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NERD
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Discussion Starter #1
I've been asking around and searching for 2 weeks on this. I know most people swap out the MC for a larger one, but I'm not sure if that's the problem. I swapped in a HP44 and 9" with discs all around. I had a 30/44 with discs all around before the swap and the brakes worked great. Do the bigger axles require a new MC? I can't get pressure after I bleed them. It's all stock, with the prop valve and everything still attached. Some say to take an o ring out and some say the take off the prop valve. Others say to thread out the screw inside the MC to make more pressure.

Can someone try to clarify what the problem is? I spent 8 hours last weekend bleeding this damn setup only to be in the same place I am now. I flipped my calipers to make the bleeder valve on top, so that's not a problem either. I have ANOTHER TJ MC ready to drop in but if I need a bigger unit, I'll do it. I just want to make sure it's not something else. Anyone have ideas? I've searched through countless threads and asked other members and no matter what I try it still doesn't help. After I bleed it, it's spongy and has some pressure. Then when I start the Jeep it goes all the way to the floor again. :mad3: I'm at a loss, please help me out guys :shaking:
 

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NERD
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8,624 Posts
Discussion Starter #3 (Edited)
Yep, and a lot of 'em go with a 3500 MC, which is what I'm thinking of trying next. It sounds like it can't pump all the fluid to the calipers, especially with the booster powered up. I'm going to try pumping up the pressure and slapping it in neutral to see if the little pressure it has when not running will stop the Jeep.

EDIT: I meant the Dodge 3500 MC. They're a bit pricey here at Schucks ($120+) but I might just order one from RockAuto. Still searching for a part #...

Anyone else have suggestions and ideas? I'm so damn tired of this, it's the only thing keeping me from finishing and driving my TJ! :mad3:
 

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What calipers do you have front and rear? On my Tj I have chevy 1/2 ton in front and ford explorers on rear with the stock mc and 4 wheel disc proportioning valve from a newer tj with discs. Before I changed the vavle my pedal was on the floor.
 

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165 Posts
sounds crazy

Make sure your calipers are not on the wrong side. Bleeders on top!!! This sounds odd but i had a buddy have this problem on a Ford 8.8. (they are reversable, not sure about your set up)
 

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NERD
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8,624 Posts
Discussion Starter #6
Ford 3/4 ton calipers in front and I think they're ford or chevy calipers in the rear. I flipped the calipers already, that's not the problem.

I'm 99% sure it's the MC. I've ordered a 99 Dodge MC (1500 2500 or 3500, all the same) and it should be here tomorrow. It's brand new, with the resevoir. I had the TJ in neutral and with the engine off it held the Jeep in place. So it must be the MC....
 

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NERD
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8,624 Posts
Discussion Starter #7 (Edited)
Swapped in the Dodge MC and took the spring and o ring out of the proportioning valve - still no pressure when the engine is running. GREAT pressure when it's not. I'm going to try bleeding it again and then a pneumatic bleeder.

I isolated the rear brakes and just had the front being pumped. They work, but they're weak. They stop the Jeep fine, but not in a hurry. The pedal is firm and only goes down slightly. I think the rear end has an air leak. I need to re-plumb them anyway since the lines are too long and meant for a D44.

I need help with that part though. I was thinking of using vinyl lines but I already have some braided pieces going from the calipers to the axle. My calipers didn't come with the banjo bolts so I had to buy some off ebay. Locally, nobody had them in stock. I believe the banjo hole is too high for my calipers since I had to use a few washers on one side.

If I have to, I'll order new everything, even calipers. I would like to start with the lines first though. Can anyone point me in the right direction?
 

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i am a noob

i am a noob when it comes to all this but i remember reading that if the pedal was real soft after a m/c change that the booster may be to small or in need of repair , and or still got air in the lines .
 

