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95 toyota 4runner 4wd

I had the drive belt and tensioner replaced; it slipped off again at 3500 mile later while my wife as driving. Brought it back to the same mechanic; he told me that he hand cranked the belt and it kept slipping. He wants to open the engine to look at the cam for a fee. Is it possible that the engine (cam) could be damage from what happened? I really felt that I am being taken adantaged by this mechanic. Please an comment? By the way I have put in around $6K on this 175K Mile car; is it worth having this car look at by another mechanic or sue the mechanic that originally worked on it?

When you say ‘belt slip(ed) off’ do you mean the accessory drive belt or the cam timing belt. The cam has no connection to the accessory drive belt and tensioner so I am assuming you are referring to the cam timing belt.

Usually the cam timing belt is tensioned using the load spring and then that idler is locked with a bolt. So the timing belt should not be slipping if the belt is correctly tensioned. If there were a problem of the cam overloading the timing belt, it would usually show up as a broken belt or teeth torn off the belt.

A problem of overloading of the belt drive could easily be determined by putting a bending beam torque wrench on the cam pulley bolt(s) and measuring the turning force. The mechanic would have to go from experience because usually that torque is not specified. If there is a problem with a cam or cams overloading the timing belt, yes a look see is in order by removing the valve covers; removing the cams; and inspecting the bearings, straightness, cam surfaces, and cam follower surfaces.

Let us know the progress on this problem.