Air coming out the intake filter

What does it mean when your air compressor has air coming out the intake filter?

This is often a symptom of an air compressor that will run, and run and the air pressure in the tank only rises a little bit. Because the air pressure in the tank cannot reach the pressure switch cut out pressure level, it is possible that the air compressor will run to the point were it starts to self destruct.

To understand what is happening when the air compressor has air coming out the intake filter, it helps to know how the valves on the air compressor work.

The valves vary depending on the manufacturer, of course. The smaller DIY type air compressors typically have a valve plate sandwiched between a couple of gaskets, a plate similar in concept to the drawing below.

In this drawing we have removed the cylinder cap and the gasket to view the valve plate from the top.

The LP – low pressure valve  controls the air intake into the cylinder head, entering the pump through the intake filter. The HP  – high pressure valve controls the flow of air from the cylinder head into the line heading down  to the tank.

As the air cylinder piston reciprocates, it alternately opens and closes the two valves on the valve plate, depending on if the piston is rising and compressing air, or dropping, which pulls closed the HP valve and opens the LP intake valve at the same time. The piston cycling up and down is very fast, and these two valves are put under a lot of stress as they are pulled or blown open each time the piston cycles. The throw of the valves is not large, but the speed with which they move is impressive, leading ultimately to metal fatigue and the valve cracking or breaking right off.

 Air coming out the intake filter

When you have air coming out of the intake filter, it is is sign that the LP – the low pressure valve, is failing, or has failed.

Just like a piece of wire that you bend very quickly in your hands, the metal in these valves gets very hot. That heat, coupled with the high cycle rate, particularly if the materials used in the valve construction are poor quality (like those typically found in a cheap air compressor) contribute to metal fatigue and valve failure.

How to repair it

Really, you have only once choice when the compressor symptom is air coming out the intake filter. You need to replace the valve plate.

Of course, that’s where the fun begins.

Compressor still under warranty?

If the air compressor you are having this problem with was purchased from a big box store,  and the air compressor is under warranty, it will be up to the store policy to either repair or replace the air compressor. Take it back – along with your original sales receipt – and request a new one.

Odds are  good that the big box store hasn’t got a lot of interest in trying to get your compressor fixed, as the net cost to them for a new one is likely less than the labor and repair costs of fixing an old one. They may just take the damaged air compressor back, give you a new one, and toss the old one into the garbage hopper.

Compressor no longer under warranty

The odds are very good that the store where you bought the air compressor will not stock parts of this type for it.

If the store does send out air compressors for repair, contact that repair company for assistance in getting parts.

If the air compressor is the stores house brand, somewhere in the bureaucracy that is the supply chain of the big box stores someone should be able to tell you the source of the air compressor that you bought in a specific year. Even though the brand of the air compressor may not have changed, it is quite possible that a specific brand of store air compressor has been made by different compressor manufacturers over the years. It will be a giant pain in the backside to do, but you will have to find out who made the compressor and contact that manufacturer directly.

Unfortunately, if the compressor manufacturer is offshore, and they do not have a sales or distribution organization here, then good luck. Getting OEM parts may be impossible.

On line parts sourcing

On line sourcing can help. Companies that supply parts to rebuild or repair the smaller, DIY type air compressor, and there are a lot of them now, can sometimes get you parts.

In all of this process, keep in mind the cost of repair in terms of time to source, money to buy the parts if you can find them, time to dismantle and rebuild the compressor and total that up.

Compare that to the price of the compressor when you bought it, and compare that total to the cost of a new compressor today.

You may find that fixing the problem of air coming out the intake filter isn’t worth the effort or the money.