ABS Brakes problem

[GrayWhale]

So my brakes are spongy and needs a bleeding bad.  I was just warming up the van and testing how far down the brakes goes while in PARK.  I stepped on it, medium (not hard), to get it to go all the way down. Did it for like 5 times.

The last time, it went "PFFFFTTTTTTTTT", like a  rubber cushion with a big filler hole was just opened. The ABS light came on and stayed lit and now the brake pedal has no resistance while going down s completely to the floor.

Turning the motor off, the brakes gets hard again and feels OK after 2-3 pumps.  Motor on, same deal with the ABS light staying on and pedal goes straight to the floor w/no resistance.

Master cylinder has no exterior leaks and looks newly replaced.  Brake fluid didn't go down at all I don't think so probably not mechanical leaks at the wheel cylinders.

Is this an electrical or fuse problem?

 

[poncho62]

Year and make of van?
Sure sounds like the master cylinder is internally leaking. If it looks new, it may be a rebuilt unit.....When replacing a MC, I put on new, not rebuilt.

 

[GotSmart]

Master cylinder has no exterior leaks and looks newly replaced.  Brake fluid didn't go down at all I don't think so probably not mechanical leaks at the wheel cylinders.

I would check every possible place.

It has all the earmarks of a bad master cylinder boost assembly.

 

[DannyB1954]

There are rubber cups or O-rings inside of the master cylinder. When they fail, the piston does not push any fluid. If you could pump up the brakes and they held, it would be air in the lines. A pedal that continues to the floor is usually a bad master cylinder.

 

[GotSmart]

My Haynes book says that a pedal that is holding when motor is off, but sinks when the motor is on is an indication of a bad master cylinder.  If it was a wheel cylinder, it would sink slowly, not quickly.  

The fact that the fluid level does not drop means it is not going anywhere, but back into the reservoir.   

I had to look it up to be sure.  I cant trust my memory any more.

 

[DannyB1954]

There are rubber cups or o-rings in the wheel cylinders. When they leak, fluid comes out and at minimum gets the wheel wet. The fluid level would be dropping.

 

[GrayWhale]

Year and make of van?
Sure sounds like the master cylinder is internally leaking. If it looks new, it may be a rebuilt unit.....When replacing a MC, I put on new, not rebuilt.

It's a 2000 Dodge B1500 conversion van by California something.

 

[GrayWhale]

Well, I just changed the Master Cylinder and it's not the problem. Bought a new one too (not remanufactured).

Brake pedal goes straight to the floor w/o any resistance. After about the 3rd time, the ABS light comes on and stays on.

Turning off the motor, I pump the brakes a few times and it builds pressure and hard/stiff. But as soon as the motor is on, it goes straight to the floor.

Please help.

 

[highdesertranger]

did you bench bleed the master before you hooked up the lines? after you bench bleed hook up your lines then bleed the lines at the master don't pump your brakes when you bleed them, if you have any air in the system you will just aerate you fluid(foam it). this is a common mistake when bleeding brakes. push the peddle down once do not pump, do this as many times as it takes. once you are satisfied the master is bleed move on to the wheel cylinders and calipers. I always do a gravity bleed first, open one bleeder at a time and wait for the air bubbles to stop, topping off the fluid often. then have someone push the peddle down once(again do not pump) then do the opening of the bleed valves when the peddle is on the floor close the bleeder. but only do this after the master has been bled. do the furthest from the master first and work your way back to the master. if someone pumped the brakes let it sit for awhile to let the air recombine. some antilock systems have their own bleeders and need to be bled according to the manufacturer specs. did you consult a shop manual? highdesertranger

 

[GrayWhale]

did you bench bleed the master before you hooked up the lines?    highdesertranger

Thanks very much for you help. 

Yes, I tried to bench bleed the MC first, but I think I did it wrong. It even came with the hose & fittings to bench bleed. I hooked it up to a vice and pumped, but I think too fast and too short (instead of slow and long pushes). It was foaming a little and the bubbles didn't cease. I got tired and thought it was the best it can be bled, so I just installed onto the van.

