Leaf Springs Need Replacing?

[jkaftan]

Hello:

I have a 1983 300. So it takes 10+ min for the airbags to get up to 90 PSI. If I decide to move before that happens I can hear it bottoming out in the rear when I hit bumps. I figure the leaf springs need to be replaced. I'm thinking the air bags should not be holding up the rig. They should be the icing in the cake.

If this P30 Chassis ended up as a UPS truck it wouldn't have had air bags and it wouldn't be bottoming out.

That said, this thing is a lot heavier than a UPS truck so maybe this is normal behavior. Is it normal for the airbags to be a major part of the suspension and the AS to be bottoming out until they are fully inflated or do I have some work to do?

I watched one video on replacing leaf springs and it looks like it's a bugger. Has anyone done it? If so do you have a good part number and supplier?

Thanks

John

[Smartstream]

Your pump is failing or you have a leak. Your leaf springs are no longer leaf springs as you think of them. The rear of the springs have been cut off and an air spring system has been installed. This is what your system looks like.

8700-351-Model.pdf 8700-542-Model.pdf

The part #2 saddle hangs over the rear of the leaf spring and the air spring system now supports the rear axle. Get a spray bottle full of soapy water and spray the system looking for leaks. If you have another compressed air source, fill the air tank directly and see how fast the air springs fill and lift the coach.

[jkaftan]

Ok so the air bag system is my suspension. So I don't need to replace the leaf springs. But it should hold air, meaning it is not normal for me to have to wait for the compressor to pump up the system.

I do have another compressor. Should I just put 90 Lbs in the little tank that I see on the underside?

Since we are on this what should I be doing to maintain this system? Oil for the compressor? What about moisture in the tank? My compressor for hand tools has a valve for letting moisture out. Could that tank be rusting from the inside? I haven't done a thing to this system for 4 years.

[uncle_bob]

Hi

If the compressor is as old as the MH .... it has served a long hard life. There's no shame in letting it retire .

If you have a leak big enough to really slow the pressurization down, that same leak should deflate the bags in a hurry. It may be easier to watch for that than anything else.

On most of these compressors , there isn't a lot you can service. It's a "swap it out" sort of deal these days.

Bob

[cmadmaxman]

The air bags, like the tires on our rigs, do not last forever. I replaced mine about 10 years ago and altho they were not leaking yet, looking at the cracks in the rubber, not far behind. The bags have an internal stop to keep the rig from going to low. Somewhere I saw that if there is no air in the bags, only do 45 mph max! This is due to the springs, they way they are cut off in the back for the air ride carrier, almost not effective.

Here is the carrier system. (good shot with the fuel tank removed)



I replaced my almost not effective compressor about 5 years ago and also put in an aluminum air tank.



This is what the new compressor looks like in its home.


I have a line going up front for my air horns, and a gauge on the dash so I can monitor the pressure. This rig does not start lifting until 75 to 80 psi. The compressor comes on at 90 and off at 105 psi.

I have also run a heave gauge wire to the battery (6 gauge) back to a relay by the compressor. Now the only thing the light wire that was used the run the compressor, only has to operate the relay! Very low voltage drop now will help with the life of the compressor and runs much better.

My air bags will stay up for days! Hope this helps.

[bkahler]

If I remember right the original tanks had a bleed valve on the bottom the tank. When I first got my 310 some PO had removed the drain valve and routed an airline from valve port over to the side of the motorhome where he placed a schrader valve so he could manually fill the tank. I found out afterwards he did this because the compressor kept blowing fuses.

[Smartstream]

Originally Posted by jkaftan

Ok so the air bag system is my suspension. So I don't need to replace the leaf springs. But it should hold air, meaning it is not normal for me to have to wait for the compressor to pump up the system.

I do have another compressor. Should I just put 90 Lbs in the little tank that I see on the underside?

Since we are on this what should I be doing to maintain this system? Oil for the compressor? What about moisture in the tank? My compressor for hand tools has a valve for letting moisture out. Could that tank be rusting from the inside? I haven't done a thing to this system for 4 years.

Yes air up the tank with your other compressor. There is a Schrader valve on the tank, looks like a tire valve stem. It is used to drain water from the tank and also add air.

If you pump the system up it should hold for a few days. Some will hold for several days or even weeks, some will go down in a day or two. There is also a check valve after the pump. This prevents compressed air from bleeding back into the compressor when it is not running. If you air up the tank and hear air leaking at the pump change the check valve. That little valve can cause lots of problems.

If the system holds air then the problem is in the pump. I use a Viair 450C which is over kill but at half the price of a Gast it's a pretty tough pump. Also as mentioned wire the pump through a relay as it's a big amperage draw through the ignition switch all the way to the rear of the coach.

It is a pretty simple and dependable system once you get it sorted out.

There are polyurethane bushings on the horizontal dog bone link, #8 in the drawing. They locate the lower air spring beam in the coach. They get sloppy but are pretty easy to replace.

[Voltair]

My 345 takes around 10min to fully inflate from being fully deflated, nothing unusual about that time.
If you have no Tag axle then apart from the internal bump stops inside the bags can't see any prob?
If you check for leaks see if the air control valve (long adjuster rod attatched) will blow soapy bubles. They have three positions ie air into bag- hold air in bag- let air out off bag. Mine were faulty, I fitted universal heavy transport ones from a Kenworth same as the original Airstream ones.
Your steel air tank is easy to drop if need be, a good internal clean then with a rust killer solution good for another 10y and they wont go pop in a nasty way like a lot off pretty looking imported alloy tanks brought in cheap from youknowhere!
Rus

[cmadmaxman]

Your right about them cheep tanks. That is why mine was made in Charlotte NC.

Same size as the steel tank, 8 to 10 min here also.