I need help.......please!!!!!! Brake problem.

[AlaskanJack]

Ok so I just replaced my master cylinder. I bench bled it. Installed it. Bled the master cylinder again. Then I bled all 4 wheels. Brakes still go to the floor.

Ok so I went today and bought a vaccuum bleeder kit. I checked the manual and it said to bleed the RABS valve. I looked all over the hydraulic valve and found no bleeder valve. Then I went to the rear and couldn't draw any fluid out. I had my wife pump the brakes after I opened the rear bleeders and at first I got a few bubbles. But no fluid came out. repeated several times and no fluid.

So help me out. Do I need to remove the hydraulic valve and is there a way to bench test it?

 

[AlaskanJack]

I'm impatient.........anyone got some tips for me?

 

[IgotTwo]

At this late hour, this is for Bronco's but it should get you in the ball park

www.asashop.org/autoinc/dec99/techtips.htm

 

[AlaskanJack]

Ah good stuff thanks. I will test this stuff out when I get home from work.

Is there any significance to this issue of firm brakes with vehicle off and then when started the brake pedal goes to the floor? I know that the booster is activated with vehicle running, but didn't know if there was any significance to it.

Also, a side note this vehicle has the rear ABS sensor disconnected at the axle I am assuming it is from when the rear was regeared with 5.13's.

 

[dogfriend]

It sounds like you might want to 'permanently' bypass the RABS valve since the rear axle sensor is disconnected already.

 

[AlaskanJack]

So if I bypass the ABS Valve will I need to get under the dash and find the ABS module and disconnect it?

 

[dogfriend]

Only if the yellow ABS light bothers you. Otherwise you don't need to do anything, since the ABS won't have the valve to control, it won't matter if the module is connected or not.

I'm assuming this is your trail rig, so not having rear ABS is probably preferred.

I was thinking that if you disconnect the RABS valve electrical connector, and your problem goes away then it would confirm that the RABS valve is bad.

 

[mrboyle]

It sounds like the RABS valve is shot. Bypass it and forget it.

 

[AlaskanJack]

Ok so I disconnected RABS valve and my problem didn't go away.

Now I have to admit I have never used a vacuum bleeder before. I don't think I am doing anything wrong it is a very simple process.

I decided to have my wife pump the brakes before I tried the vacuum bleeder on the rear again. Got fluid. I kept getting tiny bubbles out of the first rear and figured out It wasn't making a tight fit. Did the second rear and got the same. checked the resevoir and topped off it never was empty. Went to passenger side front and I kept getting large bubbles. I noticed the fluid color changed so I knew that all the old fluid was out. But I still kept getting bubbles. Same thing on the other front. I filled the resevoir on the bleeder 2.5 times and both were clear of old fluid.

So where do I go from here?

 

[dogfriend]

Sounds like you have a leak somewhere. First suspect is the RABS valve if it is still plumbed into the system. Second suspect is one of the rubber hoses or a connection somewhere.

I have used the vacuum bleeders before, and the problem is that it is easy to pull air past the threads on the bleeder screw. You can use the vac pump to get the old fluid out, but to get all of the air, its better to have someone pump and hold the pedal.

 

[AlaskanJack]

I went all over and I could find no brake fluid leaking anywhere. What are the chances that I got a bad master cylinder?

 

[dogfriend]

Its possible you have an internal leak in the master cylinder, but I would rule out the RABS valve first based on the article that IgotTwo posted. You could do this either by replacing it with another, or better yet removing it and replacing it with a straight run of tubing.

Also, I think that it is possible to have a leak in one of the rubber hoses that would let air in but might not leak fluid. If the hoses look bad, you should consider replacing them to rule that out also.

 

[AlaskanJack]

Hmmmm....... Ok I hear ya, I will read IgotTwo's article. I'm just getting frustrated because it was snowing last night and I was out under the Explorer freezing my nana's off. I think it was between 5 - 10' F outside with a light wind. I am going to set up a tarp to enclose under the vehicle and I will check every inch of brake line a second time. I have braided extended brake lines and the few rubber lines that there is all look really good.

