Who wants to diagnose a brake problem??

Lately,

When I step on the brakes sometimes they fade to the floor. If I pump it once or twice it's all good. I have looked for leaks and the only one I have found is the master cylinder. It seems to leak out of the cover. It is 30 years old, does this sound like a master cylinder that needs to be replaced??? Get's a little tricky in certain situations

High5

 

:iagree:

Sound like a master issue Rebuilt's aren't too expensive so I would go that way.

 

My experience with rebuilt MCs has been, uh, "mixed" at best. Buy a name brand new one unless money is reeeally tight.

 

The master cylinder piston has worn a groove in it that is letting fluid around it. So as you press the piston brake fluid slowly leaks around the piston back to the reservoir and your pedal drops, when you pump the pedal you reset and it starts all over. The could news is that it won't "blow out" on you and you can still apply most of the pressure to your brakes, the bad news is that it will start to get noticeably worse. All that said. Time for a remove and replace of your master cylinder. Easy-peasy. Good time for speed-bleeders too. They will really help with bleeding out all the air in the system that will result. Good luck.

 

I'm planning on ordering one from 4wd.com. It doesn't say that it's rebuilt so I am ***-u-m-ing that it's new.

Around the master cylinder is the only place I'm noticing any fluid leaks.


High5

 

I understand the issues with rebuilds. I have worked at NAPA for the last 4 years. I just mentioned the rebuilds because there can be big $$$ difference when you go to the new ones.

 

Something else. If you do not keep your rear drum brakes adjusted properly, your pedal will occassionaly go to the floor.

 

This is ironic. I just got online to ask the exact same question about the brakes on my 75 and what do you know, some one else has the exact same symptoms and problem. Is replacing the master cylinder a difficult do it yourself project? Is there any obvious or while-you're-at-it upgrades that I should consider?

 

My opinion is "as long as your already there".

Its pretty much a remove and replace operation.
There are two bolts that hold it onto the firewall.
Remove them and unscrew the brake lines and viola.
Thats the easy part.

A new MC goes in the same way. . . . but you need to do a few things first.

Since you are going to have to bleed your entire system anyway now is a great time to look at the rest of your system.

Do you need new brake shoes?
- if yes, probably want to get a new drum hardware kit (springs and things)
- if yes, what shape are my slave cylinders in? just replace, not worth rebuilding

Do you need new brake lines, especially the two rubber lines in front and one in the back.

After that you will need to bleed the brakes.
If you don't have a FSM or a Chilton/Haynes manual you should get one.
It will walk you through all the things I mentioned, including bleeding the brakes.

But those are some things to think about when doing this.
None of which are very expensive and certainly worth looking at.

This is very do-able at home. You need a couple wrenches and a buddy to help you bleed the brakes.

Good luck.
There's only one way to know you did the job right.

 

thanks brieoff for the advise...I am going to tackle the brakes this weekend and after checking for parts it won't be that expensive at all to fix everything up. This forum has been a lifesaver many times.

 

For me too!!

 

Don't be shy about replacing the steel lines either. They normally rust up real nice where they poke through the frame and join the front rubber lines. Another place they like to rot out is on the cross-member of the frame near where they join the rear rubber line. USE ONLY A DOUBLE-FLARE TOOL FOR FORMING FLARES! Single flares crack too easily and are not allowed for vehicle applications. Practice with a flare tool and you'll be able to bend factory quality flares in a few tries. I actually enjoy making brake lines from scratch. Then stand on that pedal like you mean business and see if you can blow out any other lines. I mean squash that pedal like satan himself is on the other side. Yes, you might blow out a line or cause a slave cylinder to leak. Good for you, you may have just saved your own life!

 

Yeah, I ended up having to replace most of my lines for that reason.
The PO was smart enough to run brake line across the rear axle directly below the bump stop , flat as a pancake.
Would you believe the brake pads on that wheel were almost brand new.

 

Mine does the same thing. It leaks out the cover!!!
Every time I do a quick stop the fluid splashes up and leaks between the rubber seal and the MC. I'd replace the MC but every thing works perfectly. It just spills out a little fuid with each stop. As soon as I feel the pedal get a little soft I know I need some more fluid.

Weird huh.

 

Go to your flaps and go to the Help! section. They usually have an assortment of rubber master cylinder cap seals. Cheap insurance and less messy too!

I'd also recommend bench bleeding the master cylinder before installation. Saves a lot of frustration and time. Nickmil

 

OK,
So from my search I have learned that Speed Bleeders are the best thing since sliced bread. Anyone want to tell me what size I need????

This morning I pretty much had no brakes on the way to work. Had to pump numerous times to even slow down. I'm going to replace the master cylinder tonight and if it doesn't get done, I'll ride with the wife to work tomorrow. Too scary of a ride for me

High5

 

Anyone know what size bleeders I need?????

Bueller???


Bueller??

High5

 

You going to buy the bleeders at your FLAPS? Take one off and match it ... you can't drive the Jeep anyway. I used the sell the bleeder screw replacements, but I can't recall what the sizes were - too long ago. It's a standard size...

 

If you are near a FLAPS check with them they may be able to match one from a cylinder off the shelf. I did that many times for customers I had at NAPA