Hi all, recently purchased 94 k1500 suburban and have a few questions.The doors seem to rattle over big bumps (like railroad tracks)as if there not shut good.If there is an easy fix for this please reply.Also the rear upper air vents dont seem to like blowing out warm air unless I'm highway traveling,when I'm setting at a stop light they blow cold.Is this normal?I replaced the thermostat.(no change)It seems to run at around 170 degrees tops, also curious to see if it may have a seperate rear heater core.It has 190,000 miles thinking about changing to 20w50.A coworker of mine has 340,000 miles on a k1500 5.7 (motor has never been overhauled) 20w50 is all that he's ever put in it.THANX FOR REPLY

Hi all, recently purchased 94 k1500 suburban and have a few questions.The doors seem to rattle over big bumps (like railroad tracks)as if there not shut good.If there is an easy fix for this please reply.Also the rear upper air vents dont seem to like blowing out warm air unless I'm highway traveling,when I'm setting at a stop light they blow cold.Is this normal?I replaced the thermostat.(no change)It seems to run at around 170 degrees tops, also curious to see if it may have a seperate rear heater core.It has 190,000 miles thinking about changing to 20w50.A coworker of mine has 340,000 miles on a k1500 5.7 (motor has never been overhauled) 20w50 is all that he's ever put in it.THANX FOR REPLY

I have a 94, 330,000 miles, engine has not been overhauled.
Doors, most likely need to change door hinge pins and bushings.
Engine temp does seem a little low at 170, but this year didn't have a rear heater core, so there is no heat boost by using rear fan, You may be picking up warm air from front and recerc.it again.
hope this helps, Don

i have a 94 burban and have the rattle in a rear barn door had been driving me nuts so i pulled door pad, the noise was just a peace of metal that must have broken off something and got stuck behind electric door lock selonoid, if your problem is the hinge pins when you are standing next to the door slowly close it if when near to latching it looks low simply grab door by the bottom and lift door if it is the pins and bushings the door will move up and down, if its not moving up and down there is nothing wrong with the pins. they do wear and eventually will need replacement but it sound more like something is loose inside the door. take door and swing open back and forth like it is being opened, just a few inches back and forth quickly, and sharply. if it is something loose in the door you will hear it rattle. then you need to remove door pad and look for the object, could be anything from a broken peace of metal to something loose but this is more likely then hinge pins.
hope this helps