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Topic: Air compressor blowing oil into dryer (Read 3233 times) previous topic - next topic

Air compressor blowing oil into dryer

The last couple of times that I have serviced my air dryer there has been quite a bit of oil in the dryer.  Talking to the local Cummins shop they say that in order to replace the compressor they have to remove the ECM and another part (forgot which one) and that the compressor has to be timed to engine.

My options seem to be spend $$$$ or to just replace the dryer on a more frequent maintenance cycle.  I can buy a lot of dryer parts for the cost to replace the compressor.

Does anyone have an opinion on the downside of changing dryer frequently rather than replacing the compressor? 
1998 U320 40'
2005 GMC Yukon
MC# 17609

Re: Air compressor blowing oil into dryer

Reply #1 –
If the oil is seeping thru the compressor rings at some point it will no longer compress air,as time goes by the oil will get worse,what
if it gets past the drier and gums up everything downstream?Find out what you can buy a rebuilt compressor for and find a shop other than a Cummins repair shop and see what they will charge to install it,it sounds complicated but it is not.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Air compressor blowing oil into dryer

Reply #2 –
Seems a bit premature for an air compressor on a motorhome to have this type wear. Not sure how the M11 compressor receives it's filtered air but would be checking hoses and connections for leaks.
Doug W.
96 36' U270 CSGI #4946
04 Toyota Tacoma 4x4
PNW

Re: Air compressor blowing oil into dryer

Reply #3 –
If the inlet hose to the compressor gets kinked or plugged there will be vacuum on the compressor crankcase and causes oil in the discharge line. Probably not your issue but it has happened. Doing a quick check online looks like a DIY job if you're handy.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Air compressor blowing oil into dryer

Reply #4 –
Verify, but on the vast majority the intake for the air compressor is the engine's intake manifold.  So the air is filtered by the main engine air filter, "compressed" by the turbo, cooled by the CAC before it routes to the air compressor.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Air compressor blowing oil into dryer

Reply #5 –
Steve in my humble opinion, it's a pay me now or pay me later, in our shop for oil field trucks it was a no brainier, we replaced the compressor.
If the compressor takes a dump your stuck, if you he dryer has a problem you can by pass it. Just my thoughts and as always when you go to a dealership no matter which brand it cost a lot more then a independent truck shop.
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921

Re: Air compressor blowing oil into dryer

Reply #6 –
The symptoms are known to come from a missing/dirty/malfuncting "check valve" attached to the air dryer inlet. Others have gone though the replace big parts dance only to find it does not fix the problem.

Only certain types of air compressors need this extra piece to stop from drawing engine oil into air dryer.

More forum searching needs to be done to find answers.

BJ Holden's coach had similar symptoms.

My records show reference to an 'Air Dryer Expert' named Jim Nichols 800-446-5738 / 812-528-6555 who clarified BJ's fix.

Here is the brass valve on our air dryer

Re: Air compressor blowing oil into dryer

Reply #7 –
Barry, just for reference, do you happen to have the part #?

Larry
Larry Warren
1996  U320 36' SBID "Lola" sold 2020
Build #4970
Motorcade #18318

Re: Air compressor blowing oil into dryer

Reply #8 –
Here is something from my file:

With Cummins engine running; after an air tower blow down (purge), what would create a 3 to 4 minute duration "unloaded" compressor condition, followed by a few seconds of vacuum sucking noise, then a short (30-45 second) compressor loaded condition, terminated by a normal air tower blow down (purge), all with minimal to no change in the front and rear air tank pressures?

