I have a 2000 4 door blazer. Recently I noticed that all of my doors are not closing straight. They have lowered quite a bit.
I'm new to this whole car repair stuff and would like to fix it my self. Any suggestions and information would be great.

Thanks

 

check to make sure there is no water in the doors and then just re-adjust the pillar side hinges

 

Check to see if the hinges aren't separating from the pillars.

 

dumb question. What are the pillars and how do I adjust them?

 

I also have an issue with my door the 3rd door in the extended cab, it rattles excessively when I hit a bump or pothole. Has anyone else had this problem before?

 

check the condition of the door hinge pin's and striker's they might be worn out and need to be replaced .

 

I'm fairly certain your hinge bushings are broken and the pins are digging into the hinge itself, and after the hinge is worn, the door will sag. This is a very common problem with s-10s and its easy enough to fix.

Go get the hinge pin and bushing repair kit from the dealership parts counter.
Just buy you a door spring compressor off the internet... (google search)...
Pry the hold-down clips off the old pins.
Get someone to help you hold up the door.
Clamp down on the door spring with the compresser tool.
Use a long punch or whatever works as a punch to hammer out both pins.
Pull out the spring and re-position it in the compresser so it is depressed to the max.
You have two different size bushings, so don't mix them up.
Carefully press the bushings in. I made a press.
The press consisted of a 2-1/2" bolt that would fit through both bushings, a washer, a socket, and a 13mm nut.
Be careful not to press them all the way in. it won't happen.
Hammer them the rest of the way in carefully.
Align the door and slide in the new pins hammer them a little if you need to
Put the snaps back on the ends of the pins
Place the door spring back in and carefully loosen the compressor tool.
You are done.