How do you tell if it's brake booster or master cylinder?

[TXLNGHRN10 341]

How do you tell if it's brake booster or master cylinder?

I have a friend, who's brakes went out. Meaning the pedal is to the floor, has to be stomped on to get it to stop.
I should be able to fix it, but not sure which part it is. I've never had this one before.

 

 

Edited July 17, 2018 by TXLNGHRN10

[Onboard 2.0 9083]

5 minutes ago, TXLNGHRN10 said:

How do you tell if it's brake booster or master cylinder?

I have a friend, who's brakes went out. Meaning the pedal is too the floor, has to be stomped on to get it to stop.
I should be able to fix it, but not sure which part it is. I've never had this one before.

 

 

Are the bowls in the master cylinder full or low/ empty ?

[TXLNGHRN10 341]

full

[TXLNGHRN10 341]

correction
it doesn't go tot the floor. it's hard to press down, but it does move

[RPM 26317]

Not a professional, but if the pedal moves with a lot of effort (and brakes still apply) it sounds like the booster.

[Onboard 2.0 9083]

I'd look at the booster if the bowls are full, but I have no idea what that would be though. I've only worked on old cars without boosters.

Edited July 17, 2018 by Onboard 2.0

[TXLNGHRN10 341]

kinda what I was thinking too, but wanted to double check, it's going to be a pain to change

[futureman 22444]

1 hour ago, TXLNGHRN10 said:

kinda what I was thinking too, but wanted to double check, it's going to be a pain to change

no worries, amigo.  my tio can fix it. 

[RPM 26317]

21 minutes ago, futureman said:

no worries, amigo.  my tio can fix it. 

Is he a TV repairman?

[phdhorn 6224]

I usually swap out my Brake Booster every 5K miles or so.  Here's the one I just replaced:

"Go Brakes, GO!!!"

[Ten Bears 2480]

Usually you will see brake fluid leaking out of the brake cylinders or master cylinder if the seals in them have failed.  If not then, it likely is air in the lines which would require a simple bleeding.  

[Onboard 2.0 9083]

22 minutes ago, Ten Bears said:

Usually you will see brake fluid leaking out of the brake cylinders or master cylinder if the seals in them have failed.  If not then, it likely is air in the lines which would require a simple bleeding.  

Air in the lines makes the brake pedal squishy, not hard though.

[Ten Bears 2480]

22 hours ago, Onboard 2.0 said:

Air in the lines makes the brake pedal squishy, not hard though.

I missed that part.   If the brakes work but the pedal is hard to push then, yeah, sounds like the booster.

[Onboard 2.0 9083]

1 minute ago, Ten Bears said:

I missed that part.   If the brakes work but the pedal is hard to push then, yeah, sounds like the booster.

Never worked on a car with a booster.   I'd guess it's either the plunger rod or a vacuum hose could have come loose causing a pressure issue ??

[Ten Bears 2480]

What kind of car are we talking about?
 

[TXLNGHRN10 341]

It's a 2012 Mercedes c250
turns out there is a vacuum pump on the rear of the motor that supplies the vacuum to the booster, that went out.

I replaced the booster and bled the brakes, still a hard pedal, went through the hoses and found there's no suction. So I'll be replacing that this weekend

[Ten Bears 2480]

You would think the computer would be throwing codes if there was a vacuum leak.

 

edit:  Nevermind I just realized you said there was vacuum pump not that it was using manifold vacuum.  Carry on.

Edited July 25, 2018 by Ten Bears

[Onboard 2.0 9083]

Vacuum leaks suck......

[RPM 26317]

I know you've already done this, but check the fuse/relay/wiring on the pump before you replace it.

[Jkwellborn 6691]

Vacuum leaks suck......

What you did there.