brake fail

[bruce gordon]

My brakes went to the floor on this yrs trip to Yosemite.I go almost every yr with the family and every time I get to the valley I have to pump the brakes to stop.I heard if you shut off the motorhome and restart it the brakes will work normally...they went to the floor after I did that and I used the emergency brakes to the campsite....how scaery is that.I've been all over in this rig(27 ft. fleetwood flair "95")kings, Brice ,Yellowstone, grand,It only happens in Yosemite?????oh and to make things really interesting they work more or less normally after that

[She and I]

Quote:

Originally Posted by bruce gordon My brakes went to the floor on this yrs trip to Yosemite.I go almost every yr with the family and every time I get to the valley I have to pump the brakes to stop.I heard if you shut off the motorhome and restart it the brakes will work normally...they went to the floor after I did that and I used the emergency brakes to the campsite....how scaery is that.I've been all over in this rig(27 ft. fleetwood flair "95")kings, Brice ,Yellowstone, grand,It only happens in Yosemite?????oh and to make things really interesting they work more or less normally after that

Hi Bruce...Welcome!
I think you may have what is called boiled you brakes ...in other words the brake fluid got so hot it boiled and that causes air in the system...after it sets and cools..returns to almost normal.. change fluid to high temp or dot 4..
Or ...you have glazed and hardened the pads and shoes and possibly calipers and drums..
but from your discription Brakes went to the floor I guess it's fluid related..
Richard

["007"]

Welcome Bruce to irv2.
If you have a Workhorse chassis you have a recall for all brake calipers to be replaced at no cost to you.
Check out threads in the forum.
If its a Ford check their forum.
In any case you need to replace your brake fluid.

[Gary RVRoamer]

He said it's a 95 Flair, so no Workhorse chassis.

Your brakes are overheating, which literally boils the brake fluid and puts vapor in the lines where hydraulic fluid should be. The brakes are probably somewhat undersized on that vintage of rig, but you need to work on your braking technique to help them cool. Don't ride thebrake on steep hills - press them hard, then back off for several seconds to let cooling air flow around them. And make sure you start the downhill at the lowest speed possible.

I would also have the brake system checked for good pads/shoes, true shape on the rotors or drums, good wheel bearings, etc. Poorly functioning equipment will exacerbate heat problems.

[macnkat]

Altitude will also lower the boiling temp.

[Hikerdogs]

How often (if ever) have you flushed the brake system hydraulic fluid? As others have mentioned you're probably boiling the water saturated fluid in the calipers and/or rear brake cylinders. Water has probably accumlated in the system over the years. Since it's heavier than the brake fluid it migrates to the lowest points (which is usually the calipers and cylinders).

The heat generated when applying the brakes causes the water in the fluid to boil and turn to steam. The steam then partially fills the caliper and is compressed when you step on the brake pedal. Normally the liquid brake fluid would push against the piston and move the pads against the rotor. In this case the liquid brake fluid is only compressing the steam and not applying enough pressure on the piston to move the brake pads.

The easiest and least expensive first step is to flush the system. You'll probably find what comes out of the bleeders is a brown goo rather than an almost clear liquid.

In all likelyhood your brakes originally came filled with DOT 3 brake fluid. It has a minimum dry boiling point of 401*F and a wet (water saturated boiling point of only284*F. The wet boiling point is only 72*F higher than plain water. It doesn't take a lot of hard braking to raise the fluid temperature high enough to boil the water out of the fluid.

In almost every case I am aware of DOT 4 brake fluid can be used as a direct replacement for DOT 3 fluid. DOT 4 fluid has a minimum dry boiling point of 446*F and a wet boiling point of 311*F

Be careful not to use DOT 5 series fluids in your system. Although they have a much higher boiling point they are not compatible with your caliper and master cylinder seals. The DOT 5 series fluids are silicone based and will either leak by or deteriorate conventional seals.

[DAN L]

Quote:

Originally Posted by bruce gordon My brakes went to the floor on this yrs trip to Yosemite.I go almost every yr with the family and every time I get to the valley I have to pump the brakes to stop.I heard if you shut off the motorhome and restart it the brakes will work normally...they went to the floor after I did that and I used the emergency brakes to the campsite....how scaery is that.I've been all over in this rig(27 ft. fleetwood flair "95")kings, Brice ,Yellowstone, grand,It only happens in Yosemite?????oh and to make things really interesting they work more or less normally after that

as others have said, i would recommend that you replace your brake fluid.
all brake fluid is ''synthetic''.
i use and recommend castrol gt lma dot 4 brake fluid. it is widely available and not expensive. it has a higher boiling point than most brake fluids, 509 deg f. dry and 311 deg f. wet. it is recommended that brake fluid be replaced every 2 years before it becomes wet. check the castrol website for the definition of wet brake fluid.
check oemy's website for brake bleeding procedures.

Oemys Web Site - Tech Tips

http://www.castrol.com/liveassets/bp...BrakeFluid.pdf

[bruce gordon]

Thanks all I'm pretty sure its original fluid coupled with some hard braking by previous owner.One mechanic mentioned burned drums.I asked him about a turn to clean them and he said "burned clean through"So this is gonna be my next project

[HoRotica]

Bruce,

Brake fluid is hygroscopic, it absorbs moisture out of the atmosphere. The moisture pickup can lower the boiling point and cause exactly what you described.

Flush the system out well and start there. One other thing to note... If your foot is just lightly on the pedal when sitting at a traffic light for example and the pedal just slowly creeps to the floor then most likely you have a master cylinder that is in need of replacement.

Get to flushin them brakes!
Chris

[ccook129]

Going downhill in a low gear lets you use the engine as a brake itself. The engine is throttled back, fuel flow to the engine is cut back, and the car's momentum applies power to the wheels, transmission and crankshaft, letting the pistons work like air pumps to compress air and slow the entire rig with occasional use of brakes. It's a good technique to learn how to use.