Have just replaced timing belt, plugs etc @180KM, followed recommended Haynes proceedure for timing belt adjustment.
Ended up with noisy tappets, (?), and after about 10Km, the timing belt slipped one tooth. Clearly correct initially, car ran suddenly badly and noisily, (understandably), but now sweet again after resetting timing positions, and increasiing belt tension.
The question is, if the proceedure in Haynes is followed, (5nm of torque on the tensioner pulley, etc) the timing belt seems too loose, to the extent that in the process of turning one engine revelotion by hand, the water pump pulley becomes so loose it can be easily turned (even spun) by hand. By increasing belt tension, all works well, but I am concerned about overtensioning the belt. The new tensioner piston just seems to need to be stiffer. (No, I didnt keep the old one to make a comparison. Rats!)
Have others encountered the problem, is there another (better) way of setting timing belt tension?

This is why I always tell people to get it done by someone with experience in the cars

the Haynes manual is 100% spot on if followed, if your belt was still loose post following the directions I am sorry to day you have either not set up the belt correctly in the first place, you may have left the slack on the front side of the engine prior to tensioning or you have made a mistake either way

I have done so many of these I have lost count however have never had any issue with the belt coming loose

It is normal for a belt to have a little slack when the engine is off depending where the engine has stopped and most importantly where the cams have stopped as the pre tensioner will back off a little however will take up the slack as soon as the engine is cranked

Thanks for you amazingly quick reply. What made me curious was the way the tension would vary in the course of one revolution, probably due to effect of valve spring loading the cams, but repeatedly the water pump always had a free spot?? The tensioner, (you referred to it as a pretensioner?but am I correct in saying there is no other? Some makes have hydraulic assistance over the static spring ), does not appear to be able to maintain adaquate tension on the belt.

A good rule of thumb with belts is tension enough so that you can *just* turn the belt sideways. If you cant turn it sidways its too tight, if you can turn it easily sideways its too loose.....
Hope this makes sense to you and helps.