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Topic: Air Alarm and Low Temperatures (Read 834 times) previous topic - next topic

Air Alarm and Low Temperatures

The air alarm sounded when departing French Creek State Park in Pennsylvania, with the following scenario:

- Temperature 34 degrees
- No engine pre-heat (I forgot to throw the preheater switch since it was above freezing. I usually preheat below 40 degrees)

Twice during the first 15 minutes of our 30 minute trip home the pressure went to 50 lb. Each time, I stopped the rig and watched. After 10 minutes of engine warming, pressure started building properly. YES! After 15 minutes of engine time, air cycling was back to normal.

I have read about air issues on this forum. However, I am a newbie to Diesel Pusher air systems, so my questions are:

What part should be replaced?
What are the two gauges for (newbie question)?
Why does the lower gauge sometimes read 20 lb lower than the upper gauge?
1997 U270 34FT Build 5140 Cummins 8.3 Allison 3060R
Solar 1920Watts, 14KWH lithium. Orion BMS.

Re: Air Alarm and Low Temperatures

Reply #1 –
Hold de bus!  Sounds like you've got a serious air leak at least.  The lower and upper gauges read front and rear air pressures for brakes.  You can open a rear drain valve easily, and not which gauge goes down to figure out which is front and rear.

The temp shouldn't matter unless your air system is waterlogged and frozen.  Need to check and see how long it takes to build up pressure to 120 or so....does popoff valve work.....condition of compressor. 

Your emergency brake should automatically engage at low pressures.  Did the knob pop out on its own? 

Gotta fix it, not safe to drive until done. 
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Air Alarm and Low Temperatures

Reply #2 –
Quote from: Tim –
What part should be replaced?
What are the two gauges for (newbie question)?
Why does the lower gauge sometimes read 20 lb lower than the upper gauge?
1. In any case where air pressure is acting erratically, I recommend preemptive replacement of D-2 governor.  Inexpensive, can't hurt, might help.

What is a D-2 Governor? (was What spare parts to carry?)

BENDIX D-2 GOVERNOR MANUAL Pdf Download.

2. Answered in post above.

3. Your front and rear air gauges can read differently for several reasons - it is not always a "problem".  To aid in diagnosis, you need to specify the exact conditions when you observe the differential readings.

Air tank differences
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
"Nature abhors a vacuum"

Re: Air Alarm and Low Temperatures

Reply #3 –
We had the same thing happen in cold weather.  Ice in air line, limped to small truck shop, who removed governor hose to wet tank, poured in "air brake anti freeze" and that and the warmer shop did the trick and we took off.  We have been carrying a quart of air brake anti freeze for over 10 years since it happened.  Sure air dryer is supposed to remove "all" moisture, but who knows.  Never happened again.

Re: Air Alarm and Low Temperatures

Reply #4 –
Good points made.

The governor (under $25 and easy to replace) is responsible for turning on and off (actually loading and unloading) the engine driven air compressor. So, that is one suspect.

But, a massive air leak could also render the air compressor incapable of keeping up with the leak.  And if the air dryer has not been serviced recently (an often neglected item) a valve in the dryer would be one of the first suspects. Because a valve can stick and then free itself.  Were an air line cut, etc, it would not "self heal". If the dryer has not been serviced in awhile (or you don't know how long it has been) my recommendation is to buy a FACTORY (i.e. the factory that made the dryer, not a "made to replace of unknown origin) REMAN dryer.  That replaces, not just the filters, but also valves, heater, etc.
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 Alarm and Low Temperatures

Reply #5 –
Barry,
How do you us the air brake antifreeze?  Where is it added?

John M.
John & Carm Morales

"We travel not to go anywhere, but to just go.  We travel for travel's sake.  Our great desire is to move."

Re: Air Alarm and Low Temperatures

Reply #6 –
For Tim and anyone else who might not be too familiar with air brakes, Barry's website has a lot of articles on the subject.  I would suggest the first article to read is the pre-trip check.  Technical Help - Air Brakes  Also the manual for the coach has info about the brakes.
Jerry Whiteaker former owner 96 U270  36' #4831 Austin,TX-Owner Mods LCD TV w/front cabinet rebuild - LCD TV bedroom - Dual Central AC, either can cool coach w 30 amp - Skylights at roof AC openings - Drop ceiling for ducting of AC - Shower skylight white gelcoat/wood/epoxy frame - Air Springs/Shocks replaced - 2014 CRV - 8K Home Solar - Chevy Volt

Re: Air Alarm and Low Temperatures

Reply #7 –
John, tech removed hose on governor going to wet tank, used a small neck funnel and poured the alcohol into the hose.  That was it.  Looked like he had done many the same way.

