Changing the coolant breather valve

[insite]

i noticed the other day when i put the car up that the pressure release was up, like it would be if i pulled the bleed tab. is this normal? i would think it should stay down in all but the most 'heated' situations.

[JFP in PA]

You referring to the small rectangular metal wire "handle" on the vent?

[insite]

no, the handle actuates the part i'm talking about. i know you know this, but for others reading who may not: this entire apparatus is a pressure bleed valve, much like a conventional radiator cap.

when there is too much pressure in the system, a spring loaded valve will open and allow pressure to bleed out through a tube that exits under the right side of the car. the system is supposed to hold some predetermined amount of pressure, but to relieve that pressure if it gets too high.

the bleed valve is ALSO used to 'burp' the system, and this is done by actuating the wire handle JFP is referring to.

in my situation, the valve is actually opening under normal operating temperatures & relieving pressure when it shouldn't be. i suspect the valve is bad & needs to be replaced.

[JFP in PA]

No, it should not be “open” all on its own. Either the part is acting up, or you may have air in the system and are seeing the results of a “hot spot” somewhere in the system. Do you have access to a vacuum filling tool? If you do, pull a quick vacuum on the system when it cools down, if air comes out the coolant level in the tank will drop, and you can top the system off using the tool while under vacuum. If you pull a vacuum, and nothing comes out, you should look at replacing/rebuilding the bleeder assembly.