[OMARS67]

my 73 vette (manual brakes) has a brake issue. all of a sudden the pedal goes down. so i bleed the brake and sure enough there was air. after words the pedal was stiff and would brake fantastic. but after a couple days back to no braKES. there is no leaks anywhere. fluid is always top of. but its cloudy!!! so i flushed the fluid by opening the valves on the caliper the adding new fluid. and bleeding again. but same porblem. then i replace the master cylinder (bench bleed) and same thing. replace it with again and same thing all over again!!!! any suggestion !!???

[Hick_101]

if you replaced the caliper twice then you know that its probably not that. I would search better for a leak or maybe even a bad bleeder? ( ive seen it) put cardboard under the car to make sure its not leaking anywhere.

[OMARS67]

i havnt replaced the calipers, its the master cylinder i have replaced twice. could it be the proportioning valve??? how could the bleeder be bad???? there is absolutly no leaks from anywhere the brake system ie lines, calipers, master cylinder.....

[Cape Cod Bob]

I have a similar problem. All my parts are new. I have a little brake fluid showing up at the prop valve. At the back where there is a little rubber cap covering some kinda valve. I don't lose hardly any fluid but the brakes slowly get air in the line and I end up double pumping.Its getting to be a real pain and I want to get another NEW prop vale . I will choose amnother maker. Good luck.
ps... putting paper or cardboard to check for leaks will probably not show much as most of the braking is done when moving down the road.

[cobalt327]

If there's any water in the system, the heat produced at the caliper can cause this water to vaporize, and that results in air in the system and a soft pedal.

[OMARS67]

capecodbob-i think the prop valve might be our problem. although maybe hick101 is on to something bout the bad bleeder. might replace both front bleeders first and see if that does the trick.

water in line theory might also work but i have flushed the entire brake system by opening one valve bleeder at a time and just pumping the brakes till the master cylinder goes empty. the fill it and on to the next caliper till i flush all 4. i drive for a couple days then NO BRAKES. i do another normal bleed and after a few days back to NO BRAKES. also the fluid get really cloudy to the point that eventually it turns black.

[adantessr]

Originally Posted by OMARS67

capecodbob
water in line theory might also work but i have flushed the entire brake system by opening one valve bleeder at a time and just pumping the brakes till the master cylinder goes empty. the fill it and on to the next caliper till i flush all 4. i drive for a couple days then NO BRAKES. i do another normal bleed and after a few days back to NO BRAKES. also the fluid get really cloudy to the point that eventually it turns black.

First off, you should never bleed the brakes until the reservoir goes empty, because then you are pumping air back in the brake system. Always refill the reservoir before it gets to less than 1/4" of fluid. Secondly, the fluid turning black tells me that the fluid is getting very hot and burnt. I would check and make sure that you don't have a caliper sticking or the rod on the master cylinder missadjusted not allowing the master cylinder piston to return completely.

[OMARS67]

SO A COUPLE days ago i replace the two front valve bleeders with new speed bleeders and its braking perfect!!!!! who would have know valve bleeders can go bad.

[adantessr]

Originally Posted by OMARS67

SO A COUPLE days ago i replace the two front valve bleeders with new speed bleeders and its braking perfect!!!!! who would have know valve bleeders can go bad.

Glad that it worked out for you

[Hick_101]

Originally Posted by OMARS67

SO A COUPLE days ago i replace the two front valve bleeders with new speed bleeders and its braking perfect!!!!! who would have know valve bleeders can go bad.

glad to see you tried it out and didnt just think me a fool