Are you in time with your engines timing belt?
By Craig Zale 01/10/2012
Are all timing belt jobs the same? After all when your car’s engine is due for its timing belt all the technician has to do is just pull off the old belt and pop on a new one, right? Maybe not, let's take a closer look at what this belt does.
Your car’s engine has many different moving parts that make it work. Two of these are the Crankshaft and the camshaft. The crankshaft is what is connected to the engines pistons and long metal shafts called rods connect them together. The camshaft pushes on a rocker arm that rides up and down on a pre-ground shaft called the cam. They in turn open and close the engines valves located just above the pistons. All these parts meet in the engines combustion chamber where fuel and air mix to set off a chain reaction that makes the power for your pistons to go around and make your car go. The crankshaft and the cam shaft are very precisely in time with one another by way of a timing chain or a belt. With a chain not much has to be done in the way of maintenance.
But when we are talking about a timing belt we get into a whole different ball of wax. The timing belt is basically a large rubber belt that is connected to both the crank and cam shafts. These two are set to run with very exact measurements that “time” each other to open and close the engines valves in relation to the piston locations. So air and fuel are drawn in through the intake valve then it closes as the piston that is being driven by the crankshaft returns to the top of the cylinder after its intake stroke, to compress this fuel and air mixture. The engines spark plug is fired from a signal that came from a distributor, camshaft or crank shaft sensor telling it when to fire and ignite this fuel air mixture and causes an explosion inside the cylinder that drives the piston down to make power to drive the engine that feeds through the transmission and finally out to the cars wheels. After this power cycle is complete the used up fuel and air mixture has to be expelled from the cylinder and thus the piston pushes back up to the top of the cylinder and the exhaust valve opens, also driven by the camshaft and the old used up air is pushed out, after this the exhaust valve closes the whole process starts over again. This is carried out by each piston as many as 6000 times a minute in the car that we drive every day.
After a preset mileage of driving that can range from 60,000 to as high as 105,000 miles this main belt or timing belt reaches the end of its use full life cycle and must be replaced. If this belt goes too far beyond its intended service life it can break, and when it does it is usually without any warning.
Broken and stripped timing belts
At the least this will lead to a break down and cost the owner extra money for the tow to the service center, not to mention the un scheduled disturbance to your day. At the most the crankshaft and camshaft that have been dancing with each other many times for many years and just overlapping each other by thousands of an inch at dizzying speeds all of a sudden come out of time when the timing belt breaks, go crashing into one another and damaging the top of the pistons from the valves smashing into it and bending the valves from the pistons doing the same back to the valves.
Pictured above: Stripped timing belt and destroyed piston and valve
All of a sudden a part of your car’s engine regularly scheduled maintenance has just become a very costly and long term repair that will leave every one scrambling to get your life and the car’s engine back in time.
So let’s go back to that first part of our topic, we just need to put on a new timing belt and everything is fine. Not exactly and although this will take care of the heart of the issue we still need to know what else is in there with that timing belt. After the timing belt we have a smaller pulley that is attached to a spring or is filled with hydraulic engine oil that pushes on the timing belt all its life to keep it properly tensioned against the camshaft and crankshaft, as too tight of a belt and the belt makes an annoying buzzing sound and causes the components it rides on too wear out way to early. Or to loose and the belt cannot maintain is grip and may jump out of place throwing the camshaft and crankshaft out of time. Another smaller pulley is an idler pulley that helps to keep the belt in place and hold a better-rounded grip on the belt and the last may be your cars water pump that cools the engine by pumping vital coolant through the engine and radiator.
All these components have seals and bearings that hold back the cars oils and coolants from leaking all over the place and bearings that keep it all running smooth and true. These seals and bearings wear also, and not generally at the same rate of the timing belt they do wear and should also be replaced with the exception of the cam and crank shaft bearings that with proper maintenance can be expected to last the life of the engine.
But for the others inside with the timing belt they get just as much wear and tear as the belt we have been talking so much about. Years ago it was the job of the mechanic to know and put together a kit that will replace all the things that he or she regularly sees fail with the things that work in concert with the engines timing belt. Now from many years of experience the manufactures, the parts pros and your cars automotive technician have put together kits that address all the things that wear down over time and can be replaced while the front of the engine is open replacing the timing belt.
A kit is a mixture of parts that all work in conjunction with the engines timing belt. They can be :
1. The timing belt
2. The water pump
3. Camshaft and crankshaft seals
4. Belt tensioners
5. Idler pulleys
Photos courtesy of Napa Auto Parts
Any one of these components can fail and if they do cause the engines timing belt to break or jump out of time. This is why it is very important to replace these things while doing the regularly scheduled timing belt maintenance. So next time your car’s engine is due for its timing belt ask your automotive technician or service advisor if he or she put together a complete kit for your repair? Don’t take or except a short cut to save a few hundred dollars just to have to pay thousands more later. CZ
Craig’s Car Care
Napa Auto Care Center
