Another "I can't bleed my front brakes" thread!

I replaced my front calipers and hoses and now the brake pedal is really spongy when the engine is not running and goes right to the floor when the engine is running.

I did a lot of searching on this forum and some suggestions were to check that the calipers were installed proper side up. I’m pretty sure they are...see picture below. Another suggestion to “bench bleed” the master cylinder but before I do that I’d like to know if I can avoid it.

Here's a few of my search results if interested:

http://www.naxja.org/forum/showthread.php?t=82114&highlight=bleed
http://www.naxja.org/forum/showthread.php?t=80095&highlight=bleed

To refresh everyone’s memory last month after I installed new hubs and u-joints my front brakes would overheat like a MOFO. Prior my brakes were fine and I’m still not sure why the overheating problem occurred, I was going to trouble shoot, but decided just to replace the calipers and hoses since they are the original for my ‘89 Laredo - no ABS. Also I think the brake fluid is from 1989 too!

Here’s my post from last month if interested: http://www.naxja.org/forum/showthread.php?p=714996

I installed reman calipers and new YJ brake hoses as I will be lifting my jeep later in the summer.

I started with the driver side by taking off the banjo bolt and letting the brake fluid drain until it stopped. I checked the brake fluid level and it was half way which I thought was kinda odd as I was expecting the master cylinder to be dry.

Then I did the same to the passenger side and but this time very little fluid came out and I thought that was odd....also the master cylinder was still half way.

Anyway I install calipers and brake hoses; sucked out the brake fluid in both front and back master cylinder reservoirs; wiped clean, then filled with new brake fluid. Geez forgot how clear brake fluid is!

I then proceeded to use a hand vac to bleed the front brakes but couldn’t really tell if there was a smooth stream coming out through the clear plastic hose. In the end I did it the old fashion way and had a helper pump up the brakes and bleed each.

Unfortunately the brake pedal is really spongy when the engine is not running and goes right to the floor when the engine is running.

So I’m not sure how to proceed!

Could the extra height of the YJ brake hose hold air and no amount of bleeding will help?

Why wouldn’t all the brake fluid drain after both hoses were disconnected?

When I use the hand vac does the master cylinder need to be open or shut or it doesn’t matter? My guess it doesn't matter?

Thanks guys! I'm at my wits end! I miss my Jeep!:shiver:

Is that long tube unsupported? If so I don't like it.

Calipers can be installed upside down, but it looks like in the pic, the bleed screw is at the top of the caliper, so your probably fine there.

I've crushed the copper gasket on the banjo bolt when changing Brake Hoses in the past, that caused a leak. Look for leaks around the banjo bolts. There suppossed to be moderately torqued, no more than any other bolt their size. I really torqued my banjo bolts down, figured it would seal better, it crushed the copper gasket and a leak resulted.

I've tried real cheapo vacuum pumps before, they don't work, although I've been told a moderate qaulity vacuum pump will do a fine job at bleeding brakes. How far did you crack the bleeder screws during bleeding? Air can be sucked past the threads on the bleeder screws, you only suppossed to crack them open a 1/8-1/4 turn, more and the threads get too loose and air can leak past.

in the Help! section at your local advance/autozone you'll find speed bleeders. I forget what size they are. Buy a pair and install them. Since you've got new calipers then you shouldn't have any problem. They come with a sealant/locktite on them so they go in tough.
Anyway, they're awesome, just turn them about 1/2 turn and then get out and pump the brakes a bunch of times. Might want to have a helper pour brake fluid into the master as you do that. I found I could get 5 good pumps on the pedal before it needed fluid.
Took me about 20 minutes to do a complete brake fluid change with speed bleeders.

langer1 said:

Is that long tube unsupported? If so I don't like it.

Click to expand...

Yes...that's the '95 YJ hose everyone recomends when adding a lift...which I'll do in a few months.

But the long tube bothers me too!

Do I have the correct one?

