I am trying to figure out whats wrong with my 98 durango.
I bought it used a month or so ago and have done alot of repairs to it,
ball joints, tie rods, front brakes and rotors, rear wheel cylinders.
When I got it I had alot a very stiff pedal. After doing the work I drove it was ok the first mile, then I could hear the abs noise kick on when i got on the brakes, then the pedal went to the floor. When the vehicle is off the pedal becomes firm, but as soon as you turn it on the pedal sinks and then of course the lights come on on the dash due to no brakes. We tried to bleed the brakes and can get fluid out of the fronts,but can get nothing out of the rears. It dosnt seem to me we did anything that should have cause it to have no pedal. Ive heard some suggestions from it could be the master cylinder or it could be the brake control assembly, any ideas would help guys, thanks.

 

It's likely either your master cylinder is shot and needs replacing or the brake booster needs replacing. First check out to make sure there's no obvious leaks for the brake booster vacuum lines, then check around the master cylinder to make sure it's not leaking and causing it to kill the diaphragm.

If all that checks out, remove the calipers and inspect the brake lines and bleed the lines to make sure there's nothing gunked up again that wasn't there the last time you checked. With no pressure to the pedal though, I have reason to believe the brake booster or master cylinder are the best places to start looking.

 

If you aren't getting any fluid out out the rear wheel cylinders on the bleeder screws then you have an issue up stream from both wheels. It could be bad rubber lines to the rear wheel cylinders or something restricting the flow. Once you get help by the power brake then you have nothing, well it sounds like something in the lines is bad or a Master Cylinder or Brake Booster.

The other thing I question is the check valve on the booster, but even then you should have half pressure.

I would first find out why you don't have fluid to the rears. Then question other parts.

 

+1 hydra, figure out why you arent getting fluid to the rears and i bet you find your problem

 

+3

Enrolling the pros at this point would be prudent advice.

IndyDurango

 

Yeah i had a couple places try to power bleed it with no luck,but unless you want to spend a bunch of money to get to the bottom of it. It seems weird the brakes seemed to have been fine and then nothing. I think im gonna start with the master cylinder and then go from there.

 

A good way to test the master cylinder is to shut the car off and pump the brakes till they get hard. After they are a little stiff press the brake pedal down and try to keep pressing. If it falls to the floor then the seals on the shaft inside the master cylinder have died. Do not see boosters go bad very often. Make sure to bench bleed the master cylinder if it is bad or you will have the same problems all over again.

 

I wouldn't replace the master cylinder unless you are on the last leg because if you get any air into the ABS pump then you have to have it bleed by the dealership.


You have a bleeder at the proportioning valve then go to the rear splitter and try there. If you can't seem to find this issue I think it's time to get a shop involved as Indy stated ^^^^ up there. Brakes are just something you can't go screwing around with.

 

Proportion valve is about $100 bucks at the dealership. If you can pump up your brakes when the engine is off and they stay hard with pressure it isn't the master cylinder. If it falls then there is a leak or cylinder is bad. If it falls pump it a few times to make sure you not missing a leak. fluid could be sitting on a frame rail. I got burned on that once.

 

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