Slick 60's

"My thoughts on the shoes and calipers were that they might be displacing fluid when being used in reverse. "
-----Please expand upon this concept. It's a bit too vague for me to get exactly HOW you are saying this could happen.

Yeah. it WOULD seem that there is a void that opens up somehow somewhere that has to get refilled. It just doesn't make sense though.
-----This idea just made me think- I should fail the brakes, then maneuver the truck into a level-ish position and pop the MC cap, and make somebody pop the cap and see what the fluid levels look like right then. might at least identify front or rear problem.

I'll get you guys some pics and a video clip or 2 tomorrow I hope. If I can find somebody to help me.

"also, you should have the lines going into the proportional valve like this: "
BAD PHOTO LINK it's a red X

My thoughts were along the lines of the shoes rocking because of a dissimilar arc between the drum and shoes or shifting because of a broken pivot or anchor pin. Or the calipers cocking because of a bad/broken pin or mount making the piston push in.
Most likely not the problem though.
Really sounds like its down to the prop valve adjustment/bleeding or MS anymore.

AHH. I really don't think dissimilar arcs is the problem, although that is a heck of an idea. The pads and drums have known eachother since they were all new. No strange wear patterns on pads or nasty heat traces in drums.

I did have a cailiper pin come almost falling out one time, but that had no effect on the issue at hand. it was it's own terrifying issue. At least that was a simple thing to fix. From then on, I have always made sure to seat the pin by tapping the allen wrench with a hammer.

PValve adjustment (as far as I am aware) should only affect the lockup point of the rear wheels in regard to the front. RIGHT??? It should not be able to cause something like this...
Now, it COULD be the culprit, just because of improper bleeding technique (ie not screwing the knob all the way down)... But that would create a hydraulic fault that would be All The Time, wouldn't it?

blackagatha wrote:"also, you should have the lines going into the proportional valve like this: "
BAD PHOTO LINK it's a red X

I had linked to it from FTE, I guess they killed it. I loaded it into my album, but I don't think it will help you as it seems you have a wildwood type.
the suggestion about the drum not fitting the shoes could be close. If they are not matching, there could be a significant loss of performance. I would think that there would be a noticeable lurch or clunk though, so I dunno...
I think I would just go ahead and have the drums turned, and install new shoes. They could be glazed. The only problem with that suggestion is that they seem to work when driving forward. (as long as the fronts are not doing all the stopping)

Your statement about running with the car prop valve makes me think more and more that your problems stem from not having a prop valve from a pickup on it, although I can't quite understand what it is doing. I think I would find a prop valve from a pickup, plumb it in, and see if your problem is gone or not.
Fred

I DID have a car valve. It's no more. I have my wilwood valve turned to 3/4 turn out, ALMOST full pressure. It locks the rears up right after the fronts, so I would say it is working properly.

I took some pics and videos. I May have trouble getting the videos to post. I'll figure something out...

MC

MC

Prop Valve 3/4 turn out


Left Front

Right Front

Left Rear

Right Rear

Rear splitter and hose
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On hill, pedal flat

Pedal released

another thought, do you have the spreader bar installed between the shoes near the top?

At this point, I think I would remove the prop valve (or turn it all the way to the least resistance) to see if it gets better. If it does, time to get a different valve. I am beginning to think the valve is providing too much restriction.

you know, this would be easier if it was grabbing and locking up or pulling when braking....

Videos


Backing out of a parking spot- 90 deg. 2-3 deg. uphill


Skidding- 20 seconds later. Proof that my brakes are not just screwed


I was WRONG. If I SLAM on the brakes going backward and up the hill, it smashes to the floor. like this:


I did not get a chance to pull the rear drums to take pics.
I will do that Wednesday if you guys want.

If you have good pressure going forward, it ain't the front disks.
The culprit is the rear brakes. I think you probably have the rear shoes mismatched and/ or in the wrong place. If the pedal goes flat, the plungers in the wheel cylinder are not pressing the shoes against the brake drum. You got something wrong in there.
Take it apart and check it out.
U@ss

yeah. I guess that would make the most sense. My reason to question that possibility is that it seems that would be a problem, regardless of how the truck is moving.... I'll tear them apart again, but I'll wager $20 there aint nothing obvious going on.
I had them open about a month ago. Other than being really dusty, everything seemed to be in order. I would believe all the brake dust to be an indication that they were working properly, or at least doing something... It had been under a year since the last time I had them apart and cleaned.
I blew all the dust out with the aircompressor, hung the drums back on, adjusted them with the spoon, and put it back for trial. there was no difference to be seen.

