Webasto Product N.A., Inc. 62 www.techwebasto.com
REPAIR DBW 2010/2020/300 COOLANT HEATERS
9.3 COOLANT CIRCULATING PUMP REPAIR
A defective coolant pump may cause the heater to
overheat. The heater’s overheat protection is likely to
respond in this case.
9.3.1 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.
9.3.2 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 nut and carefully pry off
impeller with two screwdrivers.
4. Remove the spring seal, ceramic and rubber seals.
5. On the U4810 pump, unscrew the pump base
screws and remove the base and the O-ring.
6. Inspect all parts and replace if necessary. Seals are
always replaced.
9.3.3 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 through Fig. 55. The ceramic seal and the
spring seal must be fitted as shown in Fig. 52 with
the hard side of the spring seal (B) against the
ceramic seal face (A).
Figure 52: Seal Orientation
9.3.4 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 53: U4810 Circulation Pump - Exploded View
A
B
U4810
18
18
1
2
4
9
10
11
3
5
8
12
6
7
1 Screw - Impeller Housing
2 Impeller Housing
3Nut - Impeller
4 Impeller
5 Spring Seal
6 Stationary Ceramic Seal
7 Rubber Seal
8 O-ring
9 Screw - Pump Base
10 Washer - Pump Base
11 Pump Base
12 Rubber Shaft Seal
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