I was having brake trouble and I went through and replaced a bunch of stuff. Here it is:

Replaced master cylinder and bench bled it, bled it on the booster. Bled brake lines. Removed the RABS proportioning valve altogether since RABS sensor is disconnected. Replaced rear drums and put in new wheel cylinders since rear shoes weren't both moving. After that I pushed brakes and the rears still weren't moving. Couldn't fully bleed rears I kept getting air no matter what I did. I pushed on and replaced my passenger side rotor, new brakes wheel bearings, ball joints and One knuckle. Oh and yes I pushed the piston back into the caliper. I then repacked the wheel bearings on drivers side, turned the rotor added new races, added two used warn hubs from salvage yard and replaced one outer tie rod. wheels went back on and the battery was dead. So today I start it up and the brakes are still spongy. I should add that the brakes are firm when vehicle is off. When I pushed the psitons back into the calipers the resevoir filled with brake fluid and I removed the excess taking it back to the full line. The booster is functioning and the master cylinder is all checked out. The front brakes are working with just a slight push of the brake and they push even harder as the pedal falls to the floor.

So it is the rear brakes that are my culprit. But what is it that I'm missing?????? Why won't the rear brakelines bleed properly. I bled a whole 2 small bottles of brake fluid out the rears and there is no more of the old fluid in the system. I have inspected them and found no leaks of any kind. I don't see any crimps to speak of either. So why is my brake pedal going to the floor.

I would have to guess that something in the brake lines going to the rear is taking in air. Some crack or something. This would make sence as to why you can't get all the air out. I would try and resolve this first. After that, just make sure that everything is ###tioning in the rear. Sounds like it's almost all new, but the springs can sometimes get bent, funky, etc.

Good luck and keep us posted.

Well I know I've got fluid moving just fine to the rear brakes. We checked and found fluid moving in and out of the master cylinder. I ran through and bled the rear and front brakes again. I removed somewhere around 18 oz of brake fluid in the process. I was getting no more air bubbles out at any wheel. I did still have air in the bleeder hose. but no more bubbles in the jar.

I spoke with my parts guy and he said he's heard of the hoses doing weird things. Usually a piece will flop down on the inside and create a valve like. This usually prevents fluid from going to the wheel cylinders or from them. This doesn't match my problem what so ever.

We checked the hose and it was extremely firm, but who knows what the inside is like.

What is th relationship in the master cylinder between front and rear? I mean the first brake line goes to front brakes and the second one goes to the rear. (starting at the booster forward) I am getting firm front brake pressure and very little rear shoe movement. My parts guy said he thought the brake system was 70% braking in front and 30% braking in rear. This seemed wrong to me I would've thought it was the other way with more braking pressure in the rear.

I am wondering is there a way to check the seals that the resevoir sits in going into the master cylinder. I was wondering if I was getting some air sucked in there.


Oh and another thing. My buddy said that he was getting good pedal fade on the front brakes when we were bleeding them but the rear never had the same fade. He said he could really tell when he applied pressure and I cracked the bleeder. He said he got another 2" of brake pedal fade, but that didn't happen when I cracked the bleeders on the rear. Does this mean anything??

1. Front brakes have always done most of the work on all vehicles, it is correct proportion of 70/30.
2. The fluid is drawn in at the bottom of the resovoir, so the seal around it wouldn't cause that, where ever you are sucking air at should also have a wet area where fluid is being forced out.
3. Try gravity bleeding them first, also may have a bad bleeder valve
4. Did you adjust the rear brakes before you bled, and is the e-brake cable hooked correctly, both of those will cause the symptoms you describe. They should not quite make one revolution when the wheel is turned by hand

Have you checked your brake lines from the proportioning valve to the rear axle for kinks and damage?? That could restrict flow.


Also, if I remember correctly, there is a mechanical safety slide valve contained in the proportioning valve (on some Fords, don't know about the X) that cuts off most of the fluid flow to either the front or the rear if there is low pressure on the line. If it is shut, you won't be able to properly bleed the brakes. My buddy's F-150 had this happen when a rear brake line rusted out. He ended up taking it to a garage to get it reset. I believe that they ended up using a power flusher to reset it by relieving the pressure in the front and then vacuum bleeding the brakes.

