Master cylinder replacement and brake woes, F350

I have a 99 F350 Super duty, 4 wheel drive, V-10. Purchased the unit used and immediately had to do brake work on it as the brakes did not enough stopping power and the ABS light came on even after replacing the rear ABS sensor (there is only one ABS sensor on this truck). I replaced all 4 disk brake assemblies (pads plus new calipers from NAPA), bled repeatedly running two quarts of new DOT 3 synthetic fluid through the system. The old brakes were in bad condition - calipers stuck, pads worn, but the rotors were not significantly grooved and I did not replace the rotors. The brakes were somewhat better after this, but still wouldn't hold the truck well on a hill with a load and the ABS light still came on after driving about 1/10 mile. I left the truck sitting for a couple months during the winter here in Colorado, and when I went to use it the brakes went to the floor and only worked marginally after pumping them up a few times. Brake fluid level was full. So, I replaced the master cylinder with a Ford rebuilt cylinder from CarQuest, bench bled the new master cylinder before installing and ran another couple quarts of fluid through the system bleeding all four wheels (RR, LR, RF, LF). So now, the brakes are soft but are better, the ABS light STILL comes on, and now the brake light comes on, as if its out of brake fluid (brake fluid level is topped off). I think the brake fluid level float got bumped off track when I removed the reservoir and installed it on the new master cylinder, but poking a rod around the float area didn't correct the problem. How do you unstick this float? Also, brakes are still soft and I wonder if I got all the air out of the system - any ideas on how to bleed this system? Lastly, the ABS warning light has got me stumped - again, ideas are much appreciated. Thanks

John

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have you had diagnastics done for the ABS light

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squeek

have you had diagnastics done for the ABS light

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squeek

Yes - the original diagnostics showed a defective sensor, which I replaced. I am going to have this done again (the first garage, Fort Collins 4X4, charged me $100 to run the diagnostics! so I'm looking for another repair shop which can do this). My main concern is the soft brake pedal and the brake light indicator. Thanks for the reply.

John

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how is the felxable rubber hoses are the worn old that could be the poblem other than that i don't know exept to laeve the truck to set more then try to rebleed the breaks we had trouble with my dads 55 we had to leave it set all summer so the breaks would have the air settle out on its own up in the master the nwe rebleed the breaks and then they were fine after that.

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squeek

"Doctor John" <nospamplease.> wrote in message news: snipped-for-privacy@trueband.net...

I don't know if the rules have changed but when I did this for a living, we were told by GM, and Bosch reps not use silicone based brake fluids in anti lock brake systems. The fluid foams from the surging that goes on in an antilock system. On bleeding, try lightly rapping the caliper housings with the HANDLE of a small hammer, then open the bleeders and let gravity bleed a few seconds, repeat three or four times. It knocks air bells loose from the inside surfaces. I do the same thing to the master cylinder when bench bleeding if I can't get plugs instead of the hose adaptors that come with most of them. Pump a few times and then rap a few times, keep doing until no more bubbles come out of compensating ports in master cylinder resovior. Also is this a four wheel system or rear wheel antilock system? I ask because there have been problems with the RWABs valve bypassing, it mimics the way a bad master cylinder feels. If you unplug the connector at the reservoir does the brake light go out? Are the tires and wheels stock size? Antilock brakes work by comparing wheel rpm to vehicle speed, via the wheel sensors and vehicle speed sensor. The system expects to see X rpm at Y speed. The system can be recalibrated by the dealer. Carquest sells A1 Cardone reman products, which I have always found to be of questionable quality. And while NAPA brake linings, calipers, wheel cylinders etc are pretty good, their master cylinders leave a bit to be desired. Raybestos, or Wagner are always my choice for American, and Beck Arnely for foreign, and if the master is aluminum, I wont install rebuilts/remans, only new masters. How do you hone an aluminum bore smooth? From a horror job, Caddy Seville, guy let his betrothed use while he was deployed for Desert Storm, went round and round trying to get decent pedal 4 wheel disc, staring dejectedly at master after three days, partner pushed brake pedal, master and booster assembly moved, "Girlfriend" had "companion" replace the booster, he didn't put all the bolts back in. And I have never driven anything with four wheel disk that felt as good pedal wise as a disc/drum combo, not chevy, ford, nor porsche, jag, rolls royce, or lotus. Whitelightning

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Whitelightning

I'm getting into the middle of this but I just had the brake done on my 95 F350 crew cab two wheel drive. New everything rotors, drums, shoes, calipers and including the master cylinder. When test drive I had soft brake pedal with excessive amount of travel. There is a service bulletin which indicated the original 95 master cylinder volume size could result in excessive brake pedal travel and should be replaced with a 96 master cylinder. This was done and for the most part have eliminated the pedal travel

MGH

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MGH

Whitelightning. Thanks for the comprehensive info. You repeatedly have shown your knowledge on this group, and I sure appreciate it. I will try the bump and bleed method you suggest - I've have also heard you can have a garage do a "power bleed" - is this worth it? I hesitated to use a rebuilt master - I had a new one on hand, but after removing the old MC I found the new one had a different reservoir rear port size and the only one I could find immediately in my nearby town in stock was at CarQuest - it was a mad scramble to get the truck back together before a winter storm blew in. At least the rebuilt was a genuine Ford, and it doesn't go to the floor anymore. The wheels are all the same brand and are stock size and the truck is a 4x4 with dually rear tires. I think I finally got the float indicator fixed by whacking firmly on the side of the reservoir. The brakes still just don't feel like they grip well. If I mash the pedal with all I've got, I can still get the truck to move forward in low range when I goose the gas - maybe this is normal and I'm just used to a firmer pedal and more holding power. The ABS light still comes on after driving a few feet - I think if it was due to fluid foaming it would take more than this distance to get the effect to occur, but I could try changing the fluid out. Thanks again, and please keep the ideas coming.

John

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