First trip out in a while, and the air pressure builds real slow. It will make it to 120psi from 20psi in about 10 minutes. Useing the brakes in the RV park to back in will cause the Air guage to fall below 60psi and spring brake will kick in. High RPM will increase speed with which air pressure will build up. I do no hear any air leaks. After 2 days in RV parks air guage show 30psi. 185K miles on my 95 U240 Cat 3116 no air bags. Can the air compressor be in need of overhaul? Cruise and throttle work fine. At 60 MPH air guage show steady at 110-120psi all the time. It does seam like the white needle on air guage will go down futher than red needle some times.
Have someone listen for air leaks while you are applying the brakes. What you are describing is a leak after the treadle valve.
Since you hear no obvious air leaks I would replace the D2 governor about 17.00 Always carry a spare if you don't already.. Air compressor last cheap part first. In conjunction to what Chuck said.
Or you could have a leak in one of the cans. If it's in the back, you would never hear it with the engine running. Pustefix Amazon.com: Pustefix Premium Bubbles Refill 8.3 fl.0z.: Toys & Games (https://www.amazon.com/Pustefix-Premium-Bubbles-Refill-fl-0z/dp/B0002HYC00) solution sprayed on with a Dollar Tree spray bottle will find the leak. The bubbles don't pop for a long time, they just get bigger and bigger when there is a leak.
Pierce
Like P said.. a canister won't blow air until you mash the brake. Get someone to listen for you.
We had the same issue you described, recently. Taking Foreforum advice....
We listened but didn't hear any leaks.
Replaced the D2 with no change.
Replaced the air hose from the compressor to the air dryer, no change.
Replaced the compressor, all fixed.
I was due for an air dryer service so we replaced it with a reman air dryer
Yes, ASSUME you have a leak "downstream" of the brake pedal. Run engine at 1,100 RPM or so to build pressure to cut out PSI. Turn off engine. Have someone step on the brake pedal while you do a "walk around/crawl around and listen".
But, it that isn't the issue, here is the order I would do a "diagnosis by parts replacement" (which I really hate to do):
Replace the D2 (governor) under $20.
If the air dryer is over 3 years old, replace with a FACTORY REMAN-- count this as preventive maintenance.
After that, back to basic diagnostic work.
The good news is with no air suspension/leveling systems your air system is VERY simplified.
When I was coming back from New Mexico last year, it took a long time to build the air. I changed the air dryer cartridge and now she comes up to pressure quickly. My next move would have been the D2, but it was new the year before. The air dryer system was new in 2018.
Larry
Thanks for all of the responses.
I made this topic at least 4 hrs ago, and I still have the 30psi from 2 days ago. I want to know why the air pressure builds up so slowly. It has never took so long to get to 120psi. Once at 120psi in the past, the air pressure would never go down much unless you pumped the brakes. Even at idle now, holding pressure on brake peddle, the air pressure gauge will stay at one number(it does not fall down). Just now as a test, engine dead, 30psi, press and hold brake peddle down for several seconds, red needle jumps down and then back up with white needle, after a couple of applies and release after few seconds, I still have 20psi both needles.
This last test you did eliminated the brake system from your problem. Now you have the air compressor, line from the air compressor to the dryer and the dryer itself as the problem. The line from the compressor to the dryer will only have air pressure when the engine is running because of the check valve at the dryer. Do a good visual check of it as it has been posted before as the culprit with your symptoms. If the dryer hasn't been replaced in the last 3 years change it out. The air compressor would be the last thing I would throw parts at.
is this black Haldex filter the air dryer cartridge ya'll are talking about?
Buy one at O'Reilys?
Pat and Thanks a lot
Yes, that is the filter. But, from the looks of the dryer itself, it (valves and heater) have not been serviced in a long time.
Again, a Factory (i.e. Haldex) reman replaces not just filters, but valves, heater, etc. Basically only the metal case is reused.
Brett, your thinking replace the whole thing that the filter is screwed onto?
what is a number and where do I get one?
I am out of town now.
Pat
Pat,
Yes, "the whole thing" would be replaced by a reman Haldex dryer.
There will be a PN on the dryer itself. Most any parts house that deals with OTR trucks will have the reman units in stock.
