Timing Belt Replacement, Is your engine on the interference list?


timing beltWhat Are Timing Belts? A timing belt is a small but crucial engine part that can keep a motor running properly and improve fuel efficiency. While not all engines have belts, they are the most common over timing chains or timing gears. The belt wraps around a series of gears at the front of the engine to aid in “timing” the opening and closing of fuel valves. Made from the same material as most other engine belts, they are not the most durable part and will wear out eventually. Timing belts are normally used in smaller engines, but only rarely in larger ones. Timing belts are relatively new additions to the modern automobile, being only sporadically utilized as early as 1945. The first practical mass-market use was in 1962 when a timing belt was successfully incorporated into the German built Glas 1004. This was followed in 1966 by that year’s Pontiac Tempest automobile and soon became the template for the future use in all commercial vehicles to follow. Function the function of a timing belt is to turn the camshafts at exactly one-half the speed of the crankshaft. The camshaft manages the opening and closing of the intake and exhaust valves with the up-and-down movement of the pistons in the cylinders. The valves must open and close at the proper rate, so the timing belt must be calibrated properly to move the valves in time with the correct motion of the pistons. The camshaft and crankshaft gear both have a timing mark on them that must be aligned correctly prior to putting the timing belt on the gear teeth or the engine will not run. It’s is important to change the timing belt at recommended intervals. If you’re unsure when to replace it, the vehicles owner’s manual, manufacturer, or dealer can offer this information. This will range from every 60,000 to 105,000 miles. It is best, though, to not let a belt go more than 80,000 miles even if the belt is rated much higher.


The lack of a timing belt makes any equipped vehicle nothing more than a stationary hunk of metal. Proper understanding, installation and maintenance of this important part will keep any engine running perfectly for years. Timing belt replacement intervals are important but you should always have your vehicle’s timing belt checked periodically as oil leaks from the camshaft and front crankshaft seals cause the life of the timing belt to be greatly reduced.

Important: Most of today’s timing belt driven vehicles are interference engines.

Here is a good list of interference/non-interference engines:

interference and non-interference engine list

To put the definition of a interference engine into simple terms is this, if you timing belt breaks or slips you will MOST likely have severe engine damage.

The interference type engine may experience serious damage when the timing belt breaks. This is because the cylinder valves stop moving while the pistons continue on a collision course. This potential for engine damage underlines the importance of servicing this key engine component before it fails. After time and mileage the teeth on the belt weaken and may break off without notice. When this happens the cam timing changes, usually radically, causing the engine to stop running.

The advantages; Intake and exhaust valve timing durations are longer and the lift is also increased. This allows more “fresh air/fuel” in and more exhaust out per cycle. The disadvantage is the piston and valve can “Kiss” if the timing belt breaks. The good thing, with normal maintenance and following manufacturer recommendations for changing the timing belt very few belts just break. If they do, it is very rare. Usually it is because the engine gets over revved, oil leaks from the cam seals on the belt, seized water pump or a bad idler pulley. If you have an interference engine change the timing belt when you should and you will be fine.

The non-interferencetype engine does not experience damage when the timing belt fails. Even so, the inconvenience and expense of an unexpected vehicle breakdown are avoidable by servicing the timing belt on schedule

Does your vehicle have an interference engine???

Does your vehicle have a timing belt???

Please verify your vehicle’s engine has timing belt first, if so then:

Contact Us || Call For An Appointment  (503)704-4687

NOTE: if your just trying to find out if your engine is interference comment this post. This way other people can benefit from the advice. We will not respond to phone calls for mechanical advice.

This post was written by: Martin Hand


If you find this information helpful please consider a donation. These articles, questions and comments are very time consuming so even a small donation gives me motivation to keep educating automotive owners. Donations will allow us to continue open questioning/comments, automotive education and repair tutorials in the future as the business grows. All proceeds go to the expansion and maintenance mdhmotors.com. Thank You

MDH Motors logo

About Martin Hand

ASE Certified L1 Advanced Mastertech. Martin Hand has over 15 years experience in Asian and European Import Auto Repair. Specializing in electrical diagnosis, engine performance, AT/MT transmission repair/rebuild. Martin is also pursuing a degree in Computers Science & Information Systems starting at Portland Community College while he plans to transfer to OIT. Certified in Java application level programming, experienced with other languages such as PHP, Ruby, JavaScript and Swift. Martin has future plans of automotive diagnostic software development.