Saturday, November 14, 2015

On the level

While here in Austin I had to make some quick repairs.
The bus has automatic leveling/stabilizing system.

When we arrive somewhere I push a button to start the process.

First the system dumps the air from the air bag suspension
Next, a hydraulic pump pressurizes the system and extends four 16,000lb jacks 
one in each corner of the bus.  Each jack is independently controlled by a solenoid.

The system is computerized and will extend each jack as necessary to level the bus.
You can also operate it manually, and you can also just use it to
put each leg down enough to stabilize the bus (stop the rocking) but not level it.

Recently I noticed that one of the legs kept retracting slowly overnight.
After some troubleshooting I determined that I had a malfunctioning solenoid.
(a solenoid is merely an electronic switch or in this case an electronic valve)

The solenoid was slowly letting the pressurized hydraulic fluid pass thru and back to the hydraulic
fluid reservoir - the springs on the jacks would then pull the jacks back up.

A quick email to Tiffin - the maker of the bus - and that same day a replacement
Solenoid was on its way to the campground via UPS 2 day.

All of the equipment that operates this system is in a tight space in a side

The photo below shows the pump, the 4 lines - one to each jack - and the pump motor.
The solenoids (1 for each jack) are located behind the pump and to remove or install it
you are working by feel in the blind.

There is only about 2" of room on the right side of the pump.

I put my hand behind the pump and took pictures that I used on the computer to
familiarize myself with the layout.

Below is the old solenoid that I removed.   It is quite hefty and weighs about 5 lbs.
It simply screws into the back of the pump and you reconnect the electric.

The threads are on the right side of the photo and the extreme right end on the right is the actual
valve seat that controls the hydraulic fluid.

A cam lever on the left serves as an emergency release should the solenoid not function and
you need to raise the jacks.   (you can't drive till the jacks are raised)

For reference here is a shot of it with my hand.

To unscrew the solenoid, I was able to use a pair of channel locks gripping
the grey hex shaped area by the cam on the left side where the wires are exiting.

It did not require a lot of effort to remove or replace.

After replacing the solenoid, the bus is once again stable, level, and the
leg remained extended all night so it looks like we are back in business.

For my reward today I will make my final Austin Barbecue evaluation
before we pick up jacks and head to Kerville, Tx tomorrow for a week.


  1. Greg:

    This is my business! Fluid power. Hydraulics more specifically. And you found one of the more common problems you have to deal with. Leakage. Internal leakage like you experienced affects load control and holding. External leakage just makes a mess.

    Could you tell what brand valve it was?


  2. I really learned a lot. I probably won't remember any of it, but I feel full of knowledge! 😁

  3. Glad to hear you are level headed once more!


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