I took the 71 out this evening to get a better feel for the car( I just got her two days ago) and just a few miles from home I applied the brakes and it was almost nothing....After changing my underwear I checked the fluid and the front reservoir was full but the back reservoir was empty.

I know that I should have checked this prior since it is an unfamiliar car, but I didn't and earlier drives the brakes seemed a little soft, but worked fine. Anyway I filled up the reservoir but the brake pedal is still spongy.

My question is if the reservoir went empty do the lines need to be bled? Would there be another reason for spongy brake pedal besides bleeding?

Thanks in advance,

Randy

I would imagine that you should just go ahead and bleed the brakes. Before you do so, check all the lines (replace/tighten as needed) and go from there.

Recently I had a problem with one of my reservoirs losing fluid. It was just a matter of tightening up the connection at the caliper.

The brakes are likely spongy because the rear circuit is empty.

The brake fluid in the rear reservoir didn't evaporate, it went somewhere. You need to look for a leak. Most commonly you will find that one of the wheel cylinders is leaking, but on a 36 year old car it could be many things. My car's brake lines were rusted completely through. I had to replace the entire line.

The worst source of leaks on my car was the rear brake proportioning valve, which on a 71 is located above the passenger side half shaft. My leaks there were the RESULT of replacing the hard lines however, so if you haven't replaced the brake lines that may not apply to you.

Clean your garage floor, park your car inside, fill the rear reservoir, and start pumping the brakes. After a few dozen pumps, look under the car. If there is a puddle of brake fluid, trace it back to the source and fix it.

By the way, my brakes are still a little spongy even after I bleed them several times, but I don't have any leaks now, so I think that after I have driven it for a while I will bleed the rears again and hopefully the trapped gases will eventually come out.

My brakes were a little spongy because one of the rear hoses was leaking just a little. I put on new hoses ( stainless braided ones) and now it's totally different.

thxZ

Thanks for the info guys I really appreciate it.

The brake fluid in the rear reservoir didn't evaporate, it went somewhere. You need to look for a leak.

Walt couldn't have said it better.

Replacing the brake hoses is also a great idea. Over time the fluid permeates the rubber hoses causing them to swell and reduces braking efficiency. You're (we're) dealing with 35+ year old cars, they need a little pampering, and safety is always a good place to spend money.

Another thing to keep in mind is that if you still have soft pedal issues after repairing all leaks and hoses, the master cylinder is the next culprit... but given the low fluid issue the problem is most likey elsewhere.

Nate