Jump to content

M2 losing air


hemsteadc

Recommended Posts

Overnight I'm dropping to 60lb. I used to be able to avoid this by pushing the water release pin on the air tank, (it occasionally would leak) but lately that's not doing much good. And there seems to be a lot of water too.

 

My suspension bags are going down, air hitch stays fine.

Link to comment
Share on other sites

  • Replies 98
  • Created
  • Last Reply

I suppose the obvious answer is I have a leak, somewhere. I just don't get why it drops to 60lb and stays there.

 

Also, after starting it up, I watch the air guage move to about 90lb (arrow straight up, warning buzzer on) and it doesn't go any higher until I goose the accelerator a bit. Wassup with that?

 

Is replacing the water bleeder valve thingy on the tank a common thing to do?

Link to comment
Share on other sites

 

Air leaks can manifest in many ways and places. This particular leak(s) may just leak above 60psi. Your air not building up correctly may also be due to an air governor that is not working correctly. The air governor is a $20 part that will stop you in your tracks when it does finally fail. Before tracing down air leaks make sure your air system is working correctly and that all service has been

accomplished. It's no fun finding leaks and fixing them only to find out you have a "larger problem" in the air generation and drying systems.

When tracking down air leaks I use shaving cream as my leak detector. I start my leak detection by bringing my air tanks up to "full pressure" and I then drain all of the air tanks of moisture. If I'm worried about moisture or oil in my tanks I hold a paper towel under the drains and look for fluids. I then will also check that the valves themselves are closing and not leaking.

Next I let the pressure return to full and shut down the truck. Sometimes the obvious leaks will be easy to locate and fix. Pay close attention around air bags and leveling valves and their respective airlines and fittings. My next step is usually the "shaving cream" test" where I will start at one end of the truck and spray the cream on all the air connections I can get too. Some folks use kid's bubbles or soapy water but the shaving cream "stays put" and will bubble better. Sometimes around valves I will tie a disposable glove around it and seal it to see if the glove fills with air. Then you can start to correct the leaks. I always seem to fix a few and find a few and then find some more. Some leaks will show up at different pressures and temperatures so be diligent and patient. This is an on going project with our type of trucks and our usage. I really prefer the compression type DOT approved air fittings and will swap out fittings if needed. My Volvo has many, many PTC

(Push To Connect) type fittings and I have found it very economical to replace the internal o-ring and brass collett pieces of these type fitting to stop the leaks. When I do find a leak in a PTC fitting I remove the air pressure from the line, remove the air line, remove the brass collett, then dig out the old o-ring carefully to not scratch up the fitting. I put it back together using a new o-ring, new brass collett and I also cut the airline back square about 3/8" if I have slack available in the airline. To reassemble Insert the airline into the fitting and check for leaks. This is for the nylon/plastic type of airline that sometimes comes in different sizes and colors.

As some will say "your mileage may vary...."

Link to comment
Share on other sites

Good explanation & troubleshooting tips above. The 60 psi leak-down limit could indicate the leak is on an air circuit that's only pressurized above this point. Cab air ride, air seats, etc will be cut off from the supply, in order to save any remaining pressure for the brakes. As far as the 90 psi delay, I think that's about where our suspension circuit gets turned back on, so rear bags, cab air bags start to fill, taking any pressure the compressor puts to the tanks.

Link to comment
Share on other sites

Yes, excellent explanation. I like the shaving cream idea. Not being much of a shadetree mechanic, sounds like a trip to the shop may be in order.

 

I just went through my paper manuals and can't find anything on the air system. But I do find some good diagrams online.

Link to comment
Share on other sites

On my M-2 the air/water bleed valve seems to need frequent cleaning or replacement. It is the usual source of bleed down overnight. I drain the tank, remove the valve and use a solvent to clean out the valve. Works for a few months to limit overnight air loss.

Link to comment
Share on other sites

On my M-2 the air/water bleed valve seems to need frequent cleaning or replacement. It is the usual source of bleed down overnight. I drain the tank, remove the valve and use a solvent to clean out the valve. Works for a few months to limit overnight air loss.

Yes, I've been watching it for weeks now, but today it's not leaking at all. Thanks.

Link to comment
Share on other sites

One thing to note, on the newer M2's with DEF, the system will do a blow down purge of the DEF doser nozzle and the SCR after a shutdown. This will happen 3 times over a 30 minute period and drop your pressure to around 60 pounds or a little lower. Not much to do about it other than cranking the engine or using shop air to get the pressure back up. Mine will leak off some from that point over a 2 or 3 day period but I'm not worried about that small of a leak.

Link to comment
Share on other sites

I finally found my 2nd air tank, near the rear axle. Sure enough, its needle valve was leaking.. I think.. and I thought I'd pushed it enough times to make it stop. We'll see.. but so far I don't think that's the whole fix.

 

Where do you find these replacement valve assemblies?

Link to comment
Share on other sites

I finally found my 2nd air tank, near the rear axle. Sure enough, its needle valve was leaking.. I think.. and I thought I'd pushed it enough times to make it stop. We'll see.. but so far I don't think that's the whole fix.

 

Where do you find these replacement valve assemblies?

As with most things on these trucks you pretty much have to go thru a FL dealer, at least I haven't found an alternate source. Once rust etc builds up in the tank it gets into the air bleed valve. When that happens the best thing to do is take it off and clean it manually. Replacing the valve doesn't really help as it just gets clogged up again the next time you use it. A possible long term fix I've thought about is to remove the tank and treat it with a cleaning acid and interior coating such as used on old motorcycle tanks. But I'm simply not that obsessed with it.

Link to comment
Share on other sites

Just got a reply from Sportchassis. I do not have an air dryer on my truck. And he suggested I install one, and there are newer valves available where you pull a cable.

 

I don't see rusty dirty water coming out.. yet. So I'd be just as well off to remove them and clean them?

 

The suspension stayed up overnight, so that's a big improvement. The front tank pressure dropped back to 60 again, but the rear suspension stayed up, and when it was airing up the gauge didn't stop and have to air up the rear bags. So, I'm not quite done yet. I'll keep messing with that drain valve.

Link to comment
Share on other sites

On my M-2 the air/water bleed valve seems to need frequent cleaning or replacement. It is the usual source of bleed down overnight. I drain the tank, remove the valve and use a solvent to clean out the valve. Works for a few months to limit overnight air loss.

I think I'll be doing this. Any special precautions in removing? (other than no air pressure in the tank) What solvent? Toothbrush to clean it?

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.


RVers Online University

campgroundviews.com

Our program provides accurate individual wheel weights for your RV, toad, and tow vehicle, and will help you trim the pounds if you need to.

RV Cable Grip

RV Cable Grip

All the water you need...No matter where you go

Country Thunder Iowa

Nomad Internet

Rv Share

Dish For My RV.

RV Air.

Find out more or sign up for Escapees RV'ers Bootcamp.

Advertise your product or service here.

The Rvers- Now Streaming

RVTravel.com Logo



×
×
  • Create New...