I have a 2000 F250 CC LB 4x4 7.3. It has 225,000 miles on it. Over the past few months, it has gone thru 4 master cylinders. They will last 100-200 miles with perfectly normal brakes, then suddenly fail. I've had the MC's bench tested and they wont hold pressure. I'm not knowledgeable enough to know what could be knocking them out. Power steering works normally and there are no lights on the dash. It also doesn't give any codes. What are your thoughts? Thank You

 

WELCOME TO FTE!!!

Where are you getting them from and who is doing the install for you?

All 4 from the same source?

Are you running through a box store's lifetime warranty/replacement program?

If the answers to the last two questions above are "yes" and "yes", I would look for a new and better source for the parts, even if it means walking away from an existing lifetime warranty issue.

When I replaced my brake MC, I bought one from Ford (a discounted online source), and I've now put probably close to 150K miles on it without a single hitch.

 

Thanks for the welcome! The first two were from Orielly, assuming they were the problem, we then went to Ford for the last two. The results were similar, Although the ford ones did last longer before failing. The work is being done at a local mechanic shop, they have contacted the local Ford repair shop as well, but have not gained a positive direction on the issue. They are leaning towards an HCU problem, but there doesn't seem to be any tested finding to point to that as the problem.

 

Well, you've gone beyond anything I've personally dealt with, then.

The only other thing which comes to my mind is fluid incompatibility causing premature seal/o-ring failure, but I honestly doubt that's the case since you've now gone through this with two different sources.

I'm sure some others will chime in soon and they may have some better insights for you.

 

What's an HCU?

I'd also suspect fluid contamination so a complete system flush with your favorite DOT 3 or 4.

 

I asked the same question. HCU is hydraulic control unit of the abs.

 

8dtrain.. What's your symptoms? I've replaced 4 MC's, 3-hydroboost and 2-power steering pumps..ALL worth fluid flush replacements. Even pulled slide pins on front calipers to decrease...still the problem exist. ...Peddle bleeds down while at stop light/sign

 

timmyboy, perhaps the piston seals inside one caliper are leaking by internally? Are you feeling the truck pull to one side when stopping, or seeing any reduced level of wear on one set of pads?

 

Pete, it's my buddys truck...CCLB 4wd. Anyhow, it came to me when I was rotating my tires prior to fishing trip. I realized that the back calipers had slide pins, SMH...so, removed them on mine to clean/regrease which took a hammer and flathead to remove... Worth that said, I'll have to hit my buddy up so we can do the same with his. Hopefully there's success...btw, there's NO fluid loss anywhere to his truck

 

OK. I understand. I was confusing myself with the piston and piston seal design.

 

You know what, when I get back from AZ Sunday, I'll mention it to him so we can inspect the pads, rear slide pins too...i get what your saying now...i need to read twice before I respond