1991 Explorer pedal to the floor!!! HELP!!

[robbieholtz]

Hello all, just joined, i have an 1991 Ford Explorer 4x4. First off it has been a great vehicle. currently has 204,000 miles on it and never a major problem wrong with it!! runs great, we have had it for its life. Im having a problem with the brakes, the pedal is real soft and goes to the floor. Last night i replaced the master cylinder and bled the brakes 3 times. Im thinking its the power booster, has anyone had this problem?? where is the cheapest place to get one??

Thank you!!!

 

[BrooklynBay]

Welcome to this forum! It sounds like there might be air in the system. How did you bleed the brakes? A bad power brake booster would make the pedal feel hard.

 

[robbieholtz]

We started at the right rear and bled that one, then move to the left rear, then the front right and finally the front left. Before you start the vehicle the pedal is stift as can be, as soon as you start it you can push the pedal to the floor. The vacuum is very strong on the booster we checked that. We bled the brakes a couple times last night.

 

[geoph1986]

Is you brake fluid going down if you pump the brakes? Have you checked for leaks?

 

[robbieholtz]

no the fluid is not going down in the resovoir, we checked that last night. I did read something about the pushrod being too long or too short, have you heard of anything like that??? i think im just going to try and replace the booster, like i said the vehicle has 204,000 miles on it so its original

 

[geoph1986]

When you replaced the master cylinder, did you bench bleed it before installing it? And yea I've always found the pedal to be hard when it's a bad booster.

 

[DeRocha]

When you replaced the master cylinder, did you bench bleed it before installing it? And yea I've always found the pedal to be hard when it's a bad booster.

Ditto... when you replace the MC you need to bench bleed it to get the air out.. air will get trapped inside the MC do to its height and angle.. Bench bleeding is key to getting out the trapped air..

Take a peek at this video on how to bench bleed a MC

Bench Bleeding a Master Cylinder

 

[robbieholtz]

thanks for the info guys but yes we bench bled the master cylinder before we bled the brakes, the new master cylinder came with 2 fittings and 2 rubber hoses and we stuck them in a bottle of brake fluid and kept pumping the brakes until we seen staight fluid

 

[geoph1986]

What happened originally to make you change the master cylinder? The pedal become soft all of a sudden? And you're not loosing any fluid right? That's weird...

If your pedal became soft all of sudden, I don't think that the length of the push rod should come into play. With no loss of fluid, it sounds like air in the system. Sorry I can't help you.

 

[robbieholtz]

not it didnt happen all of a sudden, this is a spare vehicle that hardly gets drove....its been like that i would say a couple of years. it has brakes the pedal is just really soft...so i dont know...mc was just the first thing we tried to replace

 

[SPORTEXP]

How about the possibility of the old master cylinder actually going bad by allowing fluid to leak past the piston causing the soft pedal feeling. So you replace with a rebuilt one and didn't bench bleed it correctly. Then there;s the possibility (this happened to me) of buying a bum master cylinder that was bad from the beginning.

 

[scrivyscriv]

Sportexp, I agree!!

I've replaced the master all the slave cylinders on my explorer throughout the 62,000 miles I've had it, and I can tell you that if your pedal is going to the floor soft and with no brake fluid leaking anywhere, your master cylinder piston seal is BAD. You may have a hard pedal with the engine off, but I'll bet you can get it to bleed down all the way to the floor if you put continuous pressure on the pedal with the engine off.

I'd say return the master cylinder and tell them the seals are faulty and you want a replacement.

Other than that, your other option is that one or more of your slave cylinders is (are) bad. Not likely, but possible.

 

[robbieholtz]

its just really frustrating!!! i think we may try bleeding the crap out of it and seeing what happens, thank you all so much for your help!!!

 

[bisjoe]

You have rear drum brakes? If so, are they adjusted properly? If not, there will be a lot of travel for the cylinder pistons before shoes hit drums, that would cause this.

 

[mikeinri]

I agree with bisjoe.

I thought it was odd when I was reading this that you jumped right to the master, that's usually the last place people go, after making sure the brakes at the wheels are good.

I guess I assumed you had done that. If not, I would start there before spending much more effort on the master.

Good luck!

Mike

 

[scrivyscriv]

Robbie, your original post says your pedal was soft so you changed your MC and bled everything. I didn't think about this until bisjoe and mike posted about checking your slaves and adjustment, but they are right... I think we jumped on "changed master cylinder' and assumed you'd checked the rest of the system.

You may have poorly adjusted rear brakes, which I think you can adjust by going in reverse and applying the brakes several times or by turning the star-shaped adjusting wheel on the inboard side of the drums. All it does is turn the shoe in or out, and you can adjust it by how much drag you feel on the drum as you rotate it.

 

[mikeinri]

One bit of caution, I would pull the drums and check everything out at this point, rather than relying on the auto-adjusters. Those are notorious for rusting together and "freezing" in place, meaning, they won't turn to actually adjust the brakes. (Yes, I found this out the hard way.) If left long enough, the "star" part of the adjuster will wear out as the lever tries to engage it.

In any case, I would do a rear brake job at this point, and thoroughly inspect, clean, lube, replace, etc. any hardware that looks suspicious.

After my experince noted above, I always pull apart the auto-adjusters, clean them with a wire brush and parts cleaner, and lube them with wheel bearing grease when they go back together.

Hope this helps.

Mike

 

[geoph1986]

Yea those adjusters can be a real pain. In the fall, I did the rears on my friends Ranger, and they were seized so bad I ended up heating them red hot and dropping them into a vat of old trans fluid. Then I had to put them in a vise and work them apart. What a PITA.

 

[TB3]

Brakes

You probably have it fixed by now but here are some facts.
All the answers are true . #1 If the booster was bad the pedal would be hard when running. #2 If you bench bled the master and then all the wheels and the pedal is still soft or low then #3. your rear brakes are not adjusted right or you got a bad master from parts store. Bad masters that were rebuilt and sold don't always they are good. Tommy!

 

[beauboy]

I find it interesting that no one has given a thought to a faulty abs servo control module or valve. I'm having the same problem but my pedal went straight to the floor just 2 days ago. I haven't changed or adjusted anything yet, nor was this a "growing" problem. Mine was just all of a sudden. My '91 Ex is now parked in the garage and I'm driving my '69 VW bug to and from work. My fluid was down just a little, but no drops or residue to be seen anywhere. I hate to think that I'll have to take it to a professional for something that I should be able to fix.