Originally posted by AlaskanJack
I was having brake trouble and I went through and replaced a bunch of stuff. Here it is:

Replaced master cylinder and bench bled it, bled it on the booster. Bled brake lines. Removed the RABS proportioning valve altogether since RABS sensor is disconnected.



As I stated.


X-1: I didn't ajust the brakes before bleeding. I was going to adjust them by pulling forward and backing up. To be honest I may not have the parking brake installed correctly. I tried to follow the Haynes manual, but who knows if I got it right.

Is there something I could check to see if its installed correctly.

Ok well I drove my truck around and the front brakes are stopping the truck but the pedal is still going to the floor. So I went and bought new hard brake lines that I will run from the master cylinder straight to the flexible hose in the rear. I will also be running new lines from atop the diff to each wheel cylinder.

I can't get a new flexible line until tomorrow anyways so this will allow me to eliminate the lines.

Now everything in the brake system will be new.

I am wondering is there a way to check the seals that the resevoir sits in going into the master cylinder. I was wondering if I was getting some air sucked in there.

that was close to my suggestion. i have been through this problem myself. if you get a friend to push the brakes for you while you go under the hood, you might see what i saw. when i did mine i had one side i couldnt get to bleed out properly. i was constantly getting air in the line. if i wouldnt have been under the hood putting more brake fluid in while my friend accidentally hit the brake i'd have never spotted the little bubbles that were right behind my master cyl. against the firewall. it was a leak in the master cyl seal and was bubbling out the back of the cyl and down the firewall. look it over well while you have an assistant press the pedal. also use your ear to try and hear air or bubbles while the pedal is depressed repeatedly. somewhere you will hear it, or see bubbles. mine was right at the firewall.

p/.s.= it could also be running into the cabin, so peek under the dash for leakage.

So your saying it was leaking between the master cxylinder and the brake power booster?? I had three sets of eyes on it today and one said that they saw bubbles in the resevoir when the brake pedal was released. I assumed what she was seeing was the brake fluid entering back into the resevoir.

I have seen no sign of brake fluid on the firewall, booster frame or ground. I did happen to be under the dash today and I saw nothing in the cabin side of th firewall.

Originally posted by AlaskanJack

quote:
--------------------------------------------------------------------------------
Originally posted by AlaskanJack
I was having brake trouble and I went through and replaced a bunch of stuff. Here it is:

Replaced master cylinder and bench bled it, bled it on the booster. Bled brake lines. Removed the RABS proportioning valve altogether since RABS sensor is disconnected.
--------------------------------------------------------------------------------


As I stated.

I read what you wrote and I wasn't talking about the RABS valve. The RABS valve has absolutely nothing to do with the brake proportioning valve. I was talking about a front to rear proportioning valve that controls how much pressure goes to the front and how much goes to the back. In many vehicles this valve is present just downline from the master cylinder. However, after reading up on the X braking system again, you don't have a proportioning valve in your system. The master cylinder controls it.

Excuse me for trying to help

Excuse me for trying to help


I welcome all input, sorry if that post sounded harsh. It wasn't meant to be. Where are you geting your info on the braking system?

I was reading in the 91 EVTM manual and it calls the Hydraulic Control Unit (HCU) the proportioning valve also. It states that the valve is inside the HCU.

Well I am doing nothing today but working on this. If I have to I will start back at the beginning. Check the booster pushrod for length, bleed master cylinder again, check booster, inspect resevoir seals, inspect master cylinder for signs of leaking. Go over entire length of brake lines searching for leaks, disassemble drums, remove wheel cylinders and check, remove front calipers and inspect piston check slide pins for free movement. reassemble everything and bleed starting at RR tire.

Originally posted by AlaskanJack
I welcome all input, sorry if that post sounded harsh. It wasn't meant to be. Where are you geting your info on the braking system?......



S'alright, I was in a crappy mood when I posted too. Sorry about that.

I'm getting my specific info on the X braking system from my Haynes manual, and I've been working on vehicles since I was a kid, so I have a lot of general knowledge stored up.

