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Brake Bleeding

5K views 18 replies 9 participants last post by  Pchaz1 
#1 ·
I'm starting a new thread on this one, hope someone can help with this:

1998 4.0: replaced all the rusty brake lines with stainless, pre-bent as well as the rubber lines, using new copper crush washers. Replaced the bleeder screws with speed bleeders, replaced the master cylinder while I was at it. Tried unsuccessfully (using the proper wheel sequence per the manual) to get a good pedal after bleeding. Couldn't find any leaks.... Grrrrr. So then I replaced the power booster cause the old one sounded like it was leaking air. Same deal, very little pedal. Pulled the rear drums and couldn't find any leaks from the wheel cylinders. The shoes looked fine. Bled again, same deal, little/no pedal with engine running (pretty good pedal with engine off, but still feels mushy); Don't know where to go from here. Any ideas?
 
#2 · (Edited)
Did you at any point remove both front brake calipers so both were off at the same time? If so, you probably mixed up the left and right brake calipers and reinstalled them on the wrong side. They will bolt onto either side but they will not bleed properly if mounted on the wrong side.

Check to see that the calipers are mounted so the bleeder is positioned ABOVE where the brake line bolts to the caliper. Mounting the calipers on the wrong side would place the bleeder below the brake line making it impossible to bleed the air out.

This is how things should be positioned...
 

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#19 ·
Oh my goodness. You just fixed my issue. Thank you so much!



Oh my goodness. You just fixed my issue. Thank you so much! I have been pulling my hair out trying to figure out why I could not bleed my brakes. I purchased new calipers and the parts store took them out of the boxes and handed them to me because I had my cores with me. I got them mixed up....geez. Stupid error on my part. Thanks for the post.
 
#4 ·
The calipers are installed correctly: and no, I did not use a power bleeder; I used the speed bleeders which allows for one person to do the bleeding. The level in the reservoir doesn't seem to drop, except of course when I bled each wheel, and I was careful to keep the reservoir full during the bleeding process) I certainly agree that it sounds like there is still air in the lines, I mean, what else could it be, with everything in the system new?

Let me ask, would it be feasible to block off one line at a time (coming out of the proportioning valve) to isolate which line still has air somewhere? Would the system work with one of the three lines blocked?
 
#7 ·
x2 ^^ Hopefully you bench-bled the new master cylinder and yes, you can clamp off brake lines. If you want to check if a master cylinder has air in it or is leaking down you can hose clamp all four rubber lines and pump up the pedal and hold it. If the pedal doesn't stiffen up or if it leaks down you have an issue.
Also, you can always gravity bleed one wheel at a time. A small amount of air is very noticeable :)
 
#8 ·
Sorry for the confusion; "very little" pedal in my case meant that the pedal goes close to or all the way to the floor. With the engine off, I have more pedal, but mushy. with the engine running, the pedal drops all the way down. I did bench bleed the master cylinder using the method where you let fluid drip through the ports, the plug the ports, then depressing the plunger until it wouldn't go in more than about an 1/8 inch.
I've bled the brakes more than once now, and I get good fluid flow through all four bleeders. Cubnole, can you explain what you mean by "hose clamp" all four rubber lines? Wouldn't blocking off one port at a time on the proportioning valve do the same thing?
 
#9 ·
Sounds like air in system or a bad master as excessive pedal travel with no leak means either compressible air or fluid not going out of master like it should

With all your bleeding I would suspect bad master

Clamping is better as no lines interrupted so no risk of introducing air during the process to confound the diagnosis

If you clamp all three and still have excessive travel and still have no leaks has to be master or air above clamp points

What does quick pumping do as with air pumping typically makes pedal firm up during the pumping

Also do you have a basic TJ brake system or the add on ABS crap


Sent from my iPod touch using Tapatalk
 
#10 ·
Best way to bench bleed the master cylinder is to use the plastic fittings and hose kit made specifically for this. Full strokes until no more air bubbles are seen. Then, short strokes, about 1/4" to 3/8" until no bubbles are seen at the ports in the bottom of the master cylinder.
I have also seen more than one new master cylinder that was defective out of the box and had to be returned.
 
#11 ·
ok, help me out here: I was previously advised that the block-port-using plugs) method was superior to the method of using hoses to bleed the MC (my new Dorman MC had plugs for the former method); So, who's right here? Also, I'm trying to wrap my head around the "clamping"method of closing off lines - all three rubber lines have metal fittings at both ends; where would you clamp? Mine is the basis brake system, no ABS;

So, will a bad MC still allow plenty of fluid to go through the lines, as mine does? the master cylinder is not leaking fluid, (that I can tell).
 
#17 ·
I'm starting a new thread on this one, hope someone can help with this:

1998 4.0: replaced all the rusty brake lines with stainless, pre-bent as well as the rubber lines, using new copper crush washers. Replaced the bleeder screws with speed bleeders, replaced the master cylinder while I was at it. Tried unsuccessfully (using the proper wheel sequence per the manual) to get a good pedal after bleeding. Couldn't find any leaks.... Grrrrr. So then I replaced the power booster cause the old one sounded like it was leaking air. Same deal, very little pedal. Pulled the rear drums and couldn't find any leaks from the wheel cylinders. The shoes looked fine. Bled again, same deal, little/no pedal with engine running (pretty good pedal with engine off, but still feels mushy); Don't know where to go from here. Any ideas?
Find a helper and do a two person manual bleed and report back.
 
#18 ·
My wife helped me do a manual bleed and the problem persists. I'm confident that the MC is ok, I've bench bled it twice now using blocked ports and gets really firm. I ordered some of those hose pinchers and will start the elimination process outlined in t the write up by Centric; I'll let everyone know the results.

Joe D.

Joe D
 
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