Oil In Air System - '88 R688 E6 350

[Warpman89]

I have oil in my air system, it has been a problem for a few years now. The truck did not see much use so it was not a big issue and there were no safety issues. However, it was not uncommon for a decent amount of oil to come out of the air tank if it was drained. Also, the air dryer pressure regulator would spit out a nice circle of oil spray every time it would exhaust. So, about 6 months ago I replaced both the air compressor and air dryer. There is now very little oil when I drain the air tank, but still some. The air dryer still spits out a little oil, but less than before. The "new" air compressor was a rebuilt unit from Mack and works like it should. The new air dryer is brand new. So, what is the deal here? Is a little oil common for a 20 year old truck? Is the oil I'm seeing just "residue" from years of having oil going into the air system? Any help is appreciated

[other dog]

I have oil in my air system, it has been a problem for a few years now. The truck did not see much use so it was not a big issue and there were no safety issues. However, it was not uncommon for a decent amount of oil to come out of the air tank if it was drained. Also, the air dryer pressure regulator would spit out a nice circle of oil spray every time it would exhaust. So, about 6 months ago I replaced both the air compressor and air dryer. There is now very little oil when I drain the air tank, but still some. The air dryer still spits out a little oil, but less than before. The "new" air compressor was a rebuilt unit from Mack and works like it should. The new air dryer is brand new. So, what is the deal here? Is a little oil common for a 20 year old truck? Is the oil I'm seeing just "residue" from years of having oil going into the air system? Any help is appreciated

If you've replaced the compressor and dryer the oil is most likely just residue. The inside of all the lines and tanks had oil in them and you'll probably see a little oil for a long time, but it should be less and less over a period of time.

[Underdog]

Some on the forum may agree or disagree with me, but I have been working on trucks for over 20 years and this has always been an issue with most Macks I have seen. I remember working on R models with no dryers the dashboard drips oil through the air valves if the driver was not draining the tanks. My 2000 CX with dryer still gets oil out of the tank drains. I am on compressor #3 and I change the dryer cartridge every 200,000 miles. Maybe the way the compressor is lubricated, but a lot of oil ends up in the air system. An air dryer helps(compared to a truck without a dryer) but draining tanks at least weekly and changing dryer cartridges regularly is the best way to minimize the oil.

[Rob]

Some on the forum may agree or disagree with me, but I have been working on trucks for over 20 years and this has always been an issue with most Macks I have seen. I remember working on R models with no dryers the dashboard drips oil through the air valves if the driver was not draining the tanks. My 2000 CX with dryer still gets oil out of the tank drains. I am on compressor #3 and I change the dryer cartridge every 200,000 miles. Maybe the way the compressor is lubricated, but a lot of oil ends up in the air system. An air dryer helps(compared to a truck without a dryer) but draining tanks at least weekly and changing dryer cartridges regularly is the best way to minimize the oil.

Well, I would agree with you as I've seen the same thing several times.

Rob

[Warpman89]

thanks guys, i figured it was residue

merry christmas

[rhasler]

Some on the forum may agree or disagree with me, but I have been working on trucks for over 20 years and this has always been an issue with most Macks I have seen. I remember working on R models with no dryers the dashboard drips oil through the air valves if the driver was not draining the tanks. My 2000 CX with dryer still gets oil out of the tank drains. I am on compressor #3 and I change the dryer cartridge every 200,000 miles. Maybe the way the compressor is lubricated, but a lot of oil ends up in the air system. An air dryer helps(compared to a truck without a dryer) but draining tanks at least weekly and changing dryer cartridges regularly is the best way to minimize the oil.

I have seen this happen lots of times myself and on almost every occaision the air tanks also had a substantial amount of thick syrupy oil drained from them. If I'm not mistaken, the cause of the "normal" oil passing is due to the rings on the piston in the air compressor allowing oil to slip past during the compressors unloaded cycle. If I remember correctly this was the reason Mack began using the Wabco air compressors in place of the Bendix compressor circa 2002-2003.