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Brake problems after bleeding... any advice?


HelpIAmAParrot

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Hi everyone- newbie here hoping for some advice. So I recently got my granddad’s 92 Ranger. When I got it the brakes worked, but the pedal was pretty spongy feeling and would often sink to the floor at stoplights. Thinking there was air in the lines, I bled the brakes (my first time) using the one-person method I saw on a few YouTube channels.

Now here’s the thing- when I first went to pump the pedal during the bleed (car off), the pedal didn’t travel very far and wasn’t pumping any fluid that I could see when I went to check every few pumps. So I pushed it harder and felt it kind of push past a “wall” and sink to the floor, and from there it would push fluid through the lines. So I bleed all 4 in order, then go to start the car only to find that when the car is off the pedal is reasonably firm but when on it goes straight to the floor and only gets a little bite at the very end.

I looked at a few things online thinking it was the vacuum booster but most sources say the pedal should be too hard, not too soft, if the booster diaphragm ruptured. So what’s the deal? Did I bleed them wrong and somehow get MORE air into the lines? I was religious about checking the reservoir level when doing so.
 


RonD

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Welcome to TRS :)

First I think you have a leaking caliper(front wheel) or slave(rear wheel)
Or leaking brake line

i.e. steady pressure on the brake pedal(at stop light), and brake pedal slowly goes down farther and farther means fluid is leaving the lines, not air in the lines.

Air in the lines will give you the spongy effect, because air compresses at a different rate than brake fluid, but once it is compressed, brake pedal won't keep going down

It could be Master, one of the seals is leaking fluid back into reservoir, so no leak visible.
But it is usually a caliper or slave that leaks.
You need a helper for this
Start engine
Remove Master cylinders cap
have fluid fill to top
have helper push down on the brake pedal while you watch fluid level
Fluid should be flowing out, but very little, all you are really doing is transferring pressure from Master to the 4 wheels
have them continue to push on brake pedal, hold it down, if you start to see fluid level rising as brake pedal sinks down to the floor, replace Master, it is leaking fluid back into reservoir
The reservoir doesn't have any pressure in it anytime, cap is there to stop fluid from sloshing out, the Master's piston is open to reservoir when brake pedal is up, slight gap for fluid to get into cylinder, when you press on brake pedal the gap is closed and pressure is applied to the brake lines.
If the seal between piston and cylinder wall fails then as pressure increases fluid can be push back passed the piston and back into reservoir as brake pedal sinks to the floor

Or brake line, Rangers do have a common leak point on the rear brake line between gas tank and frame rail, it rusts out and starts to leak, need to thread an new brake line thru gap.

Yes, without the Power Assist from engine vacuum brake pedal will be hard even if there is a problem, so you do need to test with engine running.
You don't need to bleed with engine running.

Test for Power assist is done like this
Start engine
Press brake pedal down one time and let it up, just making sure you have power assist
Turn off engine
If power booster and check valve are holding vacuum you should get 2 or 3 more Power assist pedal pushes before pedal gets hard to push


Front and rear brakes are separate systems
You can lose front or back but losing both is unlikely unless you run out of brake fluid in the reservoir.

I use a stick to do one man bleeding, lol.
Master cap off
Start at right rear wheel, farthest from Master
Push brake pedal down with stick and hold it down by pressing stick against seat
Open bleeder and close
Repeat as you see fit , then move to next farthest wheel
 
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