What could cause a timing belt to fail in under 15K miles? I've changed a few before and not had problems. This belt was a Mazda part with new Mazda tensioner. It broke after just 15 K miles. Not sure what the failure is as the car just was towed home. What should I look for. No symptoms of pending failure, no rubber stink or anything. Car is an 89 w/only 65000 on it. I changed the belt at about 50 when I first got it. Failed under hard acceleration going up a hill after exiting a highway ramp. Car was running at about 75 MPH for 50 miles before getting off highway.

Thanks for any and all advice.
Rich M

 

Other then a defective belt I would say the new tensioner was more then likely the problem.

 

I almost never use this forum anymore because of the way it's programmed. It uses some cross-site scrpting or some such and my AV tools kill it on my regular machines.
Anyway, turned out the upper timing idler wheel's bolt sheared off. Rather BIG mess. I tried to drill out the broken bolt, drilled through the water jacket, killed the head. I've taken it all apart and put one one new head and re-did the other side. FWIW broken belt on an SOHC does NOT wreck valves. Head job on this motor is pretty bad first time through, probably very straight-forward for a real mechanic. I've got the heads and ex manifolds back on. Waiting on some parts to complete the fix. In about a month it should be back on the road and healthy.