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Leave some room be support (jacks) and chassis
As two members of the forum know, I need to replace the center section and the driver’s side section of our coach’s rear bumper. Having been told at least 10 or 15 times by Jeff Rowe to never reach or crawl under the coach under any circumstances without having the coach supported by jackstands, blocks, or hydraulic bottle jacks properly adjusted (release the hydraulic valve so the ram bottoms out and turn the screw up to the proper height) I put both my 20 ton hydraulic bottle jacks under the trailing arm brackets behind the tag axle. I left about 3/8″ of daylight between jack pad on top of the screw and the bottom of the bracket. I had “aired up” the back of coached manually to maximum height in the rear and lowered it in the front to give me the most room under the back of the coach. I was a little surprised to see the driver’s side was 1/2″ to 5/8″ higher than the pax side, using the amount of the jack ram was screwed out on that side. This presumes that the brackets for the trailing arms are at the same height (I wouldn’t think they would be anything else other than the exact same height).
It will be a while before I can put the new parts on the coach as the center section had to be sent to International Bus Parts in Florida so they could put the holes and studs in the center section for the Liberty installed backup lights plus put a hole in the center section so I can install the RV receptacle in the bumper rather than below the bumper. So when it came time to leave for Indianapolis last week I needed to lower the coach. The coach had settled down on the driver’s side and had quite a bit of daylight on the pax side. So I fired the coach up and left the suspension rocker switches in the full up rear and full down forward positions. I let the coach run for about 10 minutes and could then easily pull the driver’s side jack out.
BUT I hadn’t pulled the pax side jack out before starting the coach. Somewhat of a mistake as the coach had now settled down on that jack and I could not budge it. The coach was still running so I thought by now it should be completely aired up as both air gauges had been at 120psi for some time. I took the free jack and tried to jack up the coach on the pax side. The jacks have a two piece handle which makes it quite long and hence pretty good leverage. I’ve used bottle jacks hundreds of times before, but never a 20 ton jack to lift one side of the rear of a Prevost up … I couldn’t budge it. All I needed was for it to move a millimeter or two and I could put the stuck jack out.
So I called Jeff Rowe and Brittany told me he was busy moving coaches in and out of the shop and would call me back. I suspected he probably had a coach owner standing there he needed to talk to and honestly didn’t expect a call for a while. The coach was running, hadn’t shut it off. I realized that my last resort would be to try to drive the coach off the jack, but with the jack mechanism facing forward I was afraid to severly damage the jack and wasn’t interested in do it without talking to Jeff first.
So I went into the house, futzed around on the Internet, read a new post or two on the PC. I thought then I might as well shut the coach off until Jeff called. But before turning the engine off I looked under the pax side against and much to my surprise there was daylight between the pad on the jack ram and the trailing arm bracket! That jack came out of there in less than a second!
So I learned four lessons:
1. Leave a little more daylight between the jack pad and the jacking location on the coach (but not enough to create a hazardous situation if coach come down while I’m under it).
2. Remove the jacks immediately when they are no longer needed (i.e. I’m done working under the coach for now).
3. Realize that it might take more time than you’d think for the coach to come completely up.
4. I couldn’t raise the coach up with the 20 ton mnanual jack. Has anyone else been able to? Do I need an air over hydraulic jack for that? or just forget about jacking up the coach and focus on getting ramps?
Once I got that second jack out I immediately texted Jeff and let him know he could stand down for me and directly move on to the next PC member with a problem. He texted back that he was about to call me and glad that I had worked out whatever problem I had on my own.
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6 Replies
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Supporting a coach requires care. I have had my coach supported literally hundreds of times because even with a pit I am not getting under it unless I am sure it is either supported, meaning the entire weight of the chassis is sitting on suitable supports, or I have supports in place beneath the chassis support points, even if there is space between the support and the support point.
I only support the coach at the rear underside of the vertical frame member behind the tag axle that has the square tube cross member secured to it. The support is actually under the square tube, directly below the vertical member. That is the correct location for my XL and XLII coaches. I do not know if that is where your coach, whether an H3 or different vintage X model is to be supported.
In the front I support mine at a forward member where there is the intersection of a cross member and forward pointing structural members. I cannot use the front support points behind the axle because of the pit. My forward support points are acceptable.
