Tuesday, July 2nd, 2013

The Truth About Timing Belts

automotive timing belts

Truth About Timing Belts

One of the most misunderstood services on today’s vehicles is the maintenance and replacement of the timing belt. The most common question we as a service facility usually hear is what exactly is a timing belt? By definition a timing belt is a toothed belt that connects the camshaft or shafts to the crankshaft thus “timing”the top and bottom of the engine. The camshafts turn at exactly ½ of the speed of the crankshaft to time the valve operation to the piston operation.

Exactly what does this mean? It really as simple as this; in order to complete the combustion sequence the valves must be opened or closed at the proper time in conjunction with the travel of the pistons. If that “timing” is off many times severe engine damage is the end result.

Surprisingly enough the original concept of the timing belt was for Singer sewing machines to synchronize the needle and bobbin drives. Originally made of a band with metal clips this proved to be expensive and noisy, in 1945 Singer in conjunction with Uniroyal which is now Gates Inc. developed the timing belt.

Now to all you guys from the 50’s and 60’s typically every engine had a timing chain. The upsides of chains were long life cycle, however the downsides were that they were noisy, had to be lubricated, and the materials used in their manufacture were expensive to produce and install.

Enter the timing belt. Timing belts are quiet, their production costs are relatively less than chains and sprockets, and they are light and needs no lubrication to function. The downside is that belts need to be replaced at specific mileage or time limits. This is where all of the discrepancy of maintenance and replacement occurs.

Depending on what schedule you may read, including information distributed by the manufacturers themselves, the average life span of a timing belt is between 60,000 and 105,000 miles or after 7 to 10 years regardless of mileage. Most manufacturers state that going more than 80,000 to 90,000 miles on the original belt is flirting with danger.

This seems to be very straight forward and easy to comprehend but here is what the manufacturers do not tell you. The beauty of timing belts are that they have self-tensioners that are made to keep the belt tension constant to prevent loss of power or worse yet to keep the engine from jumping time and ruining the engine. They have idler pulley’s that also keep the tension constant as the belts age and stretch.

Imagine just how many revolutions these pulleys and tensioners have turned in 8 years or 80,000 miles, I would guess in the millions. Vehicle manufacturers have also realized the timing belt can be utilized to run the water pump and to monitor camshaft timing and report it to the PCM.

As a service provider it is my duty to explain this concept to you the consumer. Many times it is a 4 or 5 hour job to change a timing belt, by not doing the job right and replacing all of the tensioners, idler pulleys and the water pump at the same time puts you, the consumer in harm’s way.

Here is a case history; a timing belt was replaced on a Honda Accord, no tensioners or water pump. It was done in a timely fashion at about 75,000 miles. The vehicle ran flawlessly for 5000 miles, then while on a trip to visit family on the freeway traveling at highway speeds the vehicle stalled and refused to restart.

After towing the vehicle to a shop it was checked and the new timing belt had all of the teeth sheared off of it. It was soon diagnosed as a seized water pump bearing. The result was a $1500.00 valve job as all of the valves in the head were bent. This was taken off of the internet; the real question is did the service provider recommend changing all of the key components and did the consumer refuse, or was it a matter of funds or ignorance.

Many times I receive phone calls asking how much it is to change a timing belt. As I hope that I have illustrated that there is more to the proper maintenance of the vehicle than merely changing a belt. I will ask the caller to come in so that I can look at the vehicle and see if the serpentine belts had ever been replaced, hoses may be original as well as the coolant, many times there are oil leaks from the cam or crank seals that deteriorate the belts prematurely, and without having the chance to check all of these things I will never give a price over the phone. Some people hang up, but some come in for our FREE inspection and accurate to the penny estimate.

Preventive maintenance means being proactive, not reactive. If a belt fails because I failed to inform you of all of the components and their importance in the whole spectrum of engine designs, then I am at fault.


Gregg’s Automotive Maintenance & Repair Center

236 S. Tamiami Tr.
Punta Gorda, Fl. 33950
Auto Repair, A/C Repair, Oil Change, Brake Repair & Transmission Services