problems with brakes after rear disc conversion

[IrishCJ6]

Have lost having a good brake pedal after my rear disc conversion, no residual valve or proporting valve in use. Believe it's got to be my MC/booster combo. For those running after market 4 wheel discs what system or combo are you using.

Brakes front are SSBC conversion (Wagoneer/ 1/2 tonne pickup) 75mm piston
Brakes rear are Nissan/Suzuki conversion 38mm piston.

Using original 75 Jeep manual pedals so I think 6:1 ratio

Master cylinder/booster is what was on it when I got it, Mercedes 300d disc/disc. For those who followed my build will understand why the Merc stuff is in it.

I'm willing to change MC/booster setup if I know what I change to will definitely work.

Any help appreciated

 

[Torxhead]

I would think air in the master.

 

[IOPort51]

I had one heck or a time getting mine bled. I ended up making a plastic plate with a schrader stem on it and pulling a vacuum on the master fill. I was trapping it in the line between the master and the proportioning valve.

You say you are not using a prop valve?? you may not need a residual valve but you still need to shift the bias toward the front brakes. I recommend something adjustable, I still lock the rear up a bit before the front and will surely end up putting in an adjustable prop valve.

A lot more work than I had first thought, isn't that always the way it is?, but 4 wheel power disks ROCK!!

Do you know the diameter of the MC piston??

 

[73CJ]

I'm running Waggy calipers in front and 78 Monte Carlo calipers in the rear. 78 MC and a proportioning valve like:

http://www.summitracing.com/parts/sum-g3905?seid=srese1&gclid=COe_gaHtirkCFc4-MgodU2MAsA

 

[powdertwoplanker]

Have lost having a good brake pedal after my rear disc conversion, no residual valve or proporting valve in use. Believe it's got to be my MC/booster combo. For those running after market 4 wheel discs what system or combo are you using.

Brakes front are SSBC conversion (Wagoneer/ 1/2 tonne pickup) 75mm piston
Brakes rear are Nissan/Suzuki conversion 38mm piston.

Using original 75 Jeep manual pedals so I think 6:1 ratio

Master cylinder/booster is what was on it when I got it, Mercedes 300d disc/disc. For those who followed my build will understand why the Merc stuff is in it.

I'm willing to change MC/booster setup if I know what I change to will definitely work.

Any help appreciated

I know this is years ago, but I just did the ssbc conversion an having the same issue. Did you ever get yours resolved? What resolved it?

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[Lumpy Grits]

What corrective steps have you taken?
What's the vacuum reading at the PB port?
LG

 

[powdertwoplanker]

I'm not sure what the vacuum reading is at the PB. I stopped an got a gauge tonight to test/tell me. Unfortunately I probably wont be able to test until the 18. I'll keep you posted once i do test it.

As for what I have done, new master bled and bled the brakes. I was going to (an still might) replace the flex line from the hard lines but to do this, I will also have to replace the hard lines as the nuts are all pretty round. Is it possible to just cut off the ends an reflare the lines? Guess I look into that.

SSCB says that there is air in the line, I bench bled the master then used two different bleeding methods. I just can't see how there could still be air in the system. I'll be giving them a call tomorrow an see what they say this time.

I did notice today that if I get on the brakes hard the engine will die after I come to a stop. Almost like a cold carb, except that it would have been running for a while. Could this be a vacuum issue? Guess I see once I can look at it a little more. Another thing I noticed was that the brake fluid is not as clear as I think it should be for a complete flush. The back chamber (which is the front disc) is pretty clear and the front chamber (rear brakes) is a little hazy. I wonder if that's a sign to change all the lines

Scott

 

[Lumpy Grits]

Engine dying, says booster issue to me.
Bleed/flush again.
Bleed with someone working the brake-pedal this time.

LG

 

[hagar]

Make sure the caliper brackets are mounted properly and the calipers present the pads to the rotor squarely.
In other words, look for pad(s) that don't touch the rotor surface equally with full surface contact.

 

[powdertwoplanker]

Sorry it's been so long since I did an update. I got the brakes working pretty well now. Changed out the master for no reason, then took out the proportioning value. Still not really happy with pedal feel. But I think it has something to do with a small vacuum leak in the booster. But at least I can drive it an feel comfortable

Scott

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