Installed adjustable prop. valve....same thing!!!! - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-17-2002, 09:38 AM Thread Starter
 
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Installed adjustable prop. valve....same thing!!!!

I am completely done with my dana 44 swap except for this one minor thing. I put a scout d44 rear in and a 79 waggie front d44. When I step on the brake pedal the rear still locks up.

I installed the wilwood adjustable proportioning valve and I reduced as much pressure as possible to the rear wheels and IT STILL LOCKS UP!!!!!!!

I installed the valve after the stock valve on the single hard line going to the rear. I have replaced the master cylinder and blead it as well as the all the wheels. There's no air in the lines....just to much pressure on the rear line!!!!

I am missing something here....Should I try a different MC? If so, which one?

Please help!

Alec
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post #2 of (permalink) Old 12-17-2002, 03:16 PM
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Re: Installed adjustable prop. valve....same thing!!!!

I'm assuming [img]images/graemlins/blush.gif[/img] the porportioning valve is set for the correct breaking force, front to rear.

Questions:

1. Shoes correctly installed.
2. Adjuster correctly adjusted.
3. No grease on the drums?
4. No grease/oil on the shoes?
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post #3 of (permalink) Old 12-17-2002, 03:27 PM
 
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Re: Installed adjustable prop. valve....same thing!!!!

IM guessing here but,

the front calipers require alot more fluid to actuate than the rear cylinders, so the rears are acting FIRST.

what if you added a residual pressure valve on the the front line to hold some volume of fluid in the calipers? so that a slight addition of fluid would actuate them as well as the rear cylinders?

usually there are systems built into the master cylinders to counter act the different amount of volume required, maybe a restricter in the rear line, or different sized ports ( front/rear)

if you could discern any differnce in output of the 2 circuits on the MC you could reverse the hookups, connect the front brakes to the rear port of the MC and vice versa.

just some ramblings

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post #4 of (permalink) Old 12-17-2002, 05:32 PM
 
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Re: Installed adjustable prop. valve....same thing!!!!

1. Do you have a dual stage M/C (large and small chambers)
A. If yes,, does the rear brakes tie into the small chamber? (it should)
B. If no then there is your problem.
2. Are you using the porportioning valve in conjunction with the factory unit?
A. If no ,,Ok
B. If yes ,,don't
3. Have you tried to close the rear brakes off with the valve?
A. If no,,,close the valve andtry brakes rears should not stop. open small increments till brakes start to grab.
B.If yes,, then check your master cylinder
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post #5 of (permalink) Old 12-18-2002, 07:55 PM Thread Starter
 
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Re: Installed adjustable prop. valve....same thing

I am thinking about trying a MC from a 78 waggie with manual brakes. This unit is used on several J series and full size cherokees in the 70's. This unit had dual bowls but they are the same size instead of the front being larger than the rear. Do you think this would help?

Also...let me state a few observations...when I bleed the front lines I don't get the usual high pressure stream of fluid. I only get a small trickle. The rear line however gets a really high pressure squirt! If that makes sense.

Could something be stuck in the stock proportioning valve? Like a plunger or piston or whatever floats around in there.

Now here's another thougth....the MC I currently have mounted is one from a 78 CJ with manual brakes with the 11 in rear brakes. Would anything change if I switched to one for use with 10 in rear brakes. Also, if I change to a MC that is used with power brakes the resovoirs are swapped around. Meaning the one I have has the rear brake line connected on the front (small) part of the MC and the front line is connected to the rear (large) part of the MC. A power brake MC has these switched.

I have checked the adjustments on everything and it is all correctly adjusted.

The obvious problem here is that I need to have more fluid moved to the front wheels.

Alec
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post #6 of (permalink) Old 12-18-2002, 08:26 PM
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Re: Installed adjustable prop. valve....same thing

That slight trickle of fluid to the front calipers should give you a hint . Check the flex lines on the front real close , I'd bet they are collapsed internally . One way to find out is to take the flex line loose from the hard line at the frame hangar, and see if you get a lot more fluid . I go through this a lot with cars, those lines can cause weird things to happen , usually not releasing the brakes .
Sarge
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post #7 of (permalink) Old 12-18-2002, 08:32 PM
 
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Re: Installed adjustable prop. valve....same thing

absolutely what sarge said!

if you remove the lines from teh master Cylinder, and cover the engine bay with rags, then press the pedal, is there a differnce in the ouputs of the 2 ports?

if so, you need to reverse the lines or get another MC, if not youve got a collapsed line, or trash in the line to teh fronts.

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post #8 of (permalink) Old 12-18-2002, 08:45 PM Thread Starter
 
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Re: Installed adjustable prop. valve....same thing

Great idea on taking the lines loose from the MC. I'll try that all way down to the calipers. I did have the lines just hanging there for a year while I was building these axles, so maybe they have something in them too.

Thanks guys!!

Alec
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post #9 of (permalink) Old 12-18-2002, 08:50 PM
 
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Re: Installed adjustable prop. valve....same thing

remove them and blow them out, probably a dirt dauber or spider nest in there!

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post #10 of (permalink) Old 12-18-2002, 09:02 PM
 
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Re: Installed adjustable prop. valve....same thing

On my CJ the large reservoir goes to the front discs and the small one is for the rear. The reason is that the larger reservoir is needed to supply the large front caliper pistons.

I did a D60 swap in the rear of my CJ and found that the emergency brake cables were a little to short. This made it so that no matter where I adjusted my shoes, the brakes would still lock up quickly.

If you haven’t done so already, try removing your emergency brake cables and see if you still have the problem.
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