DOHC Engine Timing System (Sierra)

TDC position of piston 1st cylinder of DOHC engine

The position of the timing marks on the camshaft sprockets corresponding to the TDC of the piston of the 1st cylinder of the DOHC engine is indicated by arrows.

Hydraulic tensioner for the timing chain of the DOHC engine

Timing chain drive

During all operations requiring removal of the camshaft drive chain, the hydraulic chain tensioner must be replaced before reinstalling it.

The method for replacing the chain has been changed. The following procedure should be followed.

Replacing the timing chain

1. Disconnect the ground wire from the battery.



2. Disconnect the air damper together with the flexible air supply line, idle control valve and crankcase ventilation line.

3. Disconnect the crankcase ventilation pipe from the cylinder head cover.

4. Disconnect the wire from the ignition coil to the ignition distributor.

5. Remove the distributor cap (two Torx socket bolts).

6. Disconnect the high-voltage wires, remove the distributor rotor and remove the distributor protective plate.

7. Remove the cylinder head cover.

8. Remove the upper timing chain cover.

9. Turn the crankshaft so as to set the piston of the 1st cylinder to TDC (see Fig. TDC position of the piston of the 1st cylinder of the DOHC engine).

10. Using a special key, lock the camshaft sprockets and unscrew the mounting bolts with a Torx socket.

11. Remove the chain guide made of artificial material after removing the two locking elements with tweezers.

12. Remove the ignition distributor drive.

13. Mark the position of the chain relative to the sprockets of both camshafts.

14. Remove the sprockets from both camshafts and tighten the chain slightly on the left side.

15. Remove the tensioner axle spring retaining ring.

16. Using the M6 bolt, remove the tensioner axle while simultaneously moving the tensioner down to loosen the chain tension (see Fig. Removal the drive chain tensioner axle of the DOHC engine timing system).

17. Remove the tensioner.

18. Remove the hydraulic tensioner plunger.

Caution! The push rod cannot be reinstalled.

19. Install a new hydraulic tappet. Check that it is properly locked (see fig. Hydraulic tensioner of the timing chain of the DOHC engine). If it is completely unlocked (ring 1 is visible) or partially unlocked (the entire upper part of the tappet piston is visible), then to lock it, press the piston into the tappet cylinder (the upper part of the piston is not visible or protrudes minimally from the cylinder). In this case, pay attention not to damage the pistons of the hydraulic tappet.



20. Insert the entire assembly into the cylinder head (piston should be facing up).

21. Install the tensioner, axle and snap ring.

22. Place the chain on the left camshaft sprocket. Set the shaft to the position corresponding to the position of the piston of the 1st cylinder at TDC, and tighten the sprocket mounting bolt by hand.

23. Perform the same operations for the right camshaft and install the ignition distributor drive.

24. Install a new chain guide (made of synthetic material) and secure it.

25. Slowly turn the crankshaft clockwise until the intake camshaft begins to rotate.

26. If the pusher piston protrudes from its cylinder, then you should press the tensioner by hand to unlock the pusher.

27. If the upper edge of the piston is at the height of the upper edge of its cylinder (blocked), then to unlock the piston, proceed as follows: lift the tensioner with a screwdriver and install, for example, a welding electrode between the body and the piston. Then remove the screwdriver and unlock the piston.

28. Lock the camshaft sprockets and tighten their bolts to a torque of 56–62 Nm.

29. Perform several revolutions of the crankshaft and check the adjustment of the tensioner.

30. Check the condition of the gasket and install the upper timing chain cover.

31. Perform the remaining steps in the reverse order of the chain removal process.

(The text is available on the specified website info portal Fordbook.ru)