What is this part??

[Jessica]

Again...I can't find it in my manual but it appears to be leaking.

It would be really helpful to have a manual that had really good pictures of everything with arrows and names of things...

 

[CJ]

Brake master cylinder. If it is leaking from the lid you can just get a new gasket.

 

[Jessica]

Thanks! Now I at least know where to look in the manual. So it's leaking brake fluid...hrmmm. Doesn't sound too safe.

 

[Old Dog]

As cj said if it's just around the lid just get a new gasket.
Now if it's leaking around a line you have a problem, but try to tighten the line before you try to change it.

 

[IOPort51]

Keep in mind that the best paint remover in the world is brake fluid. It will go to bare metal before you can wipe it off.

 

[Jessica]

It's kind of pooling at the bottom...not sure exactly where it's coming from. A whole new unit doesn't look very expensive and mine does look pretty old and rusted, however replacing it sounds a bit tricky with the brake line bleeding, etc. and since brakes are so important I'm not sure if I have the confidence to do it myself.

 

[Jessica]

Keep in mind that the best paint remover in the world is brake fluid. It will go to bare metal before you can wipe it off.

I do have a new paint job in mind! Can I wipe it down with brake fluid instead of sanding?

 

[mylittlecj5]

the only tricky part is getting the lines loose without stripping them out. Get a set of line wrenches to get them off without messing them up.
If you don't break the bleeder screws at the wheels loose, you shouldn't have to bleed the lines out again. No air will enter the lines normally if you are careful.
There is also a connection under the dash that hooks the master cylinder to the brake pedal. Normally its a cotter pin (easy to remove) but pay attention to the brake light switch and how it mounts on there. Remove it, the lines under the hood, and the 2 bolts holding the MC on, then reverse the procedure to install the new one.
Should take you about 30 minutes at the very most (an experienced mechanic will do it in less than 10 minutes).
Have fun with it, its pretty easy!

 

[Jessica]

the only tricky part is getting the lines loose without stripping them out. Get a set of line wrenches to get them off without messing them up.
If you don't break the bleeder screws at the wheels loose, you shouldn't have to bleed the lines out again. No air will enter the lines normally if you are careful.
There is also a connection under the dash that hooks the master cylinder to the brake pedal. Normally its a cotter pin (easy to remove) but pay attention to the brake light switch and how it mounts on there. Remove it, the lines under the hood, and the 2 bolts holding the MC on, then reverse the procedure to install the new one.
Should take you about 30 minutes at the very most (an experienced mechanic will do it in less than 10 minutes).
Have fun with it, its pretty easy!

That does sound easier than I thought but when you say "break the bleeder screws at the wheels" I'm not sure what you mean. By the wheels meaning not anywhere near where I'd be working? Or ???
If I can just take it out and replace it without having to drain or bleed anything I'd try it and just be sure to test the brakes really well before I drove it.

 

[mylittlecj5]

Yea thats where you would bleed the brakes, if you introduce air into the system. If you just remove the old part and replace it right away, you shouldn't have any air introduced, so no bleeding required.

 

[CJ]

I will have to disagree a bit with Mylittle, just changing the MC is not enough. You have to bench bleed it also. If you loose any fluid from the hard lines (lines fittings are not elevated above the tubing) then you will have bleed the lines all the way to the wheel cylinders.

Brakes are not what you want to learn on how to work on your CJ. If your ignition, carb, starter, clutch doesn't work on your CJ you does not move. If your brakes do not work, you do not stop!

Not stopping is inherently more dangerous then not starting.

 

[mylittlecj5]

DOH! I did forget that part, sorry! Still, that is not a hard thing to do, and the instructions are normally included with the MC.
I just did mine while it was bolted to the firewall. Just ran the lines into a jar filled with brake fluid and pumped the pedal. Of course I cheated a little and have DOT approved flexible lines running from the MC to the PV.

 

[ftwflh]

I like to "bench bleed" the MC in a vise before installing.That way I dont usually have to bleed all the wheel clinders.

 

[dave123]

Brakes are a life and death safety issue. I can tell by your questions (no offence, we all have to learn this stuff at some point) that you have no idea what you are doing. Save yourself the headache and the possible unsafe Jeep and take it to a mechanic. Unless, of course, you have someone that can help and knows what they are doing, then it’s a great chance to learn!
I hope you take this in the spirit that it is written. I don't want to sound rude or condescending. Just want you to be safe.
Dave

 

[jeepindavis]

Make sure to bench bleed the new master cylinder though or you will get air in the brake lines. This too is very simple. Just fill the new master cylinder with new brake fluid and use a screwdriver or similar to push the piston that seats in the brake booster (if you look at the new master cylinder from the back - you'll see the piston). Just push it in and out until fluid comes out where the lines hook up to the MC. Placing the MC in a bench vice makes this easier and then you can put your fingers over the holes for the lines and feel when the fluid builds pressure. pump it until the fluid comes out and you should be good for hooking it up.

Once it is installed and all the lines are tight (I tighten them until the wrench almost rolls over the nut) hit the brake petal and see how it feels. It should be nice and firm. If there is fade and the petal slowly goes to the floor, there's probably a line loose somewhere. Recheck line nuts for tightness and try again. This test is easier with the engine running which gives you the advantage of the brake boost which does not work with the engine off.

Brake work is very intimidating but it is also very straightforward and pretty simple. Its how I got started wrenching on my '84 and now I'm a full time mechanic! You can do this!

 

[Alienoutlaw]

I personally bleed them, Its been my experience that Air is quicker than we are at changing the lines, Which usually results in a " Spongy" pedal. Granted it doesnt usually take much bleeding... just how I personally do it, not saying its right or wrong.....

 

[Jessica]

I agree. Brakes are super important obviously, however in my experience paying a mechanic a ton of money doesn't guarantee a professional job either. For example, I just picked up my Dodge Ram from one who charged me 3 times as much for parts, called to say it was ready so I was dropped off and than stranded there when it wasn't ready, when I finally did pick it up the air filter wasn't properly connected, it was in 4 wheel drive (I didn't leave it like that), someone had driven it 90 miles, and it's running pretty rough. I'm a firm believer in the saying "If you want something done right- do it yourself" and that is why I try to be as self sufficient as possible. With everything- not just car fixing. If I can learn how to do it or had someone to show me how to do it it would be great. I'm thinking I'll buy the part and ask my regular mechanic (not the one who did the truck!!!) if I can watch him put it in and see if he'll look over the loose steering at the same time.

 

[Jessica]

Brake work is very intimidating but it is also very straightforward and pretty simple. Its how I got started wrenching on my '84 and now I'm a full time mechanic! You can do this!

​

Thanks for making it sound less scary Jeepindavis!

 

[warren]

this is the master cyclinder for your brakes