Proper Alignment, Gates Green Stripe PowerBand Belt May Solve Cummins N14 Engine Drive System Problems
Problem Description
Fan drive belts on Cummins N14 engines are prone to issues such as turning over, not running true in the pulley groove, or flipping out of the groove entirely. This is often an indication of misalignment between the fan hub and the pulley grooves. This problem has been documented in Cummins and Freightliner service bulletins and industry publications.
Despite improvements by Cummins, premature belt failure can still occur. For systems experiencing persistent belt failures, Gates Corporation engineers recommend a thorough inspection and realignment of pulleys.
Pulley Alignment Procedure
To check for parallel alignment, use a straight edge (e.g., a metal bar or ruler) placed along the outside face of both pulleys. Parallel misalignment is evident as a gap between an outside pulley face and the straight edge. Angular ("tilting") alignment can be measured using a spirit level.
The maximum permissible misalignment is specified as 0.5 mm per cm (0.0625 inches per foot) of distance between pulley centers.
If pulley alignment is out of specification, it is also necessary to measure the fan hub end clearance according to the procedures outlined in the N14 Troubleshooting and Repair Manual. Replace the fan hub if end play is out of specification.
If pulley alignment is out of spec but fan hub end clearance is within spec, the pulleys can be aligned as follows:
- Loosen the capscrews securing the fan support to the engine block and the top fan bracket to the fan support.
- Align the pulleys to the specified distance.
- Tighten the capscrews for the top fan bracket. Torque specifications vary based on engine serial number:
- Engines with serial numbers before 11994037: Torque capscrews (grade 5) for the one-piece top fan bracket (Part Number 3069640) to 45 ft-lb.
- Engines with serial numbers after 11994037 (with a two-piece fan support bracket): Torque capscrews (grade 8) for the top fan bracket (Part Number 3099799, 3099800) to 80 ft-lb.
- Torque the capscrews (grade 8) securing the fan support to the engine block to 80 ft-lb.
Note: Overtensioning grade 5 capscrews can damage threads. Capscrew grade can be identified by examining the head of the capscrew.
Belt Installation and Tensioning
When installing new fan drive belts:
- Install new Cummins belts. If a drive pulley uses multiple belts, replace them as a matched set.
- Tension new belt(s) to 140 lbs.
- Idle the engine for approximately 30 minutes with the fan engaged.
- Re-check and re-tension the belt(s) to 110 lbs to ensure proper seating in the pulley grooves.
Note: Do not overtension the belts, as this can cause excessive side loading on pulleys, potentially damaging the fan hub, fan hub bearings, and gear cover bushing.
It is recommended to check belt tension at each maintenance interval. Insufficient belt tension can lead to excessive slippage and accelerated belt wear.
Gates Green Stripe PowerBand Belt Solution
If drive belts continue to come off or run improperly after alignment, Gates recommends replacing them with a Gates Green Stripe® PowerBand® belt. This belt is constructed by joining two or more Gates premium V-belts with a permanent, high-strength tie band.
The PowerBand belt offers several advantages:
- Bends easily over pulleys like multiple V-belts.
- The tie band enhances stability, preventing the belt from turning over or coming off.
- Solves problems on high-load, high-horsepower drives with abrupt starts/stops and heavy vibrations.
- Reduces installation costs and inventory by eliminating the need for matched V-belts.
- Provides twice the service life of conventional V-belt sets.
- Features a thinner profile and variable notching pattern for cooler, quieter operation and reduced cracking.
In testing, Gates Green Stripe PowerBand belts demonstrated nearly twice the service life of conventional V-belt sets.
Note: Not all pulleys are designed for Gates Green Stripe PowerBand belts. To check compatibility and pulley groove spacing, maintenance technicians should obtain a set of Gates Green Stripe PowerBand pulley templates (Part Number 431-2036) from their Gates heavy-duty parts distributor. Instructions are included with the templates.
Parts Cross-Reference and Application Data
The document includes extensive tables that provide a cross-reference for Gates Green Stripe PowerBand belts for various Cummins N14 engine applications. These tables list Equipment Make, Equipment Model, Equipment Year, Application Description, OEM Part Number, and the corresponding Gates PowerBand Part Number. This data helps technicians identify the correct Gates PowerBand belt replacement for specific OEM parts and vehicle configurations across brands like Freightliner, Kenworth, Mack, Peterbilt, International/Navistar, and White GMC.
When ordering Gates replacement belts, refer to the provided tables.
