Coolant Recovery System. Buick Roadmaster 1996

For 1990-2009 cars

### Coolant Recovery Reservoir

A see-through plastic reservoir connects to the cooling system at 2 points:

• | The tee connection on the heater inlet hose

• | The throttle body heater outlet

Pressurized coolant circulates through the reservoir from the throttle body heater outlet to the heater inlet tee connection. The reservoir is at the highest point of the cooling system, allowing any air or vapor exceeding the coolant recovery reservoir cap rating to exit the reservoir. When the coolant is cold, the coolant level should appear at the FULL COLD line on the reservoir.

An integral coolant level switch is in the bottom of the reservoir. This switch is bonded into the reservoir. The switch is not removable.

The coolant recovery reservoir uses a plastic pressure-vent cap to allow a buildup of 103 kPa (15 psi) in the cooling system. The cap allows the system to operate at a higher-than-atmospheric pressure. This pressure raises the boiling point of the coolant to about 125°C (262°F) at sea level.

The pressure-type cap contains a blowoff (pressure) valve (2) and a vacuum (atmospheric) valve (1). The cap protects the radiator by relieving any pressure that exceeds 103 kPa (15 psi).

In order to prevent hose collapse (which is caused by vacuum as the engine cools), the vacuum valve allows outside air to enter the cooling system when the cooling system pressure drops below atmospheric pressure.

The cap has a new threaded design to allow for easier and safer removal. In order to safely remove the cap from a cool system, do the following steps:

Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the cap.

1. Slowly rotate the cap counterclockwise, do not press down, ¼ turn and then stop.
2. Allow any residual pressure, indicated by a hissing sound, to be relieved.
3. After the hissing stops, continue to rotate the cap counterclockwise until the cap is removed.

There is no specific orientation of the lettering on the cap versus the cap being tight. To retighten the cap, use hand tight pressure.