No Brakes ***ZERO*** Ideas?

[SteveB]

Hi All.
New here, great forum.
OK, brief history of the truck.
87 Gwag I picked up a few years ago from a guy who brought it out to Mass from California. Very clean. No rust.

Had brakes when I bought it, and drove it home.

After buying (late fall period), the rear brake line (hard line) let go, and the vehicle sat outside until spring, since I had something else in the garage I couldn't move.

So far I have replaced the following:
Master cylinder, Brake Booster, Proportioning valve, front and rear hard lines, hard lines from master cyl to Prop valve, front and rear rubber lines, front calipers, rear wheel cylinders and linings, as well as rear adjusters........ pretty much everything. The reason being most everything was either 87 vintage, or broke while going through the system.

Now, no matter the sequence ( bleeding), I can get no pressure on the brake pedal while the truck is running. The pedal can be pushed to the floor with no resistance. With the truck off, I have a firm pedal (meaning the pedal only goes down only a inch or so at most).

This truck has the proportioning valve that pulls out. I have read the Hanes manual about bleeding the system, and that book makes no mention of even touching that valve during bleeding. I haven't looked at a Chiltons...if one exists for this truck, but I do know from talking to people, seeing it in forums, and other how-to's on the net, that the valve should be opened for bleeding one way or another.

What's the sequence though, is the question. I've done bleeding with the valve opened for all 4, since I thought that was right, but reading other entries here, I see that may not be right.

Is it valve closed for the rear, and opened only for the front? Or is it the other way? Additionally, the other unknown, is if I'm sucking air somewhere I'm not aware of. No puddles or visable leaks though

I've bleed the old way with someone pumping the brake, vacume bleeding, and speed bleeders, all with no luck.

I have the correct bleeding sequence: RR,LR,RF,LF. (far to close)

Any ideas? this is driving me nuts. I've been on this for almost a month...seriously. Somethings wrong with what I'm doing...just not sure what it is.

Would appreciate any ideas or input.
Thanks!

[Tornado230]

Brakes

Sent you a PM.

[Kenall]

with the vac line discoed from the booster, will the wag come to a stop?
even tho with more effort?

[Elliott]

#1) Haynes sucks
#2) bench bleed the MC prior to bleeding the brakes with the pin pulled and starting at the furthest bleed screw working to the closest.

Bench bleed instructions: http://www.fullsizejeeps.com/gallery...BleedingMC.jpg

[SteveB]

I don't know if it will stop without the booster. I was wondering that myself. Right now I have wheels off to bleed the system, so maybe I'll bolt those back up and try it.
When I put it in the garage I had very little braking....luckily the garage is a little bit of an uphill climb to get into.

[SteveB]

Yeah, I'm no fan of the Haynes manual. It is what it is.
I've bench bled the master a few times just to make sure all the air is out, but I'll give it a go again.

Pin pulled for all wheels?

Thanks

[Kenall]

heres a REALLY dumb idea...

did you replace the rod from the booster to the master cyl?

the pin Elliot refers to is the one on the nose of the proportioning valve.
The books say to pull the pin as far forward as you can to disingage the proportining side of the valve to get full fluid flow during bleeding.

If you pumped all the bubbles from the master when you benched bled it. you should not have to do it again.

if the wheel are off to bleed the system...i take it, it is up on stands??

if so, then just put one lug nut on the rear drums (to keep them on) and then start the jeep and put it in D to test that way...( up on stands, wheels off) safer in the drive way than out on the street!

[SteveB]

Yes, the rod from the booster to the master was replaced. I did bench bleed the master before installing, so there aren't any bubbles coming from that.

I do know from trying, that with the wheels off, and up on jack stands, that the brakes do engage with the engine running, and the vehicle in drive. It's a pressure issue seemingly......getting the proportioning right.
One thing that was brought up, was resetting the proporting valve when the brake warning light comes on. While aware of how to reset it, I didn't aways clear it once set off....problem 1.

