Brakes acting goofy after fluid change
 

I borrowed my friends mityvac with the little brake fluid catch can. I drained the brake reservoir filled it back up with fresh fluid then went to the back brakes and started pumping with the mityvac. I pumped till the fluid stopped looking black on all 4 brakes.

I jumped into the car to go to my moms house and as I pushed the brake to shift the pedal went to the floor like right after you change the pads. I pumped the brake a few times and each time it got stiffer and then when it was back to normal I drove off. In about 20 seconds I needed to slow down for the stop sign and the pedal went about half way then grabbed. I pumped them a few times and it went back to normal. Then I turn and at the next stop sign, same thing. I got worried and went back home and parked it.

Maybe there is some air in the lines? I looked under the car and there was no fluid there. I thought maybe I forgot to tighten one of the bleeder screws or something, but they all looked ok.

Did you check that the resevoir is still to the fill line? It may have pumped everything you put in through and you might need to add more fluid.

I topped it off before I closed the hood but this was before I got in and hit the brake . Ill check it again tomorrow in the light.

you have air in the brake lines. This might have happened when you "drained the reservoir".

get a helper and bleed them properly.

You still have air in your brake lines. Bleed your brakes with someone pumping the brakes, the old fashioned way. Keep an eye on the resevoir fluid level. The pressure bleeders and such, only get some of the air out.

If you use a helper, make sure he/she does not push the brake pedal all the way to the floor. Doing that can damage the master brake cylinder's seals since the piston gets into an area it normally doesn't encounter, and the surface can be rough.

A pressure bleeder gets all of the old fluid and any trapped air out without risk of introducing more air, since the pressure bleeder keeps the reservoir full. All you have to do is to go from one wheel to the next, letting out the dirty fluid.

Jeremy

In my case I used a pressure bleeder at 21psi and still had air emerge when I had an assistant pump the brake. I used a gallon+ to flush the system. In ANY case, manual bleed or power bleed, the resevoir must not be allowed to empty.

I never pump my pressure bleeder up more than about 5lbs...I would have thought the reservoir would fail at 20+ for sure.

your symptoms are classic air in the master cylinder. there are two reservoirs in there. the back one is not visible from the driver's side... stupid design.
vacuum bleeding is never a good idea. the bleeder fittings are NOT air tight, and you will always get air in the pots bleeding this way.
as mentioned above, having a helper push on the pedal is a good way to remove dirty fluid, but if you push far on an old braking system, you can damage the master cylinder.
simplest way to bleed these cars is with a pressure bleeder.
you can build one with a simple garden sprayer and an extra MC cap or a chunk of rubber with a hole drilled in it...

Thanks everyone for the help. Ill have to wait a few days to tackle this again. My girl is out of town and wont be back for a few days. Its too hot to drive the benz without ac. that project is coming up soon too....

a/c? bah. that's for loosers!
you're in NORTH texas, ain't it cold up thar?

seriously though, we'll get your air working too. just post it here...

Yea its a freezing cold 98 today!
I need to part with one of my toys soon so I can afford to have this new/old one. I have a few good ideas to run with the AC, just need some time, some gauges and a vac pump!

At 5psi I couldn't get much fluid through the system. Yes, I did have to seal the top of the resevoir at 21psi. The brakes worked ok with the power bleed, but I still saw air emerge when I manually bled the system.

If you just open and close the bleeder nipple using a helper it can not go too far and hurt anything... do not wait until the stream pressure starts to get lower... perhaps one half to one second depending on how hard the pedal is being pushed.

If there is air in the braking system, using a vacuum bleeder enlarges the air bubbles creating a greater void. Takes more fluid flow then to move that air void, which the vacuum bleeder may not provide. A pressure bleeder, while compressing any air slightly, and while providing sufficient fluid flow, does not generate the pressure of manual pumping the old fashioned way. Bleeding the old way collapses air pockets significantly, making it easier to expell those voids. When an assistant is not available for manual bleeding, you can still do an atmospheric pressure bleed by using the old disposable one man bleeder. Take a plastic disposable dropper, slit the bulb with a razor about half inch along the long axis. Cut the tip off, stick the rest into end of tubing, dunk the bulb end with the slit in waste container. Put the other end of the tube on the bleeder screw, open screw. Fluid will begin to flow slowly (by gravity). Pump the brakes slowly. On the down stroke, fluid will be forced out of the dropper bulb slit. On the up stroke, the slit closes, significantly cutting old fluid pullback. Pump 5-6 times or until nice colored fluid shows in the tubing.