Community Forums

Ccrider65 · 08-01-2019, 05:03 AM

I'm puzzled by this, been a shade tree mechanic all my life. But we drove our 2000 itsca sunrise from Indiana to south dakota spent a week there & headed home. On the way back suddenly the brake pedal got real soft, they would still stop the RV but would go nearly to the floor. As I said this happened suddenly. Checked under the RV very thoroughly and found no brake fluid leaks. Since we were pretty much in the middle of no where I bought some brake fluid and added some to the master cylinder. Couldn't really see how low it was due to its location. Was thinking a bad master cylinder & planned on replacing it when we got to civilization. However after adding the fluid the brakes worked perfect again. Drove all the way back to Indiana with no issues. Rechecked carefully for any leaks and found none? Any insights appreciated.

Waiter21 · 08-01-2019, 05:13 AM

I have a Ford F53, At minimum, This is what I would do:

1) Pull the wheels and inspect the brake pads, rotors, etc. If original, replace pads.

2) Replace the brake hoses. (20 year sold they are ready to be replaced)

3) Bleed the brakes to replace fluid with new fluid.

NOTEs - Possible master cylinder and caliper replacement while doing all the other work

eieioh · 08-01-2019, 05:17 AM

Is it possible you experienced boiling fluid. I.E. hot day, stuck caliper, etc?

**Spdracr39** · 08-01-2019, 05:42 AM

Overheated brakes should cause a funky smell but an air pocket and or moisture can move around and create random havoc. I would flush the old fluid and refill bleeding them thoroughly.

twinboat · 08-01-2019, 06:02 AM

Brake fluid is hydroscopic, meaning it absorbs moisture over time. That happens thru the hoses and caliper seals

With light braking, water will work in a brake system because it, like brake fluid, is not compressible.

Problem is that water boils to steam at much lower temps then brake fluid.

With moisture ladden fluid, it will boil after a hard stop. It doesn't turn to steam under pressure, but when you let up the pedal, it does, and the steam pushes the fluid up into the master cylinder.

With the next brake application, the pedal goes low because there is now a pocket of air in place of the condensed steam.

The fix is to flush the brake fluid every 4 to 5 years in low annual mileage vehicles.

Vehicles on the road every day wear out the brakes and in most cases have the fluid changed while getting the brakes repaired, so its not as big an issue.

Most but not all Ford MH class A chassis have a requirement that the brake fluid be replaced every 2 years.

When I bought my 2000 MH in 2014, I came down a long hill to a right turn into a campground. The brakes worked fine for that stop but the next stop at the check-in booth had me holding the brake pedal to floor as I rolled by. Very unnerving.

richard5933 · 08-01-2019, 06:14 AM

Haven't worked on hydraulic brakes for a while, but if my memory is still good, as the pads wear the have to travel further and further to reach the rotors. If you were that low on brake fluid, I'd suspect that your pads are getting near the end of their useful life and should be inspected.

twinboat · 08-01-2019, 06:59 AM

Quote:

Originally Posted by richard5933

Haven't worked on hydraulic brakes for a while, but if my memory is still good, as the pads wear the have to travel further and further to reach the rotors. If you were that low on brake fluid, I'd suspect that your pads are getting near the end of their useful life and should be inspected.

The pads don't travel further because as they wear, the caliper pistons advance out of the caliper.

The piston seals work as piston return springs while always self adjusting.

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chuckftboy · 08-01-2019, 08:41 PM

At least start with flushing and replacing the brake fluid. I change brake fluid in all my vehicles and motorcycles every 5 years and never have a problem. Brake fluid is cheap, body parts, not so much!

Cat · 08-01-2019, 11:17 PM

Quote:

Originally Posted by twinboat

Brake fluid is hydroscopic, meaning it absorbs moisture over time. That happens thru the hoses and caliper seals

With light braking, water will work in a brake system because it, like brake fluid, is not compressible.

Problem is that water boils to steam at much lower temps then brake fluid.