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T, sent you a pm back. It still sounds like residual air could be in. Did u bench bleed the 3500 MC, or pedal bleed? I am assuming both front and rear calipers are single piston. I am running a prop valve in the rear, and the front I did the same you did, bypassing the internals on the stock MC. after you removed the bleeding nut on the MC to remove the centerpin coil and o ring, did u weld the nut end? on mine, it had a hole, press the brakes and fluid everywhere :D so just checking

also after turning the engine off, ho many pedal pumps until the pressure builds up, over 3? how doe sthe pedal fel, spongy or totally drops?
 

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Ok, First of all if you had to stack washers you have the wrong banjo bolts which could be causing part of the problem but not all of it.

If your still using the drum prop, you are gettting a 10lbs residual in the rear and a 2lbs in the front for disc which sucks for discs in the rear.

I would start by getting a line pressure gauge (summit sells them) and put it in line, See what your pressure is front and back, look up what it should be for that specific application according to the brake caliper not the jeep it self. This will tell you two things. 1. if your getting enough pressure to the brakes. 2. if there is an air leak or not.

3, 8 hours to bleed any system is crazy. spend the 100 bucks for the motive power bleeder on summit, I have bleed entierly new systems, (New lines,New master, New calipers, NEW) in less then 20 mins.

did you bench bleed the master?
Are the calipers moving at all?

If you increased the MC size to accomidate the bigger brakes I would first start by removing the poportioning valve from the equation. Then eliminate each circuit at a time to see if its overall or just the fronts or the rears.

And just because I didnt see it mentioned, you are running steel lines everywhere except for rubber hoses to the calipers off either a tee or hard line?
 

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NERD
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8,624 Posts
Discussion Starter #12 (Edited)
T, sent you a pm back. It still sounds like residual air could be in. Did u bench bleed the 3500 MC, or pedal bleed? I am assuming both front and rear calipers are single piston. I am running a prop valve in the rear, and the front I did the same you did, bypassing the internals on the stock MC. after you removed the bleeding nut on the MC to remove the centerpin coil and o ring, did u weld the nut end? on mine, it had a hole, press the brakes and fluid everywhere :D so just checking

also after turning the engine off, ho many pedal pumps until the pressure builds up, over 3? how doe sthe pedal fel, spongy or totally drops?
I pedal bled the system. I am new to brakes, but I'm pretty sure they're single piston since it's a HP44 and 9". I didn't see any leaking and there was no hole in that nut, so I think I'm good. :D Sent you a PM back.

Yes, over 3 or about that. It's spongy after that.

You're not getting ANY pressure?
With the engine on, hardly any. After it's off, I have to pump it.

Ok, First of all if you had to stack washers you have the wrong banjo bolts which could be causing part of the problem but not all of it.

If your still using the drum prop, you are gettting a 10lbs residual in the rear and a 2lbs in the front for disc which sucks for discs in the rear.

I would start by getting a line pressure gauge (summit sells them) and put it in line, See what your pressure is front and back, look up what it should be for that specific application according to the brake caliper not the jeep it self. This will tell you two things. 1. if your getting enough pressure to the brakes. 2. if there is an air leak or not.

3, 8 hours to bleed any system is crazy. spend the 100 bucks for the motive power bleeder on summit, I have bleed entierly new systems, (New lines,New master, New calipers, NEW) in less then 20 mins.

did you bench bleed the master?
Are the calipers moving at all?

If you increased the MC size to accomidate the bigger brakes I would first start by removing the poportioning valve from the equation. Then eliminate each circuit at a time to see if its overall or just the fronts or the rears.

And just because I didnt see it mentioned, you are running steel lines everywhere except for rubber hoses to the calipers off either a tee or hard line?
I was "told" they were the right bolts. Being a brake newb, I didn't know this but I figured so after having problems getting them to seal. The fronts are fine, however.

With the stock prop valve o ring and spring removed, should it be a problem? A local shop here should have a pressure gauge I can use but see below because I may not need it. Also, the same shop has a pneumatic bleeder that I can use.

