Leper
1/2 ton status
mlaux said:
Good thought, but no, the bleeders are on top. That reminds me of when I went 4 wheel disc on my 71 Duster. 4 piston calipers at all 4 wheels. Now that was a PITA to bleed.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
HELP..... Disc upgrade problems
- Thread starter Leper
- Start date
Good thought, but no, the bleeders are on top. That reminds me of when I went 4 wheel disc on my 71 Duster. 4 piston calipers at all 4 wheels. Now that was a PITA to bleed.
BigCountryx
1/2 ton status
Leper said:
http://www.buckeyetriumphs.org/technical/Brake%20Bleeding/Power%20Brake%20Bleeder.htm
That's what gave me the idea. I used an old MC lid and used a barbed connection to attach the tubing. I used long enough hose to reach all 4 tires so I could pump as I bleed. It doesn't take much pressure and if not careful, you will leak fluid past the MC lid seal and onto your freshly painted D60 and eat all the paint off of the knuckle. Oh wait, that was just me, lol.
Rhinopkc
1/2 ton status
Leper said:
You have the pump to inject fluid at the calipers? That's your best bet. Reverse power bleeding will save you a lot of time and headaches.
Leper
1/2 ton status
Reverse bleeding didn't work. The 1 ton MC I bought didn't fit because the vac port on the booster hit the MC. The only thing I havent done is to remove one pad from each rear caliper and let the piston come out some and try bleeding that way. Mabey there is an air pocket stuck in one of the rear calipers.
I will try that Tuesday. I am burnt out right now.
I will try that Tuesday. I am burnt out right now.
- Joined
- Mar 3, 2000
- Posts
- 9,120
- Reaction score
- 7,073
I had problems with my brakes also. We bled like crazy I am talking a gallon and a half the last time, thought we had it right and about the time we were about to quit the pedal would go soft. I gave up and took it to a mechanic friend. They reverse power bled by injecting at the cylinders as talked about earlier and they found a couple leaking fittings.
These fittings never ever leaked for me but evidently were taking on air. Mine is 1 ton master and booster, wilwood adjustable proportioning valve and a 2 pound residual pressure valve in the rear line. 14 bolt full floater rear and 10 bolt front. I was told that without the residual pressure valve the rear calipers will back off too much and that will cause problems.
Hope I didn't muddy the waters too much.
These fittings never ever leaked for me but evidently were taking on air. Mine is 1 ton master and booster, wilwood adjustable proportioning valve and a 2 pound residual pressure valve in the rear line. 14 bolt full floater rear and 10 bolt front. I was told that without the residual pressure valve the rear calipers will back off too much and that will cause problems.
Hope I didn't muddy the waters too much.
If your brake light is coming on, your proportioning valve is seeing an unusual pressure differential front to rear. It should NOT come on unless there is a problem with pressure on the front or rear hydraulic circuit.
Leper
1/2 ton status
After the reverse bleeding, no more light. Still not much pedal though.
70jimmy said:
This is what I was thinking about trying, I know the residual valves are designed to keep fluid from running back up into your resevior if its mounted below the calipers. But I was thinking that if I was to install a residual valve on the rear circuit that may keep the pressure on the rear just slightly and keep the pedal from dropping so much. I think a 10 pound valve would be too much but a 2 pounder might keep just enough fluid pressure on the rear that the calipers will not back off too much.
Hey Leper, will your truck stop by the time the pedal reaches the floor? Mine will start to lock up the tires but not until my pedal travels almost all the way to the floor. And the pedal is not real firm through the stroke. Have you thought about that residual valve? This is something I think I am going to give a shot unless someone really thinks it wont work.
What port goes to the front brakes on the mc? I noticed that with the 3/4 mc the rear circuit moved almost half as much fluid as the front circuit did. (I took the lines off and kind of "bench bled the mc on the truck" However I was real careful to make sure I took the pedal down barely at all because I didnt want to damage anything in the there)
G
goldwing2000
Guest
I'm thinking it's a combo valve problem (metering/proportioning valve). With a 4-wheel disc system, you shouldn't even need a proportioning valve, so bypassing it would be the way to go.
Disc systems require a lot more fluid than drum systems (hence the larger MC reservoir for disc brakes), so a metering valve is going to hold back on the fluid to the rear drums in a mixed system. By bypassing the valve, you should get full flow to the back brakes and it should bring the pedal up.
If you're experiencing rear lockup after that, then you can put in an adjustable valve to tweak it back to where you need it.
Disc systems require a lot more fluid than drum systems (hence the larger MC reservoir for disc brakes), so a metering valve is going to hold back on the fluid to the rear drums in a mixed system. By bypassing the valve, you should get full flow to the back brakes and it should bring the pedal up.
If you're experiencing rear lockup after that, then you can put in an adjustable valve to tweak it back to where you need it.
Leper
1/2 ton status
All good replies guys. The proportional valve I have is for disc brakes F/R. I know it could be bad, but the fact that it didn't change anything leads me to believe it is good. My next step is going to be a MC from a 1985 3500. If that doesn't work after I bleed the rears like I mentioned earlier, I will be officially out of ideas. I would prefer to keep the prop valve because this is my sons truck. That is a last resort. What I may do, if nothing works, is to temporarily bypass the prop valve. What I mean is to run new lines to a "T" in the front and rear, like described above.
