furiousgeorge experienced tensioner failure with his timing belt becoming perilously loose... apparently caused by loss of pressure in the tensioner's gas charged cylinder






when this happens, the plunger relaxes in the direction indicated above, and the timing belt's tension is lost











Steve suggested the use of a split collar as in this example...
clamped onto the tensioner's shaft to prevent the excess travel

collars are available from McMaster Carr... their split steel 8mm (inside diameter) black oxide collar is a perfect fit for the TT's tensioner. It's part number 6063K14 and McMaster delivered it in one day(!) for $5.44 + shipping












Due to the design of the casting, the split collar doesn't have a good surface on the tensioner to seat against












A 3/8 inch steel flat washer is a good remedy, seating into the casting just perfectly to function as a "stop" while not interfering with the plunger











With a new belt, and the locking pin pulled, run the engine to insure the belt/pullies are fully seated before sliding the collar into light contact with the washer. Finally tighten the collar's two cap screws. Now the belt will remain "in tension" even after a total failure of the tensioner

I've not experimented with fitting these parts on an installed tensioner/belt. But the idea is a good one. IMO it's never to late to install a fail safe against tensioner failure.


parts:

1) steel, black-oxide, split collar, 8mm ID,
pn 6063K14, $5.44
from McMaster Carr

2) 3/8 inch hardened steel SAE flatwasher
from any hardware store

• McMaster Carr, search on: split collar, then select: two-piece clamp-on