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Posted (edited)

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 by TXLNGHRN10
Posted
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 ?

Posted

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

  • Like 1
Posted (edited)

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 by Onboard 2.0
  • Like 1
Posted
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. 

Posted

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.  

  • Like 1
Posted
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.

Posted
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.

Posted
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 ??

Posted

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

Posted (edited)

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 by Ten Bears

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