I try to get the maximum height so I have a procedure where I raise trhe front while allowing the rear to be all the way down. This pivots the support point upward giving me the greatest amount of room between the floor and the chassis. If I am going to raise the wheels I use fixed height supports made for the coach.That way I have my jacks available to lift a wheel or axle. If I just want support I will use 20 ton hydraulic jacks, fully down, with the center screw turned up until it hits the support.
Then I raise the rear and place the rear supports in place.
Twenty ton hydraulic jacks will easily lift the coach. I have 12 ton as my smallest jacks and they will lift the chassis at any support point. The most weight I would expect would be at a rear support point, and at around 34000 to 36000 total weight, I presume either side will be up to 18,000 pounds maximum or 9 tons. Raising an axle with the jacks is easy, especially when the air is dumped and the chassis is sitting on the supports.
A Prevost owner was killed because he got under the coach without supports in place and the bus came down upon him. He had the supports in the bay. Do not ever attempt to do any work beneath a coach unless supports of sufficient capacity are in place directly beneath a support point as shown in the service manual for your model and year of coach
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I raise everything to maximum height using the level low, then place my stands under the the lift points, then use my shims for the stands, they were included when Jon made them, leaving about a quarter inch clearance and then dump the air. Then when I air back up to max height, jacks and shims come right out.
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When using jack stands always leave 1/4 of clearance after you high lift coach , then drop it down on stands
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Dick…I can vouch for Jeff being busy yesterday…he certainly wasn’t ignoring your call. I’m in Vonore now. Jeff got at the shop before 6:30am when I got out of the coach and he was there until at least 7:30pm when I went out for dinner. Jeff was doing a lot more than moving coaches all day. He never stopped working on at least 5 coaches that I saw. He was in the middle of a lot of fixes getting his hands dirty. And I did overhear him answer some calls in detail and then he was on the move again. He wasn’t ignoring you…he was really busy for sure. Seems a lot of people showed up the Tuesday after Memorial Day.
And then he drove last night to Atlanta for a 3 day Crestron seminar at the end of the day.
I now see first hand what all the praise is about with Jeff Rowe and his gang.
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Oh Jimmy … trust me … I’ve been to Jeff’s enough to know that he has lots going on all the time and when I call last Thursday in the late afternoon knew the shop was probably full of coaches he and the Eagle Scouts were trying to get out before Memorial Day weekend. I’m just excited I could work myself out of the problem on my own for once!
Its interesting that Jon uses one approach to raising then supporting his coach and Tom has another.
What really surprised me last Thursday was that after the engine running 25 or 30 minutes (possibly more) that the chassis went up another 1/4″. Why didn’t it go up much earlier? What was going on with the air system?
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The air system needs about 90 PSI or thereabouts to get the rear to max height on my coach. It needs about 110 for the front to go to max. But you can encourage more height with some tricks. First, make sure the air bags are getting max pressure. Only give the level low the raise command when the aux system pressure is at max pressure.. That might mean commanding “up” when the aux pressure is at 120, and turning it off when the pressure drops to 115 or 110. Then fan the brakes to get the compressor running again to pump the pressure back up where you repeat the process. That is an extreme method, but will get max height.
You can cheat a little to get the front up higher by lifting the tag while commanding the front “up”.
You can get the rear support point higher (which is behind the tag) by lowering the front. That pivots the chassis around the rear axles and gives you some additional height. You cannot get moreon one end if you have gone to extremes on the opposite end because if you get the max from the front for example the best you can do is just lift the rear to whatever it will give because the front supports are in front of the axle (in my case) so I am not pivoting the chassis to cheat a little.
I am usually leaving air space between the chassis and the support except when I have ot pull the wheels or otherwise lift an axle. I work on the coach with that air space there because the chassis is only going to drop about 1/4″ if something bad happens. Leaving air space and then coming back a week later after my work is done and being able to pull out the supports tells me my suspension is still holding well.
The height limitation is controlled by our shock absorbers. I am always afraid of trying to squeeze every fraction of inch of height from the air bags because all that force is not only lifting the chassis, but is pulling on both ends of the shock absorber.
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