Chasing air suspension leaks

[tubitz]

As I contemplate going after any air leaks on my bus, I wondered about hooking an air hose to the service port quick connect in the generator compartment.

It seems like I could keep the air pressure up in the system while snooping out the system.

I know that the tow trucks hook up to that port when getting ready to tow your bus and it releases the brakes and pumps up the air bags. (Personal experience!)

Any comments?

[tom chelbana]

We have used the air connector both front and rear to fill air system so we don't have to run the engine. After many hours myself, twice a local Spartan and 2 trips to Spartan factory and still having air leaks we found the air dryer was our problem and it wasn't till replacing the air dryer that our air leak was fixed.
One thing that Spartan factory did was after our biggest concern being the air bags leaking down over night they put one way valves on the ride height inlet ports which at least stop the coach from losing air bag pressure. Everything still worked when leveling the coach.

[tubitz]

Thanks for the help!

I thought that would work - what I didn't know is that there is an air chuck at the rear of the unit. Can you tell me where to look for it?

Bill

2003 Newmar Dutch Star

[OldHatt45]

tubitz
Not all rigs have an air port in both places.
My rig only has a "service" port up front near the air tanks.


Drew
2003 Travel Supreme 40DS02

[Dale70]

I believe mine only has a front port in the compartment below the driver.

thx Dale

[barmcd]

Originally Posted by Dale70

After these were done I checked the time between cycles of the air compressor with the engine running and the suspension aired and nothing else being operated. The time between cycling of the compressor was probably almost doubled indicating there was a good improvement in my mind. It now probably takes three to four minutes between cycles of the air compressor.

On to the next items (and back to this when I get another Pressure Prot Valve from Spartan.)

Dale, are you saying your air compressor cycles on and off every 3-4 minutes?

[tubitz]

I hooked up my air compressor to the service fitting at the front of the motorhome and started to search for leaks.

The most interesting one is at the air dryer. When the house air compressor cycles up to ~125# the purge valve on the bottom of the dryer blows air until the system air pressure is down to about 100#. I'm reading this on a gauge I installed in the line to the service fitting. There aren't any other leaks on the dryer (when I spray it down with snoop).

This seems to explain an issue I've noted with maintaining the pressure over 100# when I'm driving down the road.

Should I replace the air dryer or am I missing something? The only thing I'm not clear on is the function of the air dryer governor. I think it is a Bendix.

And, of course, the Wabco tag on the dryer is unreadable!

Bill
2003 Newmar Dutch Star
Spartan MM Chassis

[twinboat]

Originally Posted by tubitz

I hooked up my air compressor to the service fitting at the front of the motorhome and started to search for leaks.

The most interesting one is at the air dryer. When the house air compressor cycles up to ~125# the purge valve on the bottom of the dryer blows air until the system air pressure is down to about 100#. I'm reading this on a gauge I installed in the line to the service fitting. There aren't any other leaks on the dryer (when I spray it down with snoop).

This seems to explain an issue I've noted with maintaining the pressure over 100# when I'm driving down the road.

Should I replace the air dryer or am I missing something? The only thing I'm not clear on is the function of the air dryer governor. I think it is a Bendix.

And, of course, the Wabco tag on the dryer is unreadable!

Bill
2003 Newmar Dutch Star
Spartan MM Chassis

There should be a check valve after the air dryer and / or right at the wet tank. They install them to stop air loss if the dryer, or lines to and from it, get damaged.

Once the air dryer unloads ( blows off ), there should be no air pressure in it or the lines to it. That's how it drains out the moisture.

Follow the line to the tank and look there. They, sometimes, can be disassembled and cleaned.

[tubitz]

Originally Posted by twinboat

There should be a check valve after the air dryer and / or right at the wet tank. They install them to stop air loss if the dryer, or lines to and from it, get damaged.

Once the air dryer unloads ( blows off ), there should be no air pressure in it or the lines to it. That's how it drains out the moisture.

Follow the line to the tank and look there. They, sometimes, can be disassembled and cleaned.

Thanks!

I'll check it out!

[OldHatt45]

tubitz


The Purge valve is rebuildable..
The Air Dryer is a 1200 series in most of our RV's. Call Spartan, they can tell you which Air Dryer you have. If you have the diagram I posted earlier in this thread, you'll see the part numbers for just about everything.
In your case from what you posted, I would look closely at the governor. I would bet that it needs to be reset. It's an easy thing to do. And yes the original governors were mostly Bendix. The new governors are (at least on my coach) actual Wabco parts. (see my diagram).
If you haven't got it, download the Meritor Wabco Maintenance Manual. Here is the link http://www.meritorwabco.com/MeritorW...ument/mm34.pdf
It has a lot of good information on function and maintenance procedures. Last, if you haven't changed it, you should change the Dessicant filter. Many times the filter is clogged and replacing it will solve a bunch of weird problems.


Here is the procedure I got from Spartan for setting the governor.

Drew
2003 Travel Supreme 40DS02

[tubitz]

Thanks for the feedback on my issue!

I talked to Spartan and they sent me the drawings of my air system.

I traced the line from the dryer to the wet tank and did not find a check valve. The drawing shows an internal check valve between the supply (wet) tank and tank #1. I don't believe there is any access to clean it.

Dale, I appreciate your drawing and the procedure to reset the governor. I will go after that next.

As far as the air dryer itself, if I buy the filter and the purge valve kit, I am almost to the cost to just replace the dryer.. No decision yet, just thinking!

I'll update the forum after my next dive under the bus!

[tubitz]

As I promised, I was under the bus again today and followed the procedure to reset the air system governor that Drew sent me. It was a straight forward procedure to run. I found out that my governor was set too low because when I backed the screw out two turns that is exactly where the procedure had me set it.

As I left the set point, the governor purges at about 130#, right where it should be. I did install a mechanical gauge to read the pressure at the service port. What I did discover is that the gauges on my dash are reading about 15 to 20 # low. That will be my next troubleshooting effort.

It looks like I don't need to replace the dryer itself but just need to get a new cartridge for it.

I've got a couple of random leaks to repair and I should be in pretty good shape. The only one that puzzles me is on dry tank #2. It is a square fitting about 2 inches square and about 1 1/2" thick with a small line coming out of it. It is leaking at a seam along the 2" face.

Thanks for all your help, guys!

[OldHatt45]

tubitz,


Don't bother looking for the problem with your gauges reading low. That happens with many of these gauges. Just remember it or put a P-Touch sticker on the dashboard as a reminder.


That square fitting with the small line coming out of it. That may be the Control Line that goes to the Master Air Valve up on the firewall. If so, it definitely needs to be fixed.


Get the New Dessicant Filter before you go Any further!!!! And after installing, check the governor setting again. It may change with a new filter. Also, in speaking with Spartan, 130 psi up to 150 psi is fine when setting the governor.


Drew
2003 Travel Supreme 40DS02

[tubitz]

Originally Posted by OldHatt45

tubitz,


Don't bother looking for the problem with your gauges reading low. That happens with many of these gauges. Just remember it or put a P-Touch sticker on the dashboard as a reminder.


That square fitting with the small line coming out of it. That may be the Control Line that goes to the Master Air Valve up on the firewall. If so, it definitely needs to be fixed.


Get the New Dessicant Filter before you go Any further!!!! And after installing, check the governor setting again. It may change with a new filter. Also, in speaking with Spartan, 130 psi up to 150 psi is fine when setting the governor.


Drew
2003 Travel Supreme 40DS02

Drew:

Have you had any issues using an after-market filter? I don't have a ready source for the Wabco filters up here in the boonies.

Bill