Shock rebuild

[treedoc]

Behind my drive axle I a set of air shocks that are leaking. Called Prevost they told me this type of shock was used for a 4 year pierod of time. Replacement $1100 each or rebuild kit $91. I ordered 2 rebuild kits. Question is has any of you rebuilt these. I am not worried about doing it, just looking for in site as to what to look for when rebuilding. Thanks Rick

[Jon Wehrenberg]

Rick,

What is important here is an understanding of what you are specifically talking about. It is likely your coach (like mine, Hector's, Jim C's) has what Prevost called a stabilizator system.

You likely have 6 shock absorbers outside on the drive and tag axles. Inside the position of the shock absorbers on the drive axle will be the hydraulic cylinders that look like a shock but which have small diameter plastic hoses connected to them. The way the stabilizators work is they serve to keep the rear of the coach from drooping when tag axle air is dumped automatically during a sharp turn. The steering mechanism up front has a cam which senses when the steering wheel is turned to the extreme right or left. When the cam actuates a switch it automatically dumps tag axle air, while simultaneously applying hydraulic force to the stabilizators so the rear of the chassis does not drop as tag axle air is dumped.

When Prevost came out with the 45 foot coach making sharp turns was facilitated by dumping tag axle air automatically, but unless the coach had stabilizators the rear would settle down. Ordinarily that is not an issue, but if the coach was pulling out of a driveway for example it might make the rear drag on the ground, hence the option for stabilizators. I am surprised the Prevost guy actually was aware of the feature. In the past we have found very few parts or service people did not even know of the feature.

If I remember right these are rebuildable. Perhaps Hector can jump in because I think he did rebuild his. BTW most owners are unaware that their 45 foot coaches may dump tag axle air automatically and when required to make sharp turns they often will lift the tag axle. Doing so is not only not necessary, but when that occurs I believe the stabilizators are not engaged.

[dreamchasers]

Yes, my coach does have the stabilizer system. The rebuild of the pistons/shocks is straight forward with minimal mechanical skills. The shock operated with air on one side of the piston and hydraulic fluid on the other. An ingenious system containing electric solenoids and two sealed containers that are designed to absorb any shock of the coach when the system in engaged. If the coach wheels go over any bumps while the system in engaged, it is not a direct bump to the chassis, these encapsulated devices will absorb this shock. Mine are orange colored and is mounted on the control system which is mounted on the rear firewall, forward of the differential.

When the switch is activated by turning the steering wheel hard left or right, this system engages. Its purpose is to hold up the rear of the coach when the tag axle air bag release. A great feature.

In the rebuild process, you should remember the shocks are not the only component that requires servicing. An air regulator and a couple of air solenoids are in the control system. If you are noticing oil leaking from the rear shocks, you must check to assure that hydraulic oil has not leaked through the piston seal and worked its way into the air regulator and associated lines. If so, you will need to flush the regulator and lines clear of oil. The solenoids that control these shocks are located behind the tag axle, passengers side. Mine are mounted to the Prevost frame. Also, note these air regulators are sourced from an air cluster that is tied to the auxiliary air system. If these guys are leaking, your auxiliary air supply will leak down.

I posted a couple of drawings I received from Prevost concerning this device. When I queried Prevost concerning these device, it appeared that "on hand" expertise was sparse. I guess since they have not used these in a long time. Look in "Information Sharing", Air over Hydraulics, part 1 and 2. As I stated, information is sparse on the this. When I contacted Prevost Fort Worth (before I learned), they stated that I should remove the shocks and not repair them? Well, so much for that, I like the feature.

If you get involved in the repair of these devices, pm me with your telephone number. I will be glad to chat about my experiences. Their are a few tricks and tips I could detail for you. Clearing the shocks of air was a challenge, until I figured it out.

Good Luck,

Hector

[treedoc]

Thanks Jon for your in put. your help is appreciated more than you know! Hopefully this baby will learn to walk some day.

2 more questions for you or any one else who wants to jump in. First, third bay back from front left side there is a circulating pump, to where is it pumping? Second can the webasto heater operate off battery power or shore power only? Thanks Rick

[Jon Wehrenberg]

Third bay back on your coach is likely OTR (over the road air). The pump likely is the circulating pump for coolant when you are using OTR functions.

Your Webasto should have a circulating pump also, located in the small compartment behind the LH tag axle. While the Webasto is tied directly into the engine coolant system this pump is engaged when the Webasto is working. As to running a Websto off shore or battery power, it is (on your coach) a 24 VDC system so shore or generator power is not required. Be aware if you are using the Webasto to keep the coach warm when not hooked to shore power it does have a current draw because there are about 6 small fan motors, plus the circulating pump plus power to the burner head, all of which is a fairly large draw on battery power.

[Pete]

My coach has a switch on the transmission console that will disable the stabilizer system if you do not want it operable. Like Jon, I think it is a positive feature.

[treedoc]

Thanks Hector I pmed you with my number. I will be remove the stabilizers this saturday so no hurry to call. Rick

[Jon Wehrenberg]

Might not be so easy. As Hector explained the system is more than just the stabilizers and includes the air over electric device located on the forward bulkhead in front of the drive axle. Additionally there is an air supply virtually impossible to access on your coach hidden from view behind the house battery switch and circuit breaker panel. That air supply has solenoid valves controlling air to the device on the bulkhead. I suppose you could plug the lines you can easily access, but your coach is one of the few with the stabilizator feature and I can say from experience there is a real benefit in preventing the rear of the coach from dropping when sharp turns are made. I would take out the stabilizers and service them. Good opportunity to replace the bushings also since they tend to get damaged easily.

BTW, the air supply located behind your house battery switch and circuit breaker panel is a likely source of air leaks so if you ever swap out house batteries use that opportunity to service those air fittings and devices. People with batteries in the entertainer bay or in other bays are scratching their heads wondering, but Rick has his house batteries conveniently located in the small compartment behind the tag on the RH side of his coach.