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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

Weak rear brakes

Old 04-04-2005, 11:53 PM
  #1  
frankd
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Default Weak rear brakes

I've got an 89 Mustang LX with a 302 and an automatic trans. The rear brakes seem extremely weak, although everything appears to be in good condition. With the rear wheels off the ground and the car in Drive, you have to push extremely hard on the brake pedal to stop the rear tires. The elderly gentleman at the air pollution test station couldn't get the rollers to slow down when that phase of the test came up.

I suspect the proportioning valve is limiting the rear brake pressure. How can I test this, and what kind of proportiong valve would you recommend for a replacement??
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Old 04-05-2005, 12:02 AM
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86HOGT
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Default RE: Weak rear brakes

If that's what you suspect, then get a stock replacement valve.
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Old 04-05-2005, 12:35 AM
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86gt5.0HO
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Default RE: Weak rear brakes

Before replacing parts, take take the drums off and make sure the adjuster isn't siezed. Then set the brakes up by turning the adjuster out a bit at a time untill the shoes have a tiny bit of drag on the drum.

Rick Nagel
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Old 04-05-2005, 04:01 AM
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bmorrisj
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Default RE: Weak rear brakes

get rear discs
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Old 04-05-2005, 12:50 PM
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69mach1377
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Default RE: Weak rear brakes

The fronts do 60-70% of stopping anyway, so just make sure your drums are working as designed...
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Old 04-05-2005, 01:39 PM
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Pure5.0
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Default RE: Weak rear brakes

Like 86gt5.0HO said...I would check it out first.

Since we have drum brakes there is an aduster that readjusts it's length automatically so that the pads will always have a certain pressure when the brakes are applied. Make sure they are working correctly and if not buy some new ones. They are really cheap. Plus just take the rear drum apart to make sure all the parts are working...they are a cheaper design than discs but they are more moving parts that disc. If one fails then the whole thing suffers.

Also like 69mach1377 said the fronts do perform most of the stopping power, but only if the weight of the car has shifted forward. If you are in a turn enertia will cause the weight to shift to the outside therefore creating more priority for the outside wheels to be the main stopping power. Which is one front and one rear.

I have a 97 silverado also and the back breaks don't work at all. The stopping distance is SIGNIFICANTLY reduced. It is a driving hazard because of the lack of stopping distance. It does make a difference when you rears are working properly.
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Old 04-05-2005, 02:19 PM
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vfast
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Default RE: Weak rear brakes

pull the emrg. brake one click see if stopping distance improves..if so adjust rear brake...foxes have terrible brakes...an upgrade of front caliper to 86svo ones is a must
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Old 04-05-2005, 02:57 PM
  #8  
90LX50
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Default RE: Weak rear brakes


ORIGINAL: 86gt5.0HO

Before replacing parts, take take the drums off and make sure the adjuster isn't siezed. Then set the brakes up by turning the adjuster out a bit at a time untill the shoes have a tiny bit of drag on the drum.

Rick Nagel
Also check the drums and pads for glazing, if either are glazed this could cause your problem as well.

I'd do just that, check them out, check the adjuster and possibly blled the rears to make sure you don't have air in your lines.
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Old 04-06-2005, 10:26 PM
  #9  
jwriley1
 
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Default RE: Weak rear brakes

I had identical problem with a 90 LX- called ford-no help. Thought Master might be bypassing-replaced no help. Replaced wheel cylinders for the heck of it and bled-no help, Saw a proportioning valve on ebay and put it in-no help. It is possible both p valves were bad but I took one apart and I don't see how they would fail. I don't know if it is a bad design or what. Thinking of removing the pvalve and putting in an adjustable one but worried about liability if I sell the car. Have you found an answer? Thanks, Jim
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