Replacing Hydraboost

[78Chev]

I know this has been covered in the past but it must have been lost. I need to replace my leaking hydraboost. How do you remove it from the firewall? I haven't purchased it yet but pictures from NAPA look unclear to me. (I was expecting to see studs that bolt it to the firewall, but none are shown on the photo.) This is on a 78 Chevy that originally had a 350 diesel, and so the hydraboost is original. The hydraboost is the same as 82-87, I believe, with the exception of the type of hose connections. Thanks for any help.
Randy

[mhagie]

Randy, Look at your truck not the photo you will see the Hydroboost is attatched to a large plate that bolts to the firewall with 6 bolts.
I recently converted my truck to a diesel and used a 83 blazer as donor vehicle so I had to remove assy and swap it to my cab.
If your 78 cab is the same as the 83 its a PITA to swap as you will find that 4 of the bolts are from inside out(nuts outside) and 2 are the opposite they are the bad ones (nuts) to access inside the cab.
On my 80 I have a 84 cab, on it all 6 bolts are inside out I STRONGLY recomend you convert yours to that configutation when replacing unit.
I had to do mine twice as when I went to test brakes the pedal would not return only about 3/4 the way back and then stick. :mad:
Went to Auto Zone got reman H/boost all is well again cause it was easy with nuts on outside.
Wish you good luck with the replacement.
P.S. I just remembered that I have a 78 GMC factory shop manual and I looked it up,yep the center bolts have nuts inside cab :mad: :mad:
Again good luck.........Merle :D

[78Chev]

mhagie:
Thanks. Beautiful day here so I went out and checked. I see the four nuts on firewall side and then two inside cab. Looks like a socket with extension should do it although very awkward. Is there anything special about how the shaft attaches to the brake pedal? A clip or something?
Randy

[mhagie]

Randy,the brake push rod is attatched by a clip similar in style to the clip on throttle cable to inj pump, also be on the lookout for a thin washer if I remember correctly its on the brake pedal side of rod, small needle nose pliars works quite handily.
Just remove the 2 nuts holding master cyl and move to side, lines will flex no problem. :D
Its not a real bad job just a PITA
Its a six-pac job at worst. :D ............Merle

[78Chev]

Thanks, mhagie.
Had to order the unit as no one had one in stock. Should be here next weekend. I can see mine leaking a little on the inside of cab plus a little puddle of power steering fluid on the ground every so often. And I hate leaks. I can tell it in the way the brakes feel, too. They are sometimes there, sometimes not!
Randy

[aloharovers]

only problem I had with it was I got the two pressure lines back wards. Not a good thing smile.gif
Pete