Frequently Asked Questions

Fan Clutches

Q. How do I know if my fan clutch needs to be replaced?

A. These are the most common symptoms of a failed fan clutch:

• Leaking fluid - Oily build up around the bearing or thermal spring.
• Bad bearing - Seized, turns rough or has excessive play, (more than 1/4" at fan tip).
• Worn thermal spring - Spring is loose.

Some fan clutches will show no visible indication of a problem yet may still be faulty. The following may also indicate a faulty fan clutch:

• Fan spins excessively - Three or more times when hot engine is shut off.
• Poor air conditioning - At low speed or excessive high side pressures.
• Doesn't engage - Fan speed does not increase or "locks up" when the engine is hot.
• Does not disengage - Fan clutch won't slow down when the engine is cold.

Q. At what temperatures do fan clutches engage?

A. Most fan clutches engage at about 170° F air temperature (about 180-190° F engine temperature). They reduce the temperature about 20° F before disengaging.

Q. What is the difference between a standard, heavy and severe duty fan clutch?

A. Each fan clutch type is designed to simulate the performance of the original equipment clutch that it replaces. All fan clutches are for specific applications and should be applied only on the application for which they are cataloged.

Standard Duty Thermal

Turns the fan 50-60% of shaft speed when engaged. Used with fans with lighter pitch. (1-1/2" of pitch) Flat plate impeller design with 30 Sq. In. of working surface.

Heavy-Duty Thermal

Turns the fan 80-90% of the shaft speed when engaged for increased cooling. Used with deeper pitch fans. (2 1/2" of pitch). Land and groove design with 47 Sq. In. of working area allows higher operating RPM's.

Severe Duty Thermal

Turns the fan 80-90% of the shaft speed when engaged. Used with deeper pitch fans. (2- 1/2" of pitch). Land and groove design with 65 Sq. In. of working area. Larger working surface provides cooler running and longer life expectancy.

Q. My fan clutch makes a loud noise when started cold. Is that normal?

A. Yes, most fan clutches allow the fluid to drain into the working area when shut down. At startup it may take 1-2 minutes for the clutch to slow down.

Q. What is the difference between a thermal and non-thermal fan clutch?

A. Non-Thermal (also called centrifugal clutches) are a low cost replacement for some standard thermal clutches. They are always engaged providing less fuel savings than a thermal clutch.
Thermal fan clutches vary the fan speed with temperature of the air behind the radiator. The engaged (high speed) operation provides maximum cooling while the disengaged (low speed) operation provides fuel savings and noise reduction. This provides greater life expectancy than non-thermal fan clutch.

Q. I have a late model Chevrolet or GMC truck. The original equipment fan clutch does not engage until the engine is past 210° F. Does Hayden make a fan clutch that will keep the engine cooler?

A. Yes, our fan clutches for these vehicles are specifically designed to engage at lower temperatures than the original equipment fan clutches that they replace.

Transmission Oil Coolers

Q. The trans cooler in the radiator is leaking and is expensive to repair. Can I use a Hayden transmission cooler to eliminate it?

A. Yes. Always choose one of the larger Hayden coolers when eliminating the radiator cooler to compensate for the loss of cooling from the radiator. In most installations we recommend use of the radiator tank cooler to provide maximum cooling and to comply with most manufacturers warranties.

Q. Should the cooler be installed before or after the radiator?

A. Hayden recommends installing the auxiliary cooler after the radiator to return the coolest fluid directly to the transmission. Installing the cooler before the radiator will still provide additional cooling and may be necessary in some difficult access applications.

Q. Can you over cool the transmission fluid?

A. Transmissions are not highly sensitive to cool operating temperatures. However, in sub-zero (20-30° F) weather conditions transmission fluid can actually gel up in an external cooler and cease to flow, causing damage. Use of the radiator cooler actually helps warm the fluid under these conditions. It is critical in extreme cold conditions to use the original equipment cooler in series with the auxiliary cooler and allow the vehicle to warm up before driving.

Q. What is the difference between an Ultra-Cool® and Rapid Cool® trans coolers?

A. Ultra Cool® is a tube and fin, (serpentine), design that is a time proven cost effective design. The round tube design is the strongest and most reliable cooler design but only gets cooling air on the forward facing side. The Rapid Cool® design is a plate and fin design similar to most radiator designs. The flat plates allow more contact with the cooling air. This provides a design that is about 1/3 more efficient size for size than comparable Ultra Cool® models.