Camshaft Chain and Tensioner Replacement — 16V Engines

Introduction

Unlike the 8V 944, the 16V 944S and 944S2 have two overhead camshafts — one for the intake valves and one for the exhaust valves. The exhaust camshaft is driven directly from the timing belt via a camshaft sprocket (identical to the 8V arrangement). The intake camshaft is driven from the exhaust camshaft via a toothed internal chain that runs between gears near the center of each shaft. Chain tension is maintained by an oil-fed tensioner.

The tensioner itself can be a long-lived component, but other tensioner components — the plastic guide rails and the J-tube oil supply pipe — may require earlier attention. Inspect the tensioner at 45,000-mile intervals up to 90,000 miles, then at 15,000-mile intervals thereafter.

Parts

Part	Part Number
Tensioner	944 105 049 01
Timing Chain	944 105 501 01
Oil Supply Tube (J-Tube)	944 105 167 03
Seal Rings for J-Tube	900 123 115 30 or N 013 807 09
Cam Housing Gasket	928 104 447 09
Top Tensioner Pad	928 105 509 01
Bottom Tensioner Pad	928 105 347 01

Note: Part numbers are stamped on each tensioner pad individually. Whether the pads can be ordered separately from the complete tensioner assembly should be verified with your parts supplier.

Procedure

1. Disconnect the battery negative lead.
2. Remove the cam cover. Check the inside of the cam cover and the cylinder head for signs of chain rubbing.
3. Carefully stuff rags into the oil drain galleries at the lower side of the head, next to the exhaust valves. This prevents parts from falling down the oil ways when the chain tensioner and oil feed pipe are removed.
4. Inspect the chain tensioner and oil feed pipe for signs of wear or cracking.
5. Remove the air filter housing and inlet pipe up to the air flow meter.
6. Remove the power steering pump and alternator belts (and air conditioning belt if fitted).
7. Disconnect the wire to the Hall sensor on the rear of the exhaust cam sprocket rear cover and move the wire clear of the plastic covers at the front of the engine.
8. Using a 10 mm socket, remove the bolts securing the black plastic covers from the front of the engine. Remove the upper and lower covers.
9. Remove the distributor cap and plug wires (3 screws).
10. Remove the metal cover over the front of the exhaust cam sprocket.
11. Remove the ignition rotor from the cam sprocket (3 screws).
12. To lock the cam pulley timing position before removing the pulley bolt: reinstall the 3 ignition rotor screws back into the pulley assembly and tighten. This locks the pulley onto the three-armed trigger "propeller" which is keyed to the cam. If this step is skipped, removing the pulley bolt will allow the pulley to rotate on the cam, causing loss of cam timing reference.
13. Remove the fan assembly from the radiator to increase working clearance.
14. Set the engine to top dead center: align the scribed mark on the cam pulley with the line on the top lip of the metal cover behind the pulley. Verify TDC at the flywheel — on the driver's side of the clutch bell housing near the top, there is a square hole through which the flywheel can be seen and a static pointer. The line scribed on the flywheel marked "OT" indicates TDC. At TDC, the notches on both balance shaft sprockets should align with the static marks on the plastic cover: the upper (right) sprocket notch aligns with a notch on the cover at the 12 o'clock position; the lower (left) sprocket notch aligns with a molded protrusion on the cover at approximately the 7 o'clock position.
15. With the crank at TDC and the cam pulley mark aligned, mark the relationship of the cam and balance shaft belts to their sprockets, and mark the direction of belt rotation (the crank pulley rotates clockwise when viewed from the front). If balance shaft sprocket removal is needed, also mark the relationship of the balance shaft pulley covers to the pulleys.
16. Loosen the balance shaft tensioner pulley (located to the left of the lower balance shaft pulley when viewed from the front). The tensioner pulley has an eccentric hub clamped with a nut and washer. Once the nut is loose, belt tension will cause the tensioner to rotate and slacken the belt. Note the tensioner hub position before releasing it.
17. Carefully remove the balance belt from its pulleys and tensioners.
18. Locate the cam belt self-tensioner mechanism (below and to the left of the upper balance shaft pulley). The mechanism has a bracket with a pulley on the left and a spring on the right, with three nuts/bolts. Using a 13 mm wrench or socket, loosen the top nut (attached to the tensioner pivot stud) and the right locking nut.
19. Push downward on the tensioner pulley to compress the spring and slacken the belt. Remove the cam belt from the cam pulley. If helpful, temporarily tighten the right-hand nut to hold the tensioner compressed while removing the belt.
20. Remove the tensioner mechanism from the engine (secured by three nuts, one of which requires first removing an idler pulley using a 17 mm socket).
21. Carefully remove the cam belt. Removal of the crank pulley is not necessary if the belt is eased clear without kinking or damaging it.

Caution: Once the cam belt is removed, do not turn the crankshaft — rotating the crank with the belt off can cause valve-to-piston contact.

