From the engine rebuild manual;
Mounting the chain tensioner
– Press the chain tensioner together up to the first notch and lock in this position. Slide into the hole in the cylinder heads together with a new O-ring.
NOTE: – Check and lock the chain tensioner: see Chapter 5. – The piston 1 must protrude approx. 3 mm out of the chain
–Mount the plug with a new seal ring and tighten to 25 Nm.
–Press against the piston of the chain tensioner with a screwdriver to cause the mounting lock to yield and the piston to extend. The chain tensioner rail will be loaded and the timing chain tensioned.
NOTE: if you press against the chain tensioner now it will lock. This makes sure that the timing chain is tensioned when you start the engine and not enough oil pressure has been built up yet.
! CAUTION !
IF THE CHAIN TENSIONER IS NOT LOCKED AND RELIEVED AFTER ASSEMBLY AS DESCRIBED IN CHAPTER 5, THE TIMING CHAIN WILL SKIP WHEN THE ENGINE IS STARTED, RESULTING IN ENGINE DAMAGE.
Timing chain tensioner
! CAUTION !
IF YOU DO NOT FOLLOW THESE INSTRUCTIONS, THE TIMING CHAIN WILL NOT BE TENSIONED CORRECTLY AND WILL SKIP, RESULTING IN ENGINE DAMAGE.
NOTE: – The timing chain tensioner 1 operates with spring force and with oil
pressure. A stop system is used to ensure the right timing chain tension in the engine starting phase, even if the oil pressure is insufficient. The stop system prevents the piston 2 on the timing chain tensioner from being retracted.
– In a dismounted state, the piston on the timing chain tensioner extends completely.
– Fully depress the spring tensioner. This will require some effort since the oil must be squeezed out. If the timing chain tensioner is released it will extend completely again; it may not be mounted in this state, since the locking mechanism will not function.
– Press down on the timing chain tensioner to ensure smooth operation.
– To prepare the timing chain tensioner for installation, place 2 spacing washers or similar implements with a thickness of 2 - 2.5 mm next to the piston of the timing chain tensioner. This will ensure that the piston cannot be completely retracted when the piston is pressed down. If you release the piston, the stop system will lock, the piston will protrude approx. 3 mm and stay in this position - this position is required for refitting!
–If you press the timing chain tensioner again and it extends no more than half way (preventing it from extending completely), the stop system will lock and the timing chain tensioner can no longer be pressed together - this position is necessary to ensure that the timing chain is adequately tensioned, even if the oil pressure is low.