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Discussion Starter · #1 ·
So in my 91 T-bird I have just replaced the front end.
During the swap I had to disconnect a brake line, so I attempted to bleed the system and found the bleeders to be shot, so I replaced the calipers.

I have bleed the brakes, and bleed the brakes, and BLEED THEM.

And still no pedal.
I have brakes, but only the last two inches of my pedal are there.

During the proccess, I ran two quarts of fluid through the system (front only) to flush out the old crappy fluid. I had some one cycling the pedal while the fittings hung into buckets. I made sure to keep the resivoir full during the proccess. Before installing each caliper, I had my assistant press the pedal once to insure there was fluid in the ends of the lines. Then I opened the fittings and let the calipers fill, and went on to bleed them.


I got all the bubbles out, and tried the pedal and it just hisses (booster) all the way down to the floor and then catches at the bottom.

I bleed them again later, and no improvement.
Again this morning, I bleed them, no improvement.

During bleeding, I cannot use the engine for assistance. When I open the bleed valve, the pedal sticks to the floor and has to be pulled up. (returns on it's own after pulled away from floor)

The brake will pump up a little after five or so.
But the wierd thing is, If I hold the gas pedal down, they pump up in 2 strokes.
And they are also much much firmer when I do this.

So that indicates to me that the booster is probably shot.

It also seems that perhaps there is a scratch in the master cylinder wall before the last set of lines, so it doesnt build pressure until it passes the first set.

I can only assume that this came from crud passing through the cylinder during the flush.


This is the closest I can figure things, brakes worked ok (not perfect) before, now they are crap.
Also have new pads and rotors, just the be thorough.



I was wondering if there is an easy bolt on cylinder from another car that was larger. This one is the same size as my mustangs (though the valving looks different) and I think this car should have a little more behind it than that.

Plus I like my brakes stout, 4 the emergancies.


I am thinking about trying to refurbish the booster, and hopefully to obtain the master cylinder (if an easy upgrade exists) or if not, maybe try and bore this one a little bit and go with an oversized piston.

I doubt theres much space for improvement, but anything would help, and a rebuild kit might be cheap.


My only real 'question' other than the upgrade thing is this,
could the proportioning valve be clogged from the flushing as well?

I tried bleeding the rear wheels for giggles and didnt get any air, and they seems very stout, and where grabbing firmly.
I have rear drums, (for some god aweful reason) and assume that I do not have ABS, (dont have any lights anyway, but it might be burnt out, who knows)
But it looks like the lines do run through a proportioning valve to the driverside of the transmission somewhere on the frame.

I have to drive this car , and though Im not too nervous, but need to get this fixed up quick.

Any advice is greatly appreaciated, sorry for the huge 'tech report' but I wanted you guys to be able and let me know if I did anything wrong.
 

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Discussion Starter · #2 ·
Changed the master cylinder and no difference. Bench bled it, (so to speak, did it in car, but still same proccedure) and bled the wheels, and have exact same problem.

Neibhor friend (mechanic) thinks it's the booster. I'm hoping my mustang booster will work. He said it's okay that it's smaller as long as it is 4 bolt. I know the mustang had decent assist, so maybe it will work. I'm all out of ideas otherwise.
 

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yikes.. i have symptoms pretty similar.. but not as severe. lemme know how this goes.
 

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Discussion Starter · #5 ·
Badly so far. I replaced the booster with an OEM and I STILL DONT HAVE PEDAL!!!
It's different, but still isn't worth a s**t.

SOOO, I am about to gravity bleed it. If that doesn't fix it, the next thread will be

"91 5.0 Thunderbird for sale!!! needs brakes!"
 

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1. When was the last time you adjusted your rear brakes? I have OFTEN found that the Ford "self adjusting" rear brakes don't "self adjust" in any, way, shape or form!! :redmad: The symptom is what you are describing... low pedal, but better when you pump the brakes. How far down does your parking brake go?

2. When you installed the new master cylinder/booster did you make sure the plunger depth was correct?

Just my .02 :thumbsup:
 

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Discussion Starter · #7 ·
Parking brake is sufficent to hold the car. Pedal goes to the floor if desired.
My rear left drum was excessively easy to remove, I had pretty much FORGOTTEN that rear drums need to be adjusted! But, this problem came all at once.

I will adjust the rears, but I don't know if it's gonna help.
 

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Discussion Starter · #8 ·
Alright, now that I have tightened up the rear brakes and gravity bled the system my pedal is much much better. I think I still need to adjust the plunger on the booster though. I have about and inch and a half of pedal that doesn't do anything, and I want it sitting up top.
Does anyone know how the ratio works on that booster plunger?
I dont think I need to extend it the full inch or anything, but I really don't know what I need to do to it. Don't much feel like guessing at it and trying it 5 different times till I like it.
 

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There are some tools that are used to set the depth. One is just a piece of plate steel machined to specific measurements (which I can not find anywhere, but I think the measurements are listed in the manuals). The other (which I prefer) actually takes the measurement off the master cylinder that you then transfer to the booster.

Here's some general info:
http://www.classicperform.com/TechBook/BrakeTroubleshoot.htm

The rod only has to move a turn or two to get rid of 1" to 2" of pedal play. Just make sure you don't get it too tight or your brakes will drag and eventually lock up.

Good luck. :thumbsup:
 

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Any advice on how to stop crud from going down into the master cylinder? My brake fluid is long overdue for a flush. Should I just siphon it out and maybe wipe the reservoir with a clean rag?

Oh on a somewhat other note (possible PBR swap). When you remove the brake line from the caliper doesn't that cause all the brake fluid in the system to drain out? Should you put a stopper in there or does it only drip? I have always wondered this but have never had to replace a caliper. So if someone was doing the PBR swap for example, are you in danger of it going dry? Pretty basic question I know. Thanks.
 
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