VOLVO B7R - Coolant Circuit

VOLVO B7R COOLANT CIRCUIT DIAGRAM

Working of the Coolant Circuit of VOLVO B7R :

The coolant is pumped by the cooling pump 4 into the longitudinal distribution channel in the cylinder block and then via holes and nozzles to the cylinder liners and up to the two cylinder heads. the coolant from the cylinder head is led straight to the thermostat housing 2 while it from the rear comes via an outer pipe.

The Oil cooler 6 is linked with the cylinder block and thermostat housing by outer pipes.

If the bus is equipped with automatic transmission and/or built in retarder it will be cooled via pipes 5. Without automatic transmission a curved pipe will be connected between inlet and outlet instead of the pipes 5.

A - The thermostat is of plunger type. It is mounted in a press-cast aluminium housing. The plunger thermostat monitor the coolant temperature in the engine cooling circuit.

When the engine is cooled the thermostat is closed, the coolant from the front and rear cylinder heads comes to the thermostat housing via inlet 7 and 8 and is directly led to the coolant pump via oulet 12. Connection 9 is for cooling the automatic transmission while connection 10 is a return line. 11 is return from Oil Cooler, while connection 13 leads to the radiator.

B - When the engine is warm the thermostat seals against the bottom of the thermostat housing and the coolant goes via connection 13 via radiator 1. Coolant recommended for cooling system is a 40-60% mixture of VOLVO's anti-freeze type C and water. The antifreeze is most effective (-46 deg C) with a 60% mixture. The VOLVO coolant is also recommended when the coolant is not for protection against frost because it still provides very good protection against rust. A mixture ratio of less than 40% coolant will leave you with inadequate rust protection. The coolant should be changed every other year.