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These checks and tests are meant to be a quick and simple way to test a diesel brake air compressor and determine its functionality. There are always exceptions and rare occurrences, but these should be able to diagnose most leaking oil/coolant issues.
If you're in the market, browse our quality selection of new air compressor drives.
And If you're having problems with leaking oil or coolant in your compressor, below are some simple fixes to common issues.
Why Is My Air Compressor Leaking Coolant Internally / Externally?
Coolant Leaking Internally:
Most of the time, an internal diesel air brake compressor coolant leak is the result of a failed head gasket. In some cases the air compressor may have a cracked head or develop a hole in the cylinder wall.
A large problem is that since the engine and the air compressor share the same coolant, many times a mechanic will go after the engine as the source of the coolant loss. The truck owner can help prevent this by regularly draining the air tanks and servicing the air dryer. This way the truck owner has a better chance of noticing excess water/coolant in the tanks or dryer and can alert the mechanic.
If the compressor is found to be at fault you now have the option of trying to find the source of the leak or just changing out the compressor. If it's a high hour/mileage compressor, it's usually the most cost effective to change it out.
Coolant Leaking Externally:
If the air compressor is leaking coolant externally, it's probably either a head gasket or a fitting. In some rare cases the leak can be contributed to a cracked head.
In order to find the leak, you will need a can of break clean, a mirror, and a good light. Many times a slow leak will show as a white stain left by the evaporating coolant. Larger leaks will have a clean area where normal road grime has been washed away. If you get really stumped, buy a bottle of coolant dye and use a black light to find the source.
Head gasket repair kits are available for most air compressors, as are replacement fittings or the o-rings for the fittings. You need some mechanical skills to swap out these parts, but it's usually a straightforward fix.
Why Is My Air Compressor Leaking Oil Internally / Externally?
Oil Leaking Internally:
When the air compressor is leaking oil internally, one of the first noticeable symptoms is that the air dryer is passing oil. It's normal for the air dryer to collect some oil but if the dryer is maintained regularly it's easy to spot what would be considered excessive.
Another possible symptom is that the air system builds air slowly. This can be caused by the oil being passed by the air compressor burns in the discharge line and eventually blocks it off.
If you find that you're having these problems, it's usually the most economical to change the compressor. The problem possibly could the result of a failed head gasket. However, in many cases it is due to oil passing by the piston rings.
Oil Leaking Externally:
External leaks on the air compressor are usually going to be coming from the oil pan, head gasket, crank seals or mounting gaskets.
Look for areas that are dripping or are washed clean by leaking oil to find the source. If it's a small leak, oil dye and a black light are great tools to locate it.
The oil pan and mounting gaskets are simple fixes. Many times the pan is just a flat plate sealed by RTV silicon sealant. It may however require removal of the compressor to re-seal it. The head gasket is also not too difficult of a fix and gasket kits are available for most compressors.
If the crank seals are found to be at fault, most times the easiest fix is to replace the compressor.
An oil leak may be a result of seal failure. For an example of seal failure caused by installation error, click here.
What If No Problems Were Found?
At this point, either the drive is bad, or you need to change the compressor. Extensive troubleshooting may or may not reveal the cause, but factoring time and labor rates could easily exceed the cost of replacing the compressor.
We offer a wide range of new and remanufactured air brake compressors at Highway and Heavy Parts, the leading diesel engine parts supplier.
For more information on issues you may be experiencing in your engine, check out our past blog, Common Diesel Engine Problems.
Let us help you get the right air brake compressor! We have ASE Certified Techs who can help make sure you're getting the best compressor for the job. Call them at 844-215-3406, or request a quote online.
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