Have you considered that your master cylinder might have a bad seal between the front and rear pressure chambers?? That would cause a pedal pressure problem with no external leakage. One of my friends had a Thunderbird that had a bad seal between the chambers, and the pedal would go to the floor easily with no leakage. His was so bad that the pedal wouldn't even come back up without pulling on it. A minor internal leak might cause what your are seeing.

I know you installed a new one, but was it new or rebuilt?? I have seen rebuilt cylinders be defective out of the box.

It was brand new from NAPA. I thought that someone gave me a test previously to test the front and rear seal on the master cylinder. Plug rear outlet and push on brakes to test the rear, do reverse for front. I remember doing this and I got good pressure at the master cylinder outlets. I used the finger test method. Plug one and have someone press brake pedal while attempting to keep finger over outlet. I was applying a ton of force and each outlet forced my finger away.

I just completed running new brake line to rear flexible brake hose. If problem still persists I will replace hose. Then I will replace hard lines from the splitter to each wheel cylinder.

On all connections I added teflon nut tape to ensure no air is escaping or getting in.

Here it goes. I added new lines to the rear flexible brake line from Master cylinder. Then I decided to see if I could bleed the brakes. Well no luck we ran 2 bottles of fluid through the system using a vaccuum bleeder. one interesting thing that happened while my buddy was watching the resevoir was as I was bleeding he said he was seeing bubbling in the resevoir. This happened at all 4 wheels. I took trujck for test drive and again pedal spongy and only have front brakes. engaged parking brake and they engaged on both sides. My red dash brake light is lit with both of these (!) and (B) also the rear antilock light is on but I need to disconnect it.

Any thoughts? I am trying to find a real good brake man locally and see if he can ID the problem. I will still fix it. I may ask to see if he can pressure bleed the system.

Jack

Having read all your posts I would conclude that it has to be the master cylinder. Yes I know it is a new one but it could still be faulty.
Are you loosing fluid?
When you bled the rears did you get fluid out?

If no to 1 and yes to 2 then it has to be the master cylinder.
If yes to both then somewhere you have a leak. If there is nothing visable then it must be going into the brakebooster.

All I can think of for the moment.

PS new parts can be faulty swap it for another one. :D

I'm with Howard. With all you have done so far, I would begin to suspect that your new master brake cylinder might be faulty. If you had a leak, you would be seeing brake fluid leaking out somewhere.

Let me chime in here...I had TWO faulty master cylinders, both new.

Similar issue, pedal would go to the floor.

You need to adjust the rear drums by hand, dont rely on the slef adjusting method.


Also a vacuum leak can also cause the pedal to go the floor, either in the booster or in the engine/manifolds......


You can test the booster vacuum with a vacumm tester thingy...

Rebuilt master cylinders have issues, it took me 3 tries to get one that worked properly, very frustrating. Also I dont trust Checker or Autozone or any of these people when it comes to brake hydraulics, strictly Ford from now on. The bad master I had was from Car Quest, but it is a rebuilt, and I am usre lots of parts places get their rebuilts from the same people........


Got a Master cylinder from Ford eventually, works perfect...

Wife suggested that I take it to a shop and pay them to just diagnose my brake problem. She new I wanted to do all repairs. So I agreed. I found a local shop where the service guy used to work for ford in their (can't remember name) basically vehicles came to his dept when no other mechanic could fix the problem and the dealership would have to replace the vehicle. So his team just worked on these so called lemon problems.

So here goes my sad tale. The guiy takes it out for a test drive and the hood flys open while driving it. (Guess I foirgot to re-install the hood retaining pins, opps!) He was pretty panicky driving a truck with suspect brakes and now can't see.

Anyway I spoke with him on the phone and he sadi from drivng it he could tell it was the passenger side front and that the rears were engaging. He would take a look at it. I call him at 4:30 to get the news. News was he didn't have time to look at it. I was like what the H*&l. I specifically asked if they could get to it or I would go somewhere else. No problem I was told. Service guy thought I told him on the phone no hurry.

