I have a 90 Honda Civic hatchback with 165,000 miles.I'm having a problem with the brakes but only in the warm weather.When I'm sitting at a light the peddle will slowly go to the floor.IfI pump them they will get firm and higher but will slowly go down again.When I'm driving the car the brakes are fine.I tried bleeding them but it didn't help.I did break one of the bleeder bolts in the process which I'm not sure how to replace.The master cylinder isn't leaking any fluid and the level is fine.I was going to change the master cylinder but want to make sure it's not something else.In my experience of changing a bad master cylinder they always had bad seal and were leaking fluid.

 

Did you look for leaks from the front calipers and rear wheel cylinders? Is the broken bleeder bolt leaking brake fluid?

 

i have the same thing going on its not the master cylender i replaced mine and its still doing it a little and i bleed all the lines 2 its air in the master cylender i am thinking still but i have the drivers rear brake not working so good so i have to check that monday if i find out anything i will give you a heads up on it and if you have someone to push on the brakes do you hear a wine sound in the booster area ? like its leeking but its not ? push on them hard and listen to it and let me know ? thanks russ

 

i wanted to ad one more thing that i found out on replacing my master cylernder the screen in the cup,when i pulled it out it had some bad crap in it i mean bad it was like sludge of its owen kind see if that is clogging the path of the fluied also might not be getting any to the piston right away to stop it.
also try to get on a dirt road and hit the brakes hard and see what one locks up and what one does not if one does not thats were you can start to bleed that brake . i say that as you said you broke a bleeder so you might get by it that way for now but have it fixed in the future.and to get it out get a grabit by craftsman they work slick and its a must for brakes.

 

Wait...are the brakes locking up as you drive? or is the pedal just sinking?

as for the broken bleeder screw, could always just replace the caliper for like 80 bux for a set....or get one from the junk yard

 

You probably need a master cylinder. When you can stop normally but the pedal sinks down as you hold it, it's either a fluid leak somewhere (which you should have noticed by now as a lack of fluid), or an internal leak in the master cylinder. Basically the fluid leaks from the outlet side of the cylinder back to the inlet as you hold the pedal down.

 

Thanks for all the replies.The broken bleeder bolt is on the right rear wheel and it's not leaking any fluid,it broke before I got it open.As far as leaky cylinders or caliper I haven't checked that because I'm not loosing any fluid,but I'll check that today.I'll also check the screen in the master but I'm pretty sure when I bled the brakesit was clean.When I did bleed the brakesthere wasn't that much air in the lines.I haven't swapped the master because I thought it might be the booster or something else.I'm not totally clear on what the booster does.When my wife gets home I'll try the test on the booster.I know when the car is shut off the brake pedal is firm and doesn't have any problems.Also the brakes are not locking up.Is it possible for the seals in the master to go bad without leaking fluid.If the master was bad wouldn't the peddle go to the floor all the time?

 

It's real common to get the slowly sinking pedal from a bad master cylinder. The booster won't do that. Booster just increases the force from the pedal to the piston of the master cylinder. The pedal is always a lot firmer with the engine off so the booster is not active. But if you tried to drive that way it would not stop very well either.

Probably the easiest thing on the broken bleeder is to replace that wheel cylinder, they're not expensive. That is assuming you can get the line off. Use a good 10mm line wrench. An open end wrench is a poor substitute.

 

when you say broken bleeder bolt, you mean it stripped right? Not sheered off? b/c if it sheered off, it would be leaking every time you brake. if it is stripped, then you can wait. if it is sheered off, you have a very dangerous condition and I wouldn't drive it b/c you will lose all your brake fluid in the process.

 

If air is trapped somewhere between the broken bleeder bolt and the line serving that specific wheel, then the brakes will feel spongy until the bolt is fixed and that line is properly bled.