Timing belt tension

[superwhite]

I installed a new belt but the method used to set the tension is confusing in the Haynes manual. The arrows in the manual indicating the measurement points aren't eguall distance between the pullys, should it be? How do most do this? I have rotated the engine two rounds with the tensiner bolt loose then tightened it bit I'm stuck on how to insure the tension is equal as suggested in the manual.

 

[hvyman]

You need to put tension on it, the turn over by hand 1 complete revolution so the cam marks are pointing up. After that you should have equal tension in both places and it shouldnt jump a tooth when you start it.

 

[radiod]

Here's the TSRM version.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=30

And trust me, you'll know if it's too loose. I had mine looser than it should have been and at certain rpm's, the harmonic wave action of the loose belt was causing it to slap against the side of the timing casing.

 

[shaeff]

Also keep in mind, if the belt tensioner bracket is even slightly bent (which is easier to do than you think) then the belt will be loose.

 

[IJ.]

New Spring on the Tensioner, rotate the crank a couple of turns to set the belt pull the breaker bar back a little so the non tensioner side of the belt is tight and allows the spring to pull any slack out of the belt and tighten the tensioner bolt to 36 ft/lbs NOT 1 ft/lb more or less.

 

[superwhite]

That sounds like one of the easier to understand methods and I think thats what I'll go with. The TSRM says to install the belt on the pullys starting with the crank and work counterclockwise around the rest of the pulleys. Then it says to "release the idler mount bolt until the pully is moved slightly". When I loosened the bolt the pully moved sharply and stopped when it contacted the belt and tightened it as much as the spring was able. Its like they are saying you slowly move the idler to make the tension equal at points "A" to match that at point "B". That would then suggest you don't use the full strenght of the spring. But if thats so then the springs free lenght wouldn't be as critical as they suggest. Free lenght would seem to be more important when using the springs full strenght to insure proper tension. PLUS how on earth do you accuaratly check for equal tension as they suggest?

New Spring on the Tensioner, rotate the crank a couple of turns to set the belt pull the breaker bar back a little so the non tensioner side of the belt is tight and allows the spring to pull any slack out of the belt and tighten the tensioner bolt to 36 ft/lbs NOT 1 ft/lb more or less.