Checking Belt Tensioner Spring Tension and Belt Wear

Belt drive systems equipped with automatic (spring) belt tensioners cannot be adjusted or repaired. The automatic belt tensioners are designed to maintain proper belt tension over the life of the belt. If tensioner spring tension is not within specification, replace tensioner assembly.

Checking Belt Wear

The belt tensioner is designed to operate within the limit of arm movement provided by the cast stops (X and Y) when correct belt length and geometry is used.

Visually inspect cast stops (X and Y) on belt tensioner assembly.

If the tensioner stop on swing arm (A) is hitting the fixed stop (Y), check mounting brackets (alternator, belt tensioner, idler pulley) and belt length. Replace belt as needed.

Spring Tension (John Deere POWERTECH ® 8.1 L engine)

Spring Tension - 24-28 N·m (17-21 lb-ft)

Specification

Upper Spring Tension (John Deere POWERTECH ® 12.5 L engine)

Spring Tension - 18-23 N·m (13-17 lb-ft)

Specification

Lower Spring Tension (John Deere POWERTECH ® 12.5 L engine)

A-Spring tensioner
B-Upper spring tensioner
C-Lower spring tensioner
X-Cast stop
Y-Cast stop

POWERTECH is a trademark of Deere & Company.

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Spring Tension - 81-99 N·m (60-73 lb-ft)

Specification

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Upper Tensioner Spring Tension (John Deere POWERTECH ® 12.5 L Engine) and Tensioner (John Deere POWERTECH ® 8.1 L Engine)

A belt tension gauge will not give an accurate measure of the belt tension when automatic spring tensioner is used. Measure tensioner spring tension using a torque wrench and procedure outlined below:

Release tension on belt using a long handle 1/2-in. breaker bar in tension arm.

Release tension on tension arm and remove breaker bar.

Put a mark (A) on swing arm of tensioner as shown.

Measure 21 mm (0.83 in.) from first mark (A) and put a second mark (B) on tensioner mounting base.

Rotate the swing arm using a torque wrench until marks (A) and (B) are aligned.

Record torque wrench measurement and compare with specification before. Replace tensioner assembly as required.

POWERTECH is a trademark of Deere & Company.

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Lower Tensioner Spring Tension, John Deere POWERTECH ® 12.5 L Engine

A belt tension gauge will not give an accurate measure of the belt tension when automatic spring tensioner is used. Measure tensioner spring tension using a torque wrench and procedure outlined below:

Release tension on belt using a long handle 1/2-in. breaker bar in tension arm.

Release tension on tension arm and remove breaker bar.

Put a mark (A) on swing arm of tensioner as shown.

Measure 25 mm (1.00 in.) from first mark (A) and put a second mark (B) on tensioner mounting base.

Rotate the swing arm using a torque wrench until marks (A) and (B) are aligned.

Record torque wrench measurement and compare with specification before. Replace tensioner assembly as required.

POWERTECH is a trademark of Deere & Company.

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