• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Rear brakes getting no brake fluid pressure...

freerider15

freerider15

NAXJA Forum User
Location
FoCo, Crawlorado
Alright, i was driving home when my brakes decided to go out. I got it home (brake pedal went all teh way down, no stopping). I tried re-bleeding my brakes only to find that my rear brakes arent getting much fluid. There arent any kinks in the line I can see, so thats not the reason as far as I can see. The fronts are getting good pressure as they squirt the fluid out when bleeding. The rears BARELY drip when trying to bleed it. Took of the rear coupler to find that its from somewhere up the line. As we speak I have the line that goes to the rear coming out of the combination valve off, and it seems to barely drip when someone pushes on the pedal, wtf? Has anyone else had problems like this?
 
Sounds like the proportioning valve. Has there been a leaking wheel cylinder?
 
The fluid in the fluid resevoir is clean. Im trying to see if I can locate a clog, but its kind of hard to do when you don't have anyone to push on the pedal for you so you can watch. I thought when I disconnected the line from the combination valve for the front brakes (which have good pressure) that it would squirt fluid as well...but it doesn't. There is a junction in brakeline before the line coming out of the combination valve completely starts to go all the way to the rear. Im thinking that Ill pull those apart, and see if it has any pressure coming out of there. When I did bleed the front brakes, the fluid was a very dark color on the beginning of the first few pumps.
 
are you on a clean dry floor? make sure there's not a leak between m/s and rears. the fluids gotta be going somewhere.
 
Well I pulled off the combination valve, and noticed something. I could blow through the front part, or put brake fluid in it, and it would flow out the other side. Now when I tried either of those on the sides that the rear uses, nothing...won't flow through and I cant blow through.
 
The combination valve / proportioning valve restricts flow to the rear, that is by design. However if your lines are clear, you have no leaks, your master looks good, then I say change it out. Brakes are not something to gamble on, even though it's just the rear (I've driven without rear brakes numerous times) being that the problem *may* be in the proportioning valve it could affect the front. Replace it and hopefully be done. Just remember that you're going to have to bleed a lot of fluid out, I'd go through an entire large jug of brake fluid before calling it done.

Sequoia
 
I pulled off the prop. valve (combination valve) to inspect it, and after some messing around (took out valve, cleaned things up) I got more pressure flowing out of the rear brake lines. Well I then realized when the brake pedal got pumped and I had to valve out, I pulled air into the master cylinder, so I needed to bench bleed it. Well got it good and bleed, but then managed to strip one of the prop. valve's holes, so ill be putting in a new one anyway :rolleyes:. Now heres the thing, when I was out in Moab, I managed to throw power steering fluid in the brake resevoir. It wasn't much, but I know that can be extremely bad. Drove it back with no real problems until now. If my lines were swelling up and seizing, then I wouldnt be able to press the pedal all the way down to the floor either when everything is connected (major resistance). The front when bleeding, shot out fluid like it was working perfect. When I had played around with the prop. valve, the rear started to bleed, but not as much (squirting wise) as the front.
 
freerider15 said:
I pulled off the prop. valve (combination valve) to inspect it, and after some messing around (took out valve, cleaned things up) I got more pressure flowing out of the rear brake lines. Well I then realized when the brake pedal got pumped and I had to valve out, I pulled air into the master cylinder, so I needed to bench bleed it. Well got it good and bleed, but then managed to strip one of the prop. valve's holes, so ill be putting in a new one anyway :rolleyes:. Now heres the thing, when I was out in Moab, I managed to throw power steering fluid in the brake resevoir. It wasn't much, but I know that can be extremely bad. Drove it back with no real problems until now. If my lines were swelling up and seizing, then I wouldnt be able to press the pedal all the way down to the floor either when everything is connected (major resistance). The front when bleeding, shot out fluid like it was working perfect. When I had played around with the prop. valve, the rear started to bleed, but not as much (squirting wise) as the front.
Click to expand...

