Can't get the brakes bled

[Tony H]

It's been a while now since you started this Post. After time has past, are you sure there are no leaks by any of the Tires or up by the drivers rear tire where the Hard line attaches to the soft line? No wet spots by the Drivers Wheel well where the Proportioning valve is? No fluid loss at all?

This may have been spelled out but let's try again:
Engine running with car in Park... If you step hard on the pedal.. to the floor or holds?

Engine Running with car in Park.... you step softly, pedal goes to the floor or does it hold then slowly sink?

Do the same 2 things with Engine off

 

[runderwo]

I'll check again for fluid leaks, but I have never seen any yet since replacing the line.

I did go to Advance the other day and talked to someone more knowledgeable who let me go in the back and look for an adapter, and lo and behold they had the M12x1.0 flare adapter and a plug to fit it. So I will be able to test the MC directly tomorrow.

Motor off, pedal is hard and does not sink if I stand on it. Motor on, goes to floor whether you feather it or stomp on it. The truck comes to a screeching stop about 2/3 of the way down but there is practically no resistance to taking it all the way to the floor.

 

[runderwo]

OK, master cylinder is fine, I plugged it correctly and the pedal is rock hard about 1/4 of the way down with the motor running (under boost). Looks like I'm going to have to suspect a stuck RABS valve next.

 

[scas]

This may have been covered, but I'm not sure.. Check to make sure you have no fluid on your shoes in the rear. I don't think anything waas said about actually checking the wheel cylinders if they are intact or failing.

 

[huntman58]

I have to agree with scas. Do not just look under the truck for leaks but take off the tires and rims and in the back remove the drums also so you get a good look at all parts and any wetness there may be. A MC can feel good and stop you good but still have troubles with internal leaks and go to the floor but any brake pedal that go's to the floor is bad period as it is a sign of a leak in your pressures or so out of adjustment brakes your lucky to stop.

disable the ABS system and try the brakes both motor running and off see if there the same if not then keep looking if they are then enable the abs again and repeat the test if they now go to floor then your problem is isolated to the ABS system if not then it leaves only the MC or even the MC booster as a possibility. You could also have a small leak in the back of the MC and it would then leak into the booster and you would not see it unless you remove the MC and take a look. Do not ask me how I know that one. I will say a ford truck made by Mazda years ago did teach me a lot being it had bad brakes period. Two wheel cylinder per wheel and other crazy stuff. If had a habit of blowing MC or WC all the time. It also had a weak system that I over heated too many times and going down Tioga pass here in CA. is not a fun place to lose your brakes! One other thing learned then was never ever no mater what remove your E brake! Again do not ask me why LOL

 

[runderwo]

I have had the drums off several times including most recently to fix a stuck adjuster, there has been no sign of a leak at any point. Also have had the MC off several times and no sign of an external leak.

I'm going to bypass the ABS pump next and see if that gets me a hard pedal.

 

[The_Bishop]

Did this ever get resolved? I'm helping someone chase the same issue on a Ranger with RABS only.

 

[runderwo]

Most of the time I have a hard pedal but I think I have a RABS dump valve that gets stuck open sometimes. It's the only explanation I can come up with for a pedal that is only soft sometimes.