I recently changed my rear brakes about a month ago. While changing them I noticed my rear driver side caliper was seized up so I installed a new one. Bled the brakes and all was good for about 2 weeks. One day I get inside my car and my brake light, vdc/slip light is on. So I check my fluid reservoir and its low so I top it off and the lights go off and im good to go. Same thing happens again about a week later so I repeat adding more fluid thinking maybe there was some air inside the line. Good to go again up until about 4 days ago when my lights come back on and then over the next couple days I start to notice im losing pedal pressure very slowly. Today I was going to lunch and hardly had any brakes, just went straight to the floor. Stop and fill up my reservoir but that didn't really do much good, maybe a little but all my lights went back off. So I decide to bleed the brakes again thinking maybe I didn't get all the air out the first time. I pumped the pedal while a friend was at the caliper. They hardened back up immediately but after I started the car they would just go straight to the floor. My reservoir lost just a minimal amount of fluid after bleeding. I give up. This is about as far as my knowledge goes. So this is where im stumped.

My friend said he thinks its the master cylinder but I wasn't having any of these problems until I changed the caliper. Thats why I think its something other than the cylinder. Ive don't a small amount of research and seen people talk about brake boosters and vacuum lines/check valves with my similar type of symptoms but no one has seem to come up with a solution, at least with some of the old threads ive read. Any info would be greatly appreciated!

 

If you're losing fluid then it's going somewhere. Find the leak and your pedal will stop going to the floor.

 

One would think. But ive searched the whole car and couldn't find any evidence of a leak plus there is never any type of puddle/drips under my car.

 

Then you still have air in the system, did you do a full purge or were you just pumping out one brake line?

 

I just did the one line(driver rear) when I changed the caliper like a month ago and then today I bled the passenger rear.

 

That's your problem in a nutshell. With the replacement of the caliper you have air somewhere in the system that hasn't come out yet, that's the only logical solution to having fluid disappear from the reservoir with no trace of any leaking. Our cars have a specific order of what calipers to bleed in what order but I can't remember what it is, a quick Google search would probably find it or just wait until cleric visits us here again. Bleed ALL 4 calipers in the specified order and you should be good to go. Make sure you have 2 people and never let the reservoir lose all it's fluid, make sure there's always a decent amount in the tank so no air can enter they system from it.

And you probably know this but don't let the brake fluid get on any painted surfaces as it's super corrosive, might not be a bad idea to wear gloves as well.

 

As I was searching earlier I remember seeing a post about a certain order for bleeding the calipers. Now I just gotta find it again. Thanks for the info guys. I appreciate it. Ill give this a try tomorrow and see what happens.

 

RR, LF, LR, RF

Make sure you have a piece of clear tube attached to the bleed valve so you can SEE the bubbles. Longer is better so something about 24" is ideal.

Flush thoroughly until all old fluid is removed, you will see the color change, refill the reservoir often, don't let it drop below half capacity.

I also recommend putting an old towel under the brake master cylinder in case you spill fluid. If you get ANY on the paint wash it off with lots of water. That's the only time I ever suggest using pressurized water in the engine bay, water will dilute the fluid so it won't damage paint.

 

Got it! Thank you!

 

These work excellent
I just did a fluid change yesterday. I called it there as the pedal is pretty nice and tight.

But I do have one of these too https://www.harborfreight.com/brake-...der-92924.html I didnt even use it but recall two years ago when doing brakes this thing got the brake crazy tight.