HOW TO INSPECT A BELT TENSIONER
                     HOW TO INSPECT A BELT TENSIONER
Paul Norman Jasper
Writer at autopartsu.com whose favorite topics 
include,  radiator replacement advice and 
replacement radiators.
Most of the later model engines use a serpentine belt to drive the 
accessories, including the power steering pump, air compressor, and 
alternator. Unlike V-belts, which are tensioned by moving the brackets, a 
serpentine belt uses a spring-loaded tensioner to ensure the belt stays tight. 
Once the belt stretches past its useful life, it is too long for the tensioner to 
work. In this case, you need to replace the belt.
However, the tensioner is not immune to wear and tear. It is considered a 
maintenance item that needs to be replaced when it wears out. When you 
change the belt, you should also inspect the tensioner.
INSPECTING THE TENSIONER
When inspecting the tensioner, there are nine things to look for:
RUST AND CRACKS
If you see rust dripping off the tensioner or notice signs of rust between the 
tensioner arm and its base, that is a sign that the tensioner is going to fail in 
short order. Also, look for tracks, as this will cause the tensioner to fail as 
well.
SPRING FORCE
While the tensioner is bolted in place, use a wrench to move it back and 
forth. This is easier if you have a tensioner wrench. If you do not feel 
resistance, the spring is worn. Other signs of a worn spring are a squealing 
belt and components sporadically stopping.
PULLEY BEARINGS
Once you remove the belt, spin the tensioner pulley. It should spin smoothly 
and should not make any noise. If you notice noise or if the pulley doesn’t 
spin freely, the bearings in the pulley are worn. Always replace the entire 
tensioner, not just the pulley as other parts on the tensioner could be just as 
worn.
WORN PULLEY
The pulley on the tensioner could be made from steel, nylon, or plastic. 
Depending on the model of the vehicle, its surface could be flat or grooved. 
Inspect the pulley to ensure that it does not have any dents, cracks, chips, 
and that there is no debris embedded in the pulley’s grooves. Check to 
ensure that the groove’s high points are not worn, and that on plastic pulleys, 
the high sidewalls are not broken or cracked.
ALIGNMENT
If the belt is not tracking properly on the tensioner, the tensioner is 
misaligned or installed incorrectly. Check for correct installment and that the 
belt is not misaligned, which could be caused by another pulley being out of 
alignment. An alignment tool makes this task much easier to diagnose.
TENSIONER ARM
Make sure the tensioner arm moves back and forth without binding or 
grinding. A tensioner wrench makes this task easier, though you can 
sometimes use a box wrench.
If you notice smooth, shiny streaks on the tensioner housing or the arm, the 
belt is rubbing, and the tensioner arm might not be aligned properly.
If the tensioner arm moves too far in either or both directions, the spring 
torque or the damping system is bad. If this is a problem, check the 
alternator pulley as that failure could cause this. You will have to replace the 
alternator and the tensioner.
NOISE
If you hear the tensioner rattling or squeaking, either the bearings are going 
bad or the pivot area is worn.
REPLACE THE TENSIONER
If you notice any of these problems, with the exception of a belt 
misalignment caused by another component, you will have to replace the 
tensioner. In most cases, replacement is easy.
If the belt is good, loosen the tensioner and remove the belt from only the 
tensioner pulley. Remove the bolts holding the tensioner to the block. Check 
the new tensioner before you install it to ensure that there aren’t any 
defects. Bolt it to the block. Rotate the tensioner toward the center of the 
block and slide the belt on. Make sure the belt is aligned on all of the pulleys.
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