Again, think of this as preventive maintenance. As several of us have said, if all you are trying to do is get back on the road, replace the governor first. But a parts house that has one will likely have the other as well.
When my air dryer went bad after sitting in storage, I could get to 30 PSI and no more. Replaced the dryer assembly, like Brett said, worked perfect till coming back from NM. It would slooooowwwwly build air pressure to 110-120 and hold no problem going down the highway. Changed the cartridge out and pressure builds perfect now at fast idle. Haldex has a 2# and a 3# cartridge. I went with the bigger one. It wasn't cheap at Transwest. Seems like it was just south of $200, just for the cartridge. I could have gotten much better online.
Larry
I get them at NAPA part number DA33100X Haldex
Thanks Red for that part number and source.
pat,
When you unscrew the filter, spray the basin with WD 40 or ATF and toothbrush out the goo that settles at the purge port.
Hi Mike,
I have made it to Gunsmoke Rv Park, Dodge City Kansas. Going down the road, no problem, gauge stays at 110-120psi. Going to try for home in the morning. I will do as Brett suggested and change the whole air dryer. i will update when I do that. I really appreciate all the help from everyone here.
Pat,
I made it home with no problems, other that a patio awning deploy at 60MPH. I replaced the air dryer today with a napa da33100x. It is the same a my old one. I had to change 3 fittings from old to new. Hooked up the heater. I can tell no difference. The air pressure still builds real slow. It will make it to 120psi after 1300RPM for too long. Kill engine and check for leaks with windex glass cleaner, no leaks and I cannot hear any leaks. Gauge falls to 60 psi after 4 hrs. How long should it take to build air pressure from 30psi to 70psi??
Pat,
60 psi to 110 psi is fairly fast but 0 to 60 psi takes about 4 or 5 minutes on ours. Windex is not good for bubbles. You need a soapy mixture so bubbles will show leaks. Lots of places for a leak to be so it takes time to find the leak. Any water in wet tank?
Pierce
I use a product called Super Miracle Bubbles which is a bubble maker for kids to make bubbles.
I will look more tomorrow with dish soap and water. I was check my work today on the install of the air dryer. BTW the napa dryer was $275 with exchange of old unit.
Pierce are you talking about idle RPM(,ine is 700) on the 0-60psi ???
Pat
I usually build air at about 900-1000 rpm. Idle is 600.
P
Pat,
Gauge falls to 60 psi after 4 hrs. This indicates a pretty good-sized leak, as your only air is the brakes, air horn and "tire fill hose", not the complex suspension of other coaches.
Be sure to check the gate valve to the hose to fill tires. If leaking, replace with a DOT approved ball valve. Much better. Though I have not heard of it leaking, probably wouldn't hurt to check the air horn valve.
BUT, I don't think your leak accounts for that slow build. At under $25, I would sure change it and check hoses back there very carefully.
I know it has been mentioned many times, but have you replaced the governor?
Hi Brett,
I replaced The old Air Dryer with a napa reman da33100x. I don't think it made any difference. What governor?
Pat,
Pat,
The governor is what controls cut-in/cut-out PSI for the air compressor. Easy to replace and under $25 at any parts house that deals with OTR trucks: air compressor governor - Penelusuran Google (http://www.google.com/search?q=air+compressor+governor&client=firefox-b-d&tbm=isch&source=iu&ictx=1&fir=7oY5X4y_fNcmsM%253A%252C2MjE7SqTeLJPBM%252C_&vet=1&usg=AI4_-kS6048x1B54y735uEBAKwNNgHAyMg&sa=X&ved=2ahUKEwjthofqttXpAhVESq0KHUxFBUwQ9QEwGHoECAcQNw#imgrc=7oY5X4y_fNcmsM:)
Haldex D2 Governor Service Data (http://beamalarm.com/Documents/haldex_d2_governor_service_data.html)
If you put a new governor on and the pressure is not enough, take the cap off, loosen the nut and turn the screw CCW to raise the pressure part of a turn at a time until you are happy. Mark the governor with a black felt so marker you remember which way increases/decreases.
Pierce
I am clueless where the d2 governor is on my U-240 Cat 3116. I have never seen this thing!
bolted to your air compressor with two 1/4" bolts.
The short answer is "On top of the air compressor."
