Hydraulic brake gurus..I NEED HELP!!!

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  #1  
Old 08-31-10, 06:40 PM
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Hydraulic brake gurus..I NEED HELP!!!

I'm about to go nuts.. just cant get this to work!

I have a 1953 F100 with a 77 Ford Granada booster and master cylinder, a GM Monte Carlo disc setup, and it worked flawlessly for 10 years... until the master leaked out the back.

I replaced the master and the brakes were perfect BUT, and I figured this out after 2 more masters, the mfg supplied the wrong lid and it poured fluid everywhere! I replaced the master again and accidently sucked the resevoir dry with a mighty vac, that was the beginning of my problems, I have had no brakes in front since!

Recently I bled the brakes over and over again, I then reverse bled the brakes over and over again, plenty of pedal with no motor, almost to the floor with motor. I checked the adjustment of the push rod and it is exactly right. With motor I have rear brakes kinda.

I have plenty of firm pedal with no motor, if I jack up the truck and roll the tires, I have front brakes. If I plug the booster vacuum line and pull out in teh driveway, I have 4 wheel brakes but manual and an expected hard pedal which to me eliminates the possibility of air in the lines. I have quite literally run 1/2 gallon of fluid thru this thing!

I have since removed the combo valve,TEEed the front, and put a manual adjustment for the rear to eliminate a shifting combo valve possibility.

The $1 question... can a booster cause this? My booster only has 6K on it but the rear seal on the master has recently blown. The booster has a weep groove and it leaked fluid out when the master went.

Correct me if I'm wrong... with or without vaccuum I should have the same throw on the brake rod? If the brakes work with no motor, they should work the same but easier with motor? If I had air in the line, the brakes would be spongy with no motor, if not spongy with no motor they should work with motor? The booster has an input rod and a spring that pushes a diaphram, on the other side is this actuator rod that pushes the master, there is no room for slop and it is basically direct coupled..right?

Is there a way to test a booster?

 
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  #2  
Old 08-31-10, 07:30 PM
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In truth, My gut tells me you flipped a seal when you sucked the master dry.

The booster, While yes , it can cause all sorts of Anomolies, Doesnt really cause hydro issues, unless the pushrod is adjusted too long.

Try this....Remove the lines from M/C...Cover the holes with Index and ring finger, and have an assistant push the brake pedal to the floor ...ONCE....Did you get an even amount of fluid from BOTH ports????
 
  #3  
Old 09-01-10, 04:54 AM
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I'll have to try that, here is more info... I removed the line from the front on the master since that is the circuit that isnt working. I plugged the port and confirmed that I cant push the pedal.

I'm not sure if I would get equal amounts of fluid from both reservoirs doing the test that you ask since the circuits and reservoirs are not equal due to the front disks. Would not the front circuit move more fluid normally?

I do notice that when I push the pedal I get a little fountain spout of fluid in the rear circuit reservoir that I don't get in the front reservoir. I have however looked at other vehicles and I believe this to be normal.

When you say flipped a seal, in the master? Keep in mind that the master on there now is not the same master that was on there when the dry reservoir happened.
 
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Old 09-01-10, 10:10 AM
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Originally Posted by HotRod53F100 View Post
When you say flipped a seal, in the master? Keep in mind that the master on there now is not the same master that was on there when the dry reservoir happened.
Sorry, misread that...I thought it was the same one.

As far as the fluid VOLUME.....It should be very close front to back. The Proportioning valve sends the predetermined amount where it has to go.
 
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Old 09-01-10, 12:53 PM
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A few different things could be going on here. Could even be a master cylinder issue. Will eventually get to the master as well. For now take this.

Is sufficient engine vacuum getting to the booster?
Is the check valve operational?
Does the booster hold vacuum? (Confirm with hand pump).


Try this first and post back results.


Run engine for 40 seconds and turn it off. Wait 40 seconds.

Remove check valve at booster if vacuum releases booster is good.

Run engine for 40 seconds and turn it off. Step on brake pedal and hold down. If booster is good pedal will stay down. If booster is bad pedal will either come back up immediately or after a few seconds.
 
  #6  
Old 09-01-10, 03:40 PM
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I have done a vaccuum leak down test and it appears to hold vaccuum. I did not know about the rest of your test.

We contacted the vaccuum booster company who believes that it is an air bubble, which has always been my opinion. I guess I'm trying to talk myself out of that because of the 1/2 gallon of fluid that I pushed thru it. I do however have a lot of curly pigtails in the lines, I think we will cut those out. I tried to tap them as I bled but it didn't help. My buddy says that he hadn't seen those many curly Qs in the last 3 cars combined!
 
  #7  
Old 09-02-10, 03:33 AM
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HotRod53F100,

There’s no magic bullet here. Since the system worked for 10 years, and is not working now, the problem is with the work you just did. Troubleshoot and rule out the basics first.

Brake fluid leaks.
Defective brake booster.
Defective master cylinder.
Vacuum issues with the booster.
Installation of defective or wrong parts.
Power bleed brakes.


Use a hand vacuum pump to confirm that the booster is holding vacuum.

Use a vacuum pressure gauge to rule out engine vacuum leaks.




The condition of the diaphragm inside the booster is also important. If cracked, ruptured or leaking, it won't hold vacuum and can't provide much power assist. Leaks in the master cylinder can allow brake fluid to be siphoned into the booster, accelerating the demise of the diaphragm. So if there's brake fluid inside the vacuum hose, it's a good indication the master cylinder is leaking and needs to be rebuilt or replaced. Wetness around the back of the master cylinder would be another clue to this kind of problem. To check the vacuum booster, pump the brake pedal with the engine off until you've bled off all the vacuum from the unit. Then hold the pedal down and start the engine. You should feel the pedal depress slightly as engine vacuum enters the booster and pulls on the diaphragm. No change? Then check the vacuum hose connection and engine vacuum. If okay, the problem is in the booster and the booster needs to be replaced. Vacuum boosters also have an external one-way at the hose inlet that closes when the engine is either shut off or stalls. This traps vacuum inside the booster so it can still provide one or two power assisted stops until the engine is restarted. The valve also helps maintain vacuum when intake vacuum is low (when the engine is under load or is running at wide open throttle). You can check the valve by removing it and trying to blow through it from both sides. It should pass air from the rear but not from the front.
 
  #8  
Old 09-02-10, 02:39 PM
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Did you bench bleed master cylinder? If Master has a tilt to it you will never get air out of it. Needs to be bench bleed first.
 
  #9  
Old 09-02-10, 05:33 PM
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Yes, I bench bled the master probably 5 times. My master sits level and the fact that I reverse bled up into the master I would think that it would have pushed any air out.

All good suggestions, keep them coming!
 
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