I have a 1984 Chevrolet Camaro Z28 H.O. I'm have a braking problem. In order to stop I have to push the brake pedal all the way to the floor and you can hear as if air is being suctioned out of the brake pedal. I changed the master cylinder twice! It still has the stock booster and proprtioning valve. I spoke to a tech at classicindustries.com and he said it may be the vacuum hose going from the booster to the intake manifold. He said he has encountered this problem before but is a simple vacuum hose causing this problem? He said it either that or the booster itself. Does anyone have an idea if this is really it. I've had this problem for 2 years now and im tired of it.

 

Replace rubber brake lines - 2 in front, one in rear.

Bleed Bleed Bleed!

Check to make sure no vacuum leak at the rubber line from carb/intake to booster.

Did you bench bleed the master cylinder?

 

I replaced the brake lines going from all 4 calipers (by the way I think my car was equipped with 1LE option since I have all 4 disc brakes) to the brake line hose with Russell steel braided brake lines. We bled all 4 lines until there was ZERO bubbles coming out and we also bled the master cylinder and proportioning valve, same results still spongy. Does the vacuum hose connect to the EGR valve?

 

Should be a large vacuum hose (like 3/8 inside diameter) that runs from booster directly to intake, or to carb. Not sure how it's routed on a TPI car - but it's a large vacuum line (looks like a fuel hose size line).

 

The tech stated the vacuum hose is about the width of your thumb not very large. My engine to my knowledge is a 5.0L 305 4 barrel carb........ ill check it out though. I hope that is the issue I was losing faith... Ill keep posting until the issue is resolved. THANKS!

 

its not a 1le, they didnts start till 88, and they have 2 piston aluminum front calipers. Many 3rd gens have 4 wheel disc brakes, its not uncommon.

if the pedal goes to the floor, its not a vacuum issue. that will make the pedal really hard and have a very short range of movement of the pedal. sounds like you are not bench bleeding the master and have air in the system still. Or possible the booster itself is shot.

the vacuum line to the booster comes off the back of your carb, its a steel line ontop of the engine, then should have a small black plastic canister inline with it, then rubber hose to the booster. Should be simple to find and trace.

 

I was told if the booster is gone then the range of brake pedal motion would be very hard. Is that not true? So, how do you bench bleed the master cylinder? Do you suggest I replace the brake booster first?

 

I am leaning toward a bad booster.

The vacuum line that goes to the booster starts off as a metal line that is threaded into the back lower middle of your carburetor, it runs through the throttle cable bracket and then a rubber line is connected after that and then goes through a "Brake booster filter" which basically allows air to travel one way, and one way only. than from the filter it runs right into your booster. All in all, it isnt a very large or small line and it doesnt run that far.

 

ITS NOT THE BOOSTER CAUSE IF YOU TAKE THE VACUME LINE FROM THE BOOSTER OFF THE PEDAL WILL GET REALY HARD AND IT ALSO DOES THE SAME THING WHEN A BOOSTER GOES BAD THE PEDAL GETS REALY HARD AND YOU PEDAL IS SPONGY AND THAT MEENS AIR IN THE SYSTEM IF YOU DID NOT BENCH BLEED THE MASTER CYL THATS PROBLY THE ISSUE IT STILL HAS AIR..

TAKE THE MASTER CYL OFF CLAMP IT IN A VISE SO YOU CAN STILL GET TO THE PLUNGER SCREW TO FITTINGS WITH SMALL CLEAR HOSES TO THE TWO PORTS FILL IT WITH BRAKE FLUID AND PUT THE OTHER END OF THE CLEAR HOSES IN THE M/C RESIVOR MAKE SURE THE DONT COME OUT. MOW WHILE HOLDING THE TWO CLEAR HOSES IN THE RESIVOR WITH ONE HAND AND A SCREW DRIVER OR LONG PUNCH PUSH THE PLUNGER IN ALL THE WAY IN AND OUT REPEAT THIS SEVERAL TIMES UNTILL YOU CANT SEE BUBBLES IN THE HOSES..

THE OTHER OPTION EVEN THOUGH YOU SHOULD DO THIS EVEN AFETR THE BENCH BLEEDING.BUT YOU MIGHT GET LUCKY.. WHILE THE MASTER CCYL IS STILL ON THE CAR THIS TAKES TWO PEOPLE LOSSEN THE BRAKE LINES TO THE MASTER CYL AND HAVE SOMEONR PUSH THE BRAKE PEDAL TO THE FLOORAND BEFORE THEY LET UP TIGHTEN THE LINES AND LTELL THEM TO RELEASE THE PEDAL REPEAT THIS PROCESS UNTILL ALL AIR IS OUT AND/OR PERFECT BRAKE PEDAL HAS BEEN ACHIVED ....
P.S. NEVER LET THE M/C RESIVORE GO EMPTY YOU WILL BE DOING THIS ALL DAY IF YOU DO...

ONE MORE OPTION IS TO PENCH OFF THE BRAKE HOSES ONE AT A TIME WITH VISEGRIPPS OR SIMMALER AND FEEL OF THE BRAKE PEDAL AFTER EACH ONE IF YOU HAVE THEM ALL PINCHED OFF AND THERE IS NO CHANGE IN THE FEEL OF THE PEDAL THEN DEFFITNETLY AIR OR FAULTY M/C... but if there is a change when you pinched a certain one off the then that caliper has air or if the back does it problem is in the back HOPE THIS HELPS

 

ive gone through this "loss of vaccume" issue in my 86 and recently in my 92, bith times, the pedal would get hard, an braking would be reduced. the pedal never went to the floor.

I would bench bleed properly before changing the booster, thats a bit of a PITA.

To bleed properly, you have to cap off all the outlets of the master, or route lines from them up and back into the reservour, and under the fluid level of the reserviour. Then clamp the master in a level vise, and push the piston in (i usually use a rounded screwdriver handle) repetedly untill the bubbles stop coming into the reserviour. it takes a while. then install, but be sure not to let the fluid all drain out when you are hooking it up the the car.

after that, bleed all 4 corners with a vacuum bleeder of your choice, i've never had any luck with the pumping of the pedal method.

then see what happens.

you can use a vacuum pump and a gauge on the booster to see if it holds vacuum, that will give some indication if its still good.