Lost my brake fluid

got stuck in the mud real bad for a couple days. After getting it out I noticed my brake light on the dash was on. Check the fluid, nada. Refill and it’s gone before I get home. Found the leak. Anyone care to guess what went bad? Master cylinder? Brake booster? I REALLY hope it’s just an o-ring. I was able to snap a pic. I still have SOME braking power but definitely not 100%. Thanks.

 

update:

I believe my brake booster is bad. Just ordered one online.

I installed my new master cylinder and tried bleeding the brakes. The pedal would just spring back and I could hear the fluid sloshing around. That's when I noticed the same leak, even after I added RTV where the MC meets the booster (I wasn't sure). Fired the truck up and it looked like I sea foamed it. TONS of white smoke. I think I was sucking brake fluid into my intake, hence the white smoke.

I removed the old booster but one nut was behind some sort of brake controller. It said not to move it because it holds the brake in position. Had to remove it to get to the upper/left nut.

Any advice on the reinstall?

 

make sure you bench bleed the new master cylinder. What nut are you talking about?

 

There are 4 nuts around the steering shaft under the dash that holds the brake booster in place. The one the was hidden would be at the 10 or 11 o'clock position.

 

I'll take a guess. You lost brake fluid somewhere else, your fluid emptied, then the seals blew on your master cylinder because there wasn't any fluid anymore. So my guess is you may have a leak somewhere else too.

 

I’ll double check all the fitting and lines.

I keep reading the seal can go bad on the mc. Is this an internal seal or would it be on the plunger shaft? The OEM mc had a flat round seal on the plunger shaft. The new ms did not have this seal.

 

I'm not sure. I thought there was a seal on the plunger, and if it goes dry it can get chewed up.

 

Replaced booster, master cylinder, and passenger side caliper along with pads and rotors.

Now the pedal takes a lot of force to get moving then just feels stiff. Any idea on what I may have missed?

No other leaks found

 

So a couple observations. I get a whooshing sound when I let off the brake pedal.

I went and removed the master cylinder again. This time on the new booster I got the same whoosh of air as I pulled the master off the rod in the booster. Like it was holding air.

Still not sure if my new booster is good or not. I read that the length of the rod in the booster may need adjusted. Could this be the reason for the stiff pedal?

 

A stiff pedal means the booster isnt doing its job, is there good vacuum at the line going to the engine?

 

Yes I replaced the piece of fuel line that was on there with some 11/32” vac line.

Would it be any use adjusting the length of the rod going into the cab that attaches to the brake pedal?

 

Yes there is an adjustment but I dont think of what its is at the moment, but if you have a stiff pedal theres a booster problem.