Operating instructions

4.6 Plumbing the System
4.6.1 General Information
The Thermo 90 S with coolant circulating pump must be mounted at least 6" (15 cm) below the
lowest permissible coolant level of the vehicles cooling system.
Minimum amount of coolant in the cooling system should be at least 1.6 gal. (6.0 l). Independent
heating systems require a minimum of 3.0 gal. (12.0 l). A minimum of 10% of a good quality
antifreeze should be maintained in the cooling system at all times.
Heater and water pump fit 3/4” (19 mm) I.D. heater hose meeting SAE 20 R3 specifications.
Silicone hose requires special hose clamps.
4.6.2 Select your Plumbing
Instructions for optionsA-B-C-D
1. Remove radiator cap and release system pressure.
2. Close shut off valves for heating system, if equipped, or pinch off supply and return line with hose
clamping pliers or long nose vise-grip pliers.
3. Plumb the system depending on the vehicles particular set up as shown in plumbing options A, B, C
or D.
4. Remove hose clamping pliers and open shut off valves.
5. Top off engine coolant as per engine manufacturer’s recommendations and re-install the radiator
cap.
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Thermo 90 S 4 Installation
WARNING
When working on the coolant system, allow the engine to cool down and open the radiator cap
carefully.
NOTE
Heater hose must meet SAE 20 R3 specifications.
NOTE
Silicone hose requires special hose clamps.
NOTE
Hose clamps must be tightened to to 45 in/lb. (5 Nm) torque.
NOTE
Vehicles with a normally closed solenoid shut-off valve, require an additional relay and circuitry for
proper heater operation whenever vehicle is turned off.