Radiator won't drain
I replaced the thermostat on my 94 Ranger 4.0L yesterday, and tried to drain some of the coolant first. I completely removed the radiator drain plug (and removed the radiator cap) and nothing came out. I stuck a screwdriver and several different types of wire in there, and still couldn't get anything out, just a little bit of brown mud. I hooked up the air compressor and blew air in the drain, and it blew coolant out of the top (I still had the cap off), but still nothing came out of the drain. It seems like there is a one-way check valve at the drain port. Am I doing something wrong? I even hooked up a vacuum pump to try and suck the fluid out, and it still didn't do anything.
I went ahead and replaced the thermostat without draining coolant first, so a bit spilled out when I did that, but I still want to figure out what to do with the radiator drain.
The coolant that came out of the engine was normal green color, and what I can see in the radiator from the fill hole is green too. I'm just guessing there is a bunch of nasty brown stuff in the bottom of the radiator?