can't find master cylinder bleeder valve

I cant find the master cylinder bleeder valve on my 90 mj 4.0 my brakes are going to kill me if I don't get them fixed.

there is not a bleeder valve on the master cylinder. You can bleed it on the truck with the help of an assisstant. Crack open the line closest to the firewall and have them press the brake pedal. Tighten up the line. Repeat until no air comes out. Move to the front line and repeat procedure there. If you need to bleed the brakes go RR LR RF LF. Hope this helps.

I think they make a kit w/plastic connectors and little rubber hoses that bleeds fluid right back into resevoir(s), do it in a vice.

At least twenty-five years ago they did :repair:

there is no bleeder valve. It's a sealed assembly. I just had to get a new one and it sucks they are like 150. atleast for my 96

"Bench Bleeding" involves having fittings with hoses that run back into the reservoir (keep the ends of the hoses under fluid,) and then slowly and evenly work the piston. Bench bleeding can be done on the vehicle - but it involves removing the lines from the master cylinder, and you're going to end up bleeding the rest of the system at the wheels (in the order RR/LR/RF/LF, working from "farthest to closest," as previously stated.)

What sort of trouble are you having? I've run across some oddities, and knowing more of your symptoms would help me help you some more...

5-90

the brake peddal goes almost al the way down. I bought my mj wrecked the LF brake line was broken, I replaced it, when I bled it I got ahead of my self and ran the resiviour dry. now my breaks suck. can I bleed it through one of the breaks?

bigpimpinben said:

the brake peddal goes almost al the way down. I bought my mj wrecked the LF brake line was broken, I replaced it, when I bled it I got ahead of my self and ran the resiviour dry. now my breaks suck. can I bleed it through one of the breaks?

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Oh. No, it won't work that way - each port on the master cylinder feeds two wheels, so you can't get "dedicated" access to the ports.

You'll have to bench bleed the master cylinder...

5-90

If he hasn't ruined the m/c already. May have scored the cylinder when it ran dry.

If you take the master cylinder out or disconnect the lines while its in the vehicle to 'bench bleed' it you will have to bleed all the lines after that. Just bleed the brakes by starting at the wheel furthest from the master cylinder and work your way to the wheel closest to the master cylinder. You have to bleed all the wheels, that is the only way to make sure all the air in the lines is gone.

89Daytona said:

If you take the master cylinder out or disconnect the lines while its in the vehicle to 'bench bleed' it you will have to bleed all the lines after that. Just bleed the brakes by starting at the wheel furthest from the master cylinder and work your way to the wheel closest to the master cylinder. You have to bleed all the wheels, that is the only way to make sure all the air in the lines is gone.

Click to expand...

5-90 said:

"Bench Bleeding" involves having fittings with hoses that run back into the reservoir (keep the ends of the hoses under fluid,) and then slowly and evenly work the piston. Bench bleeding can be done on the vehicle - but it involves removing the lines from the master cylinder, and you're going to end up bleeding the rest of the system at the wheels (in the order RR/LR/RF/LF, working from "farthest to closest," as previously stated.)

What sort of trouble are you having? I've run across some oddities, and knowing more of your symptoms would help me help you some more...

5-90

Click to expand...

I thought I'd said that...

i know many people on here won't agree with this method, but working at different dealerships and shops, i learned a little trick to bleed new master cylinders. press your fingers over the brake line ports on the master cylinder and have somebody else very very slowly press the brake pedal. but only a very tiny little bit. no need for a full stroke. the pressure will squeeze the air/fluid past your fingers, but your fingers will seal the hole again as soon as the pedal releases. then after doing that a couple times, i just let go and install the lines. after that i bleed the system as mentioned above going from RR-LR-RF-LF. so far i've never had a problem with any brakes i've done.

oh and i've you just accidently ran your master cylinder out of fluid, you can try just filling it up and then bleeding the entire brake system in the order already mentioned. if you haven't done any damage to the master cylinder, then you might be able to get away with just bleeding it like that.

Also, he mentioned this is an MJ! There is more involved with bleeding since it has the load prop valve on the rear axle and a second line going up to the combo valve up front. Check this thread for more info. http://www.naxja.org/forum/showthread.php?t=82708&highlight=bleeding