Low brake fluid in my 69 c3
#1
Low brake fluid in my 69 c3
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?
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?
#2
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.
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.
Last edited by JoeMinnesota; 10-17-2017 at 08:57 PM.
#4
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.
#6
Pro
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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.
#8
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.
#9
Le Mans Master
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C3 of Year Finalist (appearance mods) 2019
If original they will not be stainles steel lined.
Sleeving can be done for a price or exchange rebuilt might work for you.
#11
Le Mans Master
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C3 of Year Finalist (appearance mods) 2019
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.
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.
#13
Racer
Jack-up the car and remove all 4 tires - inspect brake calipers carefully and all soft brake lines. The evidence will be there somewhere.
#14
Pro
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.
#16
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!