Brakes wont work after draining fluid????

[Positive Vibes]

Ok. Here's my story and I'm sticking to it!

My rear driver side brake line had a bubble on it so I replaced it with a ss brake line. Well I couldn't locate one for a couple of days and most of my brake fluid drained out. I bled the brakes 5 times and the brakes still will bottom out. Took it to my mechanic and he bled them and they still go to the bottom. After talking with some people, someone mentioned there is a connector of some sorts the will prime the ABS pump.

The brakes work well on road but still bottom out. When on the trail my rig just keep rolling down steep hills no matter how hard I pump them. I have disc brakes front and back.

Any ideas? Does the ABS need to be primed? Does it sound like a master cylinder failing? Whatcha people think??

Thanks!

 

[410Fortune]

Sounds kinda like the master cyl is bottomed out (was it depressed with no fluid in the system?)

If the system has been bled properly then it could be the master.

Did you change out the master cyl when you did discs in the back?

Now is your chance to do the disc brake conversion PROPERLY
Without the rear disc master your rear discs are likely dragging, and/or not working as well as they should....
I drove for 2 years with the original master on and rear discs, once I did the proper master cyl (95 explorer) I found the real reason for having rear discs....

 

[Positive Vibes]

I was hoping you would see this thread.

Jamie, do I just need to get a master cylinder from a '95 and swap it or is there more to the puzzle?

I believe it was Tom or Jefe that mentioned the connector for priming the ABS, have you heard of that?

No I don't think the pedal was depressed while the system was empty.

No of course I didn't change the master cyclinder or the proportioning valve when I swapped to disc.

 

[410Fortune]

the proportioning is built into the master cylinder, there is no valve.
I vote for ditching the ABS.

The master cylinder will bolt in place, however you MIGHT need to use some adapters to get the hard lines to thread, OR like in my case, run a new hard line to the rear axle (that was fun

The BII lines are slightly different then a 93+ Explorer with 4WABS, so this is not something I have done.
the disc braked explorer's (95+) use a metric bubble flare fitting at the master cylinder, your truck likely has standard american flares and threads. This is where it gets really exciting, and the reason I took about 14 trips to the auto parts stores and hours trying to find the correct adapters, only to realize the only way was to bend up a new hard line from master to rear axle.

My truck originally had the 7.5" rear with 10" drums and RABS. Your truck is different.
I have heard over and over againm the 4WABS valve does NOT need to be bled, cannot be bled, etc. However I personally have never messed with the 93-94 4wABS systems, just changed brakes.
To bypass that stupid ABS valve (probably what you are calling the proportioning valve, which it is, but it is for the ABS, not a typical proportioning valve you see used in half assed rear disc conversions) you may need to run new lines to both front tires and to the rear axle That sounds like FUN! (But dont be scared, just plan a weekend project, not evening)

Drum brakes and disc brakes use a different "type" of hydraulic pressure. This is done with the bore and stroke built into the master. People who slap on rear discs then introduce an adjustable "proportioning" valve in the rear brake line, may be able to adjust the line pressure to the rear discs, but it is still the half assed approach. the only true way to get the rear discs to work properly is to change the master cyl.

Did you notice an increase in braking when you went from drum to discs?
Do your rear pads wear out yearly?
Do the rear discs make noises?

they are dragging with the stock master (drums) and not performing NEARLY as well as they should be, trust me. You will be happy as can be if you upgrade to the rear disc master, ditch the "not off road worthy" ABS and do the job right My BII holds itself on the trail about 1000000 times better since I did this, I mean for rocks and the type of 4x4ing we do, having the full control of the brakes was a HUGE upgrade, not to mention this BII, even with 35's stops on a DIME.

the front to rear biast is adjustable, and will allow you to fine tune your brake system.
once you get the new master in place with the lines hooked up, we'll talk about adjusting it so the rears will lock up just before the fronts (no rollovers please) Once I got mine dialed in I was AMAZED at the increase in braking performance, and it has saved my ass a few times, on and off road....

 

[Positive Vibes]

I did notice a little difference in brakine but not much.

The rear pads don't wear as much as the fronts do.

No noises from the rear brakes that I've noticed.

Do you know anyone selling a master cylinder from a '95?

Seems like a good time to get the doubler installed, get the tranny rebuilt and install a master cylinder. Now I just need to win the lottery and I can afford it.

I just put a new roof on the house so I'm low on funds.

 

[Rick]

I swapped to rear discs and still have the stock master cylinder. You have to adjust the pushrod length of the master cylinder to get the right pedal height. If you go to far with the adjustment you will drag the brakes. It's an easy adjustment and it's all I needed to do to get a proper pedal feel and stopping power.

Rear brakes shoudn't wear as much as the front since the bias is approximately 60/40 with 60% going to the front.

 

[Positive Vibes]

Rick have you ever heard of having to "prime" the ABS if all the fluid was drained?

Do master cylinders "slowly" fail? I mean my brakes work to an extent, they feel like there is still air in them but we have bled them over 7 times???????

 

[410Fortune]

Master cylinders use O rings to seal the hydraulic pressure, yes they wear out.

the vacuum booster also will wear out.

