Auto Repair Encyclopedia
Sometimes referred to as Timing Belt, Replace Timing Belt, Timing Belt Replace, T Belt, T Belt Replace, Replace t belt, timing gear belt, timing gear belt replace
Driven by the crankshaft, the timing belt keeps internal engine components in sync by causing valves to open and close at the proper time.
In order to maintain the mechanical integrity the engine needs to operate, engine components must be in precise synchronization. If the timing belt is loose or improperly adjusted, it may "jump time" (skipping a tooth or more, usually on the cam gear). This results in a loss of synchronization and engine performance.
There are 2 types of engines you will hear about when the discussion of broken timing belts arise, "Interference" and "Non-Interference". These terms refer to the relationship between the pistons and valves when the camshaft and crankshaft are out of synchronization.
- Non-interference: When the timing belt breaks the valves and pistons will not come into contact with one another and you can merely replace the belt and all should be OK
- Interference engine: This is another matter. If the belt breaks, the pistons will hit the valves, bending them and causing major engine damage. At the very least the cylinder head will need to be removed and the valves replaced, in extreme cases the piston may be damaged and the engine may need replacement
In addition, because the timing belt is made from rubber and reinforced with fiber cords, it naturally degrades over time. It should be replaced at scheduled intervals, which vary among car manufacturers, but are usually every 60,000 to 90,000 miles.
In some cases, when the timing belt fails, the engine will simply stop running; replacing the belt will fix the problem.
Some engines cannot tolerate any deviation in precise valve control (e.g. a loose belt, skipped tooth, belt separation, or breakage). In these engines, timing belt failure can have disastrous consequences. These belt-related problems can cause major engine damage, such as damaged pistons and bent valves. The Check Engine Light may illuminate with a fault stored in the computer relating to timing deviation. In extreme cases, the timing belt may be audibly loose and noisy prior to failure; however, a worn belt can fail without warning. Timing belt maintenance and replacement intervals must be followed diligently.
To replace the timing belt, remove the fan belts, pulleys, crankshaft pulley, and timing covers. When replacing the timing belt, the mechanic also inspects components inside the timing cover and, if necessary, replaces oil seals, tensioners, and idler bearings. On certain engines, a water pump replacement should be done at the same time as the timing belt. The timing belt and timing belt idler are considered a unit and should be replaced at the same time.
About this Repair: Timing Belt Replacement
Best Practices
Timing belts have a mileage and time replacement interval. It's important on low mileage vehicles that you follow the time interval as noted by the manufacturer.
It is often recommended that you replace the water pump, front engine seals, drive belt, idlers, and tensioners along with the timing belt. *This will be an addition to the estimate you receive from RepairPal, which is for the timing belt replacement only.
Common Symptoms
It is crucial that the timing belt be replaced at or before the interval recommended by the vehicle manufacturer. Failure to do so can result in a broken timing belt, which can leave you stranded, and in some cases, it can cause severe damage to the engine.
A worn timing belt can result in trouble codes from the camshaft or crankshaft sensors, causing a dashboard warning light to be lit.
The engine can make slapping or scraping noises if the timing belt is loose or worn. Adjustment may take care of the noise, but replacement may also be necessary.
morganautomotive.com, July 31, 2010, 23:15
95% of water pumps are timing belt driven and fail around 90k so to replace a T belt without a new pump & tensioner is a failure waiting to happen.