MC9, tag air valves, usage questions.

plyonsMC9 · July 08, 2006, 06:46:10 PM

Could someone explain basic usage of the tag air valves (shown below) for the MC9?

Specifically, if I release air from the tag by using one valve, or both, how does air get back in the tag? Could they be used to do a small bit of leveling at a parking spot if necessary? Is it best to just leave them alone?

Thanks all - Best Regards, Phil

NewbeeMC9 · July 08, 2006, 07:13:07 PM

Hey PlyonsMC9,

the picture tou are showing is the drain for the Air filter. The Valves for the tags are above that. Do you have a picture of the stuff above it? The thing with the wires is one of the pressure switches for the tag axles. Mine does not have the Tag axle air bag dump solenoid valves. I just have manual 4 ways. I use them to dump sanitaries some times.

Hartley · July 08, 2006, 07:24:45 PM

The Tag axle air system should not be used to try to level the coach. Thier capacity for carrying a static load
is limited to only a fraction of the pressure used on the main rear axle bags.
Generally not more than about 4,000 lbs is carried by the tags combined. ( guestimate only ).
Due to the low pressures provided by the regulators.

I would have to look at the chassis specs for maximum tag loading, But I do know that it is very low as compared
to the high pressure main axle air system.

Leveling is usually only done on the drive axle system since it carries the most weight and moves farther than the tags.

plyonsMC9 · July 08, 2006, 07:42:18 PM

Quote from: NewbeeMC9 on July 08, 2006, 07:13:07 PM
Hey PlyonsMC9,

the picture tou are showing is the drain for the Air filter. The Valves for the tags are above that. Do you have a picture of the stuff above it? The thing with the wires is one of the pressure switches for the tag axles. Mine does not have the Tag axle air bag dump solenoid valves. I just have manual 4 ways. I use them to dump sanitaries some times.

Rats, I got the wrong picture. Will try again in the morning - OOPS!!!!

Best Regards, Phil

Beatenbo · July 08, 2006, 08:31:47 PM

The valves are used to release air if you need to jack up tag or chain tag axle with no tire in an emergency. Some coachs have a switch inside that will dump air to put more load on drive to start on ice or snow. I would't use for leveling just in case I forgot to turn back on, plus I wouldn't want the wear and tear for another possible valve leaking.I use to put blocks in between axles so when air when down the rear frame would set on blocks and when aired back up it would raise off blooks. MCI told me they have dollys they put under the coach while buildiing and they can move aroud. (I don't recomend that in a campground) but it is a good leveling point. I have owned 5 MCIs and none settled the same way. I don't care how good it looks or how well it runs, my dream would be to have a MCI that would hold air and set level over a day !!! Blessings

plyonsMC9 · July 09, 2006, 05:02:25 AM

Blessings to you too Beatenbo,

Our MC9 now settles in a few hours instead of minutes. The driver side settles fastest, so that will be the next air system repair for us. Once I get that complete, I think it will be ready for some kind of air leveling system. Well, at least that is my plan anyways!

Kind Regards, Phil

JackConrad · July 09, 2006, 05:36:27 AM

Our MC-8 manual (MC-9 should be the same) states 35 PSI from the regulator to the tag axle air bags will put a maximum of 6000 pounds on the tag axle. We weighed our bus on a certified CAT Scales at a truck stop. Front Axle: 11, 100, Drive Axle: 18,000, and Tag Axle: 4000.
When I installed our leveling system (we still use the OEM ride height valves when driving), I added a dump valve on the tags so that if leveling requires dumping the air from the drive axle, the tag is not then trying to hold all the weight of the rear of the bus. With the bus at normal ride heigth, if I dump the tags, the rear settles about 1 1/2".
I did dump the air from the tags and using my leveling system raise the bus to maximum height once to get through a mud hole that occured while we were camping on a wet weekend. I made it through, but do not think I would have without raising the bus (you cound see the track the oil pan left in the mud. Hope this helps, Jack

Kristinsgrandpa · July 09, 2006, 08:56:50 AM

If, by the scales, I only have 4000 lbs on my tag axle, it is just barely carrying its own weight. Then the only advantage to a tag axle is braking, and maybe added stabilty in a strong cross wind.