So you say that I should 1st try bleeding the system right? Starting with the MC (on the van). There are 2 lines, so I should crack each line, one at a time, while an assistant pump the brakes right? Then go to each wheel.

Or should I remove the MC and bench bleed it again?

 

[Gary68]

[video=youtube]

since i tend to work alone for the wheels i gravity bleed

 

[highdesertranger]

DO NOT PUMP THE BRAKES. leave the master in the vehicle, have your assistant push the brake pedal down one time. while the pedal is held down crack each line and retighten one at a time. you should see air come out the line nut and you should see bubbles inside the reservoir coming up from the holes that let fluid into the piston. keep repeating this until no more air. again I cannot stress this enough do not pump the brakes. if you do you need to wait awhile until the air recombines from little bubbles to one or two big ones. if the peddle is to hard to push without the engine running you can start the engine. btw any brake fluid that gets on your inner fender and anything else can be rinsed off with water make sure your cap is secure when you rinse. once you get the master done move to the wheels. you might need to bleed the antilock too. you really should have a manual for your vehicle that tell you how to do this. what type of vehicle do you have? you might have said but I don't remember. highdesertranger

 

[GrayWhale]

DO NOT PUMP THE BRAKES.  leave the master in the vehicle,  have your assistant push the brake pedal down one time.  while the pedal is held down crack each line and retighten one at a time.  you should see air come out the line nut and you should see bubbles inside the reservoir coming up from the holes that let fluid into the piston.  keep repeating this until no more air.  again I cannot stress this enough do not pump the brakes.  if you do you need to wait awhile until the air recombines from little bubbles to one or two big ones.  if the peddle is to hard to push without the engine running you can start the engine.  btw any brake fluid that gets on your inner fender and anything else can be rinsed off with water make sure your cap is secure when you rinse.  once you get the master done move to the wheels.  you might need to bleed the antilock too.  you really should have a manual for your vehicle that tell you how to do this.   what type of vehicle do you have?  you might have said but I don't remember.  highdesertranger

I'm such a dummy. I don't know if I over looked this or this just recently happened or what, but  when I press the brake pedal, fluid is streaming out from under the van, on the driver's side. There's a puddle there. So I may have bought this new Master Cylinder for nothing.  I'm thinking it's a wheel cylinder, but it's dripping down from, towards the middle; down the control arm and not right close to where the wheel is. It's raining and dark so I couldn't tell for sure until tomorrow.

And thanks for your instructions. I'd probably have to bleed it again at the MC.

Van is a 2000 Dodge B1500 Conversion V8 (probably the 5.3 and not the 5.9).  I have a Haynes manual.

 

[highdesertranger]

yep there is going to be more bleeding involved. the most likely place for it to leak is the rubber lines but there is no rubber lines in the front middle of the vehicle. let us know what you find. highdesertranger

 

[DannyB1954]

I used to have an old pump type oil can. something like this https://www.zoro.com/goldenrod-oile...gclid=CKC7usnHtc4CFQEaaQodHGsIYQ&gclsrc=aw.ds I put a hose on it the same size as the outside of the bleeder screw. Then filled the can with brake fluid.
You open the bleeder screw, then put the hose over it and pump fluid in. What this does is gets a lot of air out by reverse bleeding. Air in the system tends to go up easier than down. Be careful not to overflow the reservoir, (may need to take some out with an old turkey baster). Do this to all of the brake lines. After about 10 pumps, close the bleeder and take off the hose After all 4 lines are done go back around and bleed the brakes in the normal manner.

 

[ArtW]

I do a similar thing when I have to bleed brakes alone
I fit a hose over the bleeder, run it into a glass jar with a bit of fluid in the bottom, open the bleeder and slowly pump the brake pedal
The hose under the surface of the fluid creates a low pressure effect that keeps the fluid from moving back toward the master when the pedal is released
I've met a lot of people who think it won't work, but it's never failed me except on the type of ABS system HDR is talking about, that requires a specific sequence for proper bleeding
the puddle sounds like a hard line has ruptured or been holed