Can't get the brakes bled

[huntman58]

Sounds to me that it is either the MC bleeding back on you, the RALB valve is leaking pressure or that the MC rod is not adjusted right. On my truck (93) the peddle never is more then 1/8 easy stopping and only a bit more when hard stopping. If I stand on it with it running I still can not get it to go even close to the floor. Now this is with new brakes front and rear and all adjusted right. The MC is still the OEM one same with all lines and parts but pads, shoes drums and disks. This is at 200,000 miles plus. Ya I need to change the soft lines but can not afford the braided steel one yet.

 

[runderwo]

That's the crazy thing. The pedal doesn't fade if I stand on it with the motor off. With the motor on it doesn't "fade" either, it goes straight to the floor.
I'm going to bleed the MC again today, check the pushrod, then replace the MC if I don't get anywhere with that.

 

[Gadget X]

Try this: When driving, maybe at about 15 to 20 miles per hour, try hitting the brakes hard. If yours works the same as mine, then the brakes should grab hard and stop quickly, without going to the floor. If you hit the brakes while sitting still, then the pedal will go to the floor. I think that this is somewhat "normal" for the first gens, but I could be wrong. I was thinking that this was somehow tied into the ABS system, as it only does it when the tires are not moving. Do you have front and rear ABS, or do you only have the RABS? If I'm on to something, somebody that knows more than I do please let me know!

 

[runderwo]

I have RABS only. Wow, I can't believe that's "normal". But I've also never pressed the pedal hard before when parked. I guess it's worth a shot to try it.

 

[runderwo]

I just took it for a drive. It stops on a dime, i.e. a screeching halt. Then the pedal "sponges" its way to the floor. It remains stopped.

 

[huntman58]

I have 4 wheel abs and mine never go's to the floor even with worn out brakes front or rear. I have not had to replace the MC or the abs system parts but I did have a old truck that did that and even after changing the MC 3 times it still did it . all 3 were rebuilds by the way so I broke down bought new not rebuilt adjusted the push rod just to make sure bench bleed it twice and that was the end of the going to the floor on that truck.

I have also owned a bronco II a 93 ranger and this explorer and not a one of them went to the floor as you have said yours do.

I would say there is still some thing wrong and it would lead me to believe an internal problem in the MC and it leaking off and not holding pressure ether on the front end or the rear being they are divided into two separate circuits.

 

[runderwo]

I got another new master cylinder today. I guess I'll be putting it in next chance I get and seeing if it gives me a pedal that gives me peace of mind.

By the way, the bleed kit mentioned earlier in this thread doesn't have the correct fittings for the 91 master cylinder. One is a M12 x 1.00 thread.

 

[gaseoushaze]

It may be possible that pedal going to the floor with engine running is because RABS valve is activated with key on.Maybe try key on, engine not running and see if you get same result.I diagnosed mine by plugging the two outlet lines on master cylinder with assistant holding pedal down after bleeding MC.A good MC should hold without going to floor.At first it held but several hours later I checked it and it went to floor.I replaced it and all is good again.I will pass on a link that was helpful to me.

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

 

[gaseoushaze]

I don't believe the RABS valve will be activated with key on just to clarify my last post.I suggested that just for curiosity sake.I'll post another link that has useful info.


www.aa1car.com/library/abs_kelseyhayes_rwal.htm

 

[runderwo]

Looks like this is the bleed kit I will need:
http://www.handsontools.com/Thexton-426-Metric-Master-Cylinder-Bleeding-Kit_p_5270.html

Wish there was something cheaper that included the M12x1.0 plug.

 

[Tony H]

This one wont fit??

http://www.amazon.com/Thexton-346-Master-Cylinder-Bleeder/dp/B000P9CP4U

http://www.napaonline.com/

Upper left "Catalog Search"
looking for specific vehicle? "NO"
PART NUMBER SEARCH


NAPA # BK7001795 Brake Bleeder Kit $10

NAPA # BK7001132 Brake Bleeder Kit $8

 

[runderwo]

The Thexton 346 doesn't have a M12x1.0 plug. Neither does the second NAPA kit you posted. The first one doesn't mention what it comes with but it looks just like the Thexton kit (with different color plastic).

 

[Tony H]

The Thexton 346 doesn't have a M12x1.0 plug. Neither does the second NAPA kit you posted. The first one doesn't mention what it comes with but it looks just like the Thexton kit (with different color plastic).

It just hurts to pay $60 for something you wont use much.
It might be cheaper to grab some steel tube and flare fittings and make your own custom kit.

 

[runderwo]

I know it hurts. I actually bought a racing fuel fitting that adapted the M12x1.0 thread to a AN6 flare, but then I found out that I couldn't buy an AN6 cap anywhere cheap. I tried using a piece of aircraft fuel hose and clamping it to a tight-fitting bolt to create a makeshift "plug", but no matter how tight I clamp it it's not enough to keep fluid from squirting out under power boost.

 

[TedJ]

If you want to seal the ports for testing, get a short preflared piece of hard line with the right fitting on it at the auto parts store. (~$5) Cut one end off and fold the tubing over 3 times or so, crimping it in a vise (you NEED to use a vise) as you go. Then cover the folds with JB Weld. It won't leak.

I used this to seal off the rear brake line port on my parts truck when the line rusted out (it just needed some kind of brakes so I can move it in the yard). Pedal is hard, no leaks from it either.

You can also use sections of tubing for bleeding, they're better (and probably cheaper too) than the hoses and plugs because they don't fall out and spill fluid all over (don't ask how I know)

 

[runderwo]

Thanks, I'll try that. Didn't think they would sell the MC lines but it's worth a try.

 

[TedJ]

They should have an assortment... they're sold by the fitting size not intended use.

 

[Verno]

I've been following this tosee what ends up your problem. From my perspective, if you have good pedal with engine off, and have air bled out of system, the only difference with engine running is your power (vacuum) assist side. DO you think it may be a leaking vacuum booster?

 

[runderwo]

I suppose it's possible, but I don't know how to diagnose a leaking booster. I figured that a leaking booster would provide weak braking power, not allow the pedal to the floor. I did replace the check valve grommet with a new one as it was practically disintegrated, but performance did not change.

 

[TedJ]

The booster just multiplies the force you apply on the pedal. If it is leaky, it doesn't work as well and can cause the engine to run poorly because it creates a vacuum leak.

It does NOT affect the hydraulic portion of the brakes in any way. If anything it would decrease the braking pressure. No way is it going to make the pedal go to the floor....