Do I need to replace master cylinder or break booster?

E-break light came on in my 2003 SR5 tundra. Breaks feel fine so I assume theres a leak somewhere. All my lines seem good, only leak I found is where the MC meets the booster. Truck has been parked for a while so no active fluid running down in the images but I circled where I found it running as you can vaguely see the lines from the past.

Ive read that fluid can leak into the booster. I cant really move the booster around to determine that. Based on the images alone, what insight do you guys have? Should I replace them both?

I appreciate any insight you guys have more than you know.

 

Appears MC leaking at the piston seal. Common failure area. You have to unbolt it to tell for sure but likely needs rebuild or replace.

 

@bfunke I appreciate the insight, what should I look for once its unbolted to be able to tell for sure?

 

Fluid leaking from the back of the MC

 

Take that vacuum hose off your brake booster and stick something inside your booster, pull it out and see if it has brake fluid on it. That's how I discovered my booster was full of brake fluid (and where my brake fluid was going). I ended up replacing both my booster and my master cylinder.

 

Just to be sure, you are saying stick something in my brake booster, where the hose used to be. And then if there is break fluid in the hose, that would indicate its getting inside the booster.

 

Correct, temporarily remove the hose, carefully stick something like a wire or old clothes hanger inside the booster where your vacuum hole is and pull it back out. Check to see if the wire has brake fluid on it when you pull it out, if it does, then your booster has brake fluid in it.

 

Ah gotcha! Thanks for the clarity. Awesome advice to easily troubleshoot, thank you.

 

OP - do you have the mechanical skills to replace your MC and booster and bleed the brakes? If not we can post more directions if you are willing to tackle it. Otherwise take it to a shop.

 

Currently learning said skills. My roommate can basically do anything needed on a vehicle so ill refer to him when it comes to actually bleeding the breaks and replacing a part. If you are wondering why I am on this forum rather than talking to him, I've been bugging him a lot recently about truck issues, so trying to get as much knowledge as I can before going back to him!

Ill post in this forum what I find when removing the hose from the booster today or tomorrow when I get around to it. I really appreciate you being adamant towards be getting the info I need. Hoping its just the MC that needs replacing as the booster seems to be the more expensive part.

Thanks again guys, I appreciate it more than you know.

 

Whatever you do, don't let him do the standard 2-person-1-mashes-pedal bleeding.

Opt for vacuum or pressure bleeding. If you do the old 2-person method, put something under the pedal so it doesn't travel to the floor. That may've been what someone already did, and it blew out a seal in the MC, or a seal between MC and booster.

 

Noted. Hes the kinda guy that if he does something, he does it the right way even if its more of a b**** to do. I really appreciate that insight tho, always blown away out how much good info you can get from a forum. Seriously, thank you.