I have a 1999 Econoline 150. I suspecting that there is a problem inside the ABS hydraulic unit and it is releasing pressure when the pedal is pressed. I would really like to bypass the ABS and see if that is the problem.

BTW, the ABS light is on so that implies the ABS is shut down but the pedal still goes to the floor. I have done all the bleeding stuff. I understand that the ABS needs the factory scan tool to fully bleed the unit. I was hoping that with the ABS shut off that section wouldn't need bleeding.

I can get good pedal with the engine off but when the power brakes are active the pedal goes to the floor.

Any ideas?

Thanks

Pete

 

I highly doubt there is a "kit" but you could just make up a bypass. You'll need to figure out the tube nut size and get the right fittings. A couple 90 degree fittings and a couple T fittings and you can put it together with a little work. It will probably be a royal pain trying to get it to fit together, unless you have drawers full of fittings you can use.

The reason you think you have good pedal feel with the engine off is that there is no vacuum boost. That is why you feel a hard pedal. You just aren't getting any pressure at the wheels though so the "good pedal" is not real.

I'd recommend taking it to a shop to see what fault code is causing your ABS light to come on. That should be your first step.

 

Well, I built a bypass for the ABS. I still have no brake pedal (with the engine running=boost). I have bleed the crap out of this thing.

I replaced the Master Cylinder. It passes the recommended test. That is I put plugs in the outlets of the MC and the pedal barely moves even when the engine is running. Therefore, no internal leaks in the MC.

If I plug just the front output of the MC so just the back brakes are actuated the pedal goes half way to the floor and then when I start the engine it goes 3/4 to the floor.

If I connect both front and back, the pedal goes to the floor. NOTE I am bleeding the crap out of every line every time after I open a line. By "bleed the crap" I mean, I get some bubbles during the first two or three pumps, then none. I continue to pump for 15 more presses. That leaves me with about 1/2 the MC reservoir still full and I refill it at that time.

I can't understand where the fluid is going. The system is completely closed, no leaks anywhere. Since I can bleed each wheel I know all the connections are in place. Since I can pump up some pressure with the engine off and I can see the pads move and hear the drums move, I know things are connected.

WHERE IS THE FLUID GOING??????????

It is killing me!!! It is like there is a balloon somewhere that blows up and collects the fluid. Then returns it when I let off the pedal.

Thanks,

Pete

 

Have you checked your flex lines? Perhaps you have a bad flex line that is absorbing lots of fluid... literally blowing up like a balloon.

I would suggest replacing all the flex lines just to be safe.

 

also - confirm that someone didn't put the calipers on wrong... all your bleed screws are at the very top of the calipers, right?

 

I did take a look at them while under pressure and couldn't see anything like that but I admit it is difficult to see the entire lengths.

Right now I disconnected all but the left side front. The rear is plugged at the MC. The line to the right front is disconnected and plugged.

There is just a short length of flex line from the body to the caliper. Easy to see when the pedal is pushed. I don't see or feel any expansion of any kind. The pedal moves about 2 inches with the engine off, then another inch when I start it. Ends at about half way to the floor.

To answer the question in your next reply, the calipers are upright and I cleaned everything in that area including the pins the calipers slide on to make sure they are running smooth.

I am not going to change the flex line yet. I made sure the rear brake shoes are properly adjusted. I think I will connect the rear and see how much brake pedal I loose. I think I will loose more with the rear because the springs pull the shoes to the full open position, sending fluid back to the MC. With pads that doesn't happen, right?

I'm sure I'll be posting more.

Thanks

Pete

 

no... if drum brakes are properly adjusted it will just pull the shoes back enough for a running clearance.

They should automatically adjust during driving. If you just put new ones on you need to either manually adjust them or do some driving to get them to auto adjust.

 

One of the adjusters is broken. But I adjusted both like I used to before they had automatic adjusters.

For an update, I have connected just the Left front and Right front. The pedal goes to the floor when the engine is running (1/2 way manually). I have bleed the crap out of them. Figuring the only thing left on the right side (left side gave me great pedal) was the wheel cylinder, I installed a new one. Bleed like crazy, even left it "gravity bleed" over night. Still, the pedal goes to the floor. I may have to take it to a shop. God that hurts. This isn't rocket science. It isn't even moped science.

Pete

 

Sounds like you could possibly need calipers, lines, and new front pads. As the pads begin to wear you will lose some pedal, but not much.

 

I would suggest purchasing/borrowing a brake bleeder vacuum pump. That way you can pull fluid down the lines and not rely on gravity to get all the air out. That does not work well. Further with the pump you can insure all the old fluid is removed.

 

I am still trying to find the problem. I am starting to think that the booster is moving, just a little, but enough to let my pedal go to far to the floor.

I am going to start a new thread asking folks to tell me what their vehicle does.

https://www.f150online.com/forums/wh...ml#post4594458

Pete