No air, need help

Topic: No air, need help (Read 3199 times) previous topic - next topic

Re: No air, need help

Reply #25 – April 03, 2019, 08:00:15 pm

Figuring out air system puzzles is always fun. So what do you know so far?

With engine running, your dash air pressure gauges go to 30 psi and then stop going up. This tells us your air compressor is compressing air, which is a good thing, cuz new compressors are expensive.

Air goes from the compressor, to the dryer, to the wet tank, to the other two (front and rear) air tanks. If you show 30 psi on your dash gauges, it is a pretty safe bet that you have 30 psi in your wet tank, and 30 psi in your front and rear tanks. If the drain valves were open on either the front or rear tank, I think you would be able to hear it.

Question: What do your dash air gauges do when you shut off the engine? Do they hold 30 psi, or do they bleed off. If they bleed off, is it a fast or a gradual drop in pressure?

But the BIG question is, why does pressure stop building at 30 psi? When the coach was running, did the air dryer ever purge (make the normal sound it does when the compressor cuts out)? Or did the pressure stop climbing, but you never heard the dryer pop off?

You couldn't feel air coming out of the bottom of the dryer, so the purge valve is probably closing like it should. Like Don says, you would know if it was stuck open. Don't worry about finding dirt, grease and oil around the dryer purge opening - this is completely normal. A little oil gets mixed with the compressed air that comes out of the compressor. One of the functions of the air dryer is to remove this compressor oil from the air, and expel it out the purge valve.

If it was me (I am a lazy sot) before I messed with removing and replacing the dryer, I would first install a fresh D2 governor. It's a LOT cheaper than replacing the dryer, and a LOT less work. If it solves the problem, you're golden. If not, you have at least eliminated one possible factor. Then you can move on to the harder stuff.

But that's just me.

Re: No air, need help

Reply #26 – April 03, 2019, 10:21:19 pm

That is the next step. Get a new governor. Stopped at OReilley's. The youngster their couldn't find his way out of a paper sack let alone anything on the computer. I left after 30 minutes. I had called the same store yesterday, the guy had the part, price and could get it for me in the morning. I told him to wait till I check it out. Mistake. Will call tomorrow and get it ordered.

When I shut off the engines, the gauges held. I restarted the engine before I left and they were at 30 pounds. Probably 15 minutes with the engine shut off. Coulldn't hear anything leaking, but who knows, I have a lot of hearing loss. I have heard the pop off valve before, but not since starting this season.

Thanks for the help. I won't be able to get back till Friday night, so we will see.

Larry

Re: No air, need help

Reply #27 – April 04, 2019, 08:44:02 am

Quote from: ohsonew – April 03, 2019, 10:21:19 pm

When I shut off the engines, the gauges held. I restarted the engine before I left and they were at 30 pounds. Probably 15 minutes with the engine shut off. Coulldn't hear anything leaking, but who knows, I have a lot of hearing loss. I have heard the pop off valve before, but not since starting this season.

Still thinking about your reported symptoms. What malfunction would account for this combination:

1. The air compressor is compressing.
2. Compressor fills the system tanks to 30 psi but doesn't increase the pressure any higher.
3. You haven't heard the compressor unload (dryer pop off).
4. You shut engine off and the dash air pressure gauges hold at 30 psi.

So far, the only hypothesis I come up with is a leak somewhere between the air compressor and the wet tank. The leak would allow air pressure to build to 30 psi and then would be large enough that it would exhaust air at the same rate that the compressor supplies air. In this state of pressure equilibrium, the compressor would never unload but would keep pumping, yet the dash air pressure gauges would never rise above 30 psi. When the compressor is shut down, the inlet check valve at the wet tank would hold the pressure in the system at 30 psi.

So what components are between the compressor and the wet tank? There is a big air hose from compressor to air dryer, the dryer assembly, and the air line from dryer to wet tank. The D2 is also connected to the compressor, the dryer and the wet tank, so D2 plus any air hoses attached to it would also be suspect.

If anyone else can postulate a more logical failure mode that fits the symptoms listed above, please post it here!

In the meantime, I would still replace the D2 as the next step, but while working also carefully inspect the air hoses for abraded spots.

Re: No air, need help

Reply #28 – April 04, 2019, 08:57:20 am

Time for a lot of soapy water?

