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Old 07-21-2012, 08:20 PM
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bruner1981jpce bruner1981jpce is offline
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Brakes getting worse and worse

These projects just don't stop. My brakes had been working fairly well up until recently. A few weeks ago, the Jeep could stop well, although it concerned me that the brakes didn't start to slow it down until the pedal was about 2/3 of the way to the end of travel. Now, even when I'm going just 15 mph, if I mash on the brake pedal, the jeep rolls another 10-15 feet before it actually comes to a stop. Pumping the brakes doesn't help. I was talking about this a little at the end of my cam swap thread and decided to start a new thread just for this. So far, I have been told the MC may be going bad; check/replace the rotors, pads, shoes and drums and hardware (did that all about 3-4 months ago); and I was going to bleed the brakes. What do you all think?

Different question: my brake pedal does not travel all the way to the floor. It hits its end of travel a couple inches from the floor. Is this normal for these Jeeps? My dad is very concerned about that and I'd like to know what the deal with it is. Thanks!
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'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

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Old 07-21-2012, 08:57 PM
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talntar talntar is offline
 
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master is going i would bet
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85 gw 215k and still going
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She can dance a Cajun rhythm,Jump like a Willys in four wheel drive,

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Old 07-21-2012, 09:04 PM
Ristow Ristow is offline
 
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check the adjustment of the rear brakes. and condition. loose rear adjustment will cause a lot of problems,including low pedal. also bleed them all. do this before throwing parts at it.
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Old 07-21-2012, 09:05 PM
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Quote:
Originally Posted by talntar
master is going i would bet


X2. Or brake booster?
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  #5  
Old 07-21-2012, 09:25 PM
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bruner1981jpce bruner1981jpce is offline
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Quote:
Originally Posted by Rich88
X2. Or brake booster?
i replaced the brake booster about a year ago. wouldn't it make the pedal stiffer if the booster were going?
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Andy
'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
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Old 07-22-2012, 12:54 AM
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Put the parking brake on while driving @ 5 mph then try to stop.

Did the brake pedal travel decrease and truck stop better?
If yes, you need to adjust the rear brakes.
If no, your master cyl. may be going bad.
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  #7  
Old 07-22-2012, 12:23 PM
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bruner1981jpce bruner1981jpce is offline
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Quote:
Originally Posted by babywag
Put the parking brake on while driving @ 5 mph then try to stop.

Did the brake pedal travel decrease and truck stop better?
If yes, you need to adjust the rear brakes.
If no, your master cyl. may be going bad.
So I guess that means I need to make my parking brake hold the truck on a hill well first. Thanks for the instructions!
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'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
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  #8  
Old 07-22-2012, 12:37 PM
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The master cylinder is a two stage system.

The front breaks are one system, the rear is another.

When the peddle drops to half without becoming firm, usually you have a leak, which you must run all the brake lines to verify, or you have a by pass in the master cylinder, which requires replacement.

Crawl under and check all brake lines first.

If you replace the master cylinder, most parts houses have new and rebuilt. The new one is usually two dollars more... No core.

If you do put on a new MC, search Bleeding on site, the proporishing valve pin needs to be either compressed or pulled out, while bleeding the brakes.
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  #9  
Old 07-22-2012, 12:43 PM
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Quote:
Originally Posted by bruner1981jpce
So I guess that means I need to make my parking brake hold the truck on a hill well first. Thanks for the instructions!

If the parking brake holds on a hill, it does not mean anything in regards to the MC.

What he is saying, if you click a couple of notches on the parking brake, if it is working properly, and the pedal gets higher, your rear brakes need adjustment.
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  #10  
Old 07-22-2012, 12:49 PM
joe joe is offline
 
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Quote:
Originally Posted by bruner1981jpce
So I guess that means I need to make my parking brake hold the truck on a hill well first. Thanks for the instructions!
If your parking brake isn't working well pull the drums and look at the brakes. If the shoes are seriously worn you'll never get the parking brake adjusted. My guessing order would be 1. worn out brake shoes. 2. master cyl.
Diagnostics start with diving in and actually looking, checking, testing and not with ordering parts.
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  #11  
Old 07-22-2012, 02:20 PM
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bruner1981jpce bruner1981jpce is offline
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Thanks guys. Alright, so I'll start with checking the brake drum shoes, then I'll go to bleeding, and if nothing fixes it yet, I'll do the MC. I'll get going once it cools off a little this afternoon.
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Andy
'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
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  #12  
Old 07-22-2012, 03:49 PM
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Quote:
Originally Posted by joe
Diagnostics start with diving in and actually looking, checking, testing and not with ordering parts.

I usually dont go in that order for something like brakes. I like to have everything that I MIGHT need on site. Then, when its apart I can replace it if it needs replacing. There is nothing I hate more than having to go to the parts story once I already start working.

When Im done, if I dont use some of the parts, I just return them or put them on the shelf for next time.

