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Discussion Starter #1
Can a master cylinder go bad without leaking?
Other ideas as to the problem?

About a month ago, I pulled my 1990 from where it had been stored in the side yard for about two years (not driven). Backing out the brake pedal went to the floor, almost all the way. I pumped it and it came back some, but was still spongy. No leaks were apparent from the wheels or master cylinder. The only master cylinder I have ever had go bad was in a '62 Merc. where the MC actually leaked. The brakes have been functional, but not good for any quick stops.

So a week ago I see a leak from the right rear wheel. I am HOPING it is the wheel cylinder and my 'brake issue', not a repeat of that sides wheel bearing seal some years ago. Today I and a friend set out to replace the brakes and wheel cylinders on both sides. Yes it was the RR wheel cylinder leaking. All back together and the brake pedal still feels soft. :eek:/

This actually does make sense because the RR wheel cylinder did not fail for a week after I started driving it again, so it should not have been the culprit.

PS. I am excited to replace my front widow regulator gear plugs tomorrow and have working front windows again! :)
 

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I would check all the brake lines and make sure they are all ok, possibly may have some dry rotting. Also I would flush out all the old brakefluid from the system. Brake fluid can age and go bad over time and cause a spongy pedal. Also Yes the MC can go bad with out any external leaks. The internal seals can tear and when the pedal is pressed they can leak internaly. I would start with changing out the old brake fluid first.
 

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I had the same issue, except I bought mine like that. Pedal had way too much travel, spongy when pressed, took too long to stop.
I'm confident that there was a bad MC, push rod was in too far, and the pads were crap.

Here's what I did:

Replace rubber lines with stainless steel. [had little effect on braking, rubber lines were falling apart]

Bleed [little effect]

Bleed again [still no improvement]

Replace master cylinder, bleed again [significant improvement in final braking power, still a lot of travel in pedal]

Adjust booster push rod out [travel is reduced, brake power increased to nearly acceptable, heavy pull to left when braking]

Replace old pads with Hawk SuperDuty pads, clean and inspect rotors, clean calipers [BINGO - Brakes are now exactly as they should be, travel on pedal is perfect, no pull left or right when braking!]
 

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Discussion Starter #5
After changing both rear wheel cylinders I bled each until clear, clean fluid came through. Tomorrow I'll do the same for the front calipers. That will eliminate 'bad fluid' as a possible factor.
 

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After changing both rear wheel cylinders I bled each until clear, clean fluid came through. Tomorrow I'll do the same for the front calipers. That will eliminate 'bad fluid' as a possible factor.
Make sure you do your final brake bleed with the furthest caliper from the master cylinder first, so....(RR), (LR), (RF), (LF) it took that combo to get all the air out of my system and restore the firm pedal feel. That was after 3-4 attempts just bleeding it from front to rear......! :thumbup -Kevin-
 

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Like phobos said, Replace the flexible brake lines with SS lines. I got mine from Earls and it CURED my soft pedal for good, Cost about what stock replacment rubber lines would have cost anyways.
 

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Discussion Starter #8
HAH! from all the pumping and bleeding, I just noticed there is now brake fluid leaking from the base of the master cylinder. Very good. That answers my question on IF I should replace it as a possible reason for my spongy pedal. :eek:) Front caliper bleeder screws are rusted stuck. 7/16" and 11mm 12 pt box rounded hew a bit. Looking for remed to get them open. :eek:/
 

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After you soak them, if you use an open end wrench, use the round closed end not the open end. It grips better! Had to do the same thing with the 10.25 I just put in to bleed it. They looked like they were in there, and never loosened, since 91'..haha
 

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Oh yeah, in the future you should definitely use a 7/16" FLARE nut wrench... Ask me how I know. ;)
 

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Discussion Starter #12
Boy, I am now a big fan of PB Blaster. After two applications and it soaking an hour or so, I clamped the vise grips with all the strength in my hands, expecting it would want to slip on the bleeder screw. The bleeder screw turned without any fuss. On the other side, I did not bother to clamp it as hard. When I was done clamping it, I noticed it was was already loose as the weight of the vise grips had unscrewed it! ! That stuff is g -o -o -d !

I bench bled the new master cylinder and installed it. I'll bleed the system when I can get a neighbor to help.

I 'should' have bought a second quart of brake fluid yesterday. :eek:/ After my previous bleeds of the rear brakes and filling the new MC, I have about 16 oz in a newly opened bottle. I have a 12 oz 'opened' bottle that could be 10 + years old. They say to use fresh fluid, so this 12 oz. bottle probably fits the 'unfresh' definition. ;o). I'll probably try to save a 30 min round trip to the store by seeing if my neighbor has some (pretty fresh) brake fluid.
 

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Don't forget to buy about 50% more than you need. It saves you that extra trip to the store when enough just doesn't seem like enough.
Good luck!
 

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Discussion Starter #14
I did forget on my last parts store trip that too much is never enough. If my neighbor has none, I'm back to the store again. Dooough!
 

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Discussion Starter #15
As I am researching DOT 3 vs. DOT 4 brake fluid, I read:

" If you have ABS you may need to either leave the engine running or short out a test connector to ensure the ABS pump cycles while bleeding. This last part (ABS) will depend on you doing research on YOUR particular vehicle. " From...http://jimsgarage.wordpress.com/2007/01/09/dot-3-dot-4-and-dot-5/

The Ford manual mentions bleeding the Rear Anti Lock Brake Valve (after LR wheel), but says nothing further about the ABS. I just wanted to confirm here there is no special 'ABS bleeding' step.

Though I already have the MC filled with DOT3, I wonder if it it is worthwhile to buy 2 quarts of DOT4 to bleed thru the entire system?

Not a big difference, but... " DOT 3 brake fluid has a dry boiling point of 401 degrees while DOT 4 boils at 446 degrees. Dry boiling refers to new, unexposed brake fluid."
 
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