Hi, having refit a radiator after a full rebuild ive just filled the system at the rad neck only to find a very slow trickle of coolant coming from a very small hole in the clutch cover above the embossed honda sign as shown in picture. this hole is obviously supposed to be there but why would coolant be leaking from here?
Help appreciated. Thanks,

Andy

It's a tell-tale indicator. Warning that the mechanical water pump seal is leaking.

If gearbox oil was coming out of it, it would mean the water pump oil seal is leaking.

Unfortunately, you'll have to take the side cover off to replace the seals. When I do it, I change both of the seals and the small bearing too.

The mechanical seal is around £45 inc vat. I used Stephenrc45's advice and pressed the old one out and the new one in using my bench vice.

You have to tap the bearing out and remove the oil seal first though.

Just changed one of these myself, I heated the case in the oven (make sure the case is nicely degreased and the missus is out first) at about 150-160 c for half an hour and the bearing just dropped out, should make it easier to press the other seals out as well.When installing heat the case again and put the bearing in the freezer for a bit before assembly.

Remember when removing the impeller from the shaft that it has a l/h thread and you will need a holder to hold the gear.

cheers guys for the very detailed info that helps me a lot and anyone doing a search.
Paul the thread is actually a conventional r/h thread, the only l/h thread that ive come across on the nsr is the nuts holding the rc cables.

Anyway thanks again.

Andy