We were on our way home yesterday after a glorious trip to the Grand Canyon, Sedona and Palm Springs. We were in stop and go traffic on 101 for about an hour. Suddenly, my husband said the brakes "went soft". Luckily, he got off the freeway and we sat on the side of a very wide off ramp. We were towed to a parking lot. We called a Good Sam suggested roadside mechanic. He said brake fluid was normal in brake reservoir even tho fluid was dripping from the reservoir. All of this took a couple of hours. After testing the brakes in the parking lot, the mechanic felt we were safe to go to a nearby RV park. We're not sure whether to stay here and wait until tomorrow to have a mechanic look at it or since the brakes seemed fine on our 5 mile trip to the RV park... (were the brakes just hot from the stop and go traffic?) Should we continue on our way home? Our RV is a 1998 Fleetwood Pace Arrow. We only have 23,000 on it.

Monterey Bay Cruzers wrote:We were on our way home yesterday after a glorious trip to the Grand Canyon, Sedona and Palm Springs. We were in stop and go traffic on 101 for about an hour. Suddenly, my husband said the brakes "went soft". Luckily, he got off the freeway and we sat on the side of a very wide off ramp. We were towed to a parking lot. We called a Good Sam suggested roadside mechanic. He said brake fluid was normal in brake reservoir even tho fluid was dripping from the reservoir. All of this took a couple of hours. After testing the brakes in the parking lot, the mechanic felt we were safe to go to a nearby RV park. We're not sure whether to stay here and wait until tomorrow to have a mechanic look at it or since the brakes seemed fine on our 5 mile trip to the RV park... (were the brakes just hot from the stop and go traffic?) Should we continue on our way home? Our RV is a 1998 Fleetwood Pace Arrow. We only have 23,000 on it.sounds like the master cylinder is bypassing; replace the master cylinder;; if the brakes were over heating and boiled the fluidsthe pedal would stay soft till there were bled out (air)

Did mechanic check all wheels of coach for cylinder/caliper seal failure. It could go soft again real quick if they are bad also.

If your having brake issues get the whole system checked out, brake booster, flex lines cylinders/calipers. Its cheaper than a funeral or wreck.

As Gultfelt indicated, your MC is bypassing fluid. This can happen all of the sudden and you should not drive it that way because it can get much worse. (of course it wont get better on its own). It can also start dumping brake fluid into the booster which will eventually rot it out.

Could be moisture in the brake fluid. It does absorb water over time, that's why they recommend changing the fluid every 2 years. If this is the case, then the brake system gets hot, around 240 degrees, the moisture will boil, and the steam is a gas and does compress, creating a soft pedal. If this is the case, have all of the brake lines inspected for possible rust-thru and leaks.

Master Brake Cylinder | Good Sam Community

30 Replies

Dutch_12078
Explorer III
Nov 19, 2017
The symptoms sound more like what Wildman suggested to me. Hot brakes boiling the fluid will cause the brakes to go soft, but after parking for a bit to let them cool down, everything returns to normal. As also suggested, a complete fluid flush is called for to minimize a repeat problem.
gutfelt
Explorer
Nov 19, 2017
NutHouse2016 wrote:
Did mechanic check all wheels of coach for cylinder/caliper seal failure. It could go soft again real quick if they are bad also.

if that was the case the master cyl would empty as noted MC still full
gutfelt
Explorer
Nov 19, 2017
ScottG wrote:
As Gultfelt indicated, your MC is bypassing fluid.
This can happen all of the sudden and you should not drive it that way because it can get much worse. (of course it wont get better on its own). It can also start dumping brake fluid into the booster which will eventually rot it out.

to note; it has a hydro boost not a vacuum booster
rgatijnet1
Explorer III
Nov 19, 2017
As mentioned, I would have the entire brake system FLUSHED. This is different from the normal fluid bleed that a mechanic would do to remove air in your brake system. This will probably take 2-3 quarts of brake fluid to thoroughly flush your brake system.
To aggravate this condition, since you were in stop and go traffic, the underhood temperatures probably got pretty high from the lack of air flow. This would also help to heat the fluid in the master cylinder or any brake lines that run near any exhaust pipes.
ksg5000
Explorer
Nov 19, 2017
Low mileage doesn't mean much when it comes to brake issues on older rigs - not driving the rig creates it's own brake issues. I would take the rig in and have the brakes checked out - if your in N Calif I would recommend Les Schwab.
wildmanbaker
Explorer
Nov 19, 2017
Could be moisture in the brake fluid. It does absorb water over time, that's why they recommend changing the fluid every 2 years. If this is the case, then the brake system gets hot, around 240 degrees, the moisture will boil, and the steam is a gas and does compress, creating a soft pedal. If this is the case, have all of the brake lines inspected for possible rust-thru and leaks.
ScottG
Nomad
Nov 19, 2017
As Gultfelt indicated, your MC is bypassing fluid.
This can happen all of the sudden and you should not drive it that way because it can get much worse. (of course it wont get better on its own). It can also start dumping brake fluid into the booster which will eventually rot it out.
NutHouse2016
Explorer
Nov 19, 2017
If your having brake issues get the whole system checked out, brake booster, flex lines cylinders/calipers. Its cheaper than a funeral or wreck.
NutHouse2016
Explorer
Nov 19, 2017
Did mechanic check all wheels of coach for cylinder/caliper seal failure. It could go soft again real quick if they are bad also.
gutfelt
Explorer
Nov 19, 2017
Monterey Bay Cruzers wrote:
We were on our way home yesterday after a glorious trip to the Grand Canyon, Sedona and Palm Springs. We were in stop and go traffic on 101 for about an hour. Suddenly, my husband said the brakes "went soft". Luckily, he got off the freeway and we sat on the side of a very wide off ramp. We were towed to a parking lot. We called a Good Sam suggested roadside mechanic. He said brake fluid was normal in brake reservoir even tho fluid was dripping from the reservoir. All of this took a couple of hours. After testing the brakes in the parking lot, the mechanic felt we were safe to go to a nearby RV park. We're not sure whether to stay here and wait until tomorrow to have a mechanic look at it or since the brakes seemed fine on our 5 mile trip to the RV park... (were the brakes just hot from the stop and go traffic?) Should we continue on our way home? Our RV is a 1998 Fleetwood Pace Arrow. We only have 23,000 on it.

sounds like the master cylinder is bypassing; replace the master cylinder;; if the brakes were over heating and boiled the fluids
the pedal would stay soft till there were bled out (air)

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Master Brake Cylinder

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