Compressor getting louder and not pumping air?

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Every now and again we’ll get a question about why a compressor is getting louder and not pumping air. While the basic cause of this can be experienced in a wide range of makes and models of air compressors, this does seem to occur more frequently in lower cost compressors with one or more cylinders and pump heads that have both a low pressure (intake) valve and a high pressure (air goes to tank) valve configuration in them.

Compressor problem symptoms can include a lack of air pressure building in the tank, air pressure building in the tank but taking far longer than normal for that compressor or the air pressure building normally up to a level and then rises no more despite the compressor running on an on.

All of these can be caused by a fault in how the low pressure side of the pump head and the high pressure side are separated.

fix my compressor - air compressor valve plate kit
Compressor valve plate kit with gasket shown bottom right, and the two flapper valves shown bottom left.

The image above shows a valve plate replacement kit for a low cost, single cylinder, air compressor. While the plates themselves are not usually a wear item, the flapper valve “fingers” and the circular gasket certainly are.

In this next photo, I’ve enlarged just the gasket and market it with a couple of red lines.

Gasket for a compressor pump cylinder head
Gasket for a compressor pump cylinder head.

It’s the length of this fairly think, high-heat material gasket between these two lines that is there to prevent air from the pressure side of the pump head from crossing over to the intake or low pressure side of the pump head while the compressor is running.

Compressor pump gaskets can leak around the circumference too!

If one, or more, of the bolts holding the pump and cylinder head together vibrate loose over time, then it is possible that, with the loss of clamping on the outside of the gasket, air may escape out the side of the pump. That, too, could lead to a louder pump noise and loss of pressure build in the tank.

If your compressor gets suddenly louder then a quick first check to find the problem is to ensure that air is not escaping around the outside of the pump head where the gasket is sandwiched in.

More common though louder noise is a breach in the vertical center strip of the gasket.

More often though, if a compressor pump gets suddenly louder, it’s caused by a break in the thin gasket between the low and high pressure sides of the pump head housing.

Why?

  • Often times that strip of gasket isn’t secured by the pump head or base plates as well as it might have.
  • The compressor pump head gets very hot when the compressor is running, and that might slightly warp the head allowing that gasket to breach.
  • The high heat of the compressor pump when running can deteriorate the bracket.
  • If sump oil is getting by the piston seal and into the intake and compression head, that oil can deteriorate the gasket and cause it to weaken and fail.

No outside leak? Check inside the pump.

If the compressor gets suddenly louder, a common cause is a gasket failure.

First check the outside around the pump while the compressor is running to see if air is exiting there.

If there is no air leak felt around the pump head while the pump is running – and be careful, as the pump head will get really hot – it may be time to disassemble the pump to have a look inside.

Before you do this…

Get the make and model number, and browse for valve plate kits on line for that make and model. You may be in luck and find that they are available. Unfortunately, there may not be a kit, that depending on the cost of the compressor up front, and whether that manufacturer supports their products after sale.

If you find the kit, order it. That pump rebuild kit will likely have new valve plates, new flapper valves and a new gasket or two, depending on the make and model of compressor.

It is possible that the valve “fingers” have deteriorated over time as well so replacing them at the same time might be a good idea.

Is it the gasket?

Right. Tear down the pump and have a look.

Even if that process is undertaken very carefully, it’s quite likely that the disassembly will damage the gasket anyway, and that’s why you want to have the repair kit on hand before you start. Then, the pump can be reassembled quickly to get the compressor back in service.

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