by Jerry Hastings

Created on: October 24, 2008

Changing a timing belt can be relatively simple on some engines and very involved on others. Often removal of parts, other than timing belt covers, to gain access must be a part of this repair. Some engine and auto designs are such that very close tolerances between the engine and body in the timing belt area is also a problem. Some engines require special tools not normally found in many tool boxes.

Correct positioning of the pulleys upon installation of the new belt is critical, so an engine specific repair manual should be consulted beforehand and during the repair to get this step right. Timing marks on the pulleys and on the engine block or head must be exactly aligned before installation of the new belt, and should be double checked after replacement is completed but before the covers etc. are reinstalled.

The teeth or cogs on the pulley side of the timing belt fit into grooves on the pulleys. These grooves and cogs keep the engine timing correct throughout the timing belt's life. If, per chance, the timing belt is incorrectly installed or for some reason slips or breaks, the pistons could conceivably contact the valves and cause a very costly repair.

One should also consider the possibility of the need to unbolt one engine mount and suspend or lift the engine, making it possible to remove the old belt and install the new belt. Some engines have one motor mount on the timing belt end of the engine that bolts up under the cam pulley(s), and the timing belt runs on either side of the motor mount. This makes it necessary to unbolt the motor mount then lift the engine a little so the belt can be slipped through the gap in the two halves of the motor mount. Of course, an adequate lifting device must available that will safely lift and hold up the engine.

Correct belt tension and belt tensioner pulley mechanical condition is another very critical area. Always check the pulley on the tensioner for rough sounding operation, as this may signal future tensioner pulley bearing failure. Consult the repair manual for correct tensioning procedures upon installation of the timing belt to get this step exactly right too. A timing belt installed too loose will likely eventually strip the teeth or cogs of the pulley side of the belt. A timing belt installed too tight may eventually break. Both scenarios can have engine destructive consequences.

Proper preparation prior to undertaking this repair will help assure that you are not stuck with a car or truck partially disassembled with no hope of a timely completion. An alternate mode of transportation to secure any other necessary parts needed is also a good idea.

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