Truck Parts and Service | Heavy Duty Trucking, Aftermarket, Service Info
Issue link: https://read.dmtmag.com/i/85621
Tech Updates Identifying Slip/Heat Issues If you fi nd signs of slip/heat on a fan drive, it's an indication of an underlying prob- lem, according to Horton. Slip/heat can be found in all applica- tions with on/off and two-speed fan drives. Signs of slip/heat include: Heat cracks going past the perimeter of the fan mount- ing disc, a bubbled appearance in the fan mounting disc, excessive friction facing wear, worn fan mounting friction disc or piston friction disc or premature fan mounting disc failure. Th ere are many causes of slip/heat damage, and each repair depends on the underlying cause. If the fan drive was paired with a fan that is too large, refer to the original equipment manufacturer's specifi cations and replace either the fan or the fan drive. If there appears to be an obstruction, check for a loose, damaged or bent fan shroud or fan. Remove the obstruction and replace any damaged components. If the wrong repair kit was used during maintenance, repair the fan drive with the appropriate kit, or replace the fan drive with a new or remanufactured unit. If the wrong fan drive was installed, Horton says the solution might be an upgrade of an on/off drive to two-speed technology with a conversion kit, or a re- placement with a new or remanufactured drive. Another cause of slip/heat is low air pressure from a restricted air line, solenoid valve or solenoid valve fi lter as- sembly. You also will want to check for system air leaks. Th ese can be internal to the fan drive; internal to the solenoid valve and fi lter assembly; within the air line supply- ing air to the solenoid valve or from the solenoid valve to the fan drive; or leakage at the air line fi ttings. To determine if an air leak is the cause of slip/heat, Horton suggests that while 12 There are many causes of slip/heat damage. You must find the cause before you can properly repair the damage. air is being applied to the fan drive, listen for the sound of a leak around the sole- noid valve, fi lter assembly, air lines and fi ttings. Soapy water also can be sprayed around the spring housing, sheave and bleed holes. Bubbles will appear if there is an air leak. Excessive cycling of the fan drive also can be an issue. Th is can be the result of a mechanical or electrical problem, or an improper setting such as: overcharged air-conditioning Freon; blocked airfl ow caused by a restriction in front of the radiator; poor or loose electrical connec- tion; faulty thermal or air temperature switch, solenoid valve or engine control module; or improper temperature con- trol or ECM setting. If excessive cycling is the result of a Freon overcharge, adjust the Freon to the original equipment manufacturer's speci- fi cations and install a new liner kit. If excessive cycling is caused by a re- striction in front of the radiator blocking air fl ow, check for proper shutter opera- tion, winter front or other restrictions in front of the radiator. Low pressure because of a restricted air line also could cause excessive cy- cling. Replace the air line if it appears to have a restriction and also replace the valve or clean the fi lter. According to Horton, the minimum air pressure required to disengage the fan drive is 90 psi. Aſt er the air pres- TRUCK PARTS & SERVICE | June 2012 sure problem has been resolved, repair the fan drive with the appropriate repair kit or replace the fan drive with a new or remanufactured fan drive. Verify electrical connections and replace the air temperature switch or ther- mal switch if they are faulty. Check the ECM to ensure it is set to manufacturer's specifi cations. Improper temperature control settings also can cause excessive cycling. Accord- ing to Horton, the thermal switch should engage the fan drive at 10°F higher than the full open temperature of the thermo- stat. If the excessive cycling is caused by a non-exhaustive solenoid valve, or the valve not engaging properly, check for a plugged exhaust or intake port on the valve, check and clean the fi lter or replace the valve. Oil Leaks On Ultra- Shift Transmissions There have been reports of oil leak- ing around the filter, filter housing and cooler lines on Eaton UltraShift Plus transmissions built before Aug. 2, 2011. If oil is leaking from around the oil filter, filter housing or cooler lines, repair the leak using the fol- lowing procedure: Clean the area near the origin of the leak to determine the source. Document the source of the leak. Repair the leak as required. Top off the transmission with oil. After the repair is completed, verify the leak is repaired and oper- ate the vehicle to normal operating temperature. Inspect the repaired area to ensure the oil leak has been eliminated.