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Had a new compressor installed in Feb. because of excessive oil in air system. Well it has been 4 mo. now and I still get a large puddle of oil under the air dryer (3" in dia.) after idling about 20 minutes.

So, what should I look for now? Could this still be residual oil left in the system? I did change the cartridge once since the new compressor was put in at the dealer and the canister was full of oil. I check the tanks every once in a while and they have some moisture, but no signs of oil. This truck works every day so I guess I was expecting the the system to clean itself out by now. So I'm starting to think there could be another issue here.

Anyone have an opinion and or experience with this problem?

Thanks, Jeff

An alternative issue I have seen with excessive oil in the air brake system has to do with where your air compressor is sucking its intake air from.

If your air compressor is taking its intake air between your air filter and the turbo intake( not turbo charged but under vacum when engine loaded), under a hard pull it can pull oil past the compressor piston rings. Most engine air compressors now pull air from the turbo pressurized side of the air intake system. Older motors pull air before the air is charged ( between the air filter and the turbo compressor side intake) When the engine is pulling hard, it will cause a vacum in all intake piping before the turbo. the shorter the tube that goes to the intake of the air compressor, the more oil it can pull. May not be the answer for your problem, but i have seen this happen. Switching the piping to the turbo charged side of the intake piping solved our problems.

  • Like 1

Thanks for the replies. I checked, and my compressor does draw from the intake manifold so that probably isn't the issue here.

Maybe something to check-- turbo bearing is going and putting oil into the intake charge?

Had a knowledgable mechanic at the local dealer tell me the only way EXCESSIVE oil can get into the air system is through a worn out compressor so this is somewhat of a head scratcher......

David- thanks, I'll check on that filter kit.

Having a similar issues with my 85 MH 613 , E-6 350 . truck runs great , found the blowby hose off the valve covers had been replaced with a RADIATOR hose and the 1 1/2 inch hose had shrunk to a bout a 1/2 inch diameter, Replaced with new and that ended my excessive crank case pressure problem or so it seems for now . I had to remover the tach drive cable as it was pumping oil clean up to the junction point just below the cab floor .

Problem number two is

Now i have snot in Racor air dryer a bunch is a understatement. I ordered a new air compressor and it will be here on tuesday . Im hoping that is the problem with the oil in the dryer .

Problem number three is perhaps a leaking turbo pressurising the crank case thru the oil return line . Did a leak test and yes the turbo does leak a tiny bit of air under pressure .

New turbo may be next . Learning a lot about the Macks and having a good amount of fun doing it . This truck is a daily driver and im pulling a step deck with it . This site has already proven to be a great asset to me , cant thank you all enough for the gift of your knowledge and hands on experiance .

removed the puff eliminator , someone had stripped the threads and was leaking a little oil , from what i have been told i dont need it anyways ?

I was told that i could replace the stock turbo with a Detroit 12 7 turbo and gain a few H.P. has anyone had any exp with this concept?

Ill keep you all posted on my trials wiith this great old truck . Jerry .

  • Like 1

Having a similar issues with my 85 MH 613 , E-6 350 . truck runs great , found the blowby hose off the valve covers had been replaced with a RADIATOR hose and the 1 1/2 inch hose had shrunk to a bout a 1/2 inch diameter, Replaced with new and that ended my excessive crank case pressure problem or so it seems for now . I had to remover the tach drive cable as it was pumping oil clean up to the junction point just below the cab floor .

Problem number two is

Now i have snot in Racor air dryer a bunch is a understatement. I ordered a new air compressor and it will be here on tuesday . Im hoping that is the problem with the oil in the dryer .

Problem number three is perhaps a leaking turbo pressurising the crank case thru the oil return line . Did a leak test and yes the turbo does leak a tiny bit of air under pressure .

New turbo may be next . Learning a lot about the Macks and having a good amount of fun doing it . This truck is a daily driver and im pulling a step deck with it . This site has already proven to be a great asset to me , cant thank you all enough for the gift of your knowledge and hands on experiance .

removed the puff eliminator , someone had stripped the threads and was leaking a little oil , from what i have been told i dont need it anyways ?

I was told that i could replace the stock turbo with a Detroit 12 7 turbo and gain a few H.P. has anyone had any exp with this concept?

Ill keep you all posted on my trials wiith this great old truck . Jerry .

Jerry - Welcome to here! Do you have any photos of your truck you could post?

Dont have any pics yet but ill be taking some soon . Ill be sure to check the lines , This truck sat in a storage building for 5 to 7 years , it was a constant 40 degrees in the building year round and it had 191,000 original miles on it when i bought it . The turbo was supposed to be new but there was a few issues that made me suspect problems I.E. High crank case pressure, blowing oil out all over the place etc. There does not seem to be a lot of blowby, so im just chipping away at the obvious one detail at a time until i get this old dog figured out . as i said it runs great , and i haul with it almost everyday up here in the north west . Ill take some pics and get them posted . Jerry .

  • 2 months later...

David, could you find the part# for that filter kit? I'm on my THIRD Holset now in less than 6 months and am at the end of my rope trying to figure this out. Mack has tested everything Holset has told them to check (including the coolant lines) and can't find the problem. Does this kit reduce the boost pressure to the head of the compressor? I heard Holsets can't handle more than 30PSI or they will burn out. This could be my problem.

Just searched through Macks Technical Service Bulletins since '94 and didn't find anything about this kit using 'holset' and 'compressor' as my search words........

Thanks, Jeff

  • 1 month later...

Found out recently that the service bulletin with update kit has been discontinued for the Holset compressor. Not sure why.

As stated above, I'm currently on my THIRD Holset now in 7 months and this one seems to be passing oil from the moment I left the dealer!! Thinking about asking Holset to refund the cost of their compressor and labor to remove it so I can replace it with a Bendix unit.

Just noticed your last two post. The filter kit mounts directly on the compressor. It replaces the suction line that runs to the filter side of the turbo. The compressor is trying to get air from a vacuum with that old set up. This tube was replaced on new trucks at that time with a hose that went to engine intake manifold. At that point it's a positive pressure instead of the negative on the other side of the turbo. I'll look for the filter kit number.

  • Like 1
  • 6 years later...
On ‎10‎/‎15‎/‎2012 at 11:19 PM, David said:

Just noticed your last two post. The filter kit mounts directly on the compressor. It replaces the suction line that runs to the filter side of the turbo. The compressor is trying to get air from a vacuum with that old set up. This tube was replaced on new trucks at that time with a hose that went to engine intake manifold. At that point it's a positive pressure instead of the negative on the other side of the turbo. I'll look for the filter kit number.

let me know number is it for CL700/713 too? 350 engine

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