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Old 03-17-2019, 10:04 AM   #1
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Newmar Owners Club
Join Date: Oct 2014
Posts: 42
Dryer spitting more oil than usual and coach only airing up to ~95

I have a 2005 Dutchstar on a Spartan Mountain Master GT chassis. Recently I noticed the cover that hides my dryer and fuel filters has an external oil stain that has not been there since I bought the coach 30,000 miles ago (4 years).

On my last trip I was only airing up to about 95 psi. My dryer did purge after a few minutes as I had been parked for 6 weeks and the air tanks were low.

My dryer filter is 18 months old and I am going to replace it. I do not hear any air leaks with the coach running or immediately after turning it off.

Any ideas? When I called Spartan they suggested replacing the dryer filter and see if that fixes it.

Thanks in advance for any input.

Low on air in Tucson!

Greg & Karen
05 Dutch Star 4023 - 370 ISL
Spartan Mountain Master GT
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Old 03-17-2019, 01:20 PM   #2
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If your compressor is working overtime, it may pump a little oil.
Check for leaks while it's building air. Fix that before you change the drier filter so the new one won't get contaminated with oil.
Happy Glamping.

2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with GSXR 1100T or KLR650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!
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Old 03-17-2019, 01:56 PM   #3
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Dryer spitting more oil than usual and coach only airing up to ~95

I would air up and spray soapy water on the purge valve area and see if there is a small leak there.

I had similar symptoms. Turned out the be a gunked up purge valve. I wacked on it a little bit and hit stopped leaking enough for us to get to our destination. Then I replaced it.
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Old 03-17-2019, 04:24 PM   #4
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If your dryer is unloading ( spitting ) the governor is sending that signal. That signal comes from the wet tank ( no gauge on it ).

You either have a bad compressor governor, shutting down the pressure at 95 PSI ,

OR a restriction between the wet tank and both service tanks ( they have gauges ), caused by a plugged up double check valve,

OR leaks, possably from the suspension system. The leaks will stop around 75 PSI so you may not get there in time to hear them.
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Old 03-18-2019, 06:59 AM   #5
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All Mountain,
I am making the assumption that the 95 psi you are reading, is from the dashboard air gauges. So, that said, here are a few things to check.

1. If you have an auxiliary air connection that you can plug an air hose into, you should get or borrow a Good Air Pressure gauge that will give you a clean pressure reading. See what pressure you get.
2. You don't mention whether you have IFS on your RV. Do you? If so, there are 2 ride height leveling valves up front near each front wheel and 1 in the back. You need to check these valves for leaks.
3. If you did check the air pressure with a good gauge, and it was still telling you 95 psi, you could have a leak in the air line between the air compressor and the governor. (Happened to me.) The governor is located just to the rear of the air dryer on the passenger side frame rail to the rear of the rear wheels.
4. The governor could be clogged or in need of resetting.

5. Check the bottom of the Air Dryer. There is a turbo cutoff valve that could be leaking. I have attached a couple of pdf documents for the air dryer. They should give you an idea about the air dryer and how to check it.

The document for air dryer maintenance was too big to upload, so you should go to the Meritor Wabco web site and download a copy of it. http://www.wabco-na.com/literature/Air-Dryers

Hope some of this helps.

2003 Travel Supreme 40DS02
Attached Files
File Type: pdf AirDryerTroubleshooting-TP1343.pdf (166.4 KB, 11 views)
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Old 03-18-2019, 02:11 PM   #6
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Thanks for all of the excellent responses.

Thanks everyone for the quick responses. I have found that the governor was the issue.

I did not find any leaks in the system. I removed and disassembled the governor and found that the shuttle piston was scored. I cleaned it up and reassembled the governor. I started the bus, adjusted the pressure back to my normal pressure of ~120 psi. I could hear the compressor unload after the dryer "burped" and everything seems to be working fine now.

I also performed the "cardboard test". Disconnecting the compressor supply to the dryer, starting the coach and seeing how much oil sprayed on the cardboard. With two minutes of operation the cardboard was still clean.

Today I ordered a new Wabco governor from Spartan that I will install before I leave Tucson on Saturday.

Again, thanks for all the suggestions and expertise. I is greatly appreciated.

Greg & Karen
05 Dutch Star 4023 - 370 ISL
Spartan Mountain Master GT
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Old 03-18-2019, 11:16 PM   #7
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Location: Apple Valley CA
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All Mountain. You can purchase that same governor at NAPA for a third of the price. I know I had to replace mine several years ago on my Mountain Master Chassis. Glad you figured it out.


Craig & Carolyn Roberts Apple Valley, CA
2006 Newmar 3910 KSDP 400 ISL Cummins Spartan Mountian Master Chassis
Toad: 2017 GMC Canyon 4X4 Crewcab
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