Hi All
I have the "Hi Boost" factory power brake system. Problem is when I step on the brakes, the brakes apply......take your foot off the brakes, the system stays locked up. If I disconnect the vac line to the booster, brakes work normally. Anyone have/had this situation? What to do about it?
thanks

Reamer

 

Sounds like the booster has a blockage .. most likly on the Vac side of the booster..

 

According to the shop manual, Part Five, MAINTENANCE, TROUBLE SHOOTING, AND SPECIFICATIONS, Chapter II -Trouble Shooting, Section 3. BRAKES (p. 349), if Brakes Lock During Vehicle Operation ... "On vehicles equipped with a brake booster, the atmospheric valve may be held open due to dirt drawn in through the air cleaner. Overhaul the booster and clean the air cleaner to correct the failure."

They are, of course, talking about the air cleaner on the booster air inlet not the engine. I think its located behind the seat with the factory setup. The trouble with overhauling the booster is that parts are real hard to find and while there are some places around that will rebuild them the service is expensive. I don't know where they get the parts.

You might be able to disassemble the control valve section of the booster and clean things up and get it to work with the old parts. What I would try first is to remove the air line (not the vacuum line) from the control valve and dump a teaspoon or two of air cylinder lube into the control valve and see if it won't loosen up. It's probably just stuck from sitting. If you can't find the proper air cylinder lube that's suppose to be used for brake boosters I would use preumatic air tool lubricant which you can find most anywhere that sells air tools. Don't know if it's the same or suitable but that's what I would use.

Craig