Just bought a 1988 Lotus 40th Anniversary Model. Anyone out there know: if it needs a new water pump (I have the part) does it make more sense to change it with timing belt at same time, or is separately OK?
I also have an '88. Definitely change the belt too. Very little money for the belt. Even if you get the better blue belt (about $150 from JAE if I recall) you will have to do all the same work and remove the belt anyway, and it's not a small job or a quick one. Might want to change the idler bearing too if it's been a while. I would change all the belts while you are in there. It's a tight job and you would regret doing one thing and then having to go back and do the same work for another relatively minor expense.
If your water pump is leaking, for sure, change the new timing belt too. If it isn't, hold onto your new pump until the next C service.
Gotta watch out when buying a "new" water pump, however. Some model-year pumps had different mounting points for other engine accessories. It's a lot cheaper to rebuild your existing pump. JAE can rebuild yours and send it back to you. Or, you can buy the parts needed to refurbish your present pump.