With moisture ladden fluid, it will boil after a hard stop. It doesn't turn to steam under pressure, but when you let up the pedal, it does, and the steam pushes the fluid up into the master cylinder.

With the next brake application, the pedal goes low because there is now a pocket of air in place of the condensed steam.

The fix is to flush the brake fluid every 4 to 5 years in low annual mileage vehicles.

Vehicles on the road every day wear out the brakes and in most cases have the fluid changed while getting the brakes repaired, so its not as big an issue.

Most but not all Ford MH class A chassis have a requirement that the brake fluid be replaced every 2 years.

When I bought my 2000 MH in 2014, I came down a long hill to a right turn into a campground. The brakes worked fine for that stop but the next stop at the check-in booth had me holding the brake pedal to floor as I rolled by. Very unnerving.

X2 this is my guess too. Moisture boiling out of brake fluid.

jelag · 08-02-2019, 01:09 AM

brake fluid is hydroscopic and will absorb water... thus the change from a clear fluid to a murky pee yellow fluid... often when front brakes are done the installer will short cut the process and compress the piston pushing that old crappy fluid back to the master cylinder...

The proper method is to open the bleeder and allow the bad fluid to escape through the bleeder and later add fresh back and bleed correctly..
Hydroscopic also means that the moisture trapped in the fluid can and will boil off leaving a vapor in the system... this will mean a spongy pedal and poor breaking performance...
I personally purchase and bleed brakes on all my vehicles at least every 2 years.. my Arizona vehicles in that dry weather don't seem to be so bad but the vehicles I have in WA state are always nasty looking at 2 years...
I personally inspect the caliper boots when I change pads.. if the boots are intact and not damaged I flush and bleed when I compress the piston.. if the boots are bad than I overhaul the caliper...

I can continue with rear drum brakes but I think you get the picture...

And clean fluid means that the ABS system will function more smoothly when needed in a panic stop...

richard5933 · 08-02-2019, 04:26 AM

Quote:

Originally Posted by twinboat

The pads don't travel further because as they wear, the caliper pistons advance out of the caliper.

The piston seals work as piston return springs while always self adjusting.Attachment 255388

Correct. The point I was trying to make is that as the pads wear there is more fluid being held at the wheel ends and less in the master cylinder's reservoir. As the pads continue to wear, it's necessary to top up the reservoir.

Ccrider65 · 08-02-2019, 04:35 AM

Thanks my friends, appreciate all the input. Contaminated brake fluid sounds like a good possibility since this happened as we were coming out of the highlands west of rapid city doing a lot of braking when this happened to us. Even though it's a 2000 our RV only had 20K on it. Spent a lot of time in storage. Just for safetys sake I'm going to flush the brake fluid out and inspect the pads & hoses then go from there 😊

twinboat · 08-02-2019, 06:19 AM

Quote:

Originally Posted by richard5933

Correct. The point I was trying to make is that as the pads wear there is more fluid being held at the wheel ends and less in the master cylinder's reservoir. As the pads continue to wear, it's necessary to top up the reservoir.

Actually you don't want to top off the master cylinder. The reservoir is designed to hold enough fluid to keep the calipers full right up until the pads are at replacement thickness.
At that point the brake warning light comes on, due to low fluid, alarming you that the brake system needs inspection.
If you keep topping off the fluid, you could wear the pads down to steel on steel, destroying the rotors and loosing the brakes completely.

Waiter21 · 08-02-2019, 06:25 AM

^^ YUP What he said..

After you put new pads on all four and bleed the brakes, top off the reservoir. The reservoir will now act as a wear indicator for your pads.

When the reservoir level gets down to about 1/2, its time to think about replacing the pads..

IMPORTANT - For the above statement to be true, You need to know that it was topped off when new pads were installed, AND no fluid was added since then.

ALSO -the system is sealed. This reduces /eliminates moisture being absorbed by the brake fluid.. The rubber gasket on the cap is accordion style, as the fluid level lowers, it also pulls the cap seal down. Inspect the seal to verify its not torn or cracked.

When you open the cap, you just allowed moisture laden air into the system. (yah, I know, its not a lot.)