Currently when I attempt to brake, I have little to no resistance in the pedal, and a direct relationship of braking power (little to none). The brake fluid resivior seems to be at about 75%, the vacuum lines to the brake booster seem fine (but I do not have a mity vac to check thoroughly), the brakes were replaced rotors and all less than 6 months ago.

Any suggestions?

__________________
1985 300D 204,000+ on B100

So, I will assume that if there's little resistance, the pedal goes down quite far? This could mean air in the lines or a rotted brake line. Could also be a failed caliper on the extreme. Or a bad master cylinder. The first thing I would do is try to bleed the brakes to obtain a firm pedal & check the bottom of the car for leaks. Paul central FL
300CD '84

The first thing you are going to do is to try and find a leak.

Fill the reservoir to the top. Make sure the rear chamber, for the rear brakes is full. The fluid spills over an internal barrier into the rear chamber. Be absolutely sure the rear chamber has fluid and is the same level as the front chamber.

If you notice that the rear chamber is empty and you are filling it all the way back up, stop all further testing and post again and we'll solve the problem.

So, with the reservoir full, and the presumption that it was never completely empty, press the pedal down and release. Do this 15 times.

Return under the hood and look at the reservoir. Look at both the front and rear chambers. See if the level has dropped in one of the two chambers.
If it has dropped, the chamber with the drop is the one where the leak is occurring. Raise that end of the vehicle and remove the wheels. You are looking for a brake fluid leak at one of the calipers. If you find it, report back and we'll solve the problem.

If the fluid level in the reservoir does not drop in either the front or the rear chamber, the most likely culprit is the master cylinder. However, the same symptom can occur if there is air in the lines and they need to be bled. However, this rarely occurs unless one of the reservoirs has been run dry.

Be very cognizant of the level of fluid in the rear reservoir before adding any.

Report back with results.

Didn't bother to walk out to my car to check, but I thought that the rear chamber in the reservoir fed the front brakes and the front reservoir fed the rear brakes?

Len

You are correct, I just removed one yesterday. Front brakes are at the rear of the master cylinder, rear brakes at the front.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Thanks Brian, it was definitely the master cylinder, and to boot my rear pads are just about gone. Dropped it off last night, probably will be about $750. Hooray?

__________________
1985 300D 204,000+ on B100

A good price would be one third that. Paul