minmdm

My brake pressure slowly went all the way down today. I was totally out of fluid, but when I refilled the reservoir the pressure has not come back. Anyone have any ideas what the problem could be?

ML63 AMG

Major leak. Either master or slave cylinder seals are probably toast. Replace one or both and then get a shop with a pressurized brake bleeder to pump oit all the air & refill fluid

minmdm

Thanks

vvrjrlaw

Couple of things. First there is a light on the dash that is there for a reason and you ignored it. As a result the fluid has leaked out of the reservoir. You filled it. Did you bleed it because if not the pressure won't come back until you do. Notice anything unusual under the car like a big puddle of some unidentifiable fluid that smells like grease base? With a leak like that you should have seen something. How about the wheels. Have you looked on the inside of the wheels to see if anything that looks like water that isn't drying is trailing from the inner wheel to the outer wheel? You have to get the pressure back into the pedal so get your friend, pump up the brake hold and then crack the bleeder on each wheel bleeding the right rear first. Once to the floor hold and then while holding close the bleeder and pump it up again. Do this with each wheel and all the while start looking for the leak. If it's as you say it should be easy to find. Good luck.

minmdm

Thanks guys. My brake lines rusted out! Had to replace the lines!!!

vvrjrlaw

You can't predict or check status to failure of a brake line. My apologies.