91 econoline 150 van brakes fail when hot

Old 11-14-04, 05:59 PM
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Question 91 econoline 150 van brakes fail when hot

I hope someone can help, I have a 91 Ford econoline 150 clubwagon van,
When the brakes get hot from towing a trailer and using the brakes downhill
to keep the speed under control the brake pedal will go all the way to the floor and no brakes! This has happened three times now. The brakes will come back after a day or so. What is going on and what must I do?
Thanks in advance.
Old 11-15-04, 05:30 AM
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You're probably heating them up to the point of boiling the brake fluid. Adjust your trailer brakes or if it doesn't have them, install some. You might also try a complete replacement of the fluid in the system; this will eliminate any moisture the fluid has picked up that would lower the boiling point.

From a site on brake fluids:

So, what happens when you boil brake fluid?

"First, a more accurate description for "boiling" brake fluid would be to use the term "vapor lock." You are really raising the temperature of the fluid to the point where it becomes a vapor. And we all know how compressible a vapor is. Therefore . . . pedal to the floor and, depending on the corner you're brakin' for, ya may need to change your underwear!

However, you are boiling the brake fluid. NOT the moisture absorbed by the brake fluid. And when the fluid has cooled down and the pedal comes back, the fluid now has a lowered boiling point. Again, this has nothing to do with moisture. Boiling the fluid di not add mositure to the system in any way. What happened when you boiled the fluid was your created/started the breakdown of the structure at a molecular level. In a DOT 3 fluid, you are destroying the core material of the fluid whereas in a DOT 4 fluid you begin destroying componetents in the inhibitor pack which as the added effect of allowing the fluid to absorb moisture at an even more rapid pace."
Old 11-15-04, 05:59 AM
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I have had good luck with Ford Heavy Duty brake fluid
Even in racing situations (very high heat)

But the tow guy is right about your trailer might be taxing your van's brakes
It might me too heavy for your van, or it needs brake adjustment, or brakes

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