I'm converting my 85 from hydro-boost set-up to a vacuum set-up. Bought a used vacuum set-up from a member on here. Everything went good, got the old stuff out, got the new booster/master and pedal changed ect. My problem is the fitting on the lines are the wrong size and wont thread into the master. The fitting on front one (closest to nose of car) is too small and the rear one is too big. I searched and didn't read anywhere about needing adapters?
Hydro boost to Vacuum Conversion Problems
- Thread starter Super Kaz
- Start date
1KWIKSIX
Well-Known Member
- Joined
- Sep 29, 2007
Just curious..........Why are you removing the Hydro Boost?
I just bought the car a few weeks ago. It's a 85 wh-1 with a 87 GN motor/trans swapped in it. Guys cousin swapped it in for him he told me. So when I bought the car the guy told me the brakes where hard. The p/s works fine, so I just assumed the hydro boost was going out. So I thought it would be a good time to just convert it to vacuum. Weird part is when I removed the hydro boost and it's lines, I found the lines where not even connected to the p/s pump? And it looks like there is no where to connect them. I assume it has a 86-87 p/s pump and lines on it now. It also came with a power master unit in the trunk. I think it might work if I swapped the pump back to a 85 and bought new lines, but I'm this far into the swap so I'm just going to stick with the vacuum brakes. Funny thing is I now have all three brake set-ups.. I don't know if they work but I have them! LOL
- Joined
- Feb 18, 2006
Keep the hydro boost close by. It'll be going back on.....
Keep the hydro boost close by. It'll be going back on.....
I hope not.
- Joined
- Feb 18, 2006
I think your right... The lines are reversed.
correct. as of now, your lines are reversed
I guess I will bleed them and see what it does. Thanks for everyone's help.
But this is why I used the adapters. Here is the master cylinder specs for both hydro boost and vacuum:
hydro boost:
Application: Turbo
Notes: With hydroboost
Installation Hardware Included: Yes
Item Grade: OEM Standard
Master Cylinder Bore Diameter (in): 1.062
Master Cylinder Color / Finish: Metallic
Master Cylinder Material: Cast Iron
Master Cylinder Port Sizes: Primary 0.562"-18 , Secondary 0.5"-20
Master/Slave Cylinder Type: Push
Package Contents: New Brake Master Cylinder, Reservoir, Bleeder Kit
Product Condition:
New
Vacuum master cylinder:
Application: Except Turbo
Notes: Master cylinder comes with a new reservoir installed. Except Powermaster.
Installation Hardware Included: Yes
Item Grade: OEM Standard
Master Cylinder Bore Diameter (in): 1.417
Master Cylinder Color / Finish: Metallic
Master Cylinder Material: Aluminum or Cast Iron
Master Cylinder Port Sizes: Primary 0.5"-20 , Secondary 0.562"-18
Master/Slave Cylinder Type: Push
Package Contents: New Brake Master Cylinder, Reservoir, Bleeder Kit
Product Condition: New
But this is why I used the adapters. Here is the master cylinder specs for both hydro boost and vacuum:
hydro boost:
Application: Turbo
Notes: With hydroboost
Installation Hardware Included: Yes
Item Grade: OEM Standard
Master Cylinder Bore Diameter (in): 1.062
Master Cylinder Color / Finish: Metallic
Master Cylinder Material: Cast Iron
Master Cylinder Port Sizes: Primary 0.562"-18 , Secondary 0.5"-20
Master/Slave Cylinder Type: Push
Package Contents: New Brake Master Cylinder, Reservoir, Bleeder Kit
Product Condition:
New
Vacuum master cylinder:
Application: Except Turbo
Notes: Master cylinder comes with a new reservoir installed. Except Powermaster.
Installation Hardware Included: Yes
Item Grade: OEM Standard
Master Cylinder Bore Diameter (in): 1.417
Master Cylinder Color / Finish: Metallic
Master Cylinder Material: Aluminum or Cast Iron
Master Cylinder Port Sizes: Primary 0.5"-20 , Secondary 0.562"-18
Master/Slave Cylinder Type: Push
Package Contents: New Brake Master Cylinder, Reservoir, Bleeder Kit
Product Condition: New
Thank you for actually taking the time /having the balls to try this out. Most people on this board wouldn't.
I would hesitate to Leave the two lines connected in this manner. From what I have read the bigger line is for the front disc brakes and the smaller one is for the rear drum brakes. Not an expert, but I think GM did that for a reason. Maybe there is a pressure difference between the two lines? who knows? I know that on my big ugly hydroboost master cylinder the reservoir for the Front brakes is much bigger than the one for the rear. Your reservoir is like this too. The car will most likely stop but and this is just my opinion...... remove the adapters and bend the lines a little.