Got it from NAPA...Part TS 4138861 and TS 4138862

Rick Anderson said:

I've crushed the copper gasket on the banjo bolt when changing Brake Hoses in the past, that caused a leak. Look for leaks around the banjo bolts. There suppossed to be moderately torqued, no more than any other bolt their size. I really torqued my banjo bolts down, figured it would seal better, it crushed the copper gasket and a leak resulted.

I've tried real cheapo vacuum pumps before, they don't work, although I've been told a moderate qaulity vacuum pump will do a fine job at bleeding brakes. How far did you crack the bleeder screws during bleeding? Air can be sucked past the threads on the bleeder screws, you only suppossed to crack them open a 1/8-1/4 turn, more and the threads get too loose and air can leak past.

Click to expand...

I'll check the banjo bolts as I cranked them down fairly firm. But the ones I removed had concentric grooves in them, I'm assuming the grooves were from tightening down the bolts tightly?!

But if there was a leak by the banjo bolt wouldn't it leak fluid?

This was my first experience with a hand vac...cost about $50.00. I wondered too about how much to turn the bleeder screw and thought the same thing about opening too far and suck air past the threads...but if 1/4 turn is the most then I went too far at 1/2 a turn.

But I did the pump-the-peddle, hold and bleed and still no luck.

Thanks for your input...I appreciate it!

87manche said:

in the Help! section at your local advance/autozone you'll find speed bleeders. I forget what size they are. Buy a pair and install them.

Click to expand...

Thanks for the info on the speed bleeders...I'll add it to my list as they seem the way to go.

You can also let gravity do the work for you....

It's strange with the master cylinder cover off nothing drips out of the bleeder screws. But I'll give anything a try.

Air in the Master Cylinder?? You have to bench bleed a Master Cylinder if you get air into it, the Master Cylinder forces the air out, but draws it right back in as you pump it. You have to make little lines that connect to the brake lines on the Master Cylinder and then wrap up and into the reservour, below the fluid level. That way, air bubbles out and sucks brake fluid back.

OR, you can get speed bleeder as suggested. I have them on all my vehicles and they are god send if you accidentally suck air into the Master Cylinder. The one way check valve in the speed bleeder keeps the fluid moving in one direction, and thus the air doesn't get sucked back into the Master Cylinder, it will suck fluid from the reservour.

The vacuum bleeder should do the same, but you don't sound to confident on that went, might be worth the $20 to get a set of speed bleeders ($10 front/rear pair).

Brake fluid leaks are tough to see sometimes, they don't leak a lot of fluid, so you can sometimes miss the light dampness they leave behind. I didn't spot my leak at the banjo bolt, from the crushed copper gasket, until I had someone pump the brakes while I looked around, then I saw the tinest little drop of fluid coming from the banjo bolt and running down the side of the caliper.

I don't think air got into the master cylinder. As it was never really empty...

After everything was connected I did suck up the brake fuild in each reservoir but just added fresh back without touching the brakes. I don't think that added air into the system.

Looks like the speed bleeders are the way to go!

Thanks guys!

If you sucked too much out of the reservoirs you might well have gotten air in the system. Don't forget too that if the MC went dry you may need to bleed the rears first. Start with the farthest one, right rear, left rear, right front, left front. Keep the master cylinder open and keep it topped up. I usually vacuum bleed by volume. Figure an amount in the cup that is sure to be more than the contents of the line and less than the contents of the reservoir. Pump it out, close the bleeder, top up, and do the next. Do not worry about air being pulled through the bleeder screw threads. It is only going one way (out), so the only problem here is that you cannot tell when the bleeding is complete by looking at the bubbles. That's why I do it by volume instead.

For minor bleeding, the best one-man setup other than vacuum I've found is an old tailgate strut with a little bracket added to one end. I put one end under the steering wheel, and the other end pushes the brake pedal. Pump the pedal hard, set the strut, and bleed one wheel. Repeat for each wheel.

Hmmmm... have you thought about a plugged brake line or proportioning valve? When you say things like this:

Johnny V said:

.... my front brakes would overheat like a MOFO. Prior my brakes were fine and I’m still not sure why the overheating problem occurred, I was going to trouble shoot, but decided just to replace the calipers and hoses....

