Hi, I hope you guys can help
I have a 2000 4x4 with 4.7 engine. A couple of months ago the brake pedal was low and a couple of times it almost went to the floor. fluid level was good. I couldn't find any leaks. My first thought was maybe the master cylinder was leaking internally. I replaced it, bleed the brakes and it was good for a few days then the pedal started getting low again, but not to the floor. I had just bought four new tires so I took it to my mechanic to change the tires and check the brakes while he had it. He checked them over and found no leaks but one rear wheel cyl very slightly weeping fluid and recommended I replace it in the near future. he bleed the brakes and the pedal felt good. The next morning I got in it to go to work and the pedal went to the floor. I took it to my mechanic and had him replace both rear wheel cyl. Again good pedal stops good, but the next day pedal was low again. On my suggestion I asked him to install another master cylinder thinking maybe I got a defective one. he did, he told me that he bench bleed it and then bleed all four wheels and said he had a hard time getting the air out. I went for a test drive with him and it felt good. This morning low again. could it be the proportioning valve or something with the ABS. Please Help, Sorry for the lengthy post

 

There could be air in the abs module. If this is the case you'll have to have the dealer or another big shop with the DRB tool to bleed the abs.

 

Thanks Guy
I really didn't want to go to a dealer, I can imagine what they would charge.
I'll have to look around for a shop that has a DRB tool(don't know exactly what that is).

 

I'd call around to big shops like pepboys, etc, that might have it (specifically ask if they have the Chrysler DRB tool) and how much they'd charge to bleed the abs system. The DRB tool is what Chrysler calls their fancy computer gizmo that interfaces with all the computers in your car and allows them to be configured, customized, and bleed the abs system.

I will say that I'm not 100% sure on the abs system having air in it so it would be worthwhile waiting to see if anyone else here has any other suggestions for you first.

 

I appreciate your input Guy, thanks
I had two thoughts


(1) since the low pedal was their before any parts were changed, maybe I am still having a problem with something bypassing, maybe the proportioning valve. Correct me if I am wrong but under normal braking the ABS doesn't come into play only under hard braking. So if their is air in the ABS under normal braking it wouldn't be noticed. ??


(2) this is maybe a little more debatable. and just wondering if it would work, not sure I would do it.
If it is thought that air may be in the ABS. If I drove down a vacant road or parking lot and braked hard to activate the ABS would that push any air out of it and into the lines were a standard (or base) brake bleed could be done? theoretically it would, I think.

 

I'm not entirely sure about the abs system (this is the first one I've ever had). I'd think the fluid always goes through the abs, but it just doesn't divert it at all under normal braking. I'd be surprised if hitting the brakes hard would push the air out, but you could try.

 

Check your brake booster. Turn the key off and pump the brake peddle. Does it get hard? After pumping it, hold down on the peddle and turn the key on and see if you can feel the peddle drop.

 

Sorry for the delay in getting back


You're probable right that_guy, after thinking about it.


srch4me, I'll check that to make sure, it seemed fine to me


Thanks guys


I'm stopping buy my mechanic today he wants to plug in his scan tool(he has a big Snap On one I think) to see if it can do that DRB tool function.

 

It does exactly that, but isn't that normal?




stopped by the mechanic yesterday. plugged in his scanner and went through the brakes menu in it. Didn't see anything specifically about a DRB function. But it did say that if the car has 2 wheel ABS (which mine does)to do a standard brake bleed.


Oh, I did drive down a empty road were no one lives and applied the brakes hard enough for the ABS to come on. did it three times. I could feel it in the pedal and here the ABS pumping. No difference.

 

Yes that's normal. Could have a faulty master cylinder