- The sealing surface of the screw cap is firmly pressed against the edge of the expansion tank opening. The pressure cannot drop.
- If, during heating, the pressure in the cooling system exceeds 1.2–1.5 bar, the overpressure control valve opens. By equalizing the pressure, some water vapor can escape.
- When cooled, the liquid contracts again, and a reduced pressure develops in the cooling system. To equalize the reduced pressure, a second valve is located in the cover. It opens at a reduced pressure of 0.06-0.1 bar, and atmospheric air can enter the expansion tank.
Checking overpressure and underpressure valves with improvised means
Those who do not want to spend effort on checking can simply replace the relatively inexpensive cover. In the workshop, it is checked with a pressure gauge:
1. Pressurize.
2. At a pressure of 1.2–1.5 bar, the valve should open.
3. With cap removed, squeeze thick fluid hose.
4. Put on and screw the cap, release the hose.
5. Release the hose.
6. If the compressed hose rounds up again, the valve is OK.
7. If in the morning before the first start-up the coolant supply hoses are flattened, then the low pressure valve is probably not in order.
Visitor comments