Also I think the brake fluid is from 1989 too!

Click to expand...

I'd at least blow the lines out with compressed air and get things squeeky clean front and back. You mentioned the fronts, what did you do (if anything) in the back? You HAVE bled all 4 wheels, right?

Yea, I didn't even think of that, but if you bleed only the front brakes, then your problems may be air that has migrated to the rears.

Yes, I can't imagine how it would do that, unless you have a bad combination valve. But its worth a try to see if it fixes the problem.

I'd bleed the rears as well. Anytime I have to bleed brakes, I just go and bleed all 4, and bleed enough that I replace all the fluid with fresh fluid. Fresh fluid really does keep the brakes working well much longer.

I should add that if nothing seems to work in the bleeding department it is not unheard of to have the master cylinder fail after a job like this. Sometimes when you bleed the brakes this will be the first time in years that the master cylinder has moved the whole length of its bore, and that might just be enough. Less likely than a need to bleed again, but possible.

Thanks Matt, I forgot that also, the end of the bore of the master cylinder can get corroded, rusted and pitted. When you push the piston down the full length of the bore to the end, where it hasn't been in years, that rust/pitting can cut the seals on the piston and then your good master cylinder becomes bad.

Nevada City Sparky said:

Hmmmm... have you thought about a plugged brake line or proportioning valve? When you say things like this:

Originally Posted by Johnny V
".... my front brakes would overheat like a MOFO. Prior my brakes were fine and I’m still not sure why the overheating problem occurred, I was going to trouble shoot, but decided just to replace the calipers and hoses....

Also I think the brake fluid is from 1989 too!"

I'd at least blow the lines out with compressed air and get things squeeky clean front and back. You mentioned the fronts, what did you do (if anything) in the back? You HAVE bled all 4 wheels, right?

Click to expand...

Many things have crossed my mind about this. I was thinking when I used a c-clamp to open the calipers prior to my hub replacement that it either moved dirt some where to create a blockage or damaged the proportioning valve or something else.

I was going to do a full bleed but couldn't get the bleeder screw off the right rear. I'm going to have to pull the rear tires to have easy access today.

If I blow out the lines I'll have to bench bleed the master cylinder or can I use the hand vac?

Thanks guys.

Matthew Currie said:

I should add that if nothing seems to work in the bleeding department it is not unheard of to have the master cylinder fail after a job like this. Sometimes when you bleed the brakes this will be the first time in years that the master cylinder has moved the whole length of its bore, and that might just be enough. Less likely than a need to bleed again, but possible.

Click to expand...

Thanks Rick and Matt!

That make sense with the master cylinder as there doesn't seem like there is much pressure building up even when pumping the brake pedal to bleed manually. "Feels" like the fluid goes right past the pedal...if that makes sense.

If the front were bled properly wouldn’t there be some firmness to the pedal and not go to the floor?

Should I get a new proportioning valve incase it's seen it's better days?

I'm finishing up my coffee and getting up the courage to do battle with the brakes today.

I'm really not looking forward to this...

If you find out whats wrong with your brakes let me know! I bought my 89 used and the brakes felt very spongy so I installed a new master (bench bled) calipers,rear hose,rear wheel clinders, adjusted the rears up and bled several times. I still have a horribly spongy pedal that goes almost to the floor. The truck is barely driveable.Thanks!

The combination valve usually doesn't go bad (it has the proportioning vavle in it). Someone suggest cleaning it. BUt I'd check the Master Cylinder first. Try bleeding the rear brakes as well as the fronts, in case air got in the rears somehow. Then I'd look at the Master Cylinder. You should be getting a brake light if the Master Cylinder was bad, since one stage usually blows, its unlikely both stages blew at the same time. You could always take the master cylinder apart and inspect the seals and bore. I don't think they make Master Cylinder Rebuild kits for the aluminum master cylinders, I guess they don't trust people to hone the soft aluminum. You may have to get a rebuild, sometimes they are only $30.