Oh. it does in fact lock up all fours when I crush the pedal.

BTW, I like the truck the way it is now.
U@ss

check the front calipers when turning all the way.on both sides.the caliper maybe hitting your suspension causing the pistons to go back in the caliper. if so you need to make stops. Also when inspecting rear brakes remove the dust boot from the wheel cylinder, and carfully inspect for brake fluid. hope this helps

where are you?
roadtrip??

the calipers don't hit anything.

If you want to come out here, go for it. It'll be a bit of a drive though. I'm in Prescott AZ.

I know skip... I know you do.... and I do too, or I wouldn't own it. but I like being an oddball, and I've always liked that kind of rides...

It might not be quite as practical in that form, but I wouldn't have gotten a 2x4 shortbed if that was a concern in the firstplace.

At least I dont have a dumbass plan to drop it clear down on the frame like those gay minitruck kids... I'll probably have to reduce the volume of the bed with everything going on, but not severe...

Figured i would toss in a few...

looking at the pictures, it looks as if you bleed the front brakes and not the rear, sence i only seen the wet look on the clipers and not the backing plates of the rears.


one thing you can do is grab 3 vice grips and pintch a rubber brake hose ( dont cut it ) just crimp it to stop the fluid from passing threw.

do this to the all three lines, and push down on the pedel, if it moves ( slowly drops ) its a master.
if not
un crimp the front lines and test the pedel....
It should sink a little, but but stay firm.
if it sinks slowly its the front calipers. or the hoses.
open bolth bleaders and watch the fluid run out. it should drip fast.
if its slow around one drip a sec, replace the line and re test the front.

now lets test the rear.
crip the front lines, leaving only the rear to work.
test the pedel. it should drop alittle then be firm.
if it sinks, test the line by opening a bleader, or removing it if cloged.

again the fluid should drip faster then one drip per sec.
if not replace the line.

side notes:
check your wheel cycl.'s for rust, or any other corosion buildup behind the dust boots. slide the pistons back and forth to ensure they move freely.
check your pad wear. ( front ) low inner pad: Hardware, sliders. low outer pad: caliper. bolth pads low on one side of truck/car and not the other: hydrolic... caliper,hose, diverter valve, crimped hardline.

note:
this only works if all the air is out of the system.
( you can compress air not a fluid. )
hince the funny fealing brakes.



Marc.

Will your parking brake hold on a hill foward or backward?
This might be a quick test for how the mechanical part of rear brakes are working

I have a hard time bringing myself to smash the hoses. Both fronts have brand new shoes on them. I realized that this horrifying squeal was the warning squeaker rubbing the disk. Both sides were even.

I believe the Pbrake works fine.

And I promise, I bleed the rear brakes at leat as often as the fronts.

The wheel cylinders may well be at fault somehow, but I can't figure how they could possibly make such a difference when going backward up a hill than when they lock up and smoke all 4 tires when I mash the hell out of the brakes going forward (or backward DOWN a hill). or any other situation.

SOOO....

I replaced the front brake pads (disk) on friday, by pushing the pistons back in with a C clamp, after cleaning them, and spooned the excess fluid out of the MC. Pumped up the brakes to refill what excess was squeezed out, and pulled out of the garage, brakes flabby in the street. Not too much trouble when going forward, except the very first time.

The brakes have been perfect for a year now. They just randomly started working right and I never quite knew why.

I didnt open anything to the outside except the MC cap, and didnt even see reason to bleed them. Just a simple squeeze and swap.

Now when I back up (level) it goes flat. Up a little hill, as found to be bad last time is not so much....

what the hell is wrong????

"All bleeder screws on calipers are perfectly vertical, rear wheel cylinders perfectly stock."

Therein is your problem. Sounds like front calipers are on the wrong side of the truck. Bleeders should point to rear, not straight up.




[img]http://www.mustangsteve.com/caliperbleederposition.jpg
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