Rocker arm replacement

Lost 2 rocker arms this week and my motor died a pitiful shuddering death.

DON'T PANIC!

It's an easy fix.

The rocker arms on a 4D56 (which I have experience with) and presumably the 4M40 (which I don't) are designed to snap rather gruesomely in the event that the timing relationship between the Cam and the Crank goes a bit wobbly like when timing belt 'A' breaks. I kinda get the impression that the torque forces involved with the larger petrol engines may not result in quite the same limited damage, bur probably one of the V6 guys could answer that one.

Anyway, on a diesel, all is not lost.

1 Get the intercooler off (remember the 4 electrical connections at the bulkhead (back) end of the Intercooler and all the hoses.

2 Take the rocker cover off

3 Before you do anything else, get the shrapnel out of the way and take your time doing so as you don't want to leave anything behind.

4 On the top of the rocker arm/oil bar which has all the remaining arms on, there are 5 12mm bolts. Take them off in sequence, back/bulkhead to front/Cam belt end. and store them in order they came off.

5 Pull the bar and arms off the castles they are mounted on and lay them down without dropping any off. Inlet valve for number one cyclinder has worn into the valve guide over the years and likes being there. It won't like ending up on number 4 exhaust, so be careful

6 Check the head and castles that the rockers bolt into for cracks as the piston does hit with some force when it strikes a hanging valve before it blows the rocker arm. There may be damage and if you don't recognise it and deal with it now, you'll pay to repair the arms and maybe do more damage as a result of a fractured castle mount which will cost you more rockers and maybe the head and engine. You've got it stripped this far, so get a torch and make a good visual inspection.

7 Lay the bar and rockers out to inspect them too.

8 Take the rockers off from the bar in the order they are missing. If you have only damaged rockers upto cylinder 4, leave cyclinder 4's rockers on the bar. Lay them out on something soft like polystyrene in order: Cylinder 1 Ex/IN Cylinder 2 Ex/In etc.

9 Add your replacement rockers in the spaces left by the damaged rockers, in sequence and with the spacer springs in place.

10 Slide them all back onto the bar taking care to get them on by cyclinder and position. From the front they go 1 Ex/In 2 Ex/In 3 Ex/In 4 Ex/In

11 Offer them back up to their castles, set the spring spacers, put the 12mm bolts back in order and bolt them down.

12 You will need to re-gap all the valve clearances as any movement of the rockers and bar will change these values and the new rockers need to be reset anyway. There is a seperate post about this and the clearance is 0.25mm cold. Re-check when hot, so don't crank the rocker box down too tight.

13 When you do put the rocker box cover back on, please use new seals/gaskets and don't forget the half-moon jobbie. Also use a good quality RTV/High temperature sealant to get a good mating.

Total job time: 1 hour.

Cost: £14.00 per rocker and they do them in the clubshop.