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Andree · 02-12-2009, 07:40 PM

I have 1986 Airstream motorhome, Chevy 454 engine, hydro-boost brake system. Hydro-boost failed. Brake shop replaced hydro-boost with NAPA rebuilt unit 3 times in last week. 1st rebuilt locked brakes up; 2nd rebuilt leaked at mid-section of booster; 3rd rebuilt provides nearly OK braking, but hydro-boost unit and reservoir get really hot (can't hold fingers on it for more than a few seconds) after 10 mile drive. Brake shop purged power steering unit and replaced power steering fluid with DEXTRON III---sez same stuff, only different color. Suggestions? d with

ROBERT CROSS · 02-12-2009, 08:23 PM

Don't wanna know how much youv'e thrown in that hole already, few years back that was one very $ repair. I would power flush the system and bleed it several times. Sounds like it may have an air pocket. POWER STEERING fluid in the Hydro-boost, BRAKE FLUID in the master cylinder.
DEXTRON= auto transmission.

Never had a vehicle so equipped, but it can be more cost effective to just change it out.
We did one several years ago one at the store.

**Action** · 02-13-2009, 01:31 PM

The OK braking is a good indicator of air in the system. Either the boost system, (PS & Hydroboost) or the brake lines themselves. The Dexron III can be used in the boost system and will take higher heat loads. The PS pump supplies the fluid under pressure for the PS system and the brake hydroboost.

However making a change to Dexron III will not likely fix a problem unless there is air in the PS system now. And when they replace the fluid the air in the system is bled out. Going to Dexron III will allow you to use the fluid longer.

If the braking system isn't working as well as it was before the failure, you either have a bad booster (again) or there is an issue with the installation. The design is a more complex (and expensive) system, however when working correctly is far superior to a standard vacuum boost braking system.

Lastly as a point of clarification, there is no "T" in the fluid name. And it is found in both the automatic transmission and the power steering (PS) and hydroboost systems.

>>>>>>>>>>>>Action

Diesel1 · 02-13-2009, 01:43 PM

I do not use NAPA rebuilt parts! They have an incredible failure rate! Spend the money and buy OEM if available. If you have to buy NAPA get the high priced parts. They seem to have about 3 price/quality options. The cheeper ones are junk. Adios, John

87MH · 02-13-2009, 04:22 PM

Quote:

Originally Posted by Andree

I have 1986 Airstream motorhome, Chevy 454 engine, hydro-boost brake system. Hydro-boost failed.... Suggestions?

Andree:

Did your brakes lock up also - are they (the brakes) getting hot?

If so, PM (Private Message) me and I can probably help you out - I had the brake lockup problem several years ago, and there is an easy fix for it.