- A gasket with a screwed cap does not allow the pressure in the system to decrease.
- If the pressure in the cooling system exceeds 1.6 bar on a warm engine, the pressure reducing valve opens and a small amount of water vapor is vented to equalize the pressure.
Checking the pressure reducing valve
The pressure reducing valve of the expansion tank cap is checked by the device already described with the appropriate nozzle:
1. Increase pressure until air comes out.
2. Measure pressure and compare the received result with data on a cover of a broad tank.
Note. Recommendation: If the valve is defective, the rubber gasket is damaged or sediment has accumulated on the cover, then it must be replaced.