Premature failure of a rubber timing belt can easily cost two or three thousand dollars of repairs, possibly including a new engine. Therefore knowing the true mileage of a used car is imperative. Off lease Cars having 4 or 6 cyl. engines may have rubber timing belts and should be avoided.
Five years ago an international oil company survey found that 50% of off-lease cars had their odometers illegally turned back and suggested consumers avoid buying off-lease (used) cars, or leasing used cars having uncertain mileage. If the cars really had 50,000 miles, and the odometer read 30,000, then the timing belts would fail long before the new owners expected them to fail.
What is an “interference engine”?
Rubber timing belts are usually used in “interference” engines in which the
valves open further and project further into the combustion chamber than in a “free-running” engine. This allows outside air at atmospheric pressure to flow faster into the combustion chamber through the larger valve openings, allowing the engine to inhale more air, be smaller and still create as much power while reducing its manufactured cost and guaranteeing future repair business for the dealer.
If a rubber timing belt breaks while engine is running, some of the valves stuck in their
open position will smash into the top of the pistons, thereby breaking or
irreversibly damaging one or the other or both.
How to find out if the engine is an “interference engine”.
The salesperson may not know; ask the Service technician. Better yet, go on any search engine and type in “interference engine list” because asking the Dealer’s service technician may not be reliable. If he says it does not, have the Dealer’s Sales Manager (not the salesperson) say so on the purchase order and personally sign and thereby guarantee his assertion. For recommended replacement mileage of rubber timing belts, connect on the Internet to Gates Rubber Company, a worldwide manufacturer of such belts. On its web site, click on Replacement parts/automotive. Look for “timing belt replacement Guide”.
Get a written guarantee to cover premature failure of the car engine’s timing belt.
Because most rubber timing belts on car engines should be replaced at 60,000 to
70,000 miles to avoid the engine self destructing, insist on a written guarantee from the seller to guarantee replacing the timing belt at no charge if it fails within another 20,000 miles. If the seller won’t guarantee it then he’s admitting that the mileage may be inaccurate and by implication may have been turned back. Consider a compromise, such as a $300 price reduction on the vehicle. If not acceptable, walk away.
Simply replacing a rubber timing belt even at recommended mileage can cost $400 + dollars. Before buying any car, especially 4-cylinder foreign cars, or even a 6-cyl. BMW, be aware of the unavoidable cost of $400-$800 to replace a rubber timing belt at recommended intervals based on mileage or car age.
That’s assuming the timing belt didn’t break. If it breaks (always while the engine is running) then internal engine damage will take place catastrophically. If a timing belt on an interference engine is not replaced at recommended intervals, the repair cost when the belt breaks could increase to $3,000 to $5,000 to replace the entire engine. The sales person will invariably not mention that an interference engine powers the vehicle and may not even know what one is.
The sad part of this problem is that it is not possible to detect timing belt wear without substantially tearing down the engine. The timing belt is literally a “sleeping time bomb”.
Therefore, always buy the cars with “free-running” engines…