4981116 Engine Drive Belt Idler Tensioner Pulley For 4B3.9 B4.5 6B5.9 B6.7 ISB QSB

A belt tensioner is a device that applies a predetermined amount of tension to the engine's accessory drive belt (serpentine belt). Its primary function is to maintain constant, optimal tension on the belt as it wears and stretches over time. This prevents the belt from slipping, squealing, or throwing off, ensuring that critical components like the alternator, water pump, and A/C compressor operate reliably. This belt tensioner 4981116 is engineered for maximum durability and precise fitment in 4B3.9 B4.5 6B5.9 B6.7 ISB QSB engines. Manufactured to meet or exceed OEM standards, it ensures optimal engine performance and a long service life under heavy-duty conditions.

Whether for full engine rebuilds or quick replacements, DDP Engine provides you with the most reliable parts at unbeatable wholesale prices.

Parameter Details
Product Name: Belt Tensioner
Part Number: 4981116

Condition: Brand New / High-Quality OEM / Aftermarket
Warranty: 6 Months / 1 Year
Engine Model: 4B3.9 B4.5 6B5.9 B6.7 ISB QSB

Application:

4B3.9 (also known as 4BTA3.9): Inline 4-cylinder, 3.9L mechanical (B series), used in light trucks, construction vehicles (such as forklifts, generators, pump stations), and some agricultural machinery, with a power output of approximately 50–80 kW (68–108 hp), commonly found in equipment meeting China II/China III emission standards.

B4.5:  ISB 4.5L (actually a 6-cylinder, 2.8L or 3.9L is more common) or QSB4.5 (6-cylinder, 4.5L electronically controlled), the latter used in medium-duty trucks, forklifts, marine auxiliary machinery, and generator sets, with a power output of approximately 110–160 kW. "6B5.9": This is a non-standard notation. The maximum displacement for the B series is 3.9L (6-cylinder engines are still called 6B3.9). If it refers to 6CTA5.9 (C series), then it's 8.3L (not 5.9L). 5.9L usually belongs to the QSB or ISB series. If it is indeed a 5.9L inline 6-cylinder (such as QSB5.9), it is used in medium-duty trucks, construction machinery, and generator sets.

B6.7: There is no such designation as "B6.7". It should be ISB6.7 (6.7L inline 6-cylinder electronically controlled), used in medium and heavy-duty trucks, school buses, light passenger vehicles, and pickup trucks, with a power output of 160–220 kW (220–300 horsepower), meeting China IV and above emission standards. ISB (Interact System B): Electronically controlled inline 6-cylinder engine, mainstream displacements are 3.9L (ISB3.9) and 6.7L (ISB6.7), used in highway trucks, buses, light commercial vehicles, and RVs, with power outputs ranging from 125 to 300 horsepower, meeting China III to China V emission standards.

QSB (Quantum Series B): Electronically controlled inline 4- or 6-cylinder engine, commonly QSB3.9, QSB4.5, and QSB6.7, used in off-highway machinery (excavators, loaders, road rollers), marine equipment, power generation equipment, and agricultural equipment, emphasizing high torque and durability, with emission standards covering China II to China IV.

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