Hey guys,

I have a customer car, 1994 Honda civic hatch with an LS motor setup, bottom end is stock. Head has crower valvetrain and cams. The car had a loose timing belt when it came to us (head has been milled, not sure if that is effecting this).

We replaced the water pump, tensioner, tensioner bolt, and timing belt all at the same time. For some reason, the belt still seems to be fine when we crank the car and it idles, but on a test drive, it continues to come off the cam gears (anywhere from 5 minutes to 30 minutes during the drive). The tensioner is still tight after the belt comes loose. The customer purchased an aftermarket vibrant tensioner to help resolve the issue, but the belt came loose again and made two of the bolts on that aftermarket tensioner snap!

Any advice is much appreciated! We have done a ton of timing belts and never had this issue!

Below is a video of how the timing belt looks when the car is running. There is no slack in it when the car is idle, but you can see slack when the car is running.


--Ryan

 

Video isn't working.

Do those internals require a stronger timing belt be used? (gates,toda,greddy

 

The water pump may have a bad bearing and with belt tension on it could be angled very slightly. This would be just enough to cause the belt to walk off. Also, these ARE valve benders; how have you avoided that with the belt falling off?

Very small possability is a bad mill on the head (not sqaure to the block) and causes the belt to walk off slowly.

 

I'm a bit confused.

Does the belt eventually walk off the cam gears? Or does it skip teeth?

Or do you mean to say that you adjust the belt to have a certain amount of KOEO freeplay, but after some running time there is a lot more KOEO freeplay than you set it for?

I'm still confused. Video looks normal. There should be some slack always, with that slack showing up as belt-whip when the engine is revved. Revving the engine up and down will result in the slack being transferred back and forth between tensioner side and long-run side, which is exactly what I see in that video..

 

what brand of belt...new ? go oem Honda for for the tensioner it's self and remeber 40ft lbs for the tensioner bolt and do the exhaust cam first. stock cam gears, ?

 

when you put on the timing belt, did you make sure to put #15 on after you adjusted timing?

 

Got it guys! Took it apart and put the belt back on and all is fine. I have no clue what was causing the slack?!

 

I'm curious what a leak down test would show...