Thurston Car Talk: Timing Belt Basics

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Brons Automotive is located in the heart of West Olympia. Photo credit: Bron's Automotive.

Submitted by Bron’s Automotive

Do you know if your car has a timing belt or a timing chain?  This is critical since a timing belt must be changed at regular intervals to prevent a breakdown.  Timing chains on the other hand are lubricated with engine oil and the best thing you can do for them is to change your oil on a regular interval.  Manufacturers have a specified interval that they expect a timing belt to last and since they are the folks that engineered the engine, we should heed their advice.  The interval they come up with is safe, generally ranging from 60,000 to 120,000 miles.  Timing belts rarely break before their recommended mileage, but will break sometime after, sometimes just after and sometimes a long time after.  Since we don’t know exactly when, we have to play it safe and do it when the manufacturers recommend.

The engines valves that are opened by the camshaft to let in an air and fuel mixture, or expel exhaust gas, have to be timed to open and close at the right time in relation to the pistons coming up and down.  This is why it is called a timing belt.  On some engines the valves open far enough that if they opened at the wrong time, the pistons would make contact with them and bend them, requiring disassembly of the engine to repair it, an expensive and time consuming job.  These types of engines are classed as interference engines and are in the majority of engines produced.  When one of these timing belts breaks it may or may not cause valve damage depending on the position of the valves at the time of the break.  The other class of engines is non-interference, where it is unlikely that the valves will be bent.  These engines are in the minority.  Either way, when one breaks, your engine will die and strand you.

Many timing belts also drive the water pump, and in these cases the opinion of Brons Automotive is that the water pump should be replaced with the timing belt.  The reason is simple.  If you replace the timing belt at 105,000 miles and don’t replace the water pump, you’re hoping that the water pump will last until the next timing belt interval at 210,000 miles.  Most likely it won’t, and replacing the water pump requires you to perform all the same labor involved in timing belt replacement.  Whether this happens at 115,000 miles or 140,000 miles, paying for labor again will not make anyone happy.  It’s better to do whatever is necessary during the scheduled timing belt job to make it all last until the next timing belt replacement interval.   For this reason we sometimes replace idler pulleys due to noisy bearings or a tensioner that is showing signs of leaking. Remember that if something fails, it may cause engine damage, so it’s better to be safe.  The goal is to do what is necessary to reach the next scheduled timing belt interval mileage without incident.

Shops that quote a ridiculously low price for this job compared to other shops are usually not doing the job correctly and premature failure before the next scheduled interval can be the result, sometimes resulting in engine damage.   Make sure you know what parts will be replaced and why when you have your timing belt replaced.  Your shop should be happy to discuss this with you.  If you are unsure if you have a timing belt or a timing chain, call us at Brons automotive with the year, make, model, and engine size of your vehicle and we’ll be happy to tell you what the manufacturer recommends.  Happy Motoring!


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