The Timing Belt

Many of the vehicles we see near the CSU campus this time of year have a familiar story. They were handed down from a parent or bought used; they have somewhere between 80,000 and 150,000 miles on them, and nobody is quite sure what has been serviced. Of all the questions that come with an older vehicle, one matters more than almost any other: has the timing belt ever been replaced? In this month’s blog post, we explain what the timing belt does, why the water pump is usually replaced with it, and how to know when it needs repair or replacement.

What the timing belt does

Inside the engine, the crankshaft turns the pistons, and the camshaft opens and closes the valves. Those two shafts must stay perfectly in step so that the valves open at the right instant. The timing belt is the toothed rubber belt that links them. It runs behind a cover on the side of the engine, out of sight, and it does its job silently for years.

Not every vehicle has one. Many newer engines use a metal timing chain instead, which is designed to last the life of the engine. Our technicians can tell you in seconds which one your vehicle has.

Why a failure is so costly

A timing belt rarely gives a warning. It simply breaks, usually while the engine is running. On many engines, a broken belt means the pistons and valves collide, bending valves and sometimes damaging pistons and the cylinder head. That turns a scheduled maintenance item costing several hundred dollars into an engine repair that can approach the value of an older vehicle. Because the belt is rubber, it also deteriorates with age, not just mileage. A vehicle that has sat for long stretches can have a belt that looks fine but is brittle underneath.

Why the water pump comes along for the ride

On most engines with a timing belt, the belt also drives the water pump, which circulates coolant to keep the engine from overheating. The pump sits behind the same cover, so reaching it means removing the belt anyway. Replacing both at the same time avoids paying the labor twice, and it removes the risk of a worn pump seizing and shredding a brand-new belt a year later. The tensioner and idler pulleys are typically replaced in the same visit for the same reason.

When it is due

Most manufacturers call for replacement somewhere between 60,000 and 100,000 miles, or at a set number of years, whichever comes first. The exact interval is in the owner’s manual and in the service database we use in the shop. If the vehicle is past that mileage and there is no record of the work being done, the safest assumption is that it has not been done.

Signs that a belt is nearing the end include:

• oil leaking from the front of the engine,
• a ticking noise from the engine,
• or coolant seeping from behind the timing cover, but many belts fail with no symptoms at all.

A good time to ask

Fall is a sensible time to settle this question. The weather is still mild, winter break is a few months away, and a student who is going to drive over the mountains or home for the holidays should not be doing it on an unknown belt. Campus Auto Repair currently offers $40 off a new timing belt or water pump. Contact our service professionals, and we will check your vehicle’s service history, confirm whether it uses a belt or a chain, and tell you whether the job needs to be done now or can wait.