944 Drive-Belt & Balance-Shaft Belt Tension (Special Tool 9201)
Factory belt-tension gauge readings for the 8-valve 944 measured with the Porsche belt-tension tester (Special Tool 9201/9202): the poly-rib accessory drive belt, the toothed camshaft (timing) belt, and the toothed balance-shaft belt, plus how to calibrate the 9201. Every figure is a dimensionless scale reading — check tension only on a cold engine.
Factory belt-tension figures for the 8-valve 944, read with the Porsche belt-tension tester — Special Tool 9201 for the toothed belts and the 5-rib poly-rib belt, and the related 9202 tester for the 5-rib poly-rib check. Every value on this page is a dimensionless scale reading off the gauge dial, not a force or a torque, so nothing here switches between metric and imperial. The one true torque in the procedure — the tensioner-nut torque — is switchable and is listed with the other engine torques on the 944 engine tightening torques page.
Caution: Check and adjust belt tension only on a cold engine, at room temperature (approx. 20 °C68 °F). A warm engine reads high and gives a false tension.
The gauge is used the same way for every belt: pull the lockpin on the tool, push the test pin on the opposite side fully out, zero the drag (telltale) needle against the indicator needle, slide the tool onto the belt with the sliding shoes in full contact, then press the test point in slowly until the lockpin engages and read the dial. After the lockpin engages, re-zero the drag needle (turn it anticlockwise) before reading, and never let the tool turn or move on the belt while measuring.
Poly-rib accessory drive belt
This is the ribbed belt that drives the alternator and, when fitted, the air-conditioning compressor. Two belt widths were used, each with its own tester and target reading.
| Belt | Tester | Adjusting value (scale reading) |
|---|---|---|
| 5-rib poly-rib belt | 9202 | 9.5 ± 0.3 |
| 6-rib poly-rib belt | 9201 | 9.5 |
The 5-rib belt is set with tester 9202: slide the tool on, read the dial, and correct to 9.5 ± 0.3 scale units by turning the connecting rod.
The 6-rib belt is set with tester 9201. Back the connecting rod off one turn first to relax the belt, then bring it up to a reading of 9.5 on the scale. On cars with air conditioning, reach the 9.5 reading and then turn the connecting rod one further revolution to add tension.
Toothed camshaft (timing) belt
The camshaft drive belt is set with Special Tool 9201. Turn the crankshaft clockwise to TDC on cylinder 1 (TDC mark on the camshaft sprocket aligned with the cast mark on the distributor-cap console, and the flywheel/clutch-housing TDC marks aligned), then turn the engine back anticlockwise about 10° at the crankshaft (roughly 1.5 teeth on the camshaft sprocket) before taking the reading. The target depends on whether the belt is new or already run in.
| Condition | Scale reading |
|---|---|
| New belt | 4.0 ± 0.3 |
| Used belt | 2.7 ± 0.3 |
A separate control value is given for checking a belt in service:
| Time in service | Acceptable scale reading |
|---|---|
| Up to about 3,000 km | 2.4 to 4.3 |
| More than 3,000 km | 2.7 ± 0.3 |
So a fresh belt is fitted tight at 4.0 and is expected to settle to the used-belt figure of 2.7 as it beds in. After adjusting, tighten the tensioner nut to the specified torque while counterholding, then turn the engine two full turns clockwise, return to TDC, back off about 10° at the crankshaft, and recheck.
Toothed balance-shaft (compensating-shaft) belt
The 944's two balance (compensating) shafts are driven by a separate toothed belt with its own tensioner and an adjustable idler pulley (the roller with slot). Set it with Special Tool 9201; there is a single target for both a new and a used belt.
| Belt | Scale reading |
|---|---|
| New or used balance-shaft belt | 2.7 ± 0.3 |
Procedure, in outline:
- Remove the splash shield, the poly-rib belt and the power-steering-pump belt, and take off the balance-shaft drive-belt cover.
- Slacken the idler pulley so it no longer bears on the belt.
- Set the engine to TDC (camshaft-sprocket TDC mark aligned with the mark on the drive-belt cover; flywheel TDC mark aligned) and confirm the balance-shaft sprocket marks line up with the marks on the rear drive-belt cover.
- Read the tension with 9201 and adjust: turn the tensioning roller clockwise to tighten, anticlockwise to slacken, until the gauge reads 2.7 ± 0.3. Tighten the tensioner nut to the specified torque (45 N·m33 ft·lb) while counterholding.
- Re-set the idler pulley. Using Special Tool 9207 or a 0.5 mm feeler gauge, set a clearance of 0.5 mm between the belt and the idler pulley at the lower balance shaft while the upper run of the belt is preloaded 0 to 1 mm, and tighten the idler pulley in that position. If the clearance can't be reached, rotate the idler pulley 180° and repeat. Tighten the idler-pulley mounting nut to the specified torque.
- Refit the drive-belt cover, the power-steering-pump belt and the poly-rib belt, and re-tension the poly-rib belt.
Power-steering-pump belt
The power-steering (servo) pump belt is a plain V-belt and is not checked with the gauge. Check it by thumb pressure midway between the two pulleys — the belt should deflect approximately 5 mm. Adjust it at the pressure-rod adjuster: slacken the mounting bolt, loosen the pressure-rod lock nuts, and turn the rod until the deflection is correct, then retighten.
Calibrating Special Tool 9201
The 9201 tester is checked and calibrated against the master gauge 9201/2, which is designed to read 4.0 scale units on a correct tool. Calibrate the 9201 after about 100 measurements, or after any hard knock or slight damage.
You need a small screwdriver (1.6 × 40 × 0.4 mm) and gauge 9201/2:
- Zero the dial gauge — turn the scale ring until the needle sits on zero.
- Insert gauge 9201/2, checking that both test bearing surfaces sit centred on the sliding shoes.
- As when measuring a belt, press the test point in slowly until the lockpin engages, then read the dial.
- If the reading is outside 4.0 ± 0.3 scale units, turn the calibration screw with the small screwdriver — with 9201/2 still between the sensors — until it reads 4.0.
- Recheck after calibrating.
Caution: The sliding shoes on older tools may be bored off-centre, which changes the reading with shoe position. Repeat the check at different shoe positions, find the position whose reading is closest to 4.0, mark that shoe, and always calibrate and measure at that position. Calibration will not correct a tool that is more than 2.0 scale units out or otherwise badly damaged — such a tester must be repaired.