Bounder: No PS/PB

[Thumper221]

We have a 1993 Airstream LY that we have had for 6 years, its on a Chevy P30 chassis with a 454 in it. Most all the auto breake setups are powered by the Power steering pump. A few use a seperate reservoir and a electric pump to develoupe the 300 Psi for the system. You can get into real trouble if you ever let it run low on fluid, I found that out the hard way heres why. The Hyd cylinder that releases the spring tension on the breake unit is Hyd actuated and spring return, NO LINE BACK TO THE PS TANK. To make matters wost, its a large diameter cylinder so when the hydralic pressure is droped off to let the internal springs apply the brake it sucks a fairly large amount of Oil out of the system as it pulls the piston back to the end of its stroke. If you are low on fluid or have a broken line like we did and dont know it, and keep going from park to not park, all that happens is you are sucking air into the system. The air that gets into the auto park cylinder cant get out because with no return to tank, its traped. A good indication of this is power steering and hydroboost work untill you take it out of PARK! The only way to fix this is to bleed the autopark break cylinder. It has a cable comming out of it on one end going to the other two camles from the foot brake and the autopark break drum brake arround the drive shaft. The other end has the hydralic line comming into it fron the control valve. On that end, just above and ontop or the cylinger is a standerd bleaded fitting, just like the one used on break calipers. Thats where you must bleed it at, the same as you would with regular breaks. You have to be careful to not have the bleeder valve open at the wrong time or you will suck more air back into the cylinder. Once you get all the air out of the cylinder your breaks and power steering will work with the auto park break released. With air in it it acts as a dampener to the PS pump and it cant build up full pressure until you put it back into Park and the HYD control valve releases pressure on the cylinder. This isolates the cylinder from the system. The air in the Power Steering and Hydrobost units will eventually work its way out.
If you ever have to tow one, Dont take the clevis pin out of the cable relay box, Its a nightmare to get it back in and then you have to readjust two of the three cables! Best thing to do is to disconnect the universil joint closes to the rear differntial and tie the driveshaft up, Then have it towed. What realy works good is to take the drive shaft loose and prope it up as high as you can. Cut a 2 x 12 long enough to fit across the two main chassis frame rails and c-clamp it to the rails on each side. Let the drive shaft down till it rests on the center of the 2 x 12 and tie it in place. The drive shaft is hollow so its not realy as heavy as it looks.

Pat -

[Midniteoyl]

Originally Posted by Thumper221

We have a 1993 Airstream LY that we have had for 6 years, its on a Chevy P30 chassis with a 454 in it. Most all the auto breake setups are powered by the Power steering pump. A few use a seperate reservoir and a electric pump to develoupe the 300 Psi for the system. You can get into real trouble if you ever let it run low on fluid, I found that out the hard way heres why. The Hyd cylinder that releases the spring tension on the breake unit is Hyd actuated and spring return, NO LINE BACK TO THE PS TANK. To make matters wost, its a large diameter cylinder so when the hydralic pressure is droped off to let the internal springs apply the brake it sucks a fairly large amount of Oil out of the system as it pulls the piston back to the end of its stroke. If you are low on fluid or have a broken line like we did and dont know it, and keep going from park to not park, all that happens is you are sucking air into the system. The air that gets into the auto park cylinder cant get out because with no return to tank, its traped. A good indication of this is power steering and hydroboost work untill you take it out of PARK! The only way to fix this is to bleed the autopark break cylinder. It has a cable comming out of it on one end going to the other two camles from the foot brake and the autopark break drum brake arround the drive shaft. The other end has the hydralic line comming into it fron the control valve. On that end, just above and ontop or the cylinger is a standerd bleaded fitting, just like the one used on break calipers. Thats where you must bleed it at, the same as you would with regular breaks. You have to be careful to not have the bleeder valve open at the wrong time or you will suck more air back into the cylinder. Once you get all the air out of the cylinder your breaks and power steering will work with the auto park break released. With air in it it acts as a dampener to the PS pump and it cant build up full pressure until you put it back into Park and the HYD control valve releases pressure on the cylinder. This isolates the cylinder from the system. The air in the Power Steering and Hydrobost units will eventually work its way out.
If you ever have to tow one, Dont take the clevis pin out of the cable relay box, Its a nightmare to get it back in and then you have to readjust two of the three cables! Best thing to do is to disconnect the universil joint closes to the rear differntial and tie the driveshaft up, Then have it towed. What realy works good is to take the drive shaft loose and prope it up as high as you can. Cut a 2 x 12 long enough to fit across the two main chassis frame rails and c-clamp it to the rails on each side. Let the drive shaft down till it rests on the center of the 2 x 12 and tie it in place. The drive shaft is hollow so its not realy as heavy as it looks.

Pat -

Thanks.

[Thumper221]

Located behind and under the drivers seat on the undercariage. If you have trouble finding it just follow the foot break cable to the cable relay ASS. Its just to the left of it.

[thunderduck]

Originally Posted by RVDog

I have a 1993 Fleetwood Bounder on a Chevy chassis. When I put it into gear, I loose the power steering & power brakes. All the fluid leaves the resevoir. When I put it back into park, the fluid returns but foams over. While it is in park, the power steering is working. Any ideas?

I just had the driveline parking brake adjusted because of reservoir lacking enough fluid to operate the brake actuator and causing the loss of steering and brakes. I think a bigger reservoir would solve this problem forever but then no one would service the brake system and the dealers would be out of money,

[thunderduck]

I just had the driveline parking brake adjusted because of reservoir lacking enough fluid to operate the brake actuator and causing the loss of steering and brakes. I think a bigger reservoir would solve this problem forever but then no one would service the brake system and the dealers would be out of money,

[thunderduck]

I just had the driveline parking brake adjusted because of reservoir lacking enough fluid to operate the brake actuator and causing the loss of steering and brakes. I think a bigger reservoir would solve this problem forever but then no one would service the brake system and the dealers would be out of money,

[rkrod]

Originally Posted by wjoiner

I don't understand how the emergency/parking brake system affects the regular brakes and power steering system. I have a 1998 National Tropical with the 454 cid on a P30 chasis. The master cylinder and vaccum booster have both been replaced/rebuilt multiple times. I still get loss of braking power and steering assist, especially at low engine rpms when I'm slowing down for a turn.
I also know nothing about location and operation of vaccum assist, like where does vaccum come from. Is there a tool/guage for checking vaccum and how much vaccum should I have at idle. Is there a free website that shows diagrams of these systems on the P30? Any help would be appreciated. I've already spent $2k and need to figure this out.

I wish I new your problem, but I'm sure you have read all these post on this subject. I know my 1993 Pace Arrow has the hrydro boost braking system so not sure about your 1998.

[ga traveler]

If anyone has read my post in the past, they know how much i hate the chevy auto park brake. First the guys keep mentioning vacumn. The chevy uses the hydro boost system. no vacumn. they use the powersteering pump. the early auto park brake changed in the mid 90's. The early 90's brake used the power steering fluid to hold the brake off when you put the mh in gear. Thus you could suck all the power steering fluid out of the powersteering reservior. The later 90's used a seperate pump and reservior to release the springloaded park brake.

[4Knights]

RVDog, you need to send a PM to oldusedbear on this forum! He is THE autoparkbrake library expert! He helped me diagnose and fix my issue in less than 45 minutes on speaker phone. Roger is extremely patient and easy to talk to, he will call you or you can call him once he gives you his number. Send him a note and be ready to fix your system for good without overpaying shop to do what you can do.

[enidpd804]

Guys, I have to say thank you. I had the exact same problem in my '93 Winnebago Adventurer. We would bleed the brakes after replacing power steering pump and hydroboost. Everything would work fine until we took it out of park. I don't know if this is the best way or not but we fixed it. I'm not even sure that I can explain it. My mechanic removed the linkage (?) that connects the shifter to the system. It now works fine and he assures me that it's safe.

We went through several mechanics. It took me printing out this thread and showing it to them to convince them I wasn't crazy. My guy used the diagram to come up with a solution. So, the vacation's back on.

[conserve]

Originally Posted by Thumper221

Located behind and under the drivers seat on the undercariage. If you have trouble finding it just follow the foot break cable to the cable relay ASS. Its just to the left of it.

I disconnected the actuater from the shifter linkage and it fixed my problem just in case any one needs to do the same. From what I could tell the linkage was not activating the system totally there by creating a vaccum in the system. Hope this helps someone else.

[Inland06]

Originally Posted by RVDog

I have a 1993 Fleetwood Bounder on a Chevy chassis. When I put it into gear, I loose the power steering & power brakes. All the fluid leaves the resevoir. When I put it back into park, the fluid returns but foams over. While it is in park, the power steering is working. Any ideas?

I feel obligated to pass on information from our shops experience of issues with hyd park assist problems on a 1992 bounder motorhome in our shop with a workhorse chassis. Our techs followed every trail to no end on fixing the problem as discribed. Pump, steering gear, hydra boost, hose's, park assist cylinder where all replaced with no affect. After some research on this forum and how the system works we discovered two issues that affects this motorhomes assist brake that leads to this problem and many like it on this forum. The park assist is a closed loop system sharring oil from the same reservoir as the steering and brakes. There is not a return hose from park assist cyl. If your park assist brake shoes/drum are worn enough the park assist cylinder will stroke to far and pull enough oil out of reservoir and it will suck air in the reservoir. This causes the foam and noise in the system and also affects braking and steering. If the park assist brake is out of adjustment or the adjuster is froze will cause the same issue. After 94 I believe workhorse seprated the park assist to its own pump and reservoir. Reading this forum and others helped us identify this issue and I had to pass on what we found as to the issue. There is lots on the internet on this same problem in many motorhomes. Hopefully this helps someone else to resolve the issue easier than what we went through. If the motorhome rolls a foot or so when put in park look at brake adjustment or worn shoes and drum. Hope this helps.....

[Midniteoyl]

Thanks Inland

[romson]

I am new to this post but I have learned, the hard way, how just about anything operates on the Chevy P-30 MH, and I would like to clarify the operation of the driveshaft emergency brake on the 1993 Fleetwood Bounder.

The emergency brake operates via a mechanical spring actuator/hydraulic disengage operation. When the gear selector is put in the Park position, a valve in the pressure line from the power steering pump is bypassed, thereby relieving the pressure that is ported to the emergency brake actuator. This causes the spring in the emergency brake actuator to push the power steering fluid back into the power steering reservoir and thereby pulling the mechanical brake cable with it into the driveshaft drum brake which engages the emergency brake (similar to drum brake emergency brakes on automobiles).

Another post rightfully pointed out that the auto transmission locking pawl (that would normally lock the output shaft in the transmission) is removed in RV transmissions to prevent an engagement while the vehicle is moving which could destroy the transmission.

To make sure you have enough power steering fluid in the reservoir, you must check the level while the vehicle is in Park with the emergency brake set. Moving the gear selector out of Park will port power steering fluid back to the Emergency Brake Actuator (large volume) and you cannot fill fluid or you will overfill the system which will be pushed out the overflow hose on top of the reservoir the next time you put the gear selector in Park!

I don't know if you finally fixed your Bounder power steering/brake booster problem but an inadequate amount of power steering fluid would definitely cause the exact problem you described.

The system is designed to engage the emergency brake if the engine stalls and dies or the power steering pump or belt fails (loss of power steering pressure).

Originally Posted by rkrod

Well let me say this I'm not a mechannic, but I can turn a wrench lol Once the emergency brake shoes were replaced no more air was allowed to enter the lines causing the winning. After brakes were changed out the lines were bled and no air was allow in system.

I had the sensor that is located on the drivers side that screws into the power sterring fluid line designed to lock emergency brakes if low fluid is detected. I developed a pin hole leak which caused the fluid to drain out causing my emergency brakes to lock up. I had to go parts house get replacement to plug line add more fluid to get brakes to release. Had wait two days for the parts house to get correct part for me. Two days later went to Dealer for other items met a guy with 1994 having same problems bad sensor with leaks. The part must be designed to develope a pin leak after 15 years or more.

Not sure about your 1998, but most mech miss the diagnose of the problems associated with this type of brake system. The brake and sterring are all tide in together on this boost brake system.