The more compassionate answer is:
Looking in the engine compartment is confusing at first so break it down into things you know.
Find the Starter, the alternator, the water pump and the hydraulic pump for the power steering.
The fuel injection pump has as many steel pipes running from it as cylinders in the engine. Plus a couple more for fuel in and out. And a cable somehow connected to the foot feed. And a wire.
The air compressor is usually gear driven by the engine and looks like a two cylinder compressor with a black coolie hat. The thing wearing the coolie hat bolted to the compressor is the D-2 governor. In operation it lifts the valves in the compressor to stop the pumping action. The D-2 is the most common failure. Second is the mechanism that lifts the valves out of operation. Air dryers should be replaced on a calendar basis and never fail. Failure can be expensive. D-2 governors are inexpensive and a spare is cheap insurance.
I'll be back to normal soon.
Where do we buy a d2 governor? Part number?
Napa
Governors - Air Brake Compressor - H/D Truck D2 Bendix Haldex MBI 275491RX |... (https://www.napaonline.com/en/p/MBI275491RX)
Good Morning All,
Thanks for those quick replies, I found the governor. Never saw one before,
On my way to parts store.
Just some pics. The air gauge shows whats left of the 90psi air pressure from about 4:00pm yesterday until just now 8:55am about 45psi. The other pic is the D2 governor on my 94 Cat 3116.
It's a learning curve to be certain, but for me it's easier than trying to learn how to use my new telephone now that Tracfone has deprecated our Blackberry-like Motorola phones with the QWERTY keyboard.
Today I set up voice mail.
For our new home I started with "How do I check the oil level?" Moved on to "We're going to need a bigger pan." Through "What the hell are Wedge Brakes?" to "Oh. That's a quick dump valve, I know how those work."
Small bites. It was foolish to think I could master the new telephone technology in one sitting. Analysis determined that a land line with a rotary dial phone wasn't feasible
I got the d2 Governor replaced, it was not easy. The two bolts on each side of the air hose connection that is on the side of the governor, must be tightened leaving the flats facing the air connection fitting. The air connection fitting will not install/turn because it's point hits the mounting bolts. After standing on my head half the time and the other under the engine it is installed.
NO HELP/CHANGE!
I tried patting the gas peddle and the white needle reacts to it and falls a lot, red will not fall, this was going 55MPH.
Had to adjust the new d2 governor, it was set at 130psi, I lowered to 115psi.
130 is good 115 isn't most run from 90 to 120. Back to my reply #9 you only have an air leak when the engine is running and it will be either in the airline from the compressor to the dryer or the dryer itself. If you can spray a dish soap solution on everything from the compressor to the dryer exhaust while the engine is running you might find it.
NAPA truck shops can make those flexible air lines. After 20 years it wouldn't be extravagant of you to replace them all.
This morning I got under the MH and sprayed soap water on anything that looked like air. This includes both air tanks(all connections), things with several air connections(both at the rear and front), connections to the air dryer, connections on the air compressor, all connections and things on the cruise control board, checked the value on the aux air hose in fuel bay. Looks like a lot of my air lines are hard black plastic. Hoses to air cambers of the brakes at the wheel. Over night(15hrs) it lost from 70psi down to 25psi . The air pressure build up is still very slow. At 2000RPM it will make it to 115psi. I can hear the dryer blow off.
Pat,
Had a similar problem last year, especially in higher altitude areas with colder weather. Took forever to get enough air pressure built up. Took coach to MOT and they diagnosed the problem as the rear ride height control valve. Here is an article on the valve. ride-height-adjustment-in-motorhome-or-rv (http://beamalarm.com/Documents/ride-height-adjustment.html)
Hope this helps!
Greg
Hi Greg,
My U240 does not have air bags. I have air brakes, throttle, cruise control. and aux air hose. That is all there is to my air system.
Pat,
Pat, the air dryer blow off is switched by the D2 governor. I think you need to find the line taking compressed air from the air compressor to the dryer and the line from the dryer to the wet tank. Check them for leaks.
Update:
Today I got the Cat rebuilt air compressor installed. The air pressure problem is solved, it was the compressor.
$900 labor and $650 parts.
Pat,
I dont think that the compressor should have system pressure on it ,sitting. Should be a check valve. You may still have something faulty. I hope not .