One question. Would it make a difference if I made the diameter of the 2 lines out of the MC the same size?
One question. Would it make a difference if I made the diameter of the 2 lines out of the MC the same size?
I have read all of this and I think you need the following.
I would install on of these propotioning valves, http://www.performancebodies.com/store/product.asp?dept%5Fid=310&pf%5Fid=8419
Then I would get a 1 ton master on, because the discs in the rear are taking way more fluid to get the brakes to activate. The one ton master should be a larger diameter and therfore push the desired amount of fluid and raise your braking feel with less pedal travel. You will however loose a little line pressure because of the larger diameter master. Don't worry about this pressure drop as you will make up for it with a little bit of extra push on the pedal.
One method that I have had good luck with is to fill the master and then just crack one bleeder and just let the thing gravity bleed, this is a good way to go if you are a one man operation. Reverse bleeding is the best way to go but not everybody has the ability do this easily.
I would seriously doubt that you need a residual pressure valve because the master is high enough above the caliper to have the required pressure at the caliper to keep the pads close to the rotor.
One way to look at it is you don't need a residual valve in the front system from the factory so why would you need one in the rear system now that they are basically the same.
The same size lines front and rear will not hurt anything.
Just my .02 and hope it helps.
I would install on of these propotioning valves, http://www.performancebodies.com/store/product.asp?dept%5Fid=310&pf%5Fid=8419
Then I would get a 1 ton master on, because the discs in the rear are taking way more fluid to get the brakes to activate. The one ton master should be a larger diameter and therfore push the desired amount of fluid and raise your braking feel with less pedal travel. You will however loose a little line pressure because of the larger diameter master. Don't worry about this pressure drop as you will make up for it with a little bit of extra push on the pedal.
One method that I have had good luck with is to fill the master and then just crack one bleeder and just let the thing gravity bleed, this is a good way to go if you are a one man operation. Reverse bleeding is the best way to go but not everybody has the ability do this easily.
I would seriously doubt that you need a residual pressure valve because the master is high enough above the caliper to have the required pressure at the caliper to keep the pads close to the rotor.
One way to look at it is you don't need a residual valve in the front system from the factory so why would you need one in the rear system now that they are basically the same.
The same size lines front and rear will not hurt anything.
Just my .02 and hope it helps.
Leper
1/2 ton status
That is a residual valve, isn't it??
Leper
1/2 ton status
New Question
What are the problems with not running a proportioning valve??
What are the problems with not running a proportioning valve??
Leper
1/2 ton status
If I get to a point where any of the brakes lock up I will be happy. Hell, I'd be happy with a quick stop from 10 at this point.miniwally said:
Leper
1/2 ton status
That's assuming I get enough grab to make them lock. No need for it if they don't, and you know how far from that I am right now.
Well my theroy still stands that you are not moving enough fluid with the master cylinder you have now. You need a larger master cylinder and at that point you are going to be locking up the rear brakes real easy and then you need the proportioning valve to turn the pressure to the rear down so they work better with the front.
miniwally said:
Thats true, I never thought about the front not needing it. This weekend I am going to pull out the proportioning valve and see if that helps the pedal feel. And if the back locks up too early then I can get the wilwood valve. Any suggestions as to how to go about bypassing the valve? Do they have "connectors" that will butt the lines together, this would probably be the easiest method for getting around it.
Leper, if you dont figure out what is going on with your system by this weekend I wll definitely report back here and let you know the results of my findings without the pv. Heres a few link that I found on google and from what it sounds we need a disc/disc master and get rid of the pv altogether.
http://www.mpbrakes.com/mpfaqmasters.htm
http://www.ecihotrodbrakes.com/brake_facts.html
Those sites have good info in them.K5er4Life said:
A proportioning valve is not going to change anything about how the pedal feels to you while braking. There are only two things that effect pedal effort:
1. Master cylinder size (diameter of bore)
2. Booster size ( This is our constant and for these discusions will not be changed and also will be assumed good)
Now you get into the fun part of braking systems:
You both want more pedal feel (stiffer pedal) higher in the pedal travel. The reason you want this is to engage the brakes into a hard braking situation earlier in the pedal travel.
The part about hard braking earlier in the pedal travel tells me that you are not moving enough fluid into the brakes to get the caliper to touch the rotor hard enough. You just run out of stroke and that is always a bad thing.
IF: the truck stopped fine with normal pedal travel but the pedal just felt light and spongy you would then reduce the amount of brake boost applied from the booster(read:major PIA).
But you want these two things:
Less pedal travel
More pedal feel
SO: you increase the bore and then you move more with less stroke which in turn makes the things feel harder earlier in the travel.
The downfall of increase bore size is the need to push harder to get the same pressure at the caliper.
I would think something with a 1 1/8" or so bore will put you where you want to be with a boosted system with your caliper piston diameter and desired pedal feel.
Just to give you an idea of sizing.
I have Ford dual piston calipers on the front of the buggy and GM single piston calipers on the rear. The caliper piston diameter is about the same between the two and I run dual 7/8" masters on a Wilwood non boosted 6.25:1 pedal with good results. I have to get all over the brakes in a panic stop but they work and I think work well.
Clear as Mud??