I appreciate this help. I am also going to remove the ribbing that is covering the steel brake lines to see if there is a kink somewhere. I've got an area in the rear that looked a little smashed and another area looked rubbed on the steel lines. Even though my first check of these showed nothing I will take a much closer look now.


EDIT: I did some searching and can't find any post from IgotTwo regarding this problem or something similar. Can you direct me to the article?

 

[AlaskanJack]

Ok so I just spoke with a co-worker that had same problem on his brakes and it turned out that a caliper was malfunctioning. A little messing with it and boom he had pressure. What he was saying was that possibly I have a stuck caliper and there simply appears to be no brake pressure. He said that maybe one side is sticking so I am going to go ahead and replace the pads on the front and rear. The front pads had about 3000 miles left on them a month ago. I am hoping that there is something in the calipers.

 

[dogfriend]

Originally posted by AlaskanJack


EDIT: I did some searching and can't find any post from IgotTwo regarding this problem or something similar. Can you direct me to the article?

I was talking about the link in this thread, third post down

Dead Link Removed

 

[AlaskanJack]

Ok I printed it out, so I wouldn't forget about it. I am building a repair binder with all these helpful technical articles.

I meant to isolate the master cylinder and plug the lines to see if my problem was coming from the front or rear. I forgot to do this. I also didn't bypass the valve just disconnected it. But in doing some reading today online I discovered that the valve (at least in 4wheel ABS0 can be opened and closed by bleeding from the front instead of rr first. Which is what I did when I was in a tired stuper. I meant to just check the bleeders and make sure they were frozen. And suddenly I realized sh*t I bled the front first.

So tonight I will plug the outlets in the master cylinder and check front and rear as well as master cylinder. From there if its in the rear I will make a fitting to bypass the HCU. Bleed the rear and the front in order. Check for pedal firmness. If still soft will bleed again making sure I get old fluid completely out. From there I will start looking into the lines and make sure there is no sign of break. Then as a last effort I will get into drums or calipers depending on where I can isolate either the front or rear. If still spongy I will buy all new pads and replace brake pads this way I can look at calipers and drums.

If all this fails then I go inside and get 12 guage and blow holes in floorboard. You know so I can Fred Flintsone it.

 

[AlaskanJack]

Ok so here is where I'm at. I checked the master cylinder and it fine. I plugged each outlet and they were fine. So I bled the system again. First I bled the master cylinder then each wheel starting with rr, lr then rf and lf. Same mushy brakes. Checked all the lines extremely closely and found no leaks. I bought pads and shoes. I had my wife start up truck and push brakes while I looked at pistons with wheels on.

I can see the pistons pushing but the pads are so low I don't think they are grabbing. The whole system is now void of old fluid so that's good. I will change the front pads tonight and see what difference they make.

EDIT: I had a thought and I spun the lf tire while my wife pushed the brake pedal and it stopped immediately. I got in and pushed the pedal with my hand while she spun it and the tire stopped with only applying a small amount of pressure. I could still push the pedal to the floor and all it did was apply more pressure to the front piston on the calipers. It actually pushed the tire I could tell it was grabbing extremely hard. Even though my check at the master cylinder seemed to eliminate the RABS valve I am now wondering. I am out of light now so tomorrow I will definitely do the valve bypass since its useless with sensor disconnected.

 

[AlaskanJack]

So what do you think?

 

[dogfriend]

I think its the RABS valve based on the description in that article. If your master cylinder checks out ok on its own, and you don't have a leak somewhere else , then that RABS valve is the only thing left.

 

[AlaskanJack]

Well I'm looking at the shotgun very seriously.

I bypassed the RABS valve, and bled the rear brakes. Same thing as soon as I turn the car on brake pedal goes to the floor. I can hear all or see all the brakes functioning. I pulled the left rear tire and inspected the shoes. Look good plenty of pad. I then pressed the brake pedal and the shoes are moving.

What now!!!!!!