First, we need to understand how a Holset engine driven air compressor is set up.
Compressors are only designed to be "worked" (loaded, compressing the "siphoned off" turbocharged air) 10% to 30% of the time (depending upon designed max. air system use).  70 to 90(+)% of the time they should be running unloaded (which still robs HP, but to a much lesser degree).  In general, compressors rob horsepower, they rob turbo-compressed air whenever they are compressing air and they waste a LOT of turbocharged air whenever the air dryer is in active blow down mode.  They also waste fuel due to the lowered turbo boost pressure whenever the compressor is loaded and even more turbo boost air is lost while the air dryer is unloading.  They are oiled by engine pressurized oil. Clearly, some tricks are needed to make the HP burden on the Cummins engine as low as is reasonably achievable.
The most important design trick is using the Holset compressor as a GAS SPRING whenever the compressor is unloaded (isn't needed to be charging the wet tank).  In order for this "unloaded condition trick" to work, the compressor intake and discharge valve(s) need to be simultaneously sealed and held tightly shut.  The intakes are shut by the D2 Governor unloader output control pressure, and the discharge valve(s) are shut and held shut by the air dryer isolation valve being shut as soon as the Haldex Pure Air Plus starts to blow down (purge).  With the intake and discharge compressor valves sealed tightly, the Holset compressor piston causes the Cummins engine to work during the compression stroke, but after top dead center, compressor work is returned to the engine as the compressed air expands (minus friction losses), thus the Cummins gives and gets some work energy as the GAS SPRING cycles -- remember, 70 to 90+% of the time).
 
Now look at the purpose of the Haldex Pure Air Plus isolation valve used with a Holset engine driven air compressor.  Without the isolation valve, whenever the air dryer is in the unloaded (purged) condition, there is a direct pathway from the compressor discharge valves to open atmosphere through the dryer purge valve.  So the isolation valve has to  seal tightly, AND HOLD the compressor's last high pressure stroke, in order to provide backpressure seating on the Holset compressor's discharge valve(s).

So, if the isolation valve internals do not seal tightly or the hose fittings on the isolation valve machined block do not seal perfectly AND HOLD 125'ish PSIG air, what happens?  Well, with the Cummins engine running; after an air tower blow down (purge), depending upon how long it takes for the Holset compressor's discharge valve(s) backpressure to bleed down through partially defective isolation valve internals or through a tiny amount of isolation valve machined block FITTING leakage, (maybe 3 to 4 minutes after blow down?) then the Holset compressor's discharge valve(s) will start to flutter open.  Now the GAS SPRING is gone. With the outlet valves fluttering and the Holset intake valve(s) still tightly shut,  there will be a few seconds of vacuum sucking noise as the piston draws oil and air by the piston rings on each piston down stroke.  The D2 control pressure will bleed through the isolation block a bit until the D2 Governor shifts and the compression cycle starts again.  But the wet tank hasn't bleed down much and the good wet tank outlet check valves don't let the front and rear air tanks bleed back through the wet tank to the defective isolation valve or fitting defect, so there follows a very short  (30-45 second?)  compressor loaded condition terminated by a normal air tower blow down termination (purge), all with minimal to no change in the front and rear air tank pressure indication.

 because, in an early post on this, you said that you initially found the Haldex Pure Air Plus purge valve outlet area to have a large amount of oily residue, I wonder if the isolation valve perhaps started this and, even though rebuilt, it may be helping the problem to be inconsistent or to continue.  At any rate, the isolation valve rebuild o-rings color seems to be suspect.  Compressor outlet temperatures may be 250 F (+).  Also, it is critical to soap test all dryer/compressor vicinity air system fittings in both the loaded and unloaded condition (stop the engine with the air dryer loaded and again stop the engine with the air dryer unloaded -- so that you don't confuse the symptoms, if you find any).  A tiny Holset compressor outlet fitting leak or a tiny Haldex Pure Air Plus purge inlet air fitting leak would allow your described symptoms because the compressor discharge valve(s) rely upon trapped high pressure air to overcome compressor valve spring pressure to HOLD the discharge valve(s) shut.
I think that you are on the right course with a new isolation valve and leak tight fittings.

