Diagnosing and Repairing An Air Suspension Compressor At Home


We’ve long been fans of air suspension and have installed them on a variety of cars and trucks. The system we installed in our 1973 Ford F-350, the Hot Rod Hauler, has served us well, particularly when considering the number of times we’ve pumped up the bags on our overloaded workhorse and hooked onto a trailer, only to turn around and lower the air pressure when the workday was done—only to turn around and do it all again.

Like most mechanical things air suspension systems are susceptible to wear and tear and in our case we began to sense the compressor was getting tired. In most cases these compressors are easy to troubleshoot and rebuild.

The problem with our compressor was a bad reed valve—reed valves are thin strips of metal that open and close passages in a plate located between the head and cylinder. When the piston drops in the cylinder air is drawn through the intake reed, as the piston rises the discharge reed is blown open.

While we could have simply replaced the fractured reed valve, we opted to go for a complete rebuild kit that included a new head, spacer plate with new reed valves in place, and a new piston and rod. The cost for all the parts to refresh our compressor was a reasonable $65.

Rebuilding compressors isn’t difficult, as the following photos show. A few bucks, an hour or so of your time, and the suspension system will have fresh air.




1973 Ford F 350 Three Quarter Horse 4 Cfm Compressor

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This is the 3/4-horse, 4-cfm compressor that is the heart of our truck’s air suspension system.



1973 Ford F 350 Three Quarter Horse 4 Cfm Compressor Head Removed

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With the head removed the problem with our compressor was obvious—the tip of the discharge reed valve was missing.



1973 Ford F 350 Compressor Missing Section Of Reed Valve

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Note the missing section of the reed valve that left part of the port open at all times, obviously the compressor’s output was compromised.



1973 Ford F 350 Compressor Spacer Plate Intake Reed Valve

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On the piston side of the spacer plate is the intake reed valve, it’s forced closed as the piston rises and air goes out the hole to the lower right, past the reed valve and onto the air tank.



1973 Ford F 350 Compressor Head With Two Chambers

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The compressor head has two chambers; the intake is larger than the discharge side.



1973 Ford F 350 Compressor New Cylinder

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Included in the rebuild kit is a new cylinder.



1973 Ford F 350 Compressor Changing Piston And Rod

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Our compressor showed signs of ingesting moisture so we elected to change the piston and rod.



1973 Ford F 350 Compressor Crank Shaft

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This is what the crankshaft looks like with the connecting rod removed.



1973 Ford F 350 Compressor New Rod With Integral Piston

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The new rod with integral piston (on the left) looks different but is a direct replacement for the original.



1973 Ford F 350 Compressor New Separator Plate

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With the piston, rod, and cylinder installed the new separator plate and reed valve is put in place.



1973 Ford F 350 Compressor Assembled Only Missing Bottom End Plate

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Here the compressor is assembled lacking only the plate that covers the bottom end.



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