The lines from the master cylinder to the

The master cylinder. What you have is something that is pressurizing the front brake circuit but not the rear. The only possibilities would be the Master Cylinder or a proportioning valve.

Did air get into the master cylinder? If you can, try bleeding the master cylinder. The fact that you aren't getting any fluid out of the line suggests that the master cylinder isn't pumping fluid.

Master cylinders are (usually) on a split circuit system - that is, the front left brake is on the same line as the rear right. The front right brake is on the same circuit as the rear left.

A point to be aware of is when bleeding brakes/doing brake work and if the master cylinder runs dry, is that a seal inside the master cylinder can fail/twist over and not pressurise that particular line, even though it may pressurise the opposite brake line.

I'm in the UK. I have a 1998 Jeep Grand Cherokee 4 litre, which I am slowly rebuilding. Three weeks ago I fitted new front brake rotors, new front callipers and pads. I've been rebuilding cars for over 40 years now and have done countless brake overhauls.

.. and could I get a hard pedal after the job was completed? I must have bled the brakes three times a day for a week and couldn't get a brake pedal. I phoned a full time mechanic I know - he came and tried to bleed the brakes three times and couldn't get a hard pedal.

That's when you think 'The master cylinder was working before I started the job so it must be still working now'.

I fitted a brand new master cylinder and because some parts for older jeeps are hard to come by in the UK, I fitted a second hand proportioning valve. When I bled the brakes again the pedal became rock solid. Fixed.

You're probably fed up with your braking problem now ... and apparently this 'no fluid/brake pedal' is more common than you may think.

Try bleeding the master cylinder if you can. If you suspect that it isn't fully working - try an overhaul kit which is cheaper than a new master cylinder.

As for changing the proportioning valve .. that's your decision. My brakes now work though the truth is I don't actually know which was at fault as I changed both the master cylinder and proportioning valve at the same time. Maybe both were at fault, for whatever reason. I genuinely don't know.

The positive aspect is that you are doing your own work and know what you're doing. You're saving on labour charges.

proportioning valve

check for fluid before and after the proportioning valve by disconnection the line after the valve and applying the brakes, if no fluid after valve try before valve if fluid is there then it is a bad proportioning valve. you did bleed the master cylinder before connecting the brake line and trying to bleed the brakes all at once right? If the master cylinder was not bled first then a lot of air may have been forced into the rest of the brake lines.

Your vehicle is equipped with antilock brakes. It either has a "Rear Antilock Brake System" (RABS) or it is equipped with "4 Wheel Anti-Lock" (4WAL).

Some units use a pressure regulating valve that screws into the rear port on the master cylinder.
All units built in 1995 have lines that go to either the Hydraulic Control Unit (HCU) or to the RABS Valve. However, that vehicle does not use a conventional proportioning valve, so I am not sure what to tell you.

Could be a couple of problems, bad master cylinder (not bench bled properly or bad seal out of the box, I have had a few like that), proportioning valve seal, brake line not tight/sealed properly sucking air into system,bad caliper. First of all, are you losing brake fluid along with your pedal? Need to know that first. If you are, try to find where you losing it from, you will find your problem. There can be absolutly NO leaks in a brake/hydraulic system. If not, check that all lines are tightly seated and nuts are quite tight using a line wrench to get proper torque. If so, you can replace the master cylinder again (take old one back to store for new one under warranty) and be sure to thoroughly bench bleed. When bench bleeding, take your time, do not push plunger in too quickly, use a SLOW steady push until ALL bubbles, no matter how small have been eliminated. Tapping on the bottom of the cylinder while bleeding will help remove trapped air. Even a very small amount of air will take forever to bleed out at the calipers. If cylinder/all calipers/lines appear to be right, I would suspect the proportioning valve is faulty. To find it, follow brake lines from master cylinder to where they go into the valve. Replace. Hope that helps.

There is probably air still in the lines. Did you bench bleed the master cylinder before installing it?

It doesn't connect to master cylinder. The line should connect to a proportioning valve, then from valve to master cylinder.Star at master cylinder and follow lines to proportioning valve.

check for low brake fluid if low look around for signs of leaks.if all is good change master cylinder.

the stratus is know for clasped rear brake hoses .This stops the flow off brake fluid. try opening the brake lines at the master cylinder that go to the rear.pump up brakes first! if you got fluid than check the brake line if this is rear disc brakes on the line at the rear will be a built in proportioning valve.if drum loosen rubber hose line before the rubber part to see if you have fluid. If you do replace the brake hose! On you 74 challenger by the way i love dodge! any way on the valve there is a small button on the front of the proportioning valve that pops out it needs to be tap in lightly. also hit the brake peddel kind of hard a couple off times if that doesn't work. thanks for your question


p.s that hex bar on the is a junction not a proportioning valve .