Many Donaldson air cleaner housings come equipped with a small, wedge-shaped rubber component called the Vacuator™ Valve, commonly referred to as the vac-valve. While it looks insignificant, this clever little component is critical to your air cleaner’s performance.

What Does a Vacuator Valve Do?

Vac-valves are the most overlooked, neglected, and unappreciated components in many maintenance programs. The perception being that it is just a water drain and the water will drain regardless of the vac-valves condition.

Vac valves are essential to the pre-cleaning stage in two-stage air filter housings, automatically expelling dust and water to maximise air filter service life.

How It Works

When dirty air enters a two-stage air cleaner housing, it’s subjected to a direct change known as centrifugal pre-cleaning that throws heavier particles out of the air stream. Two-stage housings commonly incorporate a dust cup incorporating a vacuator tube with vacuator valve clamped to the tube.

Here’s where the vac valve shines in high-dust environments:

• When a diesel engine is running at idle, there is a pulsation created in the intake system, causing the vac-valve to flutter open and closed, expelling dust or water.
• When the engine shuts down, there is no vacuum in the intake system, and the vac valve eases open, expelling water or dust.
• Greater engine speed or heavier engine load demands larger volumes of air, increasing the level of vacuum in the air intake system. Higher vacuum sucks the vac valve closed.

What Happens if it’s Damaged or Missing?

In short, none of it is good; that inexpensive rubber vac-valve compromises the efficiency of your entire are filtration system. If your vac-valve is hard, perished, torn, split, damaged, or missing, expect:

• Air to be drawn in through the vacuator tube
• Housing's are often located under the bonnet, behind the wheels, exposed to extremely dirty air
• Air drawn in from the wrong direction stops the centrifugal pre-cleaning action
• Dust is no longer expelled, allowing it to build up inside the air cleaner housing
• Airflow through inlet pre-cleaners is reduced, minimising their efficiency
• The air filter will be doing all the work

Your filter will still only allow clean air to your engine, but as the first stage or precleaning is no longer functional, air filter service life will be shortened. Medium-duty two-stage housings may require 6-8x more frequent filter changeouts when the vac-valve is missing. 

Maintenance Tips

To keep your system running at its best, inspect the vac-valve regularly. Look out for:

• Cracks, hardening, or signs of wear
• Valves missing entirely

If you notice any issues, it’s best to replace the valve.

There are many simple challenges and solutions that can impact the service life of your air elements. Reach out to your Donaldson specialist for advice.