Help me with vacuum pump for brakes !

[alexd7392]

okay so vacuum pump is making vacuum,

i plumbed it with vacuum to check valve to booster and exhaust to manifold. if u start the car , don't touch the brake, go in reverse or drive u get a nice power brake stop, problem is if u hold the brake the vacuum isnt building fast enough to then stop the car in a parking lot scenario... now the car isn't on the road yet. is this a normal scenario? is something wrong? even when i plumbed it exhaust open, vacuum straight to booster i was having the same issue...

if I get a canister will this solve the problem or is this a common occurrence with vacuum power brakes?

I'm really at a loss right now idk what to do...

If the pedal gets hard and car won't stop, you might have a leak or a bad check valve. Canister should help, but I'd rule out leaks and valve. Hook up a vacuum gauge if you have one.

 

[6spdg37s]

If the pedal gets hard and car won't stop, you might have a leak or a bad check valve. Canister should help, but I'd rule out leaks and valve. Hook up a vacuum gauge if you have one.

I hooked up the vacuum gauge that we have (which isnt the most accurate but still works) and it builds and holds but as soon as u step on the brake it drops and then builds again. so in a parking lot situation after the first stop u have a hard pedal.

I picked up a comp cams vacuum canister at pep boys before for 55 bucks I planned on getting one anyway so i just got it now, gonna throw it in tomorrow and see what happens...

i know from the factory this car had a vacuum canister which was missing when i bought it actually lol but the motor was seized anyway so it didn't matter. I only have 2 vacuum lines running out 1 from manifold to the vacuum pump and one from the carb to the trans (th350).

other problem i have is the car is still open headers so its hard to hear if there is a vacuum leak... but if i pop off the vacuum line there is a noticeable change in idle so that makes me think that there is no vacuum leak.

 

[6spdg37s]

also is the proper vacuum hose size 11/32 ? I am actually using 3/8 fuel line right now, I would say this could be the problem except i ran a 25 ft roll of 3/8 fuel line from our iron duke truck to the monte booster and the brakes worked fine but i want to get the proper size vacuum hose anyway every friggen store ive been too has been sold out of vacuum hose....

 

[pontiacgp]

I hooked up the vacuum gauge that we have (which isnt the most accurate but still works) and it builds and holds but as soon as u step on the brake it drops and then builds again. so in a parking lot situation after the first stop u have a hard pedal.

I picked up a comp cams vacuum canister at pep boys before for 55 bucks I planned on getting one anyway so i just got it now, gonna throw it in tomorrow and see what happens...

i know from the factory this car had a vacuum canister which was missing when i bought it actually lol but the motor was seized anyway so it didn't matter. I only have 2 vacuum lines running out 1 from manifold to the vacuum pump and one from the carb to the trans (th350).

other problem i have is the car is still open headers so its hard to hear if there is a vacuum leak... but if i pop off the vacuum line there is a noticeable change in idle so that makes me think that there is no vacuum leak.

if you take a can of carb cleaner you can use that to check for vacuum leaks. Spray it around the base of the carb and along the edge of the intake to see if the engine speeds up.

 

[6spdg37s]

if you take a can of carb cleaner you can use that to check for vacuum leaks. Spray it around the base of the carb and along the edge of the intake to see if the engine speeds up.

yeah i gotta do that... it got cold again here so its a PITA to work on i should of just stayed all day yesterday when it was 70 and did it...
it stinks and is loud AF (open headers still) to let it run inside the shop with the doors closed and cold out to mess with outside today.

but the fact that the vacuum pump directly to the booster makes me think that i simply need a canister as well and that will solve all problems, fingers crossed

 

[6spdg37s]

What is the proper hose size ? My pats supplier told me 15/32 I got that and it's too big for the booster check valve ... I can't win . I hooked it up with the 3/8 fuel line and still same pedal

 

[6spdg37s]

so i flipped the canister setup around and now its better but not great. still not sure if i should plumb it with the T setup or the straight setup...

idk why they would give you two options

 

[6spdg37s]

if you take a can of carb cleaner you can use that to check for vacuum leaks. Spray it around the base of the carb and along the edge of the intake to see if the engine speeds up.

no vacuum leaks checked for them today...

once i took the canister out and then put it back in i get vacuum now and the brakes feel pretty good from driving around the parking lot...

what is the correct size hose for g body brake booster ? right now i have 3/8 fuel line i bought , 15/32 ( i think) from my parts guy who told me that was correct but its too big for the brake booster check valve... anyone know the right size so i can stop buying non refundable hose lolol

 

[Injectedcutty]

no vacuum leaks checked for them today...

once i took the canister out and then put it back in i get vacuum now and the brakes feel pretty good from driving around the parking lot...

what is the correct size hose for g body brake booster ? right now i have 3/8 fuel line i bought , 15/32 ( i think) from my parts guy who told me that was correct but its too big for the brake booster check valve... anyone know the right size so i can stop buying non refundable hose lolol

Glad to hear your getting it worked out. I used 3/8" fuel line for mine and didn't have any issues with collapsing, leaking, etc.

 

[pontiacgp]

I use the 3/8 vacuum line as well