OK, this one has this guy stumped. I have a 59 Ford Ranchero (very nice car). I installed power brakes along with disc's up front. It was a kit deal. They always stop very well. However, when yopu first start the car, the brake pedal goes down about 80% of the way before applying the brakes. It never fails to work, its just a queezy feeling. Once you are going and have applied the brakes 6 to 8 times or so, they pedal begins to move up to a normal location (about a 3/4 inch drop) before applying the brakes. They then work great until having the car sit for a few hours. Then it repeats the deal. WTF, over?
Vacuum problem maybe? Or the master cylinder is bleeding off slowly when it sits for a while. Are you loosing any brake fluid?
More than a few guys lately have had really poor luck with new boosters.....mostly made in China ****. One guy on the '57 forum went thru 2 new MCs, and 2 new booster replacements before he finally gave up and went hydroboost. They were no charge replacements, from an ebay seller who was doing his best to get him going.......but it turned his weekend/minimal downtime project into weeks and weeks of frustration. I'm not saying it is a booster problem, just saying don't discount it because it's new.
Not exactly the same, but I had a problem with new MC's leaking on my 40. After the second one a friend who runs a repair shop told me he had better luck with rebuilds. I replaced my expensive new remote fill one with a $20 rebuild, no more problems.
I think Tex is on to something: If you don't want to worry about a warranty I would suggest taking to a re-builder. Maybe they could confirm (or not) that the booster is faulty.
I say the booster as well. If the master was byp***ing, it may do it first thing but would be unpredictable from there. That also comes with the pedal hitting the stop for whatever circuit is impacted.
How long ago did you install the kit? Is the stated problem new, or always there since the new system was installed? Back brakes drums? Residual valve? Asked but not answered...any fluid loss? Who is the supplier of the kit?
Answers: I installed it two years ago Problem was immediate Rear brakes are stock shoe type Yes, I installed a residual valve No fluid loss at all I cannot remember the supplier. It was one of those ebay deals I never did anything because they do work, its just irritating
I'm not using a residual valve on my '59 with the front discs, master is a Speedway Ford type dual master. No power. Try adjusting up the rear shoes, go fairly tight and see what it does. You can always back it off later.
It still could be a byp***ing master, but adjusting the drum brakes tighter will either make it better... or not. If not, I'd tend to go with another master.
I had a truck do almost the same thing once. It ended up being the master cylinder. I'm no expert by any stretch but I would think if it was a booster problem the pedal would be hard and not depress fully.
Boosters have a few things that go wrong with them, internal leaks and mis-***embly and most likely the external check valve. The acid test for a booster is: engine off, exhaust all the vacuum at the pedal. Foot on the pedal (moderate pressure), start the car. The pedal should sink to its normal operating position with no hissing or a skip in the engine (vacuum leak). I've seen a lot of byp***ing masters over the years and they can be hard to diagnose, I haven't seen every case either. Some are predictable, some aren't. If you think you have one, make sure the drum brakes are properly adjusted. Check the brake fluid level. Manual masters are a little easier on older cars since they have more travel than power brakes. I would sit behind the wheel and put a little pressure on the pedal, do a light on and off, then the same with a little more pressure. I could get most of them to byp*** within a 1/2 minute. Some I had to play with the pedal pressure and tease it into byp***ing. It is quite possible it would byp*** on the first start of the day. I would play around it with the engine off on a power brake system.
Can't you isolate it to the master area by pluging the master line ports. If you disconnect the lines and plug the line holes to the master cylinder and your pedal is hard it is down stream of the master. If the pedal is still soft then you can bet the issue is probably in the master cylinder area. Just a thought to isolate the problem. I'm no expert but this may help.
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