soft brakes when warm
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soft brakes when warm
I was wondering if anyone else has encountered a problem where your brake pedal becomes soft after an extended trip. After towing my boat a few times i began to notice that the pedal would seem very soft near the end of the trip. I replaced one of the rear brake lines last summer and bled the system and everything worked fine then. It is a 1975 f100 2wd with disk up frond and drum in rear. There is no brake booster. I am not losing any fluid anywhere i can find and it seems to be an intermittent problem. I am suspecting the master cylinder but i am curious if the wheel cylinders could cause the same issue. The boat tow load is about 2000 lbs. and this seems to mainly be when i feel the soft pedal. The pedal has never gone to the floor, however.
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You can over heat your brakes and get a temporary soft pedal. Maybe the weight of your boat is causing your brakes to heat up and you end up with "brake fade". You can try a heavy duty version of brake pad or buy a more heavy duty truck. I had the same problem with my 1997 Ford E-150 utility van. While driving in San Francisco going up and down a lot of hills, my brake pedal would get very soft and would come back to normal after the brakes cooled. I now drive an E-350 and do not have that problem anymore. An F-100 is a "light duty" truck. Check your towing capacity and GVW. You are probably just over heating your brakes. Your boat is only part of the load. You have to calculate for all the stuff in the back of the truck too.
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How fresh is the fluid? Brake fluid naturally trys to attract moisture. If moisture collects in the brake system, it will not compress at the same rate as the hydraulic fluid, especially when it turns to a gas. If the brakes heat up and moisture is allowed to turn to gas, it will make the brakes work terribly.
May check for rust or corrossion under the cover in the master. If you do not see pefectly clear fluid, it is contaminated, and will not work well with heat.
May check for rust or corrossion under the cover in the master. If you do not see pefectly clear fluid, it is contaminated, and will not work well with heat.
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The fluid is kind of dirty and the inside of the master cylinder looks like a rust bucket. I bled everything last summer but i suspect that it just got dirty again through an old master cylinder. I think i'll just replace the master cylinder and get some one way bleed screws and bleed everything again this year. The new master cylinder and fluid doesn't seem like and expensive fix.
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2000 pounds with an empty bed is about the max of the whole payload. There aren't a lot of hills along the trip and i don't have to step on the brakes much along the way. I don't know what the max tow capacity is for the truck but 2000 lbs doesn't seem to be excessive, i hope.
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Maybe one of your rotors is riding on the on pads and making the fluid boil? check that out too if nothing else helps.
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From: Fayetteville, Ar
I've noticed if i'm in heavy stop and go traffic, my break pedal will go soft. Once I get through a traffic light to the next one the the brake pedal isn't soft anymore. What are some things I need to check out for my situation?
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It looks like the problem is gonna be the master cylinder. I inspected everything lines, wheel cylinders, rear brake adjusters and everything seemed to be ok, at least for now. The master cylinder rubber plunger boot was very dry rotted and when you push the plunger you can see air bubbles and a small amount of fluid leaking out. I'm waiting for the rain to stop so I can install the new master cylinder and bleed the brakes with new fluid to be sure. Thanks for the input.
cj
cj