Spongey brake pedal after replacing hoses and calipers

Golden Helmet

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Heya fellas. Today's victim is the brakes, I had the bright idea to replace the front calipers and all the rubber brake hoses since everything is 24 years / 300k miles old. Everything was working just fine, but with hydroboost on the horizon I thought it'd be smart to make sure everything else in the system is fresh. In doing so, I completely ignored rule #1, "If it ain't broke, don't fix it," and now I know never to do that again. :backoff

Anyways. To keep it short, we put the calipers and hoses on, adjusted the rear brakes (I never ever adjust them, they've always worked fine), and then bled the #^&* out of the system, and we just could not get the pedal to feel like it did with the old parts. The pedal has virtually no resistance for the first ~75% of its travel (usually I start to get a great pedal feel at about 50% pedal travel), and now I have a sinking brake pedal. The truck stops pretty good, but the pedal feels like crap. My mechanic was convinced that it was my master cylinder (which was replaced 3 years ago), so we even tried a new master cylinder and it made no difference. We put the old one back on, and that's where it stands now.

I'm convinced that there is still air in the system, but the mechanic disagrees since we're not seeing any bubbles coming out of the bleeders. Tomorrow he's gonna bleed the system yet again, and if it still doesn't behave he's gonna play with the master cylinder rod (or vacuum booster rod?) and see if that gets some pedal back. In the mean time, if any of you guys have some thoughts I'd love to hear them, if it's not air in the system then I'm all out of ideas.

This is what I get for trying to get ahead. I could have just kept on ignoring the factory original rubber brake hoses, but noooo, I wanted to fix it before it broke. No good deed goes un-punished with this truck, I swear :rotflmao
 

MTKirk

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Sounds like a RABS problem to me, did you bleed it? They are a B*TCH to bleed.

Also; dirt particles can get in the valves in the unit & prevent them from sealing, so fluid leaks into the accumulator & pedal drops until it fills. You can try running a bunch of fluid through it to try & clean it out. Or replace it. Flush the system out good or it will just get goop in it again.
 

Golden Helmet

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We did bleed the RABS a few times early on, but I don't think we ever bled it in the correct order more than once or twice. I really wouldn't be surprised if air was hiding in here, I've heard the horror stories before but the mechanic didn't believe me when I said that these things cause all kinds of trouble. If the pedal is still wrong when I get my truck back, the RABS will be the first thing I go to. It was working fine this morning, but we did notice that the brake fluid in the rear was a noticeably different color than what came out the front. We let the fluid drain out until it started looking clean, but we didn't do an actual flush or run a whole lot of fluid through.
 

IDIoit

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first and foremost,
whoever made that rule up, is cookoo

i always try to replace things before they break!
i used to not mind road side repairs.
but im getting old and i want to work on my vehicles in comfort.

address the RABS like stated. and we all hope this fixes the issues.
i would not be messing with any of the hard parts like the brake rods.
there pretty much standard and youll do more harm than good.

the word "mechanic" always rubs me wrong.
youre paying someone else to do the work that isnt really hard.
sometimes its unavoidable, and a lack of space warrants them.
but **** certs are about as good as a liberal arts degree LOL
 

OLDBULL8

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First question is. What brake fluid did you use, DOT 3 - 4 or 5? Your brake system more than likely has DOT 3 in it.

Do not mix DOT 5 with DOT 3 or 4. To use DOT 5, you have to completely flush the system using about 2 quarts of it and make sure the MC does not go empty or even close to it, refill it after a bleed at each wheel. Use about 1 quart for the rear and RABS, then the other quart for the front.
Most "Mechanics" won't do that. Oh hell, I got clean fluid, that's good enough.


NEVER reuse any brake fluid again that has been thru the brake system. Throw it away.

DO NOT let that "Mechanic" screw with the MC rod adjustment, it was set just fine before when you had good braking, don't add a problem that didn't exist.

Changing the MC from OLD to NEW and then back to OLD, it's difficult to bleed the OLD again unless it's bench bled before replacing. Bench bleeding instructions should have come with the NEW MC.

As Said before, Bleed RR then LR then RABS then RF then LF.
 

no mufflers

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as posted you really need to bleed the master really well. I have not used them but i have seen a tool that pushes fluid up from the bleeders to the master and since air rises I assume it would work really well.
 

Golden Helmet

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We used DOT 3 fluid, that's what should have already been in the system. I'm getting the truck back after work today, I told the mechanic to just leave it alone. He's still convinced there's no air in the system, but I'll bleed the lines myself today and see what happens.
 

Waystro

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I replaced the master cylinder in my Sub 6 times before I found one that didn't leak
Might be your problem. Sounds like air in your system. Way we bleed my ford(and Sub) was one in cab
Pump Pump Hold
Open bleeder
Repeat as necessary
Enjoy your Breaks ;Sweet
 

Golden Helmet

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"No air in the system" my ass. I made a little brake bleeder with some clear tubing and a water bottle so I could see any bubbles that came out, and sure enough, there was a ton of air in the lines. I spent an hour bleeding the brakes, got it pretty close to good... and then the front of the MC went dry, because I'm the best. I started bleeding them again, but I ran out of extra brake fluid so the journey shall continue tomorrow.

Thanks for the help so far guys, I think I'm on the right track now. Maybe tomorrow I'll try not screwing up and we'll see how that works out :angel:
 

MTKirk

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"No air in the system" my ass. I made a little brake bleeder with some clear tubing and a water bottle so I could see any bubbles that came out, and sure enough, there was a ton of air in the lines. I spent an hour bleeding the brakes, got it pretty close to good... and then the front of the MC went dry, because I'm the best. I started bleeding them again, but I ran out of extra brake fluid so the journey shall continue tomorrow.

Thanks for the help so far guys, I think I'm on the right track now. Maybe tomorrow I'll try not screwing up and we'll see how that works out :angel:

When you're ready to start doing brake hydraulics the right way, get one of these.


http://www.motiveproducts.com/
 

riotwarrior

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I will see about some pics of my one man bleeder I made....has worked flawlessly for me.

Takes quite a bit of time but the end result has always been good tigjt brakes.

If I am impatient I can toss my vacuum setup on the dealio and go a bit quicker...

The Motive unit is easy to make if you get a pressure pot for vegetation spraying..aka fertilizer/roundup type sprayer.. and an extra MC cap and some fittings. Add a guage if need be...

JM7.3CW
 

OLDBULL8

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I feel like I wasted all that time typing in post #7. :rolleyes:

I'm going back to my Guitar practice now.:rotflmao
 

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