Every so often, the timing belt on a car's internal combustion engine should be checked and eventually replaced. The exact timing belt replacement interval will vary by vehicle and engine, as will the replacement procedure, but overall the general replacement method is the same for most gasoline engines.
The most common interval is around 70,000 miles and most mechanics will recommend taking off one of the timing belt covers to examine the belt at the 50,000 mile interval.
A timing belt replacement usually costs about $500 in labor and about that again in parts, depending on the vehicle, so expect to pay a mechanic between $800 and $1,200 for a timing belt change. It literally involves tearing down the entire motor and will take at least a days' work to complete - often longer.
An advanced home mechanic can do a timing belt change in a weekend.
Procedures for Timing Belt Change
The procedures for removing and replacing the timing belt will vary in detail by vehicle type, but the below are common to most vehicles.
- Disconnect negative battery terminal and/or remove battery
- Drain and remove coolant, oil and radiator.
- Relieve pressure in fuel system and remove air intake system (carburetor or injection system).
- Remove timing belt covers and engine accessories (as needed).
- Set engine to top dead center (TDC)
- The engine will remain in TDC throughout, so care should be taken to keep it from moving!
- Mark TDC on existing belt, pulleys, etc. to allow for replacement in exact alignment with paint or a marker.
- Loosen camshaft pulleys and crankshaft pulley(s).
- Remove either camshaft pulleys or crankshaft pulleys, as required to remove timing belt.
- Remove timing belt tensioner and/or spring (as appropriate) for replacement.
- Replace new belt to exactly match position of old belt, torquing pulleys into place according to specifications.
- Recheck TDC position to ensure no movement has occurred.
- Replace components in reverse order to removal, again torquing bolts as required by specification.
- Turn engine carefully, without battery connected, from the crankshaft bolt, checking timing and for any resistance or scraping or other indicators of a problem. Repair these now before cranking the engine under power.
- Replace oil and coolant.
- Reconnect battery and crank engine under power, using a timing light or tool to adjust timing per specifications.
- Run engine until warm, test timing again.
- After a few hours' operation, retest timing, fuel mix, and air intake and optimize.
Timing Belt Replacement Intervals
Timing Chain vs Timing Belt
50,000 mile maintenance