So I go pick it up and talk with guy. I told him I visually saw caliper piston moving. He said he definitely felt rear brakes engaging. He said when he hit brakes the truck would pull to the left. Yep that would indicate right front not functioning. I take it for a drive and really test the brakes out. I can only feel the front grabbing and no pull to the left. I really got on it too!

In talking with him he suggested clamping off the rear flexible hose that way I would eliminate the rear brakes. He said clamp the hose off and I guarantee you still have a spongy pedal. Ok so I go home and find my hose tensioners and clamp off the rear at the hose.

Guess what I start the vehicle up and I've got hard pedal. Damn mechanic. So now I am believing that the flexible hose was bad. And to all others that were suggesting an air leak. I checked there is no possible way to get an air leak that only sucks in air without leaking fluid. Most brake systems run at around 1500psi I learned. any pin hole in the line would definitely leak.

So tonite on my way home I will pick up the needed hose install it and retest the pedal. if still spongy I will bend and add in the new brake lines from the diff to each wheel. If they are still spongy I will pull each wheel cylinder and check them out. Parts guy refused to accept that the wheel cylinders where bad when we discussed the possibility Saturday. If replacing these 3 items doesn't fix the brakes then I will go buy the EB disc brake conversion for the rear and really go insane.

I have heard of rubber lines getting old and creating a spongy pedal, but I have never seen it.

You have checked for vacuum at the booster right? No leaks in the booster?

Master cylinder is not leaking internally? (look where booster pushrod goes)

You have checked the pushrod length?

Sounds like the rear drums to me...since you cut them off and blamo, firm pedal....

Did you adjust the star wheels on the drums after installing all new springs, pads, and cylinders?

Rear discs from a 95-97 would be a nice upgrade for you.
I got so sick of the RABS and drums on my old 7.5 (88 BII) I got the entire rear from a 97 Ex and converted it to spring over.....rear discs are the way to go, especially on the trail.......

I'm done with the master cylinder and booster they check out perfectly fine. I did adjust the brakes on the rear out to just rub then backed off two clicks on the adjuster.
I may start looking for disc brake rear conversion after this summer. For now I just want to go wheelin. Trying to get ready for the 4x4 meet & greet at the end of may.

I would check the wheel cylinders and the rear brake adjustment first before I go buying new brake lines.

I would hate to buy $50 brake lines just to find out the rears needed to be adjusted. Wouldn't trust the automatic adjustment. You may want to stand on the brakes really good in reverse.

I've got all the hard lines so its not big deal to replace them. The rubber brake hose is like 17 bucks. I would feel better having a new one in. the wheel cylinders are simple little things parts guy pulled one apart there's nothing to them. The brakes are definitely adjusted right two clicks on the adjuster and they will be draggin on the drums. Actually now that I recall I backed them off 2 clicks because they grabbed and I couldn't turn the drums so they should be fine.

okay here's another thing to consider.

You are now using a master cylinder designed to be used with a 4 wheel ABS system and you removed the ABS proportioning box correct?

I dont know if this could cause it, I wouldnt think it could, but its something to consider.........

The 91s only had rear ABS to start with. The ABS module is in the frame rail and has nothing to do with the master cyl. My ABS still works just fine so I left it. MY buddy took his out without reprocussion. I need to read your post again, but did you bleed starting from the right rear? I went through my brakes a couple of times before I got all the air out. Your booster doesn't make any hissing noise, does it?

was it in 93 they went to 4 wheel ABS? Maybe 94.

ON my 88 BII I also had just RABS, I have disconected my RABS computer and stator ring wiring, added rear disc brakes, and I am using a stock BII master cylinder. No spongy pedal..


I was just concerned with the 4 wheel ABS system, dont know if it is the same.

Also I still bleed my RABS proportioning valveon the frame rail when I do the rear brakes, eventually I plan to bypass the valve with a short hard line......

bleed RABS proportioning valve on the frame rail
did you try that. The RABS valve traps air.

Lonestar he has removed the RABS proportioning valve.....

Oh, and new wheel cylinders. huh.

That leads back to the master cylinder. Maybe the proportioning in the master is messed up. Keep clamping off the rear lines further back until you have the same problem, all the way back to the wheel to isolate the problem.