In this situation, uless the pads, shoes, rotors, drums, MC, ect have been changed recently, I would have them ready to go along with fluid for bleeding.

Thats just me though...
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  #13  
Old 07-22-2012, 03:56 PM
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bruner1981jpce bruner1981jpce is offline
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Pads, shoes, rotors, drums, wheel cylinders and drum brake hardware have all been replaced within the last few months, brake booster was done close to a year ago.

Would I be able to tell if the MC is going bad while bleeding the brakes? Would the amount of fluid that passes out be less than normal? Thanks guys!
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'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
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  #14  
Old 07-23-2012, 05:15 PM
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bruner1981jpce bruner1981jpce is offline
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So I went out to go fix the parking brake today (which then went out and almost hit my mom's friend's car, but thats another story I'll tell if there's interest in it). Anyways, I stepped on the brake pedal with the engine not running (vacuum booster) and the pedal was fairly easy to press. I've driven around with the booster not connected before so I know what it should have been like. Pumping the brakes didn't make it any stiffer either. If there was some air in the lines, wouldn't the master cylinder have added more brake fluid to the lines and compressed the air further until it stiffened up? What do you guys think?
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'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
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  #15  
Old 07-24-2012, 12:25 PM
JeepWrencher JeepWrencher is offline
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You are correct if it was just air in the lines you would have, eventually, felt a better pedal just like when you bleed the lines and you know there is air in them.

If you get no pressure increase at all it means that you either aren't building pressure, master cylinder, or you are losing the pressure as fast as it builds, leak.

Eliminate the simplest first and check for leaks in the front pair of rubber hoses and also the rear rubber hose. You didn't mention that they had been changed with the rest of the stopping gear. It may be something that looks fine normally but if you are under the vehicle and someone steps on the pedal you may see leaks that only appear under pressure. Also, while your friend keeps mashing the big pedal check all of the hard lines and junctions. After the hoses and line check both rear wheel cylinders and both front calipers. I know it sucks but tear the brakes down to check for this don't just look at the inside of the wheel and call it good.

At that point you could check the volume that the MC is putting out to the various corners but it could be that the MC won't fail unless the system is pressurized.I lean to the MC being bad with the others here, just want to make sure youdon't waste any $.
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Old 07-24-2012, 12:30 PM
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bruner1981jpce bruner1981jpce is offline
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Quote:
Originally Posted by JeepWrencher
You are correct if it was just air in the lines you would have, eventually, felt a better pedal just like when you bleed the lines and you know there is air in them.

If you get no pressure increase at all it means that you either aren't building pressure, master cylinder, or you are losing the pressure as fast as it builds, leak.

Eliminate the simplest first and check for leaks in the front pair of rubber hoses and also the rear rubber hose. You didn't mention that they had been changed with the rest of the stopping gear. It may be something that looks fine normally but if you are under the vehicle and someone steps on the pedal you may see leaks that only appear under pressure. Also, while your friend keeps mashing the big pedal check all of the hard lines and junctions. After the hoses and line check both rear wheel cylinders and both front calipers. I know it sucks but tear the brakes down to check for this don't just look at the inside of the wheel and call it good.

At that point you could check the volume that the MC is putting out to the various corners but it could be that the MC won't fail unless the system is pressurized.I lean to the MC being bad with the others here, just want to make sure youdon't waste any $.
Thanks. I've already checked for leaks and all looks good, so I'm rebuilding the MC today. Would you guys recommend rebuilding or replacing the MC?
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'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
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Old 07-24-2012, 12:42 PM
Ristow Ristow is offline
 
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have you checked rear brake adjustment yet?
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Old 07-24-2012, 01:33 PM
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Quote:
Originally Posted by bruner1981jpce
Thanks. I've already checked for leaks and all looks good, so I'm rebuilding the MC today. Would you guys recommend rebuilding or replacing the MC?

i would just replace.the savings if rebuilding aint worth it to me
25 bucks ain the zone
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85 gw 215k and still going
castrated(de-wooded)360 2" espo springs 31x10.5
89 gw,free,almost legal

She can dance a Cajun rhythm,Jump like a Willys in four wheel drive,

the world is full of kings and queens who blind your eyes and steal your dreams

"Our militarized "law enforcement" has become the standing army our founders feared"
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Old 07-24-2012, 02:48 PM
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bruner1981jpce bruner1981jpce is offline
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Went ahead and got a new MC. Bench bled the first port and about half of the second port, and then my thumb got real sore. My vise isn't mounted on anything so I had to grip the vise with one hand and use my thumb to press the piston while my other hand plugged the ports on the MC. Now I'm just waiting for my assistant to get home.
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'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
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  #20  
Old 07-24-2012, 06:53 PM
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bruner1981jpce bruner1981jpce is offline
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Brakes are fixed. A new MC and a full system bleed did the trick. Thanks guys!
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'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
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