rfsod48

Air Bag Life Expectancy

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rfsod48   

A question about DP air suspension systems. Is it normal to have to replace components to this system due to age? I am not having any problem but wondering if I need to factor this into future coach repair budget.

 

 

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wolfe10   

While air bags do wear out, they usually give either visual or leak down warning of failure.

Those mounted inboard have a longer life expectancy.

If the cords are visible, it is time to replace.  I would not proactively replace due to checking like you see on older tires.

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Brett, I have to agree with you over all, but the air bags do dry out and stiffen over time, I did replace all 4 of mine over 2 years.

The rear ones had a very small leak down issue that was found with some diligent use of soupy water over a few months. After the rears where replaced the front ones where replaced the following summer. Not because of leaks - but the difference of riding on a more supple air spring was very noticeable.

Just a Note ! I did find out that the only case for roadside assistance for a failed air spring in our policy was if the bladder blowout like a tire. ?? and the coach chassis was built in 1999. The coach was built about 18 months later.

Rich.

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12 hours ago, rfsod48 said:

Rich,

Do you happen to remember the cost for replacement?

Thanks,

Roland

The cost of the parts from Freightliner was in the neighborhood of 200.00 / 220.00 per unit. The rear springs are more straight forward to replace and the front ones are a little more involved time / labor wise. The OEM cost for them was as good or better them other suppliers and the parts where the correct ones for the chassis. 

We have a truck service center in the area that  does a good job on most of the chassis work and is also medium / heavy duty inspection certified. There labor rates are about half what the RV service centers charge and they replace and service hundreds of them a year. There labor rate at the time was around 60.00 an hr. compared to  the factory centers.

FTI, They repair, dump trucks, Over the road tractor trailers, buses, ambulances, firetrucks and school buses. So you might look around the area for information on good truck spring shop(s) They did replace some brake parts for me when I asked them to do an R and R job an I was not real clear regarding the replacement of items. MY bad - they know me to well and in the past I have done work that as I have gotten older no longer have the strength to do. Kind of where the mind says go and the body says you know better. LOL

The shop could also reset the ride height properly.

Rich.

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I replaced the front air bags on my MCI last winter, also the front shocks, parts 2 bags and 2 shocks from MCI was $682.00. I have a friend that helps out with those type repairs, paid him $400.00. The bags were original on 1988 model, this was second replacement of the shocks, unless someone failed to log any others, I have service logs that date back to original purchase of the bus.

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rfsod48   

Thanks for the info. Since my coach is 12 years old I was wondering if this is something I need to think about. Next time I have it serviced I will have them checked.

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42 minutes ago, rfsod48 said:

Thanks for the info. Since my coach is 12 years old I was wondering if this is something I need to think about. Next time I have it serviced I will have them checked.

It never hurts to check on them. I don't think this is a hi failure item because we seldom hear about a problem on the forums. Maybe they all change them out and never say anything about it.:)

Bill

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On my new to me coach one of the front air bags was delaminating but still was holding air.  I changed it out with a used one, 22k miles on it, and was going to change out the other side but got too lazy.

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2001 Allegro, checked air bags about a month ago, no air pressure at all, so topped off.  Appears since then air has since drained again, so trying to set up a visit to repair shop next week. 

 

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wolfe10   

scottgbwi,

Welcome to the FMCA Forum.

Do you have a Workhorse P chassis with front air bags inside the coil springs or a diesel pusher with full air suspension.

The two are VERY different.

If P chassis, you can go back with OE style air bags OR go with stronger coil springs from someone like Henderson in Grants Pass OR.

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Brett, we have 2004 Fleetwood Providence on a Freightliner Chassis.  I have noticed air pressure seems to leak down somewhat rapidly i.e. from 125 psi to 60 psi over the course of some 5-6 hours.  Air bags are all cracked.  Mechanic working on AC recently told me he would be concerned about the amount of cracking if it were his rv.  We have 165,000 miles on  coach and want to enjoy for some more years.  Do you have any thoughts on his suggestion.  Many thanks as always.  Paul

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wolfe10   

Paul,

Cracks in the outer layer of air bags on diesel coaches are not necessarily bad.

Best to start by using soap solution to see if you can verify the source or sources of the leaks.

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Some of this note will relate some perhaps not. It was written to another Safari owner with suspension leaks.
 
Yes I have been through this drill as well. This Panther would not hold any air for much over 2 hours and then, down flat. In the process of hunting down leaks I changed many of the compression fittings to push to connect fittings. I did not use DOT approved fittings since the system is not designed with brakes.
 
The very first thing I did and for two reasons was change the front air bags. I did not like the manner in which they deflated during the early part of their life. More importantly the kinks that they had developed just sitting for years un inflated for who knows how long at a time. Suffice to say they did not roll down/collapse nicely and evenly. It cost something around $225 per bag. That is not bad when Monaco wants $1,100 each. I did not use Goodyear bags either but German made ones. That is another good story and a learning curve. Installation was easy enough only took a couple of hours total for the four in front. I might add that none of the bags had fractures in them.
 
I changed the fittings to push to connect on the front air control valve for the front end, small leak.
 
With bed lifted there is a valve in the center cross member (look down and forward) between the two dump valves that was a big leaker. It was replaced with a much smaller unit and this was the largest single leak.
 
I replaced the pressure relief check valve in the rear portion of the air tank as it too was a leaking. I believe I upped the pressure value to 110 or 120 PSI. System actually runs on 90 PSI. I did this for future addition of air chucks to inflate tires.
 
I replaced the air regulator on the front side of the Bendix compressor. It is at this point that the system air pressure can be adjusted by removing the funky looking cap on top. These fail with some degree of regularity on the trucking industry and so have a new spare as well.
 
I added an air drier so I did not have to remember to drain system periodically and regularly as all compressered air contains some moisture dependent upon where one lives, some or a lot. For me this would have been a real chore! I am not habitual, habits are tough to follow.
 
Now this last exercise resolved the largest part of the problem and I haven't a clue as to why. I installed an air restriction valve on each airbag. These coaches and many of the early airbag coaches tend to lean a lot in longer curves. My driving style tends to exacerbate this issue and drive both of us crazy. I am learning to slow down but have a ways to go. My straight line driving is not bad pretty consistent around 60/68. It is the curvy stuff that gets Janet. So these valves restrict the exiting air and slow the roll substantially making for a much nicer ride. I just clipped/cut the air lines just above the inlet to the bags and slipped them in line and vertical. I clipped some excess line out in a couple places to make them sit more vertical than they would have originally.This was also the most difficult on the rear, where the access to the top of the bags are inside the support strut. I did not change the compression fittings inside the rear struts, too difficult. I did however have to remove the outer wheel...and pull the mud flaps up. The latter 2 an SOB job. This has virtually solved the last of the leaking. The coach will stand on its own air now for a week + and be down to 60 PSI.
 
I might add that the cutter tool, same one used to cut PEX tubing is available from Home Depot for 8 or 10 bucks, cheap and red handled. These air and water systems like square cuts so the tubing goes all the way in and flat bottoms in the fittings.. Suspension air tubing is 3/8, the smaller is 1/4 on our coaches.
 
McGuyver:ph34r:
 

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jleamont   

Bill, nice write up! I have peaked at our 8 air bags, they show no signs of age or fatigue but they are on my mind often since the coach was built in July 01'. I have nylon protectors (hula skirts) in front of them to protect them from road debris kicked up and those have seen better days, I have got to locate replacements and get them swapped out soon.

 

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