Belt tensioners are on all modern vehicles to keep the belts in good working condition. They do, however, wear out and need replacing at some point. An inspection under the hood can help determine if you need to replace them due to inconsistent wear and tear.
The belt tensioner keeps your drive belts at the correct tension for your vehicle to run. It converts power from the engine to drive the power steering pump, air conditioning compressor, water pump, and alternator. Its job is to apply the right amount of tension so all the systems will work properly.
What are The Parts of a Tensioner?
The belt tensioner has four main parts: the pulley, the spring, the tensioner arm, and the base. The pulley allows the drive belt to rotate as the spring keeps the belt at the right tension. The tensioner arm allows you to adjust the drive belt, or it moves so you can change the drive belt when it’s needed. The base simply holds all the belt tensioner parts together.
What Are the Symptoms of A Failing Belt Tensioner?
Fortunately, there are several signs of a failing belt tensioner to alert you to needing a replacement. Some are found by visual inspection and others make themselves self-evident in noises.
Grinding or Squeaking Noises
The most common symptom of a failing tensioner is a funny noise that can be heard from the drive belts or the tensioner itself. If you hear a high-pitched squeal or squeak, the tensioner may be too loose and is allowing the drive belt to slip. You will notice this when you first start the engine. If you hear a grinding sound similar to brakes when they are metal on metal, then it can be that the bearings in the tensioner or the tensioner pulley are failing. It results in metal parts rubbing together, just like very worn brakes, and produces the same type of grinding sound.
Uneven Belt Wear Issues
A failing belt tensioner can also be diagnosed by uneven belt wear patterns. This is similar to uneven wear patterns on the tires of a vehicle to signal you that something is not correct. When you inspect the drive belt, the wear should be the same all around the belt throughout the entire length of it. Belts are made of rubber and wear out after quite some time from rubbing on and turning the metal components. A belt can wear out prematurely if the pulley in the tensioner wears out. This will lead to fraying edges on the drive belt and, in more severe cases, the drive belt can actually break due to a bad pulley.
Belt-Driven Accessories Don’t Work
If you have a faulty belt tensioner, then the components that the drive belt operates will fail to work. It could mean the air conditioner stops working because the tensioner can’t apply the correct tension to the A/C to make it work using the power from the engine and transmitting it to the component.
Appearance of Rust
If you see rust or damage, such as cracks between the tensioner’s base and arm, then the tensioner is faulty and not operating properly. Cracks and damage can also commonly be seen on the mounting bolts, which cause the tensioner to stop working altogether.
Pulley Bearing Wear
By removing the drive belt, you can rotate the pulley by hand. If there is resistance, noise, or it moves roughly, the pulley bearings have likely failed and the entire belt tensioner should be replaced.
Other Visual Signs of Tensioner Failure
A visual inspection of the tensioner system will tell you if it’s failing. You can crank the engine and look for these signs of failure. The belt may wobble on the components and pulleys, it turns off-center, or oil may leak from a hydraulic tensioner. If you turn off the engine and you push down on the drive belt, it should not move downward more than one inch or else it’s too loose. Other signs of failure include your battery warning light coming on in some vehicles, indicating that the alternator is not working.
Tensioner Tips for Replacement
A few tips on tensioner replacement can help your process to be a smooth one.
Let the engine cool completely as some parts remain hot for quite some time. Remove the negative battery cable, raise the front of the vehicle on jack stands, and block the rear tires behind them with chocks or bricks so the vehicle can’t roll while you are working on it.
The best idea is to take a picture or a few of the belt diagrams on the vehicle. The routing has to be correct in order for the replacement belt to fit correctly. This also helps if you need to remove parts to get access to the belt tensioner.
Round up your necessary tools, like a hex wrench and a socket wrench. The hex wrench has a long handle so you can rotate the tensioner and relieve tension to make it slack. You may need to rotate the tensioner up to 80 degrees clockwise. When the belt is loose, slip it off the pulley and remove the retaining bolt on the tensioner with a socket wrench. Remove it from the engine.
Get the correct replacement tensioner and belt for the vehicle. The belt may be slightly shorter than the old one, but it will stretch when you put it on.
Install the new tensioner by inserting the bolts and tightening them to the correct torque for the vehicle. Lift the tensioner slightly with one hand to slip on the new belt. Align the teeth on the belt with the teeth on the pulley sprockets and reroute the belt around all the components using your photo or a diagram for reference. Reinstall any parts you removed earlier.
This guide should help you to inspect your belt tensioner, the belt, and other components in any vehicle. The tips give you the most direct and easiest manner to replace the tensioner and the belt.
Belt tensioners are on all modern vehicles to keep the belts in good working condition. They do however wear out and need replacing at some point. An inspection under the hood can help determine if you need to replace them due to inconsistent wear and tear.