I've been on the tail end of weak brakes since I bought my truck 3 years ago. I've bled the brakes, replaced the rotors and pad and flushed the hydroboost/pwr steering system with ATF but nothing has fixed it. Under normal operating conditions initially the truck will slow down ok, but gradually loses stopping power and needs more brake pedal pressure to come to a stop. When the truck is off I have very little pressure in my lines and alot of pedal travel with no pressurization when pumped. If I apply the parking brake while the truck is on it won't even hold it on a grade and does pretty much nothing when the truck is shut off.

Everyone I talk to seems to think it's the Hydroboost Cylinder, but everything I have experienced seems like that's the only thing getting my truck stopped from more pressure to the system. I noticed a "compressed gas" label on the side of the Hydroboost can someone explain to me what that is and if it leaked out the effects it would have on my braking both with the vehicle on and off? One of my buddies thinks that the gas leaked out and he believes it is responsible for keeping the system pressurized. Also do you think that a bad master cylinder would cause these symptoms?

 

Well I've seen quite a few posts on this exact issue, however nothing gets posted after a fix or people simply don't fix it.

I can't live with *****ty brakes any longer so I'm ordering both the Hydroboost and the Master cylinder, I can get both for under $300 and it looks super easy to install. I'll post by the middle of next week on results here goes nothing ........

 

I would like to hear your results when you get it changed out.As far as the e-brakes,you may need to check the shoes out on the inner rear.
I went for a long time with spongy brakes.I have flushed and install new rotors and pads.STILL spongy brakes.Not sure what happened after the 4th steering box change(long story) but now I have firm brakes.
Of course,the system has been flushed 4 times in 5 months.

 

I'm not sure what your problem is, but it sounds messy.
First, the emergency brake is a totally separate system - purely mechanical. The only adjustment is the shoe clearance to the drum - starwheel, as is typical in drums. To adjust it exactly requires disassembly, but you can use the "brake drag" method to get it to work. Haynes manual goes through the brake drag, Ford manual goes through measuring the OD of the shoes vs. the ID of the drums.
Hydroboost gives you the "power" in power brakes the same way the the vacuum booster does on a normally aspirated vehicle. Power steering pump runs the assist for the brakes, and I am not sure how it would fade over time. If it did, you might notice it in the steering, too.
I would normally attribute fade to pads and rotors, but you say that these are new.
An Anti-Lock malfunction would probably give pulsations (or at least an "ABS" light.
That kind of leads to the fluid.
Is the fluid clean and of the proper type? I remember putting synthetic in a vehicle that pretty much wrecked the brakes. All of the non-steel parts had to be replaced.
I don't recall the change interval on the brake fluid. Most American vehicles don't list this - more of a Euro car thing.
Never ignore the obvious - any leaks?
Also, the hoses need to be in good shape - the rubber ones can stretch, and the stainless over teflon aftermarket can leak without it being obvious.

That's enough for now.

 

The bit about a lot of travel and little pedal pressure when not running makes me think master cylinder.

Hopefully your new parts fix it, please post back with your results.

 

The "compressed gas" label refers to the accumulator part of the hydro-boost. It provides limited power assist when the main pressure to the system fails. Air in hydraulic systems, either in the p/s or braking system can cause "sponginess". Brake fluid should be replaced at least every 2 yrs. Moisture is absorbed into the fluid and cannot be purged. The moisture in the system will release air into the fluid when it boils due to heat and pressure.

 

QUOTE from above:Is the fluid clean and of the proper type? I remember putting synthetic in a vehicle that pretty much wrecked the brakes.


If you read enough here you will find that the proper fluid is ATF and most here use synthetic.

 

How is your power steering working?
It also runs off of the hydro-boost system and might provide a clue to which piece is at fault.
Let us know what the final fix is.

Good luck,

 

[quote/]If you read enough here you will find that the proper fluid is ATF and most here use synthetic.[/quote]


Sorry I wasn't clear - You are correct as far as the power steering pump/hydroboost is concerned.

I was talking about the brake fluid - usually referred to as DOT 3,4,or 5.

I'm not remembering which my truck took - I usually try to forget so that I look it up and not trust my memory. And I won't guess as far as what somebody else's truck takes.

The synthetic brake fluid swelled the (caliper seals). All were new, but locked up on me. Lesson learned the hard way - had to do the hydraulics over again.

 

I blew a rear brake line and replaced it.Bleed the brake lines got all the air out.Had spongy brake pedal. So replaced master cylinder thinking that was it, Did not help any. Lost for what is wrong, power boost, abs.Truck pedal starts out hard and good but fades and goes part way to floor Truck stops but pedal soft and not up like were it use to be. 2000 f-350 super duty 7.3 diesel

 

Subcribing

 

I'm having the same issues. I have an 02 and been battling weak brakes for years. I ran almost 2 gallons of fluid through the brakes to bleed them. It helped. But not fixed. It's weird my dad had an 03 and that thing would break your neck on a hard brake and had a solid pedal. I may replace the hydroboost and power steering pump see what that does.

I've read about bleeding the master cylinder itself and also the abs unit can cause problems. I've ready replacing the abs unit fixed the problem as well as / or the ps pump and/or hydroboost.


Good info
http://www.thedieselstop.com/forums/...e-pedal-31484/

 

FWIW....I've read on this forum, that the front rubber brake lines can deteriat and collapse with no outward signs. This issue can cause weak brakes.

 

I put Braided lines on .. didn't help. But that is true.

 

So Madmaxz, not to high jack the tread but what kind of power are you putting out with your setup. I noticed your rebuild motor in your sig., and like matt's cam also so the motor can breathe a little better. Thanks,

Chet