I pedal bled it. I'm not sure on the rears, I need to check them to see if they're moving. The fronts, however, I'm certain are moving. I blocked off the rear from the MC and tried the fronts. Sure enough, they worked and held. They weren't very strong and wouldn't lock up, but they would stop the Jeep, even at slow speed and in gear. All my lines on the frame are stockers. On the axles, the fronts are Rubicon Express braided, like the ones in the long arm kits. The rears are hard line on the axles with braided to the calipers. I need to replace the steel line with new line because it was meant for my D44 I had in there before. I was using it temporarily and wanted to get the brakes done to make it easier to finish up other nick nacks. And yes, there's a T fitting on the rear axle.

With the rear blocked off, the pedal is high and only goes down about an inch or so. Is this normal?

I hope this answers everyone's questions. Thank you all for helping me. :grinpimp:
 

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I would start by rebleding everything, do not forget to confirm if the nut in front of teh MC has been welded shut 9it has a breather kind of thing. I posted on my thread on welding that up, since I had no idea it would splurge fluid after removing the prop internals:D

My HP 44 had dual pistons (front), shoudl be easy to see, two round "cones" on the caliper area. the reason I ask is for volume.

Even after sealing the rear off, you seem to stil have issue son the front axle. Sealed from the rear they most likely should lock easy. Also try lifting up the rig, spin your tires and have your buddy press teh brakes, one time slow, and one time pretty hard. See how it behaves.

Still seems to be something on the MC side though... I would disconnect the lines form the MC. re-bleed the MC, and keep adding fluid while you rebleed, let a good amount of fluid go through. I did not use the plastic bleeders on mine, just used lines to a container full of brake fluid and went to town.

Then re insytall fornt and rear lines, and bleed th breaks. I may be confused but in your pm it sounded like you bled the Jeep with the engine on? maybe I misread...

Good luck!
 

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NERD
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Discussion Starter #14
I bled with the engine off, then tested pedal pressure with the engine running.

I'll check all of that stuff when I get time this weekend, probably sunday. I'm going to *try* to get new lines put on the rear and source some different banjo bolts.
 

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a lot of people go with a YJ booster
Unless it's a 95 YJ, why would people want less booster on a system that needs more?

If they do swap in the 95, they are taking out the same thing they are putting in and an older one at that.
 

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What calipers do you have front and rear? On my Tj I have chevy 1/2 ton in front and ford explorers on rear with the stock mc and 4 wheel disc proportioning valve from a newer tj with discs. Before I changed the vavle my pedal was on the floor.
You solved another problem you had with air in the system when you changed out the combo valve.

Jeep has run the same valve in the TJ from 97 to 05 when they came out with the Unlimited.

The way they compensated for the rear bias being higher started in 00 by removing a strip of lining from the rear shoes so they could run the same valve drum or disc rears.
 

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I would start by rebleding everything, do not forget to confirm if the nut in front of teh MC has been welded shut 9it has a breather kind of thing. I posted on my thread on welding that up, since I had no idea it would splurge fluid after removing the prop internals:D

Good luck!
When you remove that nut with the what looks like a bleeder on it, all you have to do is remove the small o-ring from the brass plunger and put the plunger back in place.

Disables the proportioning and still seals the front of the combo valve, no welding required.
 

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I went through 3 brand new 3500 MC's, and all had a bad internal seal. None of them would bench bleed. The 4th one was good. If your getting them from AZ, or Discount or whatever, make sure you bench bleed it thoroughly. And the $69 for a Summitt Proportioning valve is money well spent. I have the same set-up as you and the stock combo valve was use-less due to the difference in caliper piston diameters I have. Good luck with it.
 

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I went through 3 brand new 3500 MC's, and all had a bad internal seal. None of them would bench bleed. The 4th one was good. If your getting them from AZ, or Discount or whatever, make sure you bench bleed it thoroughly. And the $69 for a Summitt Proportioning valve is money well spent. I have the same set-up as you and the stock combo valve was use-less due to the difference in caliper piston diameters I have. Good luck with it.
got a link to that summit prop valve?

this one?

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SSB-A0707P&N=700+115&autoview=sku
 
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