'80 Buick brake question

[Barney Eaton]

While on the BDE tour in Ohio, one of the people was feeling uneasy about the brakes on this 1983 Riviara convertible.

One evening we looked under the hood for evidence of a problem and to my supprise, it has what I think GM called Hydroboost.

On this Riviera, the power steering pump supplies hydraulic pressure to the "boost" unit located between the master cylinder and firewall.

I have seen similar units on GN's but there was no evidence of an accumulator on the Riviera and I think I remember the GN having an electric pump built into the boost unit.

Please educate me on these unit.

Is there a web site with information?

[Ben Bruce aka First Born]

Barney, I can't be much help, but GM used these on the Diesel cars. I had an 81' Olds with one.

Ben

[NTX5467]

The "HydroBoost" power brake booster is powered by the vehicle's power steering pump. It was typically used on diesel-powered vehicles (no manifold vacuum source). The accumulator is the cad plated cylinder which sticks out horizontally toward the front of the vehicle, parallel to the "booster" and master cylinder assembly. From my experiences, these boosters had rock solid pedal feel, compared to the vacuum boosters . . . even with disc brakes, which can have a somewhat spongy pedal feel depending upon the brake pad material's composition.

The "PowerMaster" is the GM booster which was probably the most-replaced power brake booster ever used. I believe THAT is what was on many of the GNs, as well as many GM B-car station wagons. It has a translucent master cylinder reservoir, which is a key difference between it and the HydroBoost. When the vehicle has been idle and not run for a while, the brake fluid level in the reservoir will look "normal", but when the system's electric pump is energized, the fluid will be pumped into the accumulator system, with the end result being what appears to be an "empty" reservoir. Hence, there is a particular protocol to check the brake fluid level, as I recall!

The accumulator in the PowerMaster system is a round, spherical item which is oriented vertically. As things transpired, the PowerMasters were much more troublesome than the HydroBoost boosters. Although the parts book would show an exploded view of the PowerMaster booster, with each item having a call-out number, the systems were sold "assembled". While the vehicles were reasonably new, the boosters were available "new". As time progressed, then "reman" units were all that we could get from GM Parts. Later still, a TSB came out with a phone number to call if you needed to get one (this phone number was allegedly to a legal office who then orchestrated the shipment of a replacement unit to the dealership). Then, that supply line dried-up later on.

In theory, the PowerMaster booster was a pretty neat item. One compelling thing was that it required no engine interaction to operate, just an electrical supply. At a time when the industry was going through it's first "decrease the load on the engine" orientation, for better fuel economy AND more power to the drive wheels. BUT it was not fully understood by the service/garage service providers NOR the customers. Seeing a basically empty brake fluid reservoir was quite "different", to say the least! Many complaints, as I recall.

Many of the PowerMaster units were replaced with normal vacuum booster/master cylinder units or HydroBoost units. This also meant that when one of the B-car wagons came into the salvage yard with ANY OTHER kind of power brake booster system, that car suddenly became "boosterless" due to existing demand.

One main reason the alternative power brake boosters were necessary was that with the smaller engines for EPA fuel economy in station wagons, the engines were operated with gearing that was "too high" and engines that were "too small" to do what these station wagons were supposed to be capable of . . . much less keep up with traffic at the same time--by observation. This basically meant the stragled Olds 307 V-8 trying to pull a 5000lb vehicle + a possible 1000lb trailer attached, as a worst case scenario . . . hopefully on flat land! So, very little manifold vacuum under these conditions. Barely enough to run the HVAC system, much less a safety system like "power brakes".

I recall a tech procedure to install the HydroBoost system on Buick turbo cars. It was quite popular when the GNs were newer. You can probably still find it on the web. In later times, it might be better to add a double-diaphram vacuum booster plus the newer GM OEM electric booster pump to replace the PowerMaster system or even the HydroBoost on gasoline engine vehicles. After all, they'll not operate at low vacuum all of the time. Just have to make sure that the aux vac pump is actuated during such low vacuum levels so that power brakes will be available--Just a thought . . . proceed at your own risk and peril.

As I mentioned, the PowerMaster was a pretty interesting concept of a free-standing power brake booster, being electrically-powered rather than relying upon the engine for manifold vacuum or power steering operation. Quite self-contained, too! It just didn't work out "after the new wore off", by observation.

Enjoy!

NTX5467

Edited June 20, 2011 by NTX5467 (see edit history)

[Larry Schramm]

My 98 Astro van has HybroBoost and it still works fine after 240,000 miles.

[NTX5467]

HydroBoosts were very reliable. Only thing that might happen, with age, is that the seals would leak PS fluid or the lines might have issues. In the earlier times, a GM rebuild kit was about $50.00. Sometimes, though, when they started leaking, they would "take the kit", but most would gamble rather than pay the $400.00+ for a new booster (back then). If the kit didn't work, they were generally happy to pay for a new GM booster--at least they'd tried the less expensive route.

Enjoy!

NTX5467