New master cylinder after brake work

My 2001 Nissan Pathfinder is at the mechanic getting new rotors and brake pads…he called me a few hours later to tell me something was wrong with the master cylinder. What do you think happened?? My brake pedal was a little lower than before, but everything was working when I drop the pathfinder off!

Help! My mechanic cannot explain to me what happened. I have to go see him on Monday.

While it is always possible that your mechanic is trying to pad his bill with more work consider the possibility that he may be telling you the truth. Sometimes things go bad just as you drop off your vehicle at the mechanic. In this case the “pedal was a little lower than before” is a sign that something was amiss. Can you give us more details as exactly what changed and when and why your mechanic is telling you that you need a new master cylinder?

Thank you so much for your reply. Well I have been out of the country for one year and someone drove my SUV regularly while I was gone. When I returned in August, the brake pedal seemed lower that I remembered. (I just thought I needed new pads) There is no shaking when I brake. Anyway I took the car to a mechanic on Saturday. He called me to say I needed to replace everything (pads, rotors, slides???) I am also getting an alignement and 4 new tires.($ 900)3 hours later the mechanic called me and said he could not put the braking system back together and that the pedal stayed down…I kept asking “what happened” and he kept saying “I am not sure”. I have been looking online and understand how the master cylinder works. It was working when I dropped the SUV off. Also he couldn’t find a master cylinder anywhere so he still has my SUV. Not drivable with no brakes! I have to pick it up on Monday? he did say it could cost $300 extra or more…I am mad!
Thank you for your help I don’t know who to talk to.

There are a few methods to bleed brakes. The easiest method (if you have a helper) is to press the brake pedal to the floor with one of the brake bleeders open to pump out the old fluid. You need to do this about a dozen times at each wheel. If your mechanic did this, it’s very possible that pressing the brake to the floor caused the master cylinder piston to hit some crud and damage a seal.

there is no easy way to decipher the “need” for a new master cylinder, VS. the need for the mechanic to do more repairs that arent really needed. i would suggest that you get the brakes done, and have him NOT do the master cylinder. take it for a test drive, and then you can take it back to him in a week, have it done then (if it still needs replacing)

Does this car have ABS?
Maybe when they pushed the calipers back some crud got in the master and damaged the seals. It happens, I am not sure if the mech is at fault.

Thank you all for replying. I ask the mechanic to just put it all “back together” but he said he couldn’t. He said the car is not drivable. The car is at the mechanic now, he also said that it wouldn’t be drivable until he replaces the master cylinder. The pathfinder does have ABS.Do you think I am responsible for paying the extra $300or more? He just said the pedal is "Stuck "to the floor! What do I do?
Thanks for all your help.

Thank you all for replying. I ask the mechanic to just put it all “back together” but he said he couldn’t. He said the car is not drivable. The car is at the mechanic now, he also said that it wouldn’t be drivable until he replaces the master cylinder. The pathfinder does have ABS.Do you think I am responsible for paying the extra $300or more? He just said the pedal is "Stuck "to the floor!

A few thoughts…

It’s an unsettling feeling when a mechanic can’t tell you why he needs to replace something on your car after he’s the one that’s worked on it. He probably did something wrong and won’t admit it because it will cost him money. This is what I would do, but you might not want to take the trouble and time:

Ask him exactly what work he has already completed and the amount you owe him so far. Once he tells you this, advise him that you will be in to pay exactly that amount for the work he has completed. Then you will have the car towed (AAA comes in handy if you have it). He can’t keep your car if you pay him for the work he’s done. Have the car towed to a reputable shop (that you’ve called ahead to advise the problem). Have them check the master cylinder. Have it repaired there if necessary. At least you’ll be sure that you really did need the master cylinder, but you’ll have the added expense of towing, and time lost. OR - you can just pay the $300 and chalk it up to experience, and never go to this mechanic again.

I actually did just this about 18 months ago. It was an alternator for a 99 Kia, and the shop that did it kept getting the wrong alternator in. Their imcompetence, along with that of their parts supplier, had me out of work for a 1-1/2 days. I had it towed about 2-3 miles down the road closer to my home. Once I realized how incompetent they were, I ordered the correct alternator online, had it shipped to the good repair shop the next day, and the car was done, pronto. THEN, I wrote a detailed letter to the owner of the chain (that was AAA-approved), and sent a copy to my AAA affiliate. I got a phone call from the service manager, and ultimately, a $454 refund from the gang that couldn’t shoot straight. Good luck.

Thank you for your help. I just spoke to the mechanic…who still cannot tell me what happened. Thanks to your reply I sounded like I knew what I was talking about. I asked about the possibility of crud damaging the seal. he said he doesn’t know.
Anyway he is going to talk to his “employee” and call me back.
I think I am going to pay him for the work and take it somewhere else!

THANK YOU, THANK YOU, THANK YOU
Just came back from picking up my pathfinder from the mechanic…and he just said you are all set!!!
Guess what??? the brake pedal is high and where it should be! he never mentioned anything else about the master cylinder…the problem miraculously disappeared!
I am soooooooooooooooooooooo grateful for all you valuable advice.

They found the low pedal problem for sure.