- I got that far. My point was OK I use the bar to calibrate the 9201 tool -- check. It appears that this is calibration for the timing belt [only] -- did that -- no problem there.

The disscussion is narrowing as to whether the tension then also reads the correct tension on the balance shaft belt even though it is much thicker (thickness effects the dial on the 9201 tool --no?)

I actually think I may not have 'excessive' whining -- just a little, and I'll give it a few hundred miles to settle in before I would go in for a second surgery. Thanks for the help men!

[kenny]

Also,
Britwrench -- I replaced all of the rollers (4)