Re: Air compressor blowing oil into dryer

Reply #9 –
more info:

8-26-2016

Expert Holset air dryer tech
who helped BJ diagnos her oil problem from her air dryer
and another BJ problem with her new air dryer also pushing oil

recommend Bendix AB9 Drop In with Econ valve built in
should be p/n 065647

??One can know if it has econ valve because it will have a small diameter hose on bottom connecting two ports ??

Jim Nichols
800-446-5738 - work
812-528-6555 - cell

Re: Air compressor blowing oil into dryer

Reply #10 –
more notes with part number:

Yes I think the brass part you describe is an isolation valve. Here is the Haldex reference for it 
 
[Haldex]( http://epi.hbsna.com/products/product.asp?msi=0&sid=4A4672626DBC41758178D5E7E81CA844&dept_id=34&pf_id=KN23500 ) 
 
See if that looks familiar. You can also find it on Amazon (KN23500). When I check the Haldex Pure Air Plus part numbers I find that the DA33100X that you installed does not have an integrated Econ valve so it would need to have an add-on somewhere or you would probably be spitting oil too. The DA33200 is the model that has the integrated Econ valve, so if I go that route that is what I would try to get. I found it very interesting that the reply from Pamela&Mike in your posting said that they had the valve installed down by the wet tank. I wonder what year their coach is. 
I think I will call FOT and try to find someone who can explain all this stuff - Do we all have Cummins/Holset Type E compressors and do we all have/need isoloation valves? If so what air dryer/isolation valve combinations have they used through the years and where have they put these things? Have they switched over to using integrated isolation/econ valves and what model air dryer did they switch to?  If I was with the gang over in Quartzsite right now and had a lot of coaches to look at I could probably figure these things out, but right now I don't even have my own. 
I will have them check the bolt hole patterns on the mounting plate on Monday to verify that it looks like a Pure Air Plus was originally in there. If so I would prefer to go back to that but I don't know how much plumbing (line lengths and fittings) might have been changed when the Wabco was installed. 
Still mystified why it was ever changed. Found a reference to a recall on N4250's in 1994 but that should have been resolved by the time mine was built in 1998. But probably whoever changed it out didn't understand the isolation valve issue and it got left off when the Wabco was put in.

Re: Air compressor blowing oil into dryer

Reply #13 –
Make sure your coach has one. I bought one after reading a post on this and when I went to put it on found out my coach doesn't have one.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Air compressor blowing oil into dryer

Reply #14 –
Would get the isolation valve coming and see if that fixes problem,in response to Andy's post,agree but if you are getting oil somehow to the dryer the last thing you want to do is bypass it and get oil beyond the drier.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Air compressor blowing oil into dryer

Reply #15 –
Quote from: Barry & Cindy –
...what air dryer/isolation valve combinations have they used through the years and where have they put these things? Have they switched over to using integrated isolation/econ valves and what model air dryer did they switch to?
Here is one data point for your research.  Our '93 U280 with C8.3 uses a Bendix AD-9 dryer.  Isolation valve is threaded into a port on the dryer bottom plate.  The bottom plate has changed somewhat during the time we have owned our coach.  Links below have some photos showing the isolation valve installed on the old style and new style AD-9 dryer.

Old Style AD-9:    Was: Air won't build... Now: Air Dryer fitment

New Style AD-9:  Bendix AD-9 Check Valve
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Surely, no age has been more fraught with insecurity than our own present time."

Re: Air compressor blowing oil into dryer

Reply #16 –
Thanks to all, especially Barry, that posted information on my problem.  Hopefully y'all saved me several thousand dollars.

I stopped by the coach to verify that I needed an isolation valve and what mine looked like.  Pictures of the dryer and location of valve.  I ordered a replacement today.

1998 U320 40'
2005 GMC Yukon
MC# 17609
 

Re: Air compressor blowing oil into dryer

Reply #17 –
Steve,

Thanks for the excellent pictures.  They are definitely worth a thousand words. 
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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