The coolant vacuum valve switch opens when the heater is turned on, and allows coolant from the engine to enter the heater core. This warm air coming off of the engine is what provides you with heat to the interior of your car. The air blows through the vents and can be controlled by switches near the driver and passenger seats.
The vacuum part of the switch helps to regulate the flow of the air coming through the vents. Over time, the coolant vacuum valve switch can become clogged with old coolant or debris. If this happens, the switch may not work properly, which means you may have a very uncomfortable ride if it is not replaced quickly.
There are three parts to the coolant vacuum valve switch. One is attached to the manifold vacuum, a second to the carburetor vacuum, and the third is attached to the vacuum advance on the distributor. While the engine is operating at a normal temperature, the distributor gets ported vacuum, which is zero psi. On hot days when the temperature of the engine can rise really fast, the switch converts the distributor from ported to manifold vacuum. This increases the timing and the engine RPM increases as well.
Once this happens, the coolant flows through the engine and radiator, and the radiator fan speed is increased. The engine temperature immediately goes down to a safe level. After the engine is at the right level, everything returns back to normal until it starts getting too hot or too cold again.
The switch can go bad over time, so if it does, have your coolant vacuum valve switch replaced as soon as possible by an experienced mechanic. You should also be aware of the symptoms the switch gives off before it goes bad so you can be prepared and replace it before it completely fails.
Signs your coolant vacuum valve switch needs to be replaced include:
- The heat does not warm up like it is supposed to
- The coolant is leaking inside the vehicle or underneath the vehicle
- Cold air blows through the vents even if the knob is indicating to blow warm air
If you are experiencing any of the issues above, it may be time to have your car checked. Set up an appointment with a certified mechanic in order to have your problem diagnosed and repaired.
