Broken air filter mount/bracket

[kerry]

Replaced the motor mounts on my daughter's 84SD and the air filter bracket with about 6k miles on it was broken at back and right end. Installed a new one and decided to take a close look to see why it failed so rapidly. While the engine itself was almost perfectly still, at idle the bracket was vibrating so fast the right end was just a blur. If I increased the rpm by 25-50 the vibration went away completely. It was/is some weird harmonics between the engine and bracket. I decided to try to stop the vibration by increasing the idle rpm's. I loosened the lock nut on the idle bolt and started turning it with a screwdriver but before the idle actually increased the harmonics went away and the bracket became still. Not sure how long this will last but if you have a broken air filter bracket, don't put it down to a shaky engine. Take a look to see if you are getting the weird harmonics and try to get rid of them. I don't see how the new bracket could have lasted more than a few weeks at the rate it was vibrating. (and all the bolts were completely tight).