Rick's Free Auto Repair Advice

Replace timing belt idler rollers

Do you have to replace timing belt idler rollers?

When performing a timing belt change most shops recommend replacing the timing belt idlers, timing belt tensioner, camshaft seals, and the water pump. Many readers ask me if all that is necessary and the answer is simple; if you have an interference engine where the failure of the tensioner or idler can destroy the engine, you absolutely should replace all those parts. Here’s an example of what can happen if you reuse the timing belt idler rollers or the timing belt tensioner.

Subaru that reused timing belt idler rollers

All timing belt idler rollers use a sealed bearing. The grease inside the bearing is designed to last the life of the timing belt, which can be 60,000, 90,000 or up to 110,000 miles depending on the carmaker and the engine. Timing belts are cheap, but the idler rollers, tensioner and water pump can really add to the cost. Here’s what happens if you reuse old timing belt idler rollers.

Cog idler roller burned up its grease

On the left you can see a cog idler roller with the grease seal removed. This idler roller is low on grease but the balls and cage still have some grease left. The cog idler roller on the right is one that should have been replaced when the timing belt was replaced. It ran out of grease and overheated, destroying the cage and actually melting some of the ball bearings.

timing belt idler roller

Idler seizes and breaks off and destroys the engine

Next, the idler seizes. In this case, as the inner race spun, it broke the retaining bolt. Once that happened, the cog idler ran into the tensioner located above it. The timing belt lost tension, the valves went out of time and the entire engine was destroyed.

idler destroyed

Idler damages other components

As the cog idler let loose, it hit the tensioner and engine and ground off teeth on the idler and damaged the engine.

damaged idler teeth

bent valves

Notice where the valves contacted the piston. There were matching impact areas on each piston.

bent valves

Timing belt idler replacement cost

The timing belt idler rollers and tensioner shown below cost about $200. This engine was destroyed because the owner opted to replace just the timing belt and not these other wear components. Remember, they’re designed to last the life of the timing belt, not the life of the engine.

timing belt tensioner

©, 2020 Rick Muscoplat

Posted on by Rick Muscoplat


Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN