Motorhome brake experts needed

I have 1995 Chevy P30 motorhome. Hydroboost with 4 wheel disc. I repaced a leaking hydroboost and put in a new power steering pump. A stuck caliper led to replacing 3 of them, the pads and the master cylinder. Using a pressure bleeder got me no pedal. This weekend I pulled the lines off the master cylinder and put the plugs in and had had a real hard pedal. After bleeding the brakes using the 2 person method I got a lot of air out of the system and a very spongy pedal. I took it for a very slow test drive and could not get the brakes to lock up. Additional bleeding yielded no more bubbles and no improvement in the pedal feel. Any advise or places to look for problems would be appreciated.

Does it have RWABS like the C30 and K30?  I think there is a special bleeding procedure at the ABS module.

Also- did you replace the gasket on the reservoir? That worked for me. 

I suppose it could also be time for new rubber lines. 

My GMC was a different animal but shared long brake lines and was a challenge to bleed.  I finally made a plate adapter to fit my master cylinder and used a pressure bleeder.  After 2 quarts of fluid I could lock up the rear drums, which was a first.  I think we share the issue of very long brake lines and getting a decent fluid flow is the challenge.

Does it or did it ever have a hydraulic over air brake system for a toad? 

If so there is a brake system actuated valve in the middle somewhere that controls the airflow to the toad vehicle. That also has to be bled. 

Also, if it's like my 1996 F53 Ford with the hydroboost, great pedal feel just doesn't exist. You can run a gallon of brake fluid through it and it still feels a little mushy. 

I do not believe it has any abs system, I will carefully check for an ABS module. As far as the reservoir it is a new master with new cap. Rubber lines might be a culprit it came to me last night. There is not a brake system for a toad. I have already run over a gallon of fluid through the whole system.  On the test drive I could not get any more than a gentle stop from 20mph, no matter how hard I hit the brakes.

Does the pedal go to the floor or are you just not getting any pressure?

My 1987 P30 (Holiday Rambler Imperial 33) has an add-on tag axle. The drive axle brake line is teed to a relay valve controlling a separate vacuum-powered slaved-master cylinder for the big Bendix drums on the tag axle. Similar to what Toyman was referring to for a toad. Not only was bleeding a royal pain, but any compliance in the independent tag axle system (air or hose flex) lead to compliance in the main system despite it being purged of air. Think I went through almost a gallon of brake fluid when I overhauled my whole system. I also threw all 7 (yes, seven!!) brake hoses in the trash and converted to Russell DOT stainless-braided PTFE lines. Between the high pressures and number of hoses, I wanted to make damn sure hose flex wasn't a major detractor from overall feel and performance.

Zordak, does yours have the big 14.5" rotors? I dislike the calipers.

Any chance of having a caliper on upside down?  Been there, done that.  No T-shirt.

Curtis73 (Forum Supporter) said:

Does it have RWABS like the C30 and K30?  I think there is a special bleeding procedure at the ABS module.

Connect the input and output lines with a union.    If it's the same awful RWAL unit as on the K1500s.

I can get the pedal to the floor if I push hard enough. The problem is I can get it to stop normally (a good gradual stop) but in a panic stop all I get is a gradual stop. I did not look underneath last night ( usually exhausted after 10 hrs of work). There is a drum brake on the drive shaft. I am assuming that is the parking brake and just is cable operated. I am wondering if I might have an air bubble at the pressure differential switch and a bad switch. I am thinking maybe the bubble is moving from side to side as I try to bleed. Then again I am grasping at straws. 

This thread is giving me flashbacks- our P30 based RV had the opposite problem and locked the brakes on, it turned out to be a collapsed rubber line.

I had some ambition after work last night, and looked underneath. It is just a normal split braking system, no abs. I am thinking next spring(yes I am getting ready to winterize this thing) I will start with replacing the front rubber lines, if I do not see improvement, I will by pass or rework/replace the the differential switch.