22. Before removing the cam pulley, scribe precise alignment marks on the exhaust cam and the adjacent front bridge piece, on the cam pulley tooth timing mark and the pulley rear cover lip. These marks must be exact — a 0.5 mm misalignment at the cam equals approximately 2 degrees of cam rotation. Using a steel rule to extend the line is recommended.
23. Using a pin spanner in the slotted holes of the pulley to prevent rotation, remove the pulley bolt using a 10 mm spline drive bit (12-point). The bolt is tight. Remove the pulley bolt and its hexagonal washer.
24. Pull the pulley off the cam (a puller should not be necessary). If using the locking tip from step 12, the metal shield and three-armed trigger propeller will come off with the pulley. Do not remove the woodruff key.
25. Remove the three bolts and the rear metal pulley cover.
26. Remove the four bolts and the front bridge piece that clamps the ends of both cams to the head.
27. Remove the exhaust cam end seal and the inlet cam end sealing bung.
28. Before removing the tensioner and cams, compare the new cam chain alongside the old one. With the cams at the crank TDC position, a cast-in triangular pointer on each cam should be pointing straight up. The cam chain has two copper-colored links. Between the copper links, there are five plain links. These copper links must align with the sprocket tooth that lines up with the triangular pointer on each cam, on the top run of the chain. This copper-link alignment governs the intake-to-exhaust cam timing and is critical on reassembly.
29. Remove the metal J-tube oil pipe from the chain tensioner and head by unscrewing both banjo bolts. Remove all sealing washers (2 per banjo fitting).
30. Before removing the tensioner, depress the upper rubbing block against the tensioner spring pressure and temporarily lock it in position (for example, by inserting nails into the holes in the metal tensioner body alongside the plastic rubbing block). This step is unnecessary if the tensioner is being replaced.
31. Remove the two bolts attaching the tensioner to the head and remove the tensioner.
32. Remove the cam retaining cap bolts using an 8 mm spline drive bit (12-point). Loosen each bolt very gradually and evenly — approximately one quarter to one half turn at a time — because some valves will be open and their springs exert uneven pressure on the cam. Each cap is numbered 1–8; matching numbers are stamped on the head next to each position. Note the orientation of each cap before removal — the caps are not interchangeable and are line-bored with the head during manufacture.
33. Carefully lift out both cams together, complete with chain. Take care not to damage cam bearing surfaces or cam followers.

Chain Replacement and Cam Reinstallation

34. Install the new chain on the cam sprockets: ensure the two copper-colored links align with the sprocket teeth that line up with the triangular pointers on each cam.
35. Reinstall both cams. Before fitting the cam retaining caps, confirm the triangular pointers are in the same position they were before removal, and that the copper links are correctly aligned. Lubricate all bearing surfaces. Refit each cap in exactly the same position and orientation as before. Tighten the cam cap bolts gradually and evenly. Torque the cam cap bolts to 15 ft-lbs.
36. Refit the exhaust cam end seal and inlet cam end bung.
37. Refit the bridge over the end of both cams. Apply a thin smear of gasket sealant (such as Hylomar) to the mating surfaces.
38. Refit the cam pulley rear metal cover.
39. Slide the pulley onto the cam. Check the alignment of all scribed marks — on the cam and front bridge, on the end of the pulley and camshaft, and on the pulley tooth and pulley rear cover. The cover bolts may need to be slightly loosened and the cover shifted to align the marks. Once all marks align, tighten the pulley rear cover bolts.
40. Refit the three-armed trigger propeller and metal shield, then refit the pulley. Apply Loctite to the pulley bolt before installing. Hold the pulley with the pin spanner and torque the pulley bolt to 48–52 ft-lbs. After torquing, recheck all scribed marks.

Caution: Cam timing alignment is critical. Incorrect alignment can cause loss of torque at a minimum, or valve-to-piston contact and severe engine damage at worst.

41. Install the new tensioner, ensuring the plastic rubbing block is properly depressed before installing the mounting bolts.
42. Install the new J-tube oil pipe with new sealing washers (2 per banjo fitting) and tighten both banjo bolts.
43. Remove all rags from the oil drain galleries inside the head.
44. Refit the cam and balance shaft belts with the crankshaft at TDC and the cam sprocket mark aligned with the static mark on the sprocket rear cover. The notches on the balance shafts should align with the static marks on the plastic cover. If old belts are being reused, refit them to run in the same direction as before removal.
45. Inspect tensioner and idler roller bearings; replace if worn or rough. Inspect the water pump if it has high mileage.
46. Tension the cam belt using the special tension tool where available. Balance belt tension must also be set correctly.
47. Before starting the engine, turn the engine over slowly by hand through several full revolutions with the spark plugs removed. Any hard fouling of pistons and valves will be detected this way.
48. Reinstall all remaining components in reverse order of removal.