78 eldo replace hydro boost

[78caddy]

 fluid leak and soft brakes on my 78 eldo changed master cylinder i thought bad master  was leaking.  so new master and bled still fluid leak. checked power steering fluid very low, so my hydroboost is leaking saw inside interior by pushrod  fluid.  saw cardone unit rebuilt $218 does this come with gold round cylinder marked caution high pressurized.  any precautions replacing this hyro boost with high pressure gold cylinder connected?  do you bleed pressure off first?   thanks steve

[TJ Hopland]

Apparently the hydro boost units are more or less one size fits all over many years makes and models.    The gold can is gas filled that acts as the spring to build up hydraulic pressure when the system is operating normally.  When the engine stops or you loose hydraulic (power steering) it provides the reserve pressure so you get 2-3 normal boosted stops more or less just like the vacuum units do.  Over time apparently that gas leaks out so it looses its reserve function.   You discharge the fluid from that section by operating the brake pedal with the engine not running.  $200 ish seems to be the going rate for a rebuilt unit.   I am told the worst part about the swap is getting the 4 bolts under the dash that mount the unit, perhaps on a 78 its not so bad but on my 80 it looks like quite a project so I have sort of got used to the odd pedal feel for now. 

[78caddy]

found usa rebuilts  california 140  plus 50 core charge  so today i will pump brake with engine off to bleed any pressure in system and pull off leaking hyroboost. looking under the dash not too bad to remove 4 bolts and cotter pin to  brake pedal.   then to clean up all leaking fuild.  what type power steering fluid to use? just nomal type?  ok  thanks for your help  steve

[TJ Hopland]

I think the book just says use GM power steering fluid which one would assume is universal power steering fluid that all the stores seem to sell.   With that design dextron ATF seems to work fine also and that is usually what I find in them.    I was running universal steering fluid in my 80 and its got problems but I assume that is more age related than fluid.  Also likely that no one ever changed the fluid before causing extra wear.  If nothing else running steering fluid helps to identify the puddles under the car. 

[TJ Hopland]

I just swapped out my bad booster.    It got too unpredictable.   I did not really mind not having power brakes but was got hard to deal with is if and when the boost would kick back in.   Locked up the brakes several times last week.    What a crappy project on my 80!   I got 3 hours into it so far and was able to go for a test drive.  Now I just have to put the dash back together.   Besides horrible access to the 4 bolts under the dash to make it even more difficult it appears they used those washer clip things on the inside of the firewall to hold the booster on while they assembled the rest of the car.  Problem is there is no way to get in there to remove them like you can say on a brake drum.   Ended up just wacking the heck out of the booster till it came out.