Good Timing for Replacement of Belt
Question: My mechanic has recommended that I change the timing belt on my four-cylinder engine. It hasn’t caused any problems so far. The car has 80,000 miles on it. What do you think?--E.K.
Answer: Automobile manufacturers and mechanics differ significantly in their recommendations on timing belt replacement. Many manufacturers suggest that belts be replaced every 60,000 miles; many others make no recommendation at all.
The timing belt transfers power from the engine crankshaft to the overhead camshaft, which operates the engine valves. But unlike the belts on the outside of the engine that power the alternator or the water pump, timing belts are heavy duty and contain notches that fit into a similarly notched pulley. They are usually hidden inside the engine by a shroud.
In some respects, timing belts are like a chain, except for the fact that a chain is much more reliable and does not ordinarily require replacement during normal engine life. Belts are cheaper to manufacture and lighter in weight, both important considerations to auto designers. But in the long run they are more likely to cause trouble. Unfortunately, few car buyers inquire whether engines have belts or chains, thereby providing little incentive for manufacturers to use the more reliable chains.
Timing belts can last 200,000 miles or they can last 40,000 miles, depending on the car and the driver. Ford took a lot of lumps on the timing belts on some early Escorts, which often failed after only 30,000 or 40,000 miles.
Quick Starts
Heavy-footed drivers cause additional fatigue on a timing belt, since quick starts put quite a lot of stress on the engine valve train. The belts are made of a reinforced-rubber compound, which can also be susceptible to damage from high temperatures.
When a timing belt fails, the camshaft stops, the valves no longer operate and the engine immediately dies. If that were the only hazard in putting off servicing the belt, it might be acceptable.
But when a timing belt fails, it often causes catastrophic engine damage. At the instant a belt breaks, the engine valves stop their normal sequence, but the pistons continue to move up and down while the car coasts to a stop. Once the valves are out of sequence, they can collide with a piston and cause serious engine damage. The cost of repairing such damage can easily exceed $1,000.
It is obviously a smart move to replace an engine belt before that happens, but it’s difficult to know when a timing belt is shot. On some cars, timing belts can be easily inspected for such telltale signs of wear as cracking and drying. But on many cars, the labor cost to inspect the belt is almost as great as it is to replace the belt.
Owner’s Manual
If that isn’t confusing enough, some manufacturers go back and forth in recommending belt changes. The same manufacturer can recommend regular belt changes every 60,000 miles and then make no recommendation the next year. Honda, for example, has followed this practice.
You should consult your owner’s manual and closely follow the recommendations laid out in it. If it makes no recommendations, you might ask the mechanics at several dealerships or contact the manufacturer’s representative to ask about the average service life of the belts in your car. In any case, if you are not a risk-taker, you might want to replace the belt after 60,000 miles.
Update
Here’s an update on a recent column about new black plastic bumpers that are prone to fading. Ford Motor has recalled about 28,000 Tracers to check plastic bumpers for fading as the result of exposure to ultraviolet light. Faded covers will be replaced with covers that contain light stabilizers. As recommended before, motorists should keep plastic bumpers clean and use a plastic or rubber preservative, many of which are available at auto-parts stores.
Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.
