Operating instructions

4.6 Plumbing Into the Coolant System
4.6.1 General Information
An efficient heating system must have an adequate supply of hot
water to all heater cores. The amount of hot water available to a
typical three or more heater core system depends on the water pumps
capability and the amount of restriction within the coolant system.
Webasto high performance circulating pumps designed for extensive
heating applications are available. Installing a Webasto heater and
circulating pump in accordance with the following instructions will
maximize the heating systems efficiency.
Coolant typically is routed out of the engine, through the Webasto
coolant heater and then through the vehicle’s heating system.
A path for coolant flow must always be maintained while the Webasto
heater is in operation. A bypass loop will be required if an
uninterrupted coolant flow path cannot be assured due to valves being
closed while the Webasto heater is in operation. The coolant
circulating pump(s) must operate while the Webasto heater is “ON.”
The coolant circulating pump must be mounted as low as possible in
the vehicle’s cooling system. A minimum of 10% of a good quality
antifreeze should be maintained in the cooling system at all times.
Heater and water pump fit 1.5” (38 mm) I.D. heater hose meeting SAE
20 R3 specifications. Silicone hose requires special hose clamps.
4.6.2 Engine and Passenger Compartment Heating
A: Heater Cores arranged in Series (fig. 401)
A series heating system works in this fashion:
Heated water (coolant) from the engine travels through the first heater
core in the circuit, then on to the next heater core in circuit, and on to
the next, etc. Each core adds some restriction, resulting in decreased
water flow. Not only is water flow reduced, but also water temperature
is reduced by each successive heater core resulting in the last core
receiving water that is usually too cool to be effective.
NOTE
Heater hose must meet
SAE 20 R3 specifications.
Silicone hose requires
special hose clamps.
Hose clamps must be
tightened to 45 in/lb.
(5 Nm) torque.
CAUTION
The Webasto heater relies
on coolant flow to transfer
heat from the heater to the
vehicle’s heating system.
The coolant pump(s) must
be operating and there
must be a path for coolant
to flow or the heater will
overheat.
WARNING
When working on the
coolant system, allow the
engine to cool down and
open the radiator cap
carefully.
Thermo 230/300 4 Installation
403