Latest news I clamped off the rubber hose just past the hard line and got a hfirm pedal. I am trying to get a new brake line but now I find out I have to order it from 4x4 shop since its the extended line.

I can order a Skyjacker 6" lift braided line for the rear will be here on the 8th $50.

This is where I am at. I just wish I could swap it out to make sure it is the culprit. I am planning on getting creative tonight and see if I can bypass the flexible extended brake line with some hard line I have. Just to make sure its the extended brake line.

I had posted a question on my brakes to some FORD ASE mechanics. This reply just baffled me!! I even asked him if he realized this was a vehicle with Rear ABS only. He said it didn't matter. I was like ok whatever.


The proportioning valve should never be bypassed. If you do that, only one
> set (front or rear) of the brakes will engage fully. Whichever set engages
> first will "attempt" to stop the travel of the (dual) piston in the master
> cylinder, so in theory no PRESSURE will be exerted on the other set (only
> volume). The pads or shoes of the "second" set will move towards
> engagement, but will stop short when the first set engages. In practice,
> some additional motion of the second set will occur as more pedal force is
> applied because of seal and tubing flexing, and compression of any air in
> the system. This can give you a "soft" feel because no back-pressure is
> being applied from the second (unengaged) set of brake cylinders and all of
> that pedal force is flexing the **** out of the first system.
>
> (warning - don't try this at home!) If you want to test the system without a
> proportioning valve, you will have to run all wheel cylinders from the same
> master cylinder. You will probably run out of pedal travel, though, because
> of the increased system volume. If you really are insistent about following
> this line of thought, tie both master cylinder outputs and all wheel
> cylinders together with tees etc. Now you have a system mimicking the "old
> days" without a (fail-safe) dual fluidics system. Front-to-rear
> proportioning will be dependent only on wheel cylinder piston diameters,
> effective friction surface radius, and friction materials. Say hello for me
> to Peter at the pearly gates, or to the other guy!
>



What do you guys think of this after reading it??

What he is saying looks like what I was talking about earlier, and I think he's making the same assumption that I did. It seems to me that he's not talking about the RABS valve, but a conventional proportioning valve. I think you might have confused him by calling it a RABS proportioning valve. The RABS valve is not a proportioning valve at all, it's a line pressure modulation valve.

However, with that said, his assesment of a conventional system with a proportioning valve is correct. There are safety features built into the system that prevent you from having zero braking if one part of the system fails. What you may want to consider if you can't solve the problem any other way is to install an aftermarket conventional proportioning valve.

Ok I gotcha!!

Lazy me I should have been calling it the Hydraulic Control Unit (HCU) is that more correct. I just think of it as a proportioning valve/bleeder valve. I believe that my EVTM called it a bleeder valve.

I better work on calling a spade a spade and an orange an orange huh!

what was the outcome or fix for your problems? I am trying to 'help' a buddy with an '95 EX 2wd... he is having very similar problems and the culprit may be the 'new' master cylinder (I don't know it may be rebuilt :( Any additional info I can pass to him (along with making him read this thread; will aid in troubleshooting. I am not brake savvy, but I have an 01 EX and let him and another guy look at how mine is set up to get an idea on his. Thanks in advance :)

Well I am not brake savvy either but I believe the 95 would have 4 wheel ABS and so that would be quite a bit different.

As for my problem it turned out to be a rear rubber brake line that was expanding from the inside and stealing brake pressure, almost impossible, well yes it is impossible to see or feel.

Thanks for the quick reply. Boy all that mess you had to troubleshoot and it ended up being a non-visible line problem!! aghh! Yeah, they are still looking at his Ex;

Bleeding the rear squirts fluid and then nothing. After applying the brakes there is fair actuation of all the calipers on each disc, it just won't hold pressure. He is going to clamp the rears and check the front ones independently, just to check that.

Each of the 2 replacement master cyclinders (autozone, checker) have been different than the OEM one... both replacement ones aren't of the same type either :rolleyes: Go figure. Tomorrow, they are getting a Ford one. Hopefully it will turn out that the Master cylinder was the culprit. Again thanks for the reply, even though it is a different year Ex, it helped my buddy out. :)