You are here:

Chevrolet Repair/1977 Chevy P3 Master Cylinder Replacement...Leads to Inability to Brake

Advertisement


Question
Hi-
I just purchased a 1977 Chevrolet Stepvan Truck (Boyertown); 8 cylinders, 5.7L, 4BL 1 ton, forward control chassis, rear drum brakes.

I drove the vehicle directly to the mechanic for inspection because only 50 miles had been put on it since the last inspection in 2000; only 40k original miles.

The mechanic inspection report stated that the master cylinder was wet.

So...my boyfriend purchased a replacement master cylinder and installed it. Afterwards, without starting the vehicle he had me pump the brakes a few times. The brake pedal never really depressed.

Upon starting the truck...there were no brakes and the pedal seemed to be locked in an up position. He says it needs to be bled properly.  But since the brake pedal won't depress at all...he tried to bleed the vehicle from underneath...unsuccessfully.

He now states that the brake booster is sticking and not pushing brake fluid to the vehicle and that I need to purchase a new brake booster.

Please help...it didn't seem like the booster was the original problem. Does his trouble shooting sound accurate? How do you properly bleed these brakes? Is there a way to adjust the booster so as not to purchase a new booster?

I appreciate all insight. Be blessed :)

Answer
GOOD MORNING SHAR,IF I WERE YOUR BOYFRIEND I WOULD REMOVE THE MASTER CYLINDER AND PUSH DOWN ON THE BRAKE PEDAL TO SEE IF THE PEDAL MOVES LIKE THIS..IF THE PEDAL MOVES LIKE THIS THEN I WOULD THINK HIS DIAGNOSES IS NOT CORRECT. WE HAVE TO BACK TRACK HERE AND FIND WHAT THE CAUSE OF THIS IS.SO WITH THE M/S NOT ON AND THE BRAKE PEDAL NOW MOVES WE HAVE TO ASSUME IT IS IN THE REBUILT M/S.HAVE HIM TRY TO PUSH THE PISTON OF THE M/S IN AND SEE IF IT MOVES LIKE THIS. IT SHOULD NOT MOVE IF THIS IS THE PROBLEM..ALSO DID HE BENCH BLEED THIS BEFORE HE INSTALLED IT..THIS IS VERY IMPORATANT.  BECAUSE WHEN THIS IS MOUNTED ON THE TRUCK IT IS TIPPED FORWARD FROM THE FRONT, CAUSING TRAPPED AIR IN IT.SO BENCH BLEED THIS BEFORE INSTALLING IT..AIR IN THE SYSTEM WILL NOT CAUSE A HARD PEDAL... [[[[IF THERE IS AIR IN THE LINES THE PEDAL WILL BE SOFT AND DROP]]]].SO FIND OUT WHAT IS BINDING THIS AND GET THIS REPAIRED EITHER BOOSTER OR M/S.CHANCES ARE IF THE PEDAL WAS OK BEFORE THE NEW M/S I WOULD THINK THE M/S IS AT FAULT..BUT TRY WHAT I SAID FIRST.
GET BACK TO ME ON WHAT YOU FIND AND IF YOU NEED MORE INFO ON BLEEDING THE BRAKES[[WHICH YOU SHOULD NOT HAVE TO DO ONCE THE M/S IS BLED CORRECT..]]GOOD LUCK TO YOU,,TOM


PS/PS/PS/////JUST THOUGHT I WOULD ADD THIS TO MAYBE HELP YOU,YOU DO KNOW THAT THE BRAKE PEDAL WILL BE HARD TO PUSH DOWN WHEN ENGINE IS NOT RUNNING,,THIS IS NORMAL,BECAUSE THE IS NO POWER ASSIST LIKE THIS..BUT YOU STILL WILL BE ABLE TO PUSH THE PEDAL DOWN IT JUST WILL BE HARD..IT WILL NOT BE LOCKED UP HOWEVER...HOPE THIS HELPS,,TOM

Chevrolet Repair

All Answers


Answers by Expert:


Ask Experts

Volunteer


TOM SHEETS

Expertise

PLEASE READ ALL OF THIS BEFORE ASKING ANY QUESTIONS. IF THIS CHEVY SECTION IS MAXED OUT.YOU CAN REACH ME IN THE OLDS/BUICK SECTION. Will answer questions from 6:00am to 10:00pm all days [EST][[[ NO DIESEL OR PAINT QUESTIONS]]] will answer all 1965 to present QUESTIONS ON ALL GM'S on mechanics of these cars. Keep in mind i am not there in person i am going on what you are telling me !! PLEASE IF ASKING A QUESTION GIVE ME AS MUCH INFO AS POSSIBLE. THE MORE THE BETTER. SUCH AS YEAR,MAKE,MODEL,ENGINE SIZE. THIS WILL HELP ME HELP YOU. I will not be able to answer all questions because of some situations that i would really need to be there and see things for myself,such as electrical issues. In many cases i would need wiring diagrams. I can also give you an estimate on what the cost would be at our repair shop as an idea to help you. Keep in mind that my answer is ONLY MY ADVICE,ck with your mechanic as well.. >> THANK YOU, TOM..

Experience

I have been a ASE certified master mechanic for over 30 years and certified IN ALL 8 CATEGORIES,[engine repair,engine performance,auto trans,manual trans,clutches,steering and suspension,brakes,electrical systems,heating and air/cond. I am also a state CERTIFIED inspector for over 30 years. I do computer work [pcm]fault codes,pcm flashing,state inspection monitor readiness,repairs on exhaust,fuel service,[injection and carburetor,] charging system problems, running issues,alignments,frame problems,tire balance,struts and of course standard and anti-lock brakes.

Organizations
nys state auto repair industry and ase group.

Publications
N/A

Education/Credentials
high school,4 years of tech school,and many many hours of auto training with many gm classes and aftermarket training classes..

Awards and Honors
ASE MASTER TECH CERTIFIED IN ALL 8 CATEGORIES.NYS INSP LICENSE AND A/C CERTIFIED

Past/Present Clients
MANY CUSTOMERS IN OUR BUSY SHOP.

©2016 About.com. All rights reserved.