I also came to the conclusion that the pin on the proporting valve should only be pulled out for rear brake bleeding, and left in it's normal position for front brake bleeding.....I realized this by literally sucking the front system dry with the mightyvac...problem 2.

Basically, it's the procedure I following which seems to be the issue here.
Tonight, I'll go at it again, and see if I have any luck. This time with someone pumping the brake while I crack the bleeders.

[babywag]

Just my .02
I've never had to touch the prop. valve. on a Jeep, and I've owned a bunch of them.
I'd crank down the new line fittings (possibility of air entering the system?)
Then I'd try to gravity bleed the system.

EDIT: Just because the master was replaced doesn't mean it's good.
I've had more than one that was bad right out of the box.

I replaced the entire brake system on my '73 w/ '79 parts.
(hard lines, hoses, master, booster, etc.)
Bench bled the master first, then just gravity bled the system.

On my '88, I've gravity bled it several times.
1 - replaced front/rear hoses w/ lift
2 - replaced front calipers
3 - converted to rear disc

Again never touched the prop. valve., and never had a problem.
Your mileage may vary

[chrisnsarah]

I think there was a proportioning valve change in the late 70's. I know on my '75, you have to hold it open (push in the pin) for it to bleed properly.

I've never heard of having to "reset" a brake light switch. When you do a bleed job after a partial brake failure, the valve should automatially reset.

[Headhoncho]

Just my .02
I've never had to touch the prop. valve. on a Jeep, and I've owned a bunch of them.
I'd crank down the new line fittings (possibility of air entering the system?)
Then I'd try to gravity bleed the system.

I replaced the entire brake system on my '73 w/ '79 parts.
(hard lines, hoses, master, booster, etc.)
Bench bled the master first, then just gravity bled the system.

On my '88, I've gravity bled it several times.
1 - replaced front/rear hoses w/ lift
2 - replaced front calipers
3 - converted to rear disc

Again never touched the prop. valve., and never had a problem.
Your mileage may vary

X2 but mine is an 80 j-10 w/ hydroboost,Ford front axle and rear discs. Never touched the proportioning valve pin on anything I've ever bled brakes on and always had good response. Are the bleeders on the front calipers facing up? Did you adjust the rear brakes to a slight drag on the drums? I would have another person helping bleed if not up till now.

JR

[Kenall]

i just dont like the phenom of mushy brakes eng on, and viagra brakes eng off.

The only difference is vacum...and the vacum only applies to the booster.

now if the rebuild master is bad...woodnt u get mushy brakes 24/7?

[SteveB]

I ended up ordering another master cylinder (quality one). All of the lines have been gone over and tightened up as much as possible. I don't see any leakes, or signs of leaks at the couplings.

While waiting for the new master to arrive, I have the original master that was in the Jeep when I bought it, and it worked fine then. I'll bench bleed that, and bleed the system again.

I am starting to think the problem may be the master sucking air or leaking around the reservoir. I came across a suspect wet spot , where the reservoir goes into the master cylinder body.....didn't notice that before, and it's not from me dripping fliud, so it could be something.

I've got other things I need to do, so I'll let it gravity bleed as well.

[Kenall]

wait a sec.

isnt this the years of the 'pull away' master cyl. the type the pulls the caliper piston further from the rotor to decrease friction hence increasing fuel economy??

if something is fouled in that part of the system...would that give mushy pedal??

[back2spool]

Well...

I had the same problem a few weeks ago and thanks to some helpful fellas on here, I solved my problem.

#1) I was bleeding the fronts at the line and not the bleeder. This will not be effective at removing air form the system.

#2) After I got new calipers (cheap fix), I bled them, but I had the bleeders facing down instead of on top. The calipers need to be switched if the bleeders are down...

I am not trying to insult your intelligence, but sometimes we hurry to get stuff back together...