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I have a 1985 Winnebago Class A Motorhome on a P30 chassis with a GM 454 cid engine. The RV has 4 wheel disc brakes. On a trip last year I unexpectedly experienced a soft brake pedal. Fortunately this happened as I was leaving a campground and there was no danger to me or others. I inspected the vehicle and found that the brake fluid reservoir was very low on fluid. More in the front reservoir than the rear. Because of this I checked for leaks at each wheel cylinder, the master cylinder and all brake lines. I found everything to be perfectly dry. I replaced the low fluid and the brakes worked perfect for the rest of my trip and ever since. I check the reservoir frequently and find that it drops down about a half an inch ( more loss in the front reservoir than the rear) every 2000 miles. Still no sign of leaks and the brakes work perfect. Can anyone tell me how this brake fluid could be escaping the brake system without showing signs of leaking. Thanks.
I have seen the same symptoms when the seal between the two braking systems in the master cylinder (front/rear) began leaking. The fluid was being transferred from one reservoir to the other. In extreme cases one of the reservoirs will completely fill and the fluid will be forced out of that part of the master cyclinder and evaporate leaving only a damp looking reservoir but no other sign of a leak. Typically the two reservoirs are different sizes to allow the pads to wear and additional fluid to end up in the caliper which requires much more volume than the drum brake portion.
Typically the disk brake portion has plenty of capacity to allow the pads to wear completly out before the fluid level has been lowered to the danger point.
In my opinion it is time for a master cylinder. It is an easy repair and much less expensive than running out of brakes at unexpected moment when you really need them.
Sorry to disagree on the "no vacumn booster". Please take a look under your rig in the area behind the transmission. I do not have a P30 chassis but lost my brakes as you did. It turned out I have two vacumn boosters, one for front and one for the rear brakes. When I removed the brake vacumn hose from the intake manifold I found it was wet inside and smelled of brake fluid. The missing fluid was getting sucked into the engine. I had both boosters rebuilt at a local brake and clutch shop. Hope I am wrong but give it a check. Good Luck
Guy..
I have a 97 class A and just lost my
brakes on our last trip. There was no
leaking of fluid. I found that the
master cylinder cover warped from heat
and the MC bladder would drop into tank.
Also, fluid was being boiled from heat of the engine (454) manifold, which is
only 5 or 6 inches from the master cylinder. Build a heat shield between
the manifold and MC and changed to DOT
4 fluid. So far things seem to work..
Ken.
Thanks for your advice. This might be the problem although the master cylinder cover is not warped and the seal is good. I will, however, check for heat buildup on my next trip and proceed from there.
I lost my brakes completely on a steep grade in wyoming, on a chevy chassis under a 96 pace arrow.
I managed to stop it thanks to the brakes on my trailer.
After inspecting the lines and master cyl. i checked the brake pads and at 25 thousand they were just 2 32nds.
The reason for my dry master cyl. was that the pads had gone away so fast it caused the master cyl to put the fluid into the lines and the calipers leaving the master cyl dry. i keep checking the fluid at least once a year and always have to add.
The brakes on my gm chassis are absolutely terrible
email Guy
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