I hate to be the bearer of bad tidings, but it's possible that the PS fluid ruined the cups and seals in the master cylinder. It can turn that rubber to goo, and if that has happened, all sorts of problems will occur and recur, including bits of that goo clogging the proportioning valve or other passages, and if the wrong fluid got down the lines, you risk blown slave cylinders, softened caliper seals, swollen flexible lines, and total brake failure. If the soft lines swell, you might still feel pedal firmness, but the fluid won't necessarily be going through them.

You could, of course, be lucky, but having a problem like yours at this point suggests that some kind of gradual deterioration may have started to take its toll. At the very least, I'd make sure the system is totally, totally flushed, and I'd be very wary of taking it on the road until I was dead sure that there was no damage to rubber parts in the system.
 
If I were to replace the MS, and the prop valve, I would think that I should be pretty good. I dont have any soft lines other than the possible rubber in 1 of 3 short sections of steel braided hose. It didnt swell the fronts as those had good pressure. Otherwise everything in my system is hard lines. When I bench bleed the MS, when I pushed on the push rod, it put alot of fluid out. There wasn't much steering fluid put in, about what it would take to make it go from the "add" line to the "full" line, which is maybe 1/8th of the container.
 
Yes, Power Steering Fluid will be the death of your brakes system. My brother put some PS Fluid in his master cylinder and every piece of rubber and seal in the system swelled to 3 times its normal size. It destroyed the entire brake system.

From the sounds of your trouble shooting, it does sound like a MS or Prop Valve, but if the problem is still there after replacing those, then;

Have you pulled apart the rear wheel cylinders. Its possible the cups/seals in those wheel cylinders swelled so bad they are actually blocking the port to bleed, maybe even the rear brake hose. Its only a couple of bucks for the parts to rebuild the rear wheel cylinders, you don't even have remove them, although you do have to disassemble the rear shoes.
 
I was very careful not to select the PS fluid that looked exactly like the brake fluid container and they were right next to each other at the gas station. Starting pouring it in the master cylinder, Oh Sh*t, noticed the label was PS fluid. I immediatly sucked and wiped the master cylinder reservoir dry, never even pumped the MS once, and put brake fluid back in after I hand dried it with a towel. Too late, it wasted the Master cylinder piston cups already. Had to replace the Master cylinder to get any brake pressure the next day!
 
Alright, heres an update...still not doing much better. First, I got the prop. valve replaced...still no pedal. Then replaced both wheel cylinders...still no pedal. I just replaced the Master Cylinder today and bench bleed it...still no pedal. I did notice that the MS and booster are not sealing 100%, so I need to fix that. Could I use a small amount of RTV to seal them? I think I will try replacing the calipers as well, since they're not to expensive. Other thgan that the only thing in the system that is rubber would be the SS braided brakelines up front. But when I bleed the system last night, there was alot of fluid still streaming out of the front brake, enough to squirt halfway toward the opposite tire. Im thinking about getting the system sealed as best possible, then replacing everything under warranty, and having a go at it again. This is my DD, so I really need to get these brakes working again.
 
So what happend? Did you get them fixed? My brakes feel very week now Just happend they fell strong at first but then as I come to a stop they get softer and the pedal is all the way down. I tried to lock them up at 60mph with all my weight on them 175lb, and they wouldn't lock
 
Well, I did get them fixed for a while, until i think I killed my booster from having someone winch from me for most of a trail. I found that I really needed to go through and tighten up all the fittings, and everything seemed allright. I did change out the prop. valve and I do think that helped quite a bit, as well as wheel cylinders. BUT what was really really needed, was a good vaccuum bleed. I had Tom (Old Man) vaccuum bleed my brakes, and they were 100% again.
 
You must log in or register to reply here.

Similar threads

O
Brake failure light randomly coming on
Replies
4
Views
2K
RCP Phx
R
O
Resetting Brake fault light
Replies
1
Views
973
kastein
kastein
S
Master cylinder issue
Replies
2
Views
2K
SurplusFan98
S
X
My brakes are crap
Replies
12
Views
3K
xjklmnop69
X
B
Left rear brake went kapow
Replies
6
Views
2K
Rob Mayercik
R
Back
Top