Re: No air, need help

Reply #29 – April 04, 2019, 09:17:07 am

Replace the D-2 by all means,check the plugged ports on the D-2 and see if you can put a gauge on the D-2 (it's 1/8 npt).Then
you can verify the 30psi,if the air compressor is only reaching 30 because of a leak that's a hell of a leak.I know we don't have
many actual air compressor problems but that does'nt mean they don't fail.

Re: No air, need help

Reply #30 – April 04, 2019, 09:34:23 am

Quote from: John44 – April 04, 2019, 09:17:07 am

I know we don't have many actual air compressor problems but that doesn't mean they don't fail.

I don't know anything about air compressors, or what could go wrong with one. Any Forum "air compressor experts" feel free to chime in.

Could a engine driven compressor suffer some malfunction such that it would compress system to 30 psi and then "stall out" at that point?

Re: No air, need help

Reply #31 – April 04, 2019, 09:41:41 am

Quote from: Chuck & Jeannie – April 04, 2019, 09:34:23 am

I don't know anything about air compressors, or what could go wrong with one. Any Forum "air compressor experts" feel free to chime in.

Could a engine driven compressor suffer some malfunction such that it would compress system to 30 psi and then "stall out" at that point?

The unloader valves can get stuck and cause the same symptoms. I have had it happen and freed them up with Corrosion X sprayed into the port after removing the D-2 governor.

Re: No air, need help

Reply #32 – April 04, 2019, 03:31:07 pm

If you connect the 2 large lines and cap off the 1/4 inch line coming from the governor, you don't even need the air dryer. The coach will cut in and cut out as usual. Drive it until you decide to replace it.

Re: No air, need help

Reply #33 – April 04, 2019, 04:02:29 pm

Might do that as a last resort but would not want to chance moisture in the system,a few drops goes a long way.

Re: No air, need help

Reply #34 – April 04, 2019, 04:19:49 pm

Quote from: John44 – April 04, 2019, 04:02:29 pm

Might do that as a last resort but would not want to chance moisture in the system,a few drops goes a long way.

Completely agree. I bypassed mine to get the coach home while awaiting the delivery of the new air dryer, but I wouldn't regularly drive it without an operational dryer.

Re: No air, need help

Reply #35 – April 04, 2019, 05:09:32 pm

Back in the day, trucks and buses did not have air dryers, and the driver used to have to drain his tanks manually every day to remove water from the bottom of his tanks.

Re: No air, need help

Reply #36 – April 04, 2019, 05:14:08 pm

Quote from: jcus – April 04, 2019, 05:09:32 pm

Back in the day, trucks and buses did not have air dryers, and the driver used to have to drain his tanks manually every day to remove water from the bottom of his tanks.

Thankfully those days are just memories for most of us!

Re: No air, need help

Reply #37 – April 04, 2019, 11:25:12 pm

Picked up my new D2 tonight. Will try to work on it tomorrow after work, weather permitting. Told one of the mechanics at work what it was doing. First words out of his mouth was, "replace the governor". I don't think he was talking politics.

Craneman, I don't have any Corrosion X, any other brand worth mentioning? Is it like PB Blaster, WD 40 or something entirely different?

Thanks for all the advice so far, I do appreciate it.

Larry

Re: No air, need help

Reply #38 – April 04, 2019, 11:57:43 pm

Larry, PB blaster should work. The unloader valves are spring operated and can get hung up either way. Creating high pressure or low pressure.

Re: No air, need help

Reply #39 – April 05, 2019, 12:15:23 am

Thanks Chuck, got PB at the coach. gotta get to be d now, 4 o'clock comes early.

Larry

Re: No air, need help

Reply #40 – April 07, 2019, 06:45:59 pm

Update: Replaced the D2 governor, didn't fix the problem. Coach stops at 30#.

I identified the drier as a Haldex Pur Air Plus Dryer

As per a comment on "No Air Pressure" from 4 years ago from Twig when Amos Harrison had this same problem, I tried removing the desiccant filter, still no go. Removed the coalescing filter, nothing. Put back together and checked the purge valve. It was stuck open and with the coach at 1300 rpm idle, I couldn't hold the pressure back with my palm. I have hope that this is the problem. I'll be checking on new purge repair kit, coalescing filter kit & desiccant kit. Since I don't have any idea when filters were last changed, ain't no time like the present.

