Danspeed1

iTrader: (1)

Hello,

I could use a little diagnostic help with the brake system on my 1972 Chevelle. About two years back I decided to switch from Front Disc/Rear Drum and Vacuum brake booster to Wilwood Front and Rear Disc brakes and calipers, new brake lines, and a Astro Van Hydroboost unit. The only item still factory within my braking system is my proportioning valve which is going to be changed very shortly for lack of remaining parts to throw at this car. Initially the brakes stopped very well, although I had some issues with my hydroboost pedal not retuning quickly enough. In September of last year I took a 500 mile road trip with the car. On the way back the power steering pump failed. This would be the beginning of my problems. I replaced the pump, and took the car out for a ride. First stop sign, I hit the brakes and the pedal went to the floor and I rolled through the stop sign. I thought to myself, it was odd that the new master cylinder would go so quickly, but I decided to replace it anyway. Installed the new master cylinder. Same result. So I figured the hydroboost unit must of gotten damaged on the trip. Grabbed a remanufactured one, and installed it; and the same result. Today I decided to swap from Power steering fluid to ATF because of fear of aeration causing braking problems. Here's what I've got. When the car is off the pedal is rock hard. When I start the car and try driving it, the pedal moves to a certain point, the car slows down but does not stop. In fact the harder I press the slower it stops. If I only press the pedal softly it stops quicker. To my surprise I jammed the brakes a few times today, most times the car would just keep going but twice it caught me off guard and locked them up, which I was not expecting. This is a horrible situation and I am totally out of ideas on how to fix it. Any guidance would be greatly appreciated

Thanks!

JROC

I don't think I'm going to pose much help but I'll try giving you a few thought.

About 7-8 years ago I converted my 03 Ford Lightning to a hydroboost setup as the factory vacuum booster produced a pulsing sensation under hard braking. I have been nothing but pleased with it on my truck. I used an OEM booster I got off a wrecked 02 F250 PSD. Being an OEM part as opposed to an aftermarket booster (which is available for a F150 if you want) might be more desireable in this circumstance. Kind of like is often the case with things such as alternators or whatnot sometime OEM is the best way to go. When dealing with your brakes you want absolute reliability. Also the biggest thing to consider when going hydroboost is that it will tax your powersteering system harder. A cars PS pieces aren't as beefy or strong as they are on a full-sized truck. Is an old Chevelles PS pump up to the task of managing/supplying the brakebooster as well? You may need to use a beefier/better flowing pump if ones available.

The Modular Mustangs from 96-04 used a hydroboost setup due to head clearance issues. It's booster is noticeably smaller than the ones used on Fords PSD vehicles. I'm not sure how a 96-04 Mustangs PS pump compares to another Mustangs PS pump without hydroboost.

EddieK

Sounds like you may have a bad PS pump.

Is this an LS engine?
Did you burp all the air out if the system??
How is the HB installed, with a T in line or do you have dual return ports on the pump reservoir??