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I would finally like to lay rest the mystery surrounding the P30 hydraulic brake malfunction. Based on my experiences and after reading about 25 previous forum threads, I can see that I am not alone in this, and very few threads really touched thoroughly on the specific issue. Please read on for the solution.
My story:
1993 Tiffin Allegro Bay 30 footer Chevy Control Chassis 454 FI engine gasoline. Hydrobooster braking system. 4-wheel disc. P30 Chassis. I have been fighting this brake locking issue for a while. One day I jacked up both front wheels. Applied the hydraulic brake and I could not spin the wheels, (after 2 minutes I could make the left front spin with great force, the right was perpetually locked) I sought out the solution. I cracked the bleeder screw on caliper and the wheel loosened up completely and the fluid shot out under pressure. I reapplied the brakes, I used a 9/16 and a 5/8 wrench to loosen the union where the rubber flexible line meets the steel tubing. No pressure came out (it just dribbled a bit) and the wheel remained locked. I reapplied the brakes and this time loosened the 7/16 fastener that holds the brake line to the caliper, and fluid shot out under pressure and the wheel loosened. Therefore i determined that the flexible brake line was restricted closed somewhere (at the metal clamp that fixes it to the upper A-arm, there was no rust present on this clamp.) Pressure would force the fluid past the restriction, but when the natural dynamic of the pressure trying to equalize and go to the area of non-pressure, the restriction prevented it from releasing. My best guess is that the excessive heat generated during normal driving inside the front brake lines and caliper damaged the rubber component and caused this restriction (heat swollen rubber) I then consulted a chevy dealer and they wanted $73 for each brake line. It was the steel line and rubber. I said I wanted only the rubber, they said, too bad. I then consulted O'Rielly's Auto Parts and they had the rubber hose for $18 each. I purchased them and within 30 minutes had them installed and bled. This problem has been finally solved. Many parts were replaced trying to satisfy my initial thoughts of diagnostic. Both Rotors (they were heat damaged badly) Pads, Master Cylinder. None of these fixed the problem at all.
The vehicle currently drives like a dream, no squealing from the front brakes, no oven like heat generated from the front wheels (when checked at a stop), The vehicle doesnt hesitate at takeoff because the front brakes are holding while the rear brakes have released. I will add these brake lines to the maintenance schedule for every 2 years. They are cheaper to replace at $40 than to burn up another set of pads and rotors.
I hope this helps all who own a P30 chassis under some type of motorhome who experience this problem and seek this forum for answers, but instead, someone asks a new question over your question, and overrides your question. I cant stand that. Ask your question in your own forum thread.
Hi John, I seem to have the same problem and will go through the same diagnostics you did to confirm so thanks a lot. A few questions: how much trouble was changing the hose; what tools did you need; any tricks to it; what was the part number of the hose? Thanks again. Bob.
Hi John
I had mentioned it here somewhere,I have 6 GM vehicles 2 which are Motorhomes and have replaced all of the flex hoses on them.I am glad you have replaced the hoses and are able to drive again
richard in virginia
PLEASE HELP ME. I am a cancer survivor and on a very low fixed income. Needless to say I can not afford to take to dealer and have to do repairs myself. My problem is kind of the oppisite of what was described above. I have no brakes. After finally finding the fluid resivor, behind a sheild that had to be removed, it was empty. Ha-ha the problem, oops not so quick. I filled the res. blead all four brakes, but still nothing. This is a P30 chassis on a Fleetwood Southwind RV 1982 model. Is this electronically controlled? Could there be a fuse somewhere that I have not located? I'm at my wits end. My 6 years old son and I loaded up and was headed out to go camping and no brakes. I beg any help you can give me and thanks so much. Walter Wallace
Walter may need more info, you say no brakes,does the pedal just go to the floor with no or little resistance.?If so you may need a new master cylinder.You say no fluid was in master cyl. Its a closed system so it had to go somewhere.Do you see any place near wheel cylinders for signs of a leak.?Not much electrical stuff on the old p30.May have a pressure light on dash that lights if front or back systems have different pressure /safety issue.Usually not much trouble with light circuit.Just tells you that you might have a brake problem.May still have some air in system.I like the new type bleeder screws about 5to 6 bucks per wheel.real easy to install on front a bit more on rear.does a good gob when bleeding.Have you checked rear shoes and front pads,do they still have 1/4 in of meat on em.? Just a few ideas here so keep us posted and may be able to help.but may need more history MIKE
I need some help. I have not seen this specific problem discussed but it is similiar to those above.
I have an 84 28' P30. Everything worked before except for a right then left pull as the calipers did not apply simultaneously.
I changed the calipers, pads, and flex lines.The problem is that I cannot bleed the brakes now. The fluid will not leave the reservoir but will stay there. I have tried flushing it through, cracking the bleeder under pressure, engine on, engine off, etc. It seems as if the front chamber of my master cylinder is full of air which does not want to leave.
I am an RV newbie but have 30 years of experience with cars, boats, race cars, etc. I have missed something obviously. I expect that I have jammed the piston to the end of the brake switch but have been unable to find it yet... or something similiar.... but am open to suggestions. The master is up above the driver front wheel so access is very limited. I will focus on that area as I start today.
Please help.
Thanks!
Greg
Dale I guess you have a P30 chassis. The problem you have may be due to some small amount of water in your system.If it were my coach I would install the new type bleeders on the calipers. Then open up master cylinder top and remove as much fluid as I could with a turkey baster, Then bleed cylinders and flush in new brake fluid.Keep the cylinder full or half full when when flushing.Don't let it get low or will suck in air.The trouble in city hard braking is not much air is moving around rotors to keep things cool.Things start heating up fast.At highway speeds lots of air moving around rotors to cool them.If your coach is a P30 I think most master cylinders are still in back of drivers side front wheel.A real PITA to get to. Then its behind a metal cover about 4 bolts to remove to get off.Just look up behind front wheel and should see access hole in cover.Tra the new fluid first but if goes to floor again my need new master cyl. Good Luck Mike
Problem may be the same maybe not. Two years ago the left front caliper locked after a short drive. The calipers and rotors and hosess were replaced at that time. Two weeks ago, after going through Atlanta in heavy traffic the brake pedal went to the floor with no braking at all. I slowly got to an exit and safely got off the interstate. After cooling the brakes worked fine again and I was able to get home with no further problems. Are these rigs suseptable to vapor lock in the brakes when high heat is encountered? and can anyone suggest a solution to this?
Hello John,
How are your brakes working now? I have had the same problem, paid a lot of money to correct it and just last week the problem of front brake lock up returned in 104 degree weather. When it is cooler, I have no problem. I was going to change out the hydro boost but brake lines are a lot less costly
Thx,
Jon
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