In the topic which I I commented on, Amos stated that he had found "the broken parts inside the drier" but he didn't elaborate any further. When I was looking down inside where the coalescing filter goes, there was a piece laying there. I can move it back up into position that somewhat resembles the Turbo Saver Valve shown in the cutaway view on the dryer. It appears that the valve part might have broken off. The cutaway also shows a valve assembly coming through the purge orifice but I see no evidence of it being there, Anyone have any ideas what this is and is it likely broken?

My first plan of action is to build a set of bypass connectors and bypass the dryer completely to see if it will build pressure. If so, I'm hoping someone can tell me the likely hood that the drier is bad or just the purge valve. I appreciate any comment or advice from the ones here wiser than me on this system.

Larry

Re: No air, need help

Reply #41 – April 07, 2019, 06:54:37 pm

Larry,

OK, back to basic first question-- how long since the air dryer has been replaced/completely (yes completely, not just filter replacement) serviced??

Re: No air, need help

Reply #42 – April 07, 2019, 07:14:01 pm

Brett, I have no records from the previous owners showing it was done. However the desiccant filter was dirty on the outside but you could still read the factory writing with little difficulty. It also removed reasonably easy with a strap wrench to break it loose and then the rest by hand. The drier on the other hand is filthy and caked in dirt/grease from the road it appears. The purge valve is dirty, but wiped clean enough to read with a rag. It may have been replaced along with the heater element. It looked reasonably clean considering its location in the engine bay.

Larry

Re: No air, need help

Reply #43 – April 07, 2019, 07:30:30 pm

Should'nt have much oil or grease if everything is clean and working good,if too much oil is coming from the engine air compressor
then that is a concern.

Re: No air, need help

Reply #44 – April 07, 2019, 07:46:36 pm

If the air was working ok before storage I don't think your missing a part ,how would it have worked before?Think you either need to
get every kit for the drier and rebuild it yourself or get the reman,When I did mine I had it in a vise and cleaned and blew out and
had to sand a ridge from a passage,at some point you will have to get a reman anyway now might be the time.

Re: No air, need help

Reply #45 – April 07, 2019, 07:49:13 pm

Quote from: John44 – April 07, 2019, 07:30:30 pm

...if "too much" oil is coming from the engine air compressor then that is a concern.

"too much" is difficult to quantify. Everything I have seen concerning air compressor performance standards leads me to believe that SOME oil is OK, but TOO MUCH is not OK. Bendix Advanced Trouble Shooting Guide seems to think oil being purged from dryer is not a cause for concern. See Symptom #3 (Page 5):

https://www.bendix.com/media/documents/products_1/compressorsgovernors_1/troubleshootingguide.pdf

OTOH, if there is oil in your wet tank (or worse, in your front and rear tanks) then that requires further investigation (see Bendix Guide above)

Re: No air, need help

Reply #46 – April 07, 2019, 08:13:36 pm

If the system will build proper air pressure after you bypass the dryer then replace the dryer with a completely remanufactured unit. They are not that expensive and it just makes to start with a fresh unit.

Re: No air, need help

Reply #47 – April 07, 2019, 08:18:12 pm

It looks to me like you just need to replace the drier. You can make the bypass kit but from everything you have said the drier needs replaced.

Re: No air, need help

Reply #48 – April 07, 2019, 08:20:26 pm

There is oil and water on the inside where the coalescing filter is. Not a huge amount, but some. I'm not terribly worried about the amount from the compressor, at this point. That can always change as we know. The main dirt/grease is on the outside of the dryer where it is exposed to the elements of highway travel.

When I put it into storage in November, we had just driven it 600-700 miles within the preceding couple of weeks. Everything worked fine. I'm thinking of the purge valve to see if it is the culprit. With no prior knowledge of maintenance from previous owner(s) I will be changing the filters anyway. I've read to many stories on the result in contaminating the air system.

Keep em coming,
Thanks,
Larry

Re: No air, need help

Reply #49 – April 07, 2019, 08:21:53 pm

Ron, was typing when you replied. Does a reman dryer come with the filters already or is this a separate line item?

Larry

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