Front Airbags not filling at idle??

[supercub]

I start the motor home in the morning and let idle to let it warm up. The rear bags inflate to above 100PSI. The fronts only go to about 60psi. As soon as I go about 100 feet the fronts inflate to above 100PSI. Just started having this problem. I don't know if it's extra power or moving the motor home. Tomorrow, I'll try giving it a little power before moving to see what happens. Once the pressure comes up, it holds stable. Is there a sensor that might be sticking? or ?? Any help? Thanks
Brian

[supercub]

Still don't know what the problem is, but I know the sequence of events
I start the motor home, both rear and front gauges pop up to above 100 psi. I let it idle for a couple minutes, then fast idle (1000 rpm) for several minutes and pressure doesn't change. Shut off the engine and went outside and walked around the RV, but couldn't hear anything. Started back up and pressure went to over 100 psi. By the way, I initially thought just the fronts weren't airing up.....well, it's both front and rear bags. Anyway, released the parking brake and front pressure dropped to 65, rear dropped to about 90 and bags filled. Gauges indicated well over 100 psi with a minute or so.............so at that point everything is fine, however, the bags should fill prior to releasing the parking brake. When I say above 100 psi, my gauges have markings at 100 then 150.......and needles appear to be about midway. Called the shop I use and taking it in next week. Any ideas? Thanks........and a Merry Christmas.
Brian

[johnsonbert]

I just went through a situation similar to this, except it was the whole system was airing up slow even at fast idle. It worked well and fine going down the road at higher rpm, but took forever to build initial air, raise chassis and rebuild air before leaving. I took a squirt bottle under the coach with it running and trying to build air, tires blocked and emergency off, and started looking for leaks. Accidentally bumped a line and got a shot of air out of it. Found the leak in the main line running from the compressor to the air dryer. It had chaffed a hole through it in a clamp that was holding it to prevent chaffing. Once fixed, Air builds up normal and ready to go. I would also check your airlines running from the air dryer to the front tank in the process of looking for a leak. Move the line around. To find a leak in the source line, you probably should have the engine running and compressor pumping also. Just what happened to me, Hope this may help, Happy trails Bert

[holstein13]

If this ever happens again, try pumping the brakes to see if it activates the pump to fill back up the tank before moving the motorhome. Remember that if you dumped the air in your front tank and then try to make a turn, it could easily damage your wheel wells.

[randallb]

I do not have a schematic available for your system but I will make an educated guess. Somewhere in the system there is probably a one way/poppet valve to maintain pressure in the front suspension and another for the rear in case there is a failure of the pump, air storage tank or plumbing. You do not want the suspension collapsing unexpectedly at speed. The one for the front may be sticking shut and not allowing the front pressure to come up. You could also have a system that uses a rotary valve to feed the suspension systems separately and it has an internal poppet/valve to the front sticking intermittently.

[supercub]

Well, after sitting for 3 days, started it up this morning, and the pressure popped right up to well above 100psi..........read the same as the rear tanks......and bags were inflated. The only thing I might have done different is...........I might not have used the switch to cump the air before leveling. When I parked it tonight, I' made sure I dumped the air, so I'll try tomorrow and see what happens. Thanks for all the replies.
Brian

[WILDEBILL308]

Trackrig wrote:

WILDEBILL308 wrote:
I think Wolfe has the right idea. Your front ride height valves may be sticking.
After you move the motion of the coach loosens them up and they start working.
Bill

Why would his front air pressure gauge be reading so much different (lower) than the rear pressure gauge? If his ride height valve was sticking, then no air would be going to his front air bags (they wouldn't be using any air) and therefore his two air pressure gauges should read a lot closer - right?

Bill

I think Wolf answered that. The valve is tied to the suspension and movement may free it. Once the valve closes the tank/bags can fill normally.
Bill

[Crazy_Canuk]

Firstly, your gauges read the wet tank and the dry tank,you have a wet tank and then a dry tank, most motorhomes have a supply tank too - which makes 3 tanks. The rear air bags will fill with the dry tank, the front air bags will fill from the dry tank or the supply tank. Most air bag systems will not inflate until you have at least 80 to 85 PSI. You might be in to much of a hurry to leave, always do a pre-trip/walk around and let it warm up for 5 minutes. Maintenance might need to done on your air stabilizer arms.
If you need help with that let me know.

Crazy Canuk.
See you on the road

[big_buford]

wolfe10 wrote:


Start the engine. After 20-30 seconds, engage high idle (around 1100 RPM).

After air pressure builds, you are "free to move around the country".

Sure, this means under light load until coolant operating temperature is reached-- like exiting CG, low speed driving. If you overnighted at a freeway entrance, yes, stay at high idle until temperature gauge is at least half way to normal operating temperature before jumping on it.

Also good advise. You need to know what your cut-out pressure is. Usually around 120 psi. Both front and rear tank need to read that psi and you hear/ feel the compressor unload. At a minimum you would release parking brake, pull foward about five feet and make a brake application to test system function. Then your ready to roll.

My apologies if you know all this. Just want to make sure your not idleing a bit then hitting the road before system reaches full pressure.

Other possibilites off the top of my head, air compressor not moving volume of air it was perviously? Air ride/dump Valve sticking which allows air to bleed, once you start moving rpm increases moving more air into system and seats valve.

[supercub]

Yes, mine has a dump switch for the air bags. I will do the above check, thanks

[big_buford]

wolfe10 wrote:


If the ride height valve is stuck on EXHAUST, it will lower air pressure on the gauge and front will not rise. Not saying this is the issue, but really easy to verify:

Air up to cut out PSI. Turn off engine. Go out and listen near the front axle. If air is exhausting, replace the ride height valve. The are not expensive.

Great advice, first check I would make. Do these rigs have have a toggle to dump air pressure in bags while parked?

[big_buford]

I would take the air bag not filling out of the question for now. If your front and rear tanks are not filling to full cut out pressure, you must deal with that issue first. I would bet when that gets corrected your bags will fill just fine.

To be clear, when your talking about front and rear guage, you are refering to front and rear tanks used for your air brakes? Just want to make sure you dont have seperate set of guages that read just air bag pressure?

[wolfe10]

Trackrig wrote:


Why would his front air pressure gauge be reading so much different (lower) than the rear pressure gauge? If his ride height valve was sticking, then no air would be going to his front air bags (they wouldn't be using any air) and therefore his two air pressure gauges should read a lot closer - right?

Bill

If the ride height valve is stuck on EXHAUST, it will lower air pressure on the gauge and front will not rise. Not saying this is the issue, but really easy to verify:

Air up to cut out PSI. Turn off engine. Go out and listen near the front axle. If air is exhausting, replace the ride height valve. The are not expensive.

[Valkyriebush]

Have air dryer inspected. Air leak maybe?

[Trackrig]

WILDEBILL308 wrote:
I think Wolfe has the right idea. Your front ride height valves may be sticking.
After you move the motion of the coach loosens them up and they start working.
Bill

Why would his front air pressure gauge be reading so much different (lower) than the rear pressure gauge? If his ride height valve was sticking, then no air would be going to his front air bags (they wouldn't be using any air) and therefore his two air pressure gauges should read a lot closer - right?

Bill