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Old 12-07-2012, 11:18 AM   #1
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Angry **PLEASE HELP!! Soft Brake Pedal!**

Hello, I recently purchased a 1983 CJ7 and am having some serious problems diagnosing the soft brake pedal I have. The Jeep has a 1989 Wrangler body, 1985 Wagoneer rear end/drum brakes, and 1986 Comanche front brakes. When the Jeep is off, I have plenty of resistance on the brake pedal but as soon as I start the Jeep, the pedal goes right to the floor. When I drive it, I do have stopping ability but if I put the pedal all the way to the floor it rolls a lot longer than it should before it stops.

I replaced the rear brake pads, checked the drums and calipers, and did the same on the front of the Jeep as well. Disc brakes in the front. I bled the brake system a few times, still the same issue. I replaced the master cylinder using a new one for a 1989 wrangler but that didn't help, so then I tried a master cylinder for a 1986 Comanche/Wagoneer since those are the brakes I have (both models use the same cylinder/have the same part #) and still having the same problem. Used new fluid too. I checked for fluid leaks, there are none. All of the bleed screws are facing up too.

I am lost, what else can I try? Is it possible it can be the proportioning (combination) valve? If not, what else is left??

I need some help please!!

Thanks.

Matt from Rhode Island.

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Old 12-07-2012, 12:28 PM   #2
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Bleed Order

Sounds like you still have air trapped somewhere. It's important to bleed brakes in order. Work farthest away from the master cylinder to the closest. Start with the right-rear wheel followed by the left-rear then the right-front and lastly the left-front.

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Old 12-07-2012, 12:50 PM   #3
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Sounds like air to me also. Did you have help bleeding them or use a 'one man bleeder'? Did you bench bleed the master cylinder before installing it?
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Old 12-07-2012, 01:02 PM   #4
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TJ-GTR,

Thanks for the advice - I bled them in that order multiple times. No luck. Are there any potential malfuntioning components of the brake system that I haven't tried yet that could be causing the issue?
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Old 12-07-2012, 01:05 PM   #5
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Div4gold,

When I did the brake bleed, yes I had help - It's at my mechanic right now and I would imagine he had someone help him bleed the brakes but I am not sure if he bench bled the master cylinder. I will check with him. I got a reman master cylinder do they ever come pre-bench bled from the factory?
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Old 12-07-2012, 01:17 PM   #6
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I don't think they are ever pre-bled at the factory. Let me get this right in my head. You have a dual master cylinder, disk front and drum back. The disk portion of the master cylinder shouldn't have a residual pressure valve in it where the drum portion should have. Did you remove the valve for the front brakes?
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Old 12-07-2012, 01:29 PM   #7
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I don't think they are ever pre-bled at the factory. Let me get this right in my head. You have a dual master cylinder, disk front and drum back. The disk portion of the master cylinder shouldn't have a residual pressure valve in it where the drum portion should have. Did you remove the valve for the front brakes?
Yes, dual bowl, front disc rear drum. I am confused - you said the disc portion of the cylinder shouldn't have pressure valve but you asked if I removed the valve for the front brakes? Unless I am reading it wrong, it sounds like you are saying there isn't a valve for the front disc brakes. Did you mean the rear?
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Old 12-07-2012, 04:26 PM   #8
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I don't know if the master cylinder for you front brakes had a residual pressure valve in it or not but if it did it should have been removed. The rear drum brakes require the pressure valve. The disks don't.
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Old 12-07-2012, 05:20 PM   #9
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what about the booster
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Old 12-07-2012, 05:22 PM   #10
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I don't know if the master cylinder for you front brakes had a residual pressure valve in it or not but if it did it should have been removed. The rear drum brakes require the pressure valve. The disks don't.
I will take a look and see if that works. If it doesn't work, I will have to see what else is going on.

Let me ask you this. Since I now have a reman master cylinder in there for the 86 comanche/wagoneer, I am wondering if the power booster that is currently in there is from a 1989 wrangler since that's the body thats on it. Do you think I should get a reman power booster for an 86 comanche/wagoneer was well? My initial reason for putting the comanche/wagoneer master cyl in there was because that's what i have for front/rear brakes. I am also wondering if the brake pedal and the parts/linkage that go up to the power booster could possibly not be the right one if the pedal is from an 89 Wrangler as well.

Just thinking out loud. Any thoughts on this?
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Old 12-07-2012, 05:24 PM   #11
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what about the booster
The booster is definitely something I will look at, just not sure which on I should get since this Jeep that I bought was pieced together. I didnt know how pieced together it was until after I bought it and started digging deep into it.
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Old 12-07-2012, 05:30 PM   #12
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I would think that the one for the wrangler because the bolt pattern will match and the arm will be right to attach to your pedal..comanche may be the same but I don't know
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Old 12-07-2012, 05:40 PM   #13
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If your mechanic has it now have him check the master cylinder for the front disk brakes to see if it has a residual pressure valve in it. Then again since your system is mixed you don't really know how the master cylinder came set up. It could have been for both front and rear drums or front disk and rear drums or all 4 wheels disks. Could you check with where you got the master cylinder and see how it was valved?

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