Bhebert449

I haven’t driven my car in about 3 weeks. When I drove it today the pedal was very soft and went to the floor. Car still stops but takes a lot of pressure on the pedal. This is a manual brake car.

I checked the the master cylinder and one side of the reservoir is full and the other side is almost empty. Would the fluid dissipate from not driving? I did not see any evidence of leaks. Should I just refill and see if that solves the problem? Might there be air in the system? What kind of fluid do I use?

JoeMinnesota

Which side of the master was low - front or rear? I would assume a leak, and calipers before anything else. It may not leave a puddle - look at the insides of your tires for shiny/wet run marks. Sometimes the insides of the wheels have enough dirt or grime to absorb fluid from a caliper.

DOT3

You are also correct - a lip seal leak at the caliper may leak very little fluid and suck air when you let the peddle up.

Bhebert449

The rear, closest to the dash, was low.

JoeMinnesota

Okay - rear 1/2 of the car, then. I would top it off and get in and press or pump on your peddle. You will likely find the leak. I did have one that caused a soft peddle when driving but didn't show an obvious leak when I looked under the car. With my son working the peddle I could hear the caliper bubbling a little, and then spotted the wet wheel on the inside. It could also be a line, but in my case it's been calipers. I've replaced all but one now with stainless sleeved o-ring replacements.

Bhebert449

Thanks! Was hoping it was just a symptom of sitting so long but could be a slow leak that finally emptied the reservoir enough to cause the brakes to stop working.

71VetteLover

You most likely have a leak in one of your rear calipers. You can easily tell which side by looking at the insides of the tires as the tire will appear darker than the other side; the result of brake fluid getting on the tire.

Bhebert449

Can a caliper be repaired? I believe they are the original ones that came from the factory and would like to keep the car as original as possible

JoeMinnesota

Yes - look at the Corvette vendors online for rebuild kits, or search these forums for good advice. You can also exchange for rebuilt units, including proper date codes for a price. Many people rebuild theirs.

Peterbuilt

Post the numbers of the calipers and someone can tell you if they are originally from 1969 or not.

If original they will not be stainles steel lined.
Sleeving can be done for a price or exchange rebuilt might work for you.

Bhebert449

The numbers of the calipers are as follows:

lft front 6413726
rt front 5473796
lft rear 6473080
rt rear 5432281

Peterbuilt

Calipers #=
546XXXX = 65-66
545XXXX = 67-72
547XXXX = 73-82

Your 5473796 might be 73 -82 and mounted on the left front.

Subject to review by someone that pays more attention to caliper numbers.

Bhebert449

I added brake fluid and now the brakes function normally. Should I still be concerned about a leak? Is it dangerous to drive?

Lagonia

Yes, you should be concerned and yes it is dangerous to drive. You have a leak somewhere. Brake fluid does not just disappear into thin air. The good thing is that when it leaks, it is messy.
Jack-up the car and remove all 4 tires - inspect brake calipers carefully and all soft brake lines. The evidence will be there somewhere.

jts90vette

Try not to let the master cylinder go dry, it could create more issues for you. I just went through this with my 1974. My combination valve was leaking.

lvmyvt76

could be the master leaking since it is the rear going low??? look for fluid down the firewall?

jacgillam

Original brake calipers??? They almost always develop corrosion and pitting in the cylinder walls and leak so little at a time it is almost unnoticeable until it sets a couple of months and the peddle goes to floor. I replaced my calipers with Stainless steel sleeved ones years ago. It still needs brake bleeding and more fluid every 2 years but not every month like it used to. If you want to retain year specific calipers there are some companies that will rebuild yours with stainless steel sleeves. Look it up on the internet. but as I said, minutely leaking brake calipers is a characteristic of old vettes. I've had mine 42 years, I have reamed and rebuilt the originals numerous times to very little difference until I got the stainless steel sleeved ones. You can't possibly hone out all of the pits and corrosion and get the factory spec'd piston seals and sleeves to hold fluid for any time. Good luck!