still having brake problems:(

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63dartman

63dartman

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I've been trying to get a good pedal on my brakes for about two weeks now. I've swapped three master cylinders, first one was a remanufactured unit from autozone. Second one was a 15/16 bore from doctor diff and the last one is the 1 1/8 from doctor diff. All three have the same symptoms which leads me to believe my issue is not the master cylinder. I can pump up the brakes and get a good pedal that holds but if I release it for 5 seconds it goes to the floor with just a little pressure building at the end of the stroke. I have bled the system several times with a power bleeder from harborfreight. It is the unit that creates vacuum with a compressor hooked up to it. Works very well and I have probably bled close to a gallon of brake fluid through the lines. I even tried to gravity bleed all four corners. I swapped out the rear drums a while back for disc and have not had a good pedal since. Also using a wilwood proportioning valve to the rear brakes that was there with the drums.No visible leaks and I am stumped. I am going to swap all the lines in the near future it's the only parts that are not new and I'm thinking it can't hurt to put new lines in to replace the 50 yr old ones:) Wilwood disc up front that have been there for about three yrs with no issues. I can't help but think I am missing something:( Any help would be greatly appreciated. Sorry for the long post just wanted to make sure I give enough info.
 
sounds like fluid is bypassing in the system, are you using a factory proportion valve along with the wilwood one?

the factory ones require you to not allow the pedal past 1/2 way when bleeding, pressure bleeding is always the best way as air can get trapped in the lines on bends or parts that are higher then the rest of the system
 
I believe the master cylinder from doctor diff has no built in proportioning but not 100% sure. The wildwood is the only one in the system. No power assist, the weird part is that if I don't let off the pedal completely after pumping them up the pressure stays but if I release it the last inch or so it goes back to hardly any pedal after about 5 seconds. Almost feels like air is getting in somehow but I am at a loss on it. Also I've been bleeding the system with the pedal in the upright position is this wrong?
 
Have you got the calipers mounted so that bleeders are to the tops of the calipers?

Is it "using" (IE leaking) fluid?

When you do get a pedal is it actually stopping the wheels, that is, building pressure at the wheels?

I do NOT like vacuum or gravity bleeding. I fully believe in KEEPING positive pressure on the system. For me this means pressure bleeding "old school" which consists of a special cap on the master which applies air pressure to the master. The "pro" systems also fed additional fluid through the feed tube to keep the master filled

Either that or a "two man" operation where one pumps up the pedal to provide the pressure, and the other bleeds. CLOSE THE BLEEDER as the master gets to the end of the stroke, thus maintaining POSITIVE pressure.
 
I used a vacuum power bleeder. It comes with a bottle that sits in the master cylinder to keep it full. Starting at the farthest wheel I hooked up the vacuum bleeder to the wheel cylinder bleeder created the vacuum and cracked the bleeder to bleed each one. Every time I did this I left the pedal in the upright position which means that it was not depressed at all. I think that might be the issue, is it supposed to be depressed to the flloor during bleeding?
 
No you want the pedal up. I don't care what others say, I'd give up on the vacuum bleeder. Get someone to help and bleed with pressure, someone maintaining at the the pedal. Watch fluid level, add as necessary, and close the bleeder before the pedal "runs out."

You did not answer the question...............you have the calipers mounted with bleeders UP?
 
what 67dart is saying is completely correct, most times you will get nowhere with vacuum bleeding brakes, they need to be pressure bleed, either from pressure bleeding system or by old method with 2 people
 
Yes the bleeders are up on the rear disc. The front wildwood have 4 bleeders two on top and two at the bottom, one for each piston in the caliper I believe. Thanks for the advice on the vacuum bleeding. I have always used the old school method of bleeding with the pedal. I wanted to try the vacuum bleeding since it only takes one person:) Guess it's back to old school!
 
Hell I almost forgot. This is what, 4x disc? front disc? If it's rear drums, tighten up the adjusters and see if the pedal comes up
 
No it's 4 disc. I wasn't quite sure what you meant by bleeders up on the rear and I think I need to swap the calipers side to side. the bleeder is actually lower and behind the line that comes in.
 

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63dartman said:
No it's 4 disc. I wasn't quite sure what you meant by bleeders up on the rear and I think I need to swap the calipers side to side. the bleeder is actually lower and behind the line that comes in.
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Yes. You'll never get the air out the way they are installed now.
 
I cannot tell from that photo which end is up, but if the bleeders are lower than the line inlets, you need to swap 'em
 
thanks for the help. I guess I have more work to do. I'll start with the swap and go from there. Thanks again. I will follow up with the progress if any:)
 
system. No power assist, the weird part is that if I don't let off the pedal completely after pumping them up the pressure stays but if I release it the last inch or so it goes back to hardly any pedal after about 5 seconds.
Click to expand...

my gut instinct tells me the master cylinder pushrod might be just a smidgen too short...

http://chucker54.stores.yahoo.net/brakcylpuspa.html
 
You guys are AWSOME:wav: Especially 67Dart273!!! I swapped the calipers and just gravity bled about 3 ounces of fluid off each bleeder and I got friggen awesome brakes!! I can't believe it was something that simple:banghead: Many thanks to all that replied and got me going in the right direction.
 
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