Re: Air Alarm and Low Temperatures

Reply #8 –
Thanks for the overwhelming response. Just bought two new D-2 governors, air dryer kit and air system anti-freeze and conditioner. OK wolfe10, they are aftermarket governors for $13 each on eBay with a seller that has decent feedback. I will report on their quality. I'm a sucker for cheap prices.

As soon as it gets warm enough to work, I'll be crawling under the rig, safely.
1997 U270 34FT Build 5140 Cummins 8.3 Allison 3060R
Solar 1920Watts, 14KWH lithium. Orion BMS.

Re: Air Alarm and Low Temperatures

Reply #9 –
Tim,
 I think Wolfe was referring to the dryer for a factory rebuilt unit. The governors are pretty basic.
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 Alarm and Low Temperatures

Reply #10 –
Quote from: craneman –
Tim,
 I think Wolfe was referring to the dryer for a factory rebuilt unit. The governors are pretty basic.

Correct:  New governor if one is needed.  Factory Reman for air dryer.
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 Alarm and Low Temperatures

Reply #11 –
Replaced the air governor, air dryer, coalescing filter and the relief valve (it came with the kit). All went well, except the relief valve broke off when it was torqued for removal. This brass device must have been over-torqued when it was installed and is rated only for 12 ft-lb of torque. Four hours later, after several unsuccessful removal attempts, I drilled and cut out the relief valve from the air dryer assembly without damaging the threads too badly. Used teflon tape and thread compound to ensure the partially damaged threads do not leak. See the photo.

There was hardly any water in any of the parts replaced, so there is no conclusive cause of the air pressure loading cycle failure at 32 degrees F. There is a heater element surrounding lower cylindrical middle part of the air dryer assembly. It wouldn't have hurt to have let the rig warm up for 15 minutes to give the heater time to melt any possible ice.

Question: Where should air system anti-freeze/conditioner be added? I bought some, but did not want to add it to the wrong place.
1997 U270 34FT Build 5140 Cummins 8.3 Allison 3060R
Solar 1920Watts, 14KWH lithium. Orion BMS.

Re: Air Alarm and Low Temperatures

Reply #12 –
Tim, Looks like you have done that before as your drill looks like it was centered great. Nice job. I have done that removal dozens of times when a machinist.
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Air Alarm and Low Temperatures

Reply #13 –
We have not changed our air dryer pressure relief valve, and have little collection of new ones somewhere.  So we are happy that we did not chance breaking ours, but have changed out our air dryer with a rebuilt unit so our valve is not ancient.
Air brake anti-freeze is used to eliminate already built-up ice in air lines, not air dryer.  It is alcohol and is poured into the disconnected rubber hose between the governor & wet tank.

Re: Air Alarm and Low Temperatures

Reply #14 –
The CRC brand Air System Anti-Freeze has methanol. Could that harm rubber components?
1997 U270 34FT Build 5140 Cummins 8.3 Allison 3060R
Solar 1920Watts, 14KWH lithium. Orion BMS.

Re: Air Alarm and Low Temperatures

Reply #15 –
Methanol is methyl alcohol.
Regards,
Brett

'99 42' Foretravel Xtreme
'14 Brown Motorsports Stacker
'05 Chevy SSR
'02 BMW R1150R

Re: Air Alarm and Low Temperatures

Reply #16 –
You should not need to add any air system anti-freeze unless you have allowed your air dryer to fail.

Said another way, with the air dryer functioning, there will be no moisture in the wet tank.  Easy to check (when above freezing)-- just open the wet tank valve.  It is basically your "report card" on air dryer condition.  All you should get is clean, dry air. Water, oil or worse white powder all indicate a neglected, failed air dryer.
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 Alarm and Low Temperatures

Reply #17 –
     A trucker told that he has had to change several governors in cold weather.  Mine gave me trouble two times while on top of mountains in cold air.. I assume a weak governor does not like cold air.
Laurel Hill, FL
 To do is to be---- Nietzsche
  To be is to do-----Kant
  Do be do be do----Sinatra

Re: Air Alarm and Low Temperatures

Reply #18 –
Not all trucks come with filter dryers. The only way to get moisture out of my crane is to drain the three tanks daily. I get moisture at the governor sometimes. If in freezing weather the governor would stick where ever it landed at shutdown. I don't ever have that problem is Southern California.
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