I originally posted this thread in the "Brakes, Suspension...." forum, but response there has been very slow. Since my brakes are getting worse and I need to be ready for some quick action very soon, I decided to tap into you guys' knowledge because there are so many more of you in here and you guys are simply better "responders" - I don't necessarily have 1-2 weeks to ferret this issue out unless I want to end up crashing into someone!

Here's waht I have going on....

My truck is still running stock size tires and no lift (LT 265-75-R16).

I am failrly certain that my master cylinder is leaking by internally. Not too much yet, but getting worse. When I break on a downhill grade and come to a stop at a light, the trucks stops nicely and then after 10-15 or so seconds begins to creep forward a tad... push harder and she stops... then creeps forward again.

I've tried the brake pedal test... stop, let up half-way and push hard again, and repeat that and the pedal ends up landing all the way down after 4-6 repititions. I also tried to simply perform my stops by leaving a heavier foot-pressure on the pedal from the time I get to a complete stop, and found that when I do this, the pedal will slowly (over about 20-30 seconds) creep all the way down to the floor until she bottoms out (and then I have to quick-pump the pedal to keep from nudging the vehicle in front of me).

Also, I want to eventually run cryoed powerslots and possibly the larger SSBC calipers as well, and want to make sure that I lay the proper foundation from the beginning.

So...

1) Have I diagnosed the problem correctly?

2) If the answer to #1 is "yes", then I want to consider an upgrade when I replace the master cylinder.
a) Is it better to simply rebuild the MC myself, buy a rebuilt unit, or buy a NEW unit?
b) What is a "better" master cylinder"? Brand? Model?
c) Would a MC work that was designed for something like an F450 -F650 and provide the kind of upgrade I'm wondering about? SEE EDIT below...
d) Does a larger piston diameter help?


EDIT... I just found out that the part for the F450 and F550 are the exact same part numbers as the one for my F250... so that is not an upgrade option.

 

you do have a M/C bypassing internally

as far as replacements I have had no luck with the chain part store brands
I have had the last as little as a couple days,

I always buy wagner brand or equivalent or new then have no other problems

you have to use a M/C that is sized for the other brake componants,so you want to use the part for your truck

 

Brake systems are kinda' "tuned" by the engineers to act together properly as a complete system.

I wouldn't go "upgrading" (i.e. using different sized components), as you are bound to upset the way everything plays together.

As Ray said above, buying new Wagner replacements should get you what you need, reliability, with no surprises.

The brake system is no place for "mods", unless they are factory-approved, like new caliper pins, etc.

At this point, it looks like a master cylinder is what you need. It should be available separately from the hydroboost unit.

When you're all done, completely flush all the old fluid by thoroughly "bleeding" your system. A complete fluid flush every two years helps to preserve all the pistons and other rubber brake parts by removing the dissolved moisture that will cause internal rusting, and the resultant abrasion on the parts.

Pop

 

Thanks, guys. You have summarized pretty much what I've been finding on the internet... not much room for upgrades without installign a complete system (aside from changing lines to SS, pads, calipers, and rotors). Looks like the lines are the only real potential gain on the hydraulic side of things, and that's only from the standpoint of long-term cleanliness and "firmer" hydraulic action due to lack of flexure in rubber lines.

Also, I'm seeing that the Raybestos units are more expensive than the Wagner units, but not by much. Does anyone have any experience with Raybestos MC's?

 

Just a thought, have you checked Y2K ford parts ( I dont remember the new name) for a replacement factory cylinder? Are you sure you dont have a bleeder valve slightly cracked open, a loose connection, or a piston seal going bad?

 

No evidence of any external leaks at all, Brandon, so whatever is "leaking by" is doing it internally. With all the hills around here and the driving I've been doing, i would have lost all my fluid in a couple of days if there were an external leak, because I can go through the equivalent of two full pedal strokes at a single steep stoplight.

I'll check out Y2K as well.

Thanks

 

UPDATED information....

I tracked down Raybestos ($150 plus shipping) and Wagner ($171 plus shipping) parts from Rock Auto. Rock also carries A-1 Cardone and a few other makes.

I talked with some reputable machanics here in Birmingham who have done good work for me but knew up front I was going to do the MC myself, and the unanimous answer was "Ford parts only - the aftermarket ones are not as good, especially if they're made by A-1 Cardone".

Following Brandon's suggestion, I called Y2K Ford and am getting the new FORD MC delivered 2nd day air for $163, which means I will get it in time to do the job on Saturday (assuming that the brakes hold out that long, which I am expecting that they will).

Next question is... what's the best brake fluid?

 

I believe the DOT 4 is non hygroscopic(it doesn't hold water), and has a higher temp rating than the DOT 3. but my limited understanding is you cannot mix them, so you may have to stick to DOT 3 (or whatever is in the system).

I'll shut up now and wait for someone else to post up the real answer as I may be way off base.

 

No... you're right, Brandon. Changing over to DOT 4 would simply require a complete system flush, which I'll be doing anyway. The other potential downside of the DOT4, though, is that since it will not blend with (abdsorb) the water, there can (or will) eventually be "pools" of water in the system that will be undetectable unless they happen to show up in the MC itself... this means that I could get water in the system and have it stay there for quite a while being completely undetected. [ I did a lot of reading during lunch].

 

you normally have some water in the system anyway,I have tore down very few cylinders or calipers that didn't have rust pits in them from water

 

You guys are confusing DOT-4 with DOT-5 (silicone) fluids.

DOT-4 is completely compatible with DOT-3, mixes well with it, and is also hydroscopic, meaning it also will absorb moisture.

However, it has a higher wet boiling point, so it's still an improvement over DOT-3.

A complete flush is advisable, anyway.

My personal preference is Castrol GT/LMA DOT-4, and that's what's in mine.

DOT-5 isn't very compatable with any ABS system, as it easily entrains air.

Pop

 

Gosh... after all that reading I did at lunch and I still got confused. You're right, Pop. Thanks for the clarification. I guess it is a lot of information to try to crash into my brain in a short time. Thanks for the recommendation, too.

 

Hey Pete, I'm think'n that if you do all four powerslot rotors with hawk pads you will be impressed at how much quicker your truck stops. The difference is huge. I'm one for overkill when it comes to buying parts for my truck, and the SSBC calipers are definetly that. I love those things. That is until I saw the price. Which I can't remember off hand. But I do recall that they are very expensive. I really like how my truck stops and handles under extreme braking conditions with the PowerSlot Rotors and Hawk pads. Just off my own experience. Take Care. Country

 

OT, sorry Pete, Country, how is it going out there? are ya'll O.K.? Fires still moving away from you?

 

Do some research and find out what the bore is on your factory master cylinder. If up upgrade your master cylinder to one with a larger bore than your brake pedal will feel alot firmer. I know that on trucks with larger tires, upgrading your master cyl. can help out some. Good luck.