I considered removing mine before the conversion process started and was told that the frame would have to be re-inforced at the rear axle.
If you look, it is re-inforced at the rear axle. That is where the tag is attached.

After removing all the seats, the A/C above the motor and the heavy windows, I probably dropped another 1000 to 1500 lbs.
The only reason I didn't do it, is it would have looked funny with all that overhang on the rear.

Plyons MC 9, I didn't mean to hi-jack your thread, its just that I haven't done a weight and balance yet and was surprised to see the figures that Jack quoted.

Ed.

JackConrad · July 09, 2006, 10:52:03 AM

A friend purchased a MC-8 already fully converted in Ohio and drove it directly to one of our Bussin' rallies. Afterwards, he drovit to my place to do a couple modifications on the interior. He said it did not seem to handle well and would I take it for a test drive. This bus had been changed to intergral steering. I drove it and was not impressed with the handling. He called after he got home to tell me that when he got home and was walking to his house, he put his hand on the tag tire as he walked by and noticed the tire was not even warm. He checked the tag valves in the engine compartment. Yep, you guessed it, they were closed, no air to the tags. He opened the valves and took the bus for a test drive, the handling was greatly improved. I told him to check the adjustment on the tag brakes, that they have been sliding the wheels with a firm brake application. Tag brakes did need adjustment. He had no idea how long they had been like that, but it occurred before he purchased the bus. Jack

NJT5047 · July 09, 2006, 11:44:23 AM

Hi Phil,
Short answer...leave them alone. Your pix of the plumbing doesn't show the tag valves...looks like the airline drain. The tags won't level your coach...they only support approx 2K, and they have (as Jack has already described) 35 lb regulators to prevent pressures above 35 lbs. I don't let the air out of my tags when leveling the bus laterally. The tag regulators will exhaust the air as it increases on the low side. Each side has its own regulator and low pressure switch.
My valves were labled wrong...when in "on", they weren't...had to reach behind the tag wheels and verify that the valves were in the correct position for inflation. Obviously I remarked the valves.
The tag inflation can be easily verified by reaching behind the tag wheels and feeling the airbag.
Regarding holding air, if the airbags are good, and the leveling lines are isolated from the coach air system, the bus will stay aired up for months. Mine will....but, I've got ball valves that isolate the airbags. Once leveled, I shut everything off. It'll stay leveled.
Use the drive axle airbags for L-R and rear height for leveling...front for height relative to rear. If you building a leveling system, don't let all the air out of the front axle...keep it off the stops. Once it goes on the stops with the bus will twist and may cause sedan doors to become cantankerous to open.
You need some way to over-pressurize the airbags for leveling...otherwise you'll start at the ride height...which is lower than the max potiential.
The only purpose the tag valves serve is to release pressure from a tag for chaining up, and to allow both to release in slick conditions...the "slick condition" ain't gonna help a lot. Generally the tag air system, if working properly, can be forgotten.
Well...now I've forgotten what the question was??

Been down in the bus checking out the satellite thingie...works fine, and finding the sat with a portable dish was relatively easy...found that there are more satellites than 101. Have to try the rooftop once the bus is out of the barn...that may be a little more difficult to operate. Back to work!
Cheers, JR

plyonsMC9 · July 09, 2006, 12:04:12 PM

Hi all,

I now have the correct picture of the valves for the tags shown.

Best Regards, Phil

plyonsMC9 · July 09, 2006, 12:31:14 PM

This seems obvious at this point - but just to be sure -

T0 empty the tags, move the lever 1/4 turn. Just the tag pressure (air bags) is released.

To refill the tag air bags, turn the valves 1/4 turn (with air pressure in the bus) and they will refill.

Thanks - Phil

NJT5047 · July 09, 2006, 07:45:29 PM

That's it. You may want to verify that the bags deflate in the "dump" position, and that they re-inflate when moved back to the "normal op" position. The valves will only empty the tags...nothing else. Unless the valves have been replaced and they are not correctly oriented...then they may do something untoward. Yours are probably correctly installed. When mine were replaced by NJT they left the stops off...that should have been a sign. I got a "sign" for them. I drove the bus several hundred miles before realizing that the RH tag wasn't inflated.
These type valves are known leakers. Just seep a little. My tag control valves don't leak but the blower control did. The valves are cheap to replace....cheap to buy anyway.
JR