02 Monterey 36', air over hydraulic brake pedal assembly

[Robert Paisley]

Maybe this is getting into the nit picking category, but I'll ask any how.

My 2002 Monterey drives like a Cadillac, except for the air over hydraulic brakes.
The brake valve assembly is a Bendix E7 type, pn 107435.
The pedal assembly does it's job. But it takes a fair amount of actuation force for normal driving.
I'm 230 lbs, and I can handle it. For a 150 lb person, it might be an issue.
It would sure be nice if the pedal force was a bit more proportional and if the brakes required a bit less pedal force for normal stopping.

I dropped the pedal arm from the valve while inspecting the unit. If you remove the plunger that the pedal pushes on, there is a spring inside that is retained by a locknut.
Perhaps, the pedal pressure is controlled by how much this spring is compressed by the locknut?
Back the nut off a little to reduce spring preload and hence reduce pedal pressure?

I hesitate to monkey with the valve too much without knowing more about it.
Any brake valve gurus lurking?

Thanks,
Robert
Upland, CA

[Dave Atherton]

Ran into problem with a motorhome air over hydraulic very hard pedal on master cylinder
what we found out the little pin size hole in fluid housing that control fluid into the cylinder
was plugged and no fluid movement. Brake fluid was black and seem like contaminates settled
into this little pin size hole. We cleaned master cylinder and opened plugged pin size opening,
flushed brake fluid and system worked just fine. Movement on foot pedal was easy to move
again. Maybe Gerald can touch more on the subject about master cylinders and this little pin hole in question plugged.  Dave Atherton Retired Cat Mechanic

[Robert Paisley]

Thanks for the tip Dave,
I will take a look at the master cylinders.
On this system, is one master cylinder for the front and the other for the rear brakes?

Robert

[Dave Atherton]

Robert, the system you should have (wheels have hydraulic brakes and the air cylinder just is a helper
to master cylinder when applying the wheel brakes. Should be real easy to determine the master cylinder
is cast iron housing behnd the round air cylinder pod. Just a thought you might want to look at your air
cylinder movement it may not be working and giving you a signal that hydraulic master is not working
via the foot pedal movement.  Dave Atherton Retired Cat Mechanic

[Al Lewis]

I have the same coach and the same complaint. It has been this way since I bought it in 04 @ 4000 miles. I am 180 pounds and don't know if I could slide the tires using both feet. I hope you find a fix and maybe I should troubleshoot mine. Brakes have been worked on twice and fluid has been clear and replaced but I have not complained about this issue.

[Robert Paisley]

Hi Al,
One of the issues was that the pedal was nearly into the carpet.
As you pushed the pedal, your heel would hit the carpet and impede the process of applying the brake.
I pulled the pedal off the actuator assembly and pulled out the cylinder that the pedal pushes on.
I made a 1/4" high spacer to go in on top of the cylinder. This put the pedal into a position about two inches higher than it was originally.
This got the pedal up off the carpet. Now all the force of my foot goes into the pedal when I apply the brakes.
This helped a lot. I would say that it is a non-issue at this point.

Robert

[Al Lewis]

Mine has the adjustable pedal assembly. I keep it moved all the way back and do not experience my heel hitting the floor. I would like the accelerator pedal rotated upward more. And there should be a way to reduce the brake pedal pressure since we are just opening an air valve.

[Robert Paisley]

I also have the adjustable pedal assembly. I leave it all the way back as well.
If you remove the brake pedal and pull out the cylinder that the pedal pushes on, this will reveal a nut on a stud that sets a preload on the spring that the pedal pushes on.
You may be able to wind the nut back a little to lessen the spring preload and decrease the pedal force.
I am no expert on adjusting this device, so this is just speculation.

Robert

[Al Lewis]

I looked at the assembly since the last message. The brake is close to the floor and I am extending my ankle to use the ball of my foot and toes. Applying force more toward the center of my foot should make it easier. Maybe I will do what you did. When you say cylinder you must be talking about just a cylindrical slug of steel that falls out easily without effecting the integrity of the valve. While I am at it maybe I should take the accelerator pedal off,heat the arm with a torch, and bend it maybe another 20 degrees. I won't be in a hurry. It is hot now in Texas. I guess Beaver could not afford an ergonomics engineer. I am thinking our coaches were built in Bend even though they were owned by Monoco at the time. Do you know?

[Robert Paisley]

Hi Al,
Yes, you are correct on the cylinder that falls out when you remove the pedal.
The new pedal height after installing the spacer on top of the cylinder gave me a good workable pedal position without any further modification.
You may want to start with the spacer and see if you are happy with the change.
In my case, this was a sufficient improvement to the ergonomics.

These are Magnum chassis coaches. I would guess they were built on the SMC line, but I don't really know.

Robert

[Al Lewis]

Mine has a rubber bumper stop in the up position. It is adjustable but not much left. I am guessing you removed the bumper and maybe replaced with some tape or thin rubber.

[Robert Paisley]

I was able to adjust the bumper up to get enough room.

Robert

[Al Lewis]

Robert

Well I followed your lead and made a spacer.  I chose to go 3/16 inch thick.  Made from a slice of 1 1/4 X 1/8 inch steel pipe.  I got it to go in smoothly but it does not fall out from its own weight.  The rubber bumper would still work.  I did not adjust on the nut inside.  I am thinking the spring just limits the max force that can be put on the valve.  When I press the pedal, at some point it feels like a spring compressing.  I don't know if standing on the brake with both feet would make it stop any faster.  I can slide the dishes in the cabinet but not slide the wheels or activate the ABS unless I am on gravel or wet pavement.  Fortunately I have not had any real panic stops but I drive very defenseably.  I do use the exhaust brake all the time.  I have burned up an abs sensor due to hot brakes before deciding to leave the exhaust brake active all the time.  I have brakes on the toad also.  I do not have any trips planned for the summer so I will not be doing any road testing.  Let me know if any issues show up on your modification.

[Robert Paisley]

Hi Al,
I have two trips so far after the spacer was installed.
The improvement was enough to take this item off my project list.

I am finishing my power up project now:
Added a boost gauge.
Added a pyrometer gauge.
Added a manual boost controller.
Installed a TS Performance MP-8 fuel enrichment box.
I turned up the boost from 23psi stock to about 28psi now.
Drives much better up hills now.
Just starting to play with the MP-8 box.
Thinking about pulling the muffler and replacing it with a resonator.

Robert

[Al Lewis]

Sound like you keep interesting projects going all the time much like myself. My engine performance expertise stops with carburetated small block Chevies. Never got into diesels. I hope mine keeps purring along. Not easy to get to. Had to get my grandson to help change the belts. Keep us informed.

Al