Fuel/Water separator O-ring upgrade
M-233-002
(February 2007)

Valid for
All Mack models Built with Davco 382 Fuel/water separator.

Case description
Effective August 16, 2006, DAVCO Technology, LLC made a change to the O-ring material used in the bottom plate
seal of the DAVCO 382 Fuel Pro® Fuel/Water Separator with integral fluid heating system.
Note: Does not apply to Mack Trucks Australia.

Repair
The new O-ring material provides the following advantages:
Higher temperature range
Better compatibility with various coolants
Better compatibility with Ultra Low Sulfur Diesel (ULSD) fuel

DAVCO Bottom Plate Exploded View (Collar-Style Shown)
1. Radiator O-rings

4. Spool Assembly

2. Thermo Valve Assembly

5. Bottom Plate Plug (without O-ring)

3. Bottom Plate O-ring
A seal kit (part number 5479–382124) which contains the upgraded O-rings is available through the MACK Parts
System. It is recommended that DAVCO 382 Fuel Pro® Fuel/Water Separators manufactured prior to August 2006 be
upgraded with this seal kit at the next scheduled fuel filter service interval.

The seal kit includes two different bottom plate O-rings; a square-cut O-ring or a regular O-ring. The bolt-on version
bottom plate utilizes the square-cut O-ring, and the collar-version bottom plate utilizes the regular O-ring. Refer to the
attached DAVCO service instructions for additional information and assembly instructions.

Bottom plate seal upgrade for bolt-on version assembly instructions

Approximate Service Time: 15 minutes

Requires parts:
1. Radiator O-rings (2)
2. ThermoValve Assembly
3. Bottom Plate Seal (Square Cut)
4. Spool Assembly
5. Bottom Plate Plug w/o-ring

Tools Required:
Davco Collar Wrench (part number 380134)
3/16″ Hex key
1 5/16″ Box end wrench
3/8” Diameter punch to rod
Rubber mallet

Disassembly
1. Drain 382 Fuel Pro® completely, dispose of fuel in environmentally safe manner.
2. Using a Hex Key remove bottom plate (C).
3. Using hex key, remove 1/4”-20 bolts (A) from radiator. Remove radiator seals (1) from the bottom of each
Radiator leg. Dispose of seals; retain Radiator (B) for later use.
4. Using box end wrench, remove and dispose of ThermoValve (2).
5. Using box end wrench, remove and dispose of Bottom Plate Plug (5); keep Spool Spring (D) for later use.

Caution
Bottom Plate Plug is spring loaded, use care when disassembling!
6. Using punch and rubber mallet, carefully remove and dispose of Spool (4).
7. Remove and dispose of bottom plate seal (3).
8. Clean O-ring sealing surfaces as needed.
Note: Use caution when cleaning to ensure sealing surfaces are not damaged.

Assembly
1. Carefully press new Spool into Bottom Plate, smaller diameter end goes in first.
2. Place Spool Spring on end the Spool, install Bottom Plate Plug compressing Spool Spring. Tighten to 15–30 ft
lbs.
3. Install new ThermoValve. Tighten to 15–30 ft lbs.
Note: Ensure Pin is installed in the bottom of the ThermoValve (See Detail).
ThermoValve Detail

Caution
Pin must be in place before installation.

If the ThermoValve gets too warm, the Pin may be forced out of the Bushing. To reinstall,
place ThermoValve under cold water for 15–30 seconds before reinserting the pin.
4. Install new Radiator Seals on Radiator. Install Radiator on Bottom Plate using 1/4”-20 screws. Tighten to 14 ft
lbs.
5. Install Bottom Plate Seal (Square Cut) on Bottom Plate. Reinstall Bottom Plate on Fuel Pro. Tighten bolts to 10
ft lbs.
6. Fill Fuel Pro with fuel, start engine and run at high idle for 30 seconds.

Bottom plate seal upgrade for collar version assembly instructions

Approximate Service Time: 15 minutes

Requires parts:
1. Radiator O-rings (2)
2. ThermoValve Assembly
3. Bottom Plate O-ring
4. Spool Assembly
5. Bottom Plate Plug w/o-ring

Tools Required:
Davco Collar Wrench (part number 380134)
3/16″ Hex key
1 5/16″ Box end wrench
3/8” Diameter punch to rod
Rubber mallet

Disassembly
1. Drain 382 Fuel Pro® completely, dispose of fuel in environmentally safe manner.
2. Using a Hex Key remove bottom plate (C).
3. Using hex key, remove 1/4”-20 bolts (A) from radiator. Remove radiator seals (1) from the bottom of each
Radiator leg. Dispose of seals; retain Radiator (B) for later use.
4. Using box end wrench, remove and dispose of ThermoValve (2).
5. Using box end wrench, remove and dispose of Bottom Plate Plug (5); keep Spool Spring (D) for later use.

Caution

Bottom Plate Plug is spring loaded, use care when disassembling!
6. Using punch and rubber mallet, carefully remove and dispose of Spool (4).
7. Remove and dispose of bottom plate O-ring (3).
8. Clean O-ring sealing surfaces as needed.
Note: Use caution when cleaning to ensure sealing surfaces are not damaged.

Assembly
1. Carefully press new Spool into Bottom Plate, smaller diameter end goes in first.
2. Place Spool Spring on end the Spool, install Bottom Plate Plug compressing Spool Spring. Tighten to 15–30 ft
lbs.
3. Install new ThermoValve. Tighten to 15–30 ft lbs.
Note: Ensure Pin is installed in the bottom of the ThermoValve (See Detail).
ThermoValve Detail

Caution
Pin must be in place before installation.

If the ThermoValve gets too warm, the Pin may be forced out of the Bushing. To reinstall,
place ThermoValve under cold water for 15–30 seconds before reinserting the pin.

4. Install new Radiator Seals on Radiator. Install Radiator on Bottom Plate using 1/4”-20 screws. Tighten to 14 ft
lbs.
5. Install Bottom Plate O-ring on Bottom Plate. Reinstall Bottom Plate on Fuel Pro. Tighten collar to 50–60 ft lbs.
Note: The use of 2-3 drops of Loctite® 406 is recommended to secure the bottom collar.
6. Fill Fuel Pro with fuel, start engine and run at high idle for 30 seconds.

For additional kits contact DAVCO customer service at 800-328-2611 or
[email protected]. Reference O-Ring kits part number
382124.
Issued by
Technical Service
Mack Trucks, Inc. engages in a continuous program of testing and evaluating to provide the best possible product.
Mack Trucks, Inc., however, is not committed to, or liable for updating existing chassis.