Rick I know all about the biast adjust front to rear, I believe it was Brett who wrote that article long ago. You may have rear discs, and they are working okay, but you are not using them to their full potential AT ALL, trust me on this. The difference is night and day, especially with big tires, on the trail. Can you currently lock up the rears?
I drove without the master, jsut like your setup with rear discs for 3 years. Finally one day I decided to doit right with a new $85 master cyl, one of the best mods I have done. Brett and Joe are both now running around similar.
Brett being the maniac he is has also gathered parts from a hydro boost super duty, (booster and master) hahahaha talk about big brakes for an explorer

 

[Rick]

The Explorer was originally built with rear ABS to keep the back end from passing the front during hard stops like so many vehciles with low weight in the rear do. They eventually went to 3 channel ABS so that you could steer during a skid. I think I would rather have a little less bias to the rear given the conditions I use the truck in. I would hate to stomp on the brakes while blasting down a wash only to have the rear end pass me. Same can happen on a wet road.

As my truck is now, I can't imagine it any stopping any better or more predictably.

Brett did write the article a long time ago, but I believe I did my first rear disc brake swap with the SSB kit before that. The pushrod adjustment was in the instructions that came with the kit.

I have since swapped out the SSB calipers for '95+ Explorer calipers, no further adjustment to the pushrod was needed.

 

[Rick]

Rick have you ever heard of having to "prime" the ABS if all the fluid was drained?

I have heard of this, but have never had to do it so I don't know of the procedure. I do know there are bleeder screws on the ABS unit, maybe you have to bleed the air from there, but again I don't know the procedure.

Do master cylinders "slowly" fail?

Jamie is correct about O-rings wearing. Another possiblility is that you over extended the piston in the master cylinder while trying to bleed the brakes. The piston moves in the same path over and over for years... If you press the pedal all the way to the floor while bleeding you can push the piston into an unused portion of the bore causing the piston to become scored which will allow fluid to seep by. Nothing you can do at that point, but replace the MC.

When I bleed my brakes with a helper I tell them to only depress the pedal half way down. I actually don't even count on them to do that. As the fluid is being pumped out of the bleeder I will tighten the bleeder screw while there is still a strong stream being pushed out. That way they can't push the pedal all the way down unless they do it real fast, which they shoudn't be doing anyway.

 

[410Fortune]

Correct, people always try to bleed by stomping the thing to the floor over and over, this can actually do more harm then good. All thats needed is a few light presses, then hold it down and open the bleeder for jsut a second, dont hold it open for a long time, just for a second or two.


Makes life much easier.

Also have you tried getting up to a decent speed in reverse then slamming on the pedal? This self adjusts the parking brake, but has also been known to cure soft pedal situations for whatever reason...

 

[Positive Vibes]

I can use a master brake cylinder from '95-00' correct?

 

[410Fortune]

95 is the one you want, no ABS, no nothing except the low level sensor for the resevoir.

Carquest has them new for like $85, I dont trust used or rebuilt from places like Autozone with this stuff.

 

[Positive Vibes]

95 is the one you want, no ABS, no nothing except the low level sensor for the resevoir.

Carquest has them new for like $85, I dont trust used or rebuilt from places like Autozone with this stuff.

Cool! Thanks!

I was going to post in the want ads, but I it sounds like I'm better off ordering one from Carquest?

I have the sensors pulled for the ABS already so this will be good.

Jamie, you gonna hold my hand again for the install???

 

[410Fortune]

Sure, except its different from my BII slightly

I will get pics of my adapters at the master cyl. Even though I ran a new line I still had to make a jump from metric bubble flare to standard lines....

I wouldnt trust a used master myself.
You might consider a new booster now too, they are cheap, but depends on your mileage. My booster was still working at 220K miles, but def needed to be replaced, I dropped one in from a 96 Ranger Brett parted out.

 

[Positive Vibes]

I looked on carquest but couldn't locate a master cylinder, any other dealers I should check out?

Oh, now the booster too!!!

I was going to ask you what else you think I should replace. So master cylinder and booster. My truck has 170k miles so I guess it couldn't hurt. So is buying a booster of the site a good idea or should I go new also?

 

[410Fortune]

Used with low miles or new, whichever

If the booster holds vacuum and the bladder/diaphram is still good rubber, then a booster is a booster.
I did it because we had one laying around with way less miles on it.

Rick my BII had RABS, and that RABS got me in more trouble when it would come on, in wet/ice/snow it definatley did not HELP! BII is much shorter however.

I dont want to lock up any of the tires, the BII doesnt need that, HOWEVER I do have it set so if I mash the pedal (emergency situation) the rears will lock up just before the fronts, I played with the biast for hours to get it just right, You DONT want the fronts to lock up first, that = sideways.

I noticed the rear disc improvement in performance after the master mostly on the trail, when desending hills, and also when towing it became obvious.

 

[410Fortune]

Also Rick when you adjusted the biast to the rear you are taking away pressure to the front It may stop good now, but it can stop better, thats all I am saying.
In hindsight, on my truck, it was well worth the effort IMO, but then I am ****, I mean come on I built a new gas tank so my new OBD-II computer would have its precisous fuel tank pressure sensor I could have easily just had the PCM flashed to ignore it, or wired in a radio shack resistor.....

 

[Rick]

I didn't do anything to adjust the bias, I just adjusted the pushrod to get the correct pedal height. I don't think that actually affects the proportioning of the system.

 

[410Fortune]

yes it does, adjusting the end of the pushrod adjusts the front to rear biast
You should turn it out about 4 complete turns then go drive it all rear brakes. A little goes a long way