Ticking TD5

My TD5 has started making ticking noises from the top end. i'm going to take the rocker cover off tomorrow to see if there is a broken injector spring or something similar. I was going to check the injector/rocker clearances are correct. what is the correct way of doing this?

I believe if you take the injectors out you need to use new copper washers, or at the very least you should re-anneal them.

I have had a TD5's injectors out because the washer failed, so its certainly worth re-annealing them - if they don't seal properly combustion gases will contaminate the fuel in the fuel gallery. This results in the fuel becoming aerated. If this happens, the engine will suffer poor starting and poor performance. Even with relatively small amounts of combustion gas in the fuel, the engine performance will suffer noticeably.

The injectors if removed have to be very carefully handled, so take great care.

Something else I was going to say but I have forgotten what it was... I will post it when I remember.