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Air compressor leaking oil

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How much is "a little" and how hard do you run the truck?  I don't know how hard oil is on a drier?  It's likely only going to get worse, so I would say replace it when you can.



1959 B61 Liv'n Large......................

Charter member of the "MACK PACK"


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Does the MR have a hard pipe coming from the compressor output? If so, check it for a blockage.  Oil builds up quick..  I would consider doing it now,  since you see oil leaking.

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Posted (edited)

Ok, I will freely admit I don't know your system. However, oil pumping is not rocket science. Before makeing a replacement  of the compressor, look at the whole air system. A new compressor on a leaky system that is compressing all the time, is going to put you right back where you are now in short order.

 Take the truck out for a steady run on the freeway. watch when the compressor unloads, the needle on the gauge should climb until it unloads and the drier purges. when that happens time until it happens again. On the freeway, where you are not using your brakes the time between cycles should be at least TEN MINUTES, I hear trucks with the unloader popping off ever few seconds. My 30 year old truck would do 45 minutes (air ride truck and trailer), That was a tight system, most will not do that well.  I looked at 15-30 minutes as "good enough". I had air start, so made sure the air system was in good shape. 10 minutes is the minimum I would accept. You can't test sitting still, all valves for brakes etc must be in "driving position" and the compressor at speed.

 Replacing the compressor (the source of the oil) without addressing the cause of the oil will be disappointing. A Windex bottle with soapy water and spray down air lines and valves will show where the leaks are. Address the leaks 1st, then check inlet and outlet piping (no restriction on the inlet is as important as on the outlet). Since this is a newer truck, this shouldn't be a problem, but some older systems fitted with older air driers (AD-2, AD-4) with the compressor inlet connected to the engine intake manifold on a turbo'd engine will pass air and oil when the purge valve is open, and require an "econ valve" between the compressor and drier to prevent this.  Without it, boost passes right through the compressors valves and out the purge at the drier. Newer driers all have turbo cut-off valves in the drier to prevent this.

Edited by Geoff Weeks
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  • 2 weeks later...

If you have 40 psi the next morning, I wouldn't worry about anything on the protected side (after the primary and secondary tanks) and concentrate on the system from the compressor through the wet tank to the inlet check at the primary and secondary tank. That is where your leak will be. With the drier purging every 20-30 sec it will be a big leak.

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