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Found this strange hydroboost

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,833
Connected to the low pressure side of the power steering
no accumulator that I could see
Works without the engine running
Electric motor on the bottom of the unit
'88 GMC C70? ex-Ryder truck. Drove it a little, very powerful brakes. Don't think I will be using it, but it was an interesting find
 

eb66to77

Bronc'Ownly
Joined
Mar 26, 2005
Messages
2,558
Loc.
NOVA
I rented a uhaul one time and the brake was electronically supplemented. I am not sure why. I didn't look under the front clip at all to see what the hell it was though.

I would imagine the low pressure hookup was for feeding a reservoir for the electric brake support.
 

JIMJEO

Jr. Member
Joined
Nov 26, 2008
Messages
116
Loc.
CORNELL, MI
Connected to the low pressure side of the power steering
no accumulator that I could see
Works without the engine running
Electric motor on the bottom of the unit
'88 GMC C70? ex-Ryder truck. Drove it a little, very powerful brakes. Don't think I will be using it, but it was an interesting find

Does it look like this? Standard fare for M/D trucks & buses w/o air brakes. The electric motor is a safety to give good pedal if the engine dies.
 

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Broncobowsher

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,833
Does it look like this? Standard fare for M/D trucks & buses w/o air brakes. The electric motor is a safety to give good pedal if the engine dies.

Close to that. I think the motor was turned 90°.
Yea, noisy bastard when it kicks on. I know about them not staying running, that is why I only drove it a little.

The pressure line really does go from the pump to the steering box then to the booster. I checked that a couple of times because it didn't look right to me.
 

haydenjsle

Jr. Member
Joined
Dec 22, 2006
Messages
91
Loc.
Southern CO
Back in the mid 80's GM used an electric/ hydraulic unit in some station wagons and a few turbo cars. It might have come in some bigger delivery type trucks and RV's--it was called the "powermaster" system. It used an electric pump mounted right below the M/C and a nitrogen accumulator--no lines attached to the power steering system, though--the pump provided all the hydraulic boost. These units were actually very quiet and gave tremedous braking power-- engine running or not. I ran this unit on my bronco for 5-6 years--more boost than my current hydroboost, and was nice if the engine died on a hill/ obstacle--still had all the brake power you could imagine. The drawback/ problem was the pressure switch on these weren't reliable which prompted me to try the hydroboost. If an aftermarket/ upgraded switch were available, I would still be running it over the hydroboost.
 
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