Webasto Product N.A., Inc. 64 www.techwebasto.com
REPAIR DBW 2010/2020/300 COOLANT HEATERS
9.4 MP SCHOOL BUS CIRCULATION PUMP
9.4.1 REMOVAL
1. Drain the coolant. Alternatively, the hoses leading
to the pump can be pinched closed with hose
clamping pliers.
2. Disconnect the circulation pump electrical leads.
3. Disconnect coolant hoses from pump.
4. Dismount coolant pump.
9.4.2 DISASSEMBLING
1. Clean the exterior of the pump and hold pump in a
soft-jaw vice.
2. Unscrew the impeller housing screws and remove
housing and O-ring.
3. Unscrew the impeller lock screw and remove
impeller.
4. Remove the seal assembly.
5. Remove the pump adapter (base).
6. Inspect all parts and replace if necessary. Seals are
always replaced.
9.4.3 ASSEMBLING
1. Connect pump motor to a power source. With a
strip of very fine emery cloth, polish the pump shaft
to remove any contamination.
2. Remove power source from pump motor.
3. Assemble pump with all parts in order as shown in
Fig. 53.
9.4.4 INSTALLING
1. Mount the pump.
2. Connect coolant hoses to pump and tighten hose
clamps.
3. Remove hose clamping pliers if used.
4. Connect the electrical leads and seal connector with
dielectric grease such as Permatex® Dielectric Tune-
up Grease or 3M™ Silicone Paste (Dielectric
Grease).
5. Refill coolant system and bleed trapped air out of
the coolant circuit according to instructions in
Sec.8.8.1.
6. Switch on and check function and for any leakage.
Figure 56: MP School Bus Circ. Pump - Exploded View
1
2
3
4
5
6
7
8
1 Impeller Housing
2 O-ring
3 Impeller
4 Spring Seal Assembly
5 Pump Base
6 Screw - Impeller Housing
7 Nut - Pump Base
8 Motor
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