Heard quiet popping sounds after key removal

THOMAS1117

MEMBER
1999 GMC SUBURBAN
5.7L
V8
4WD
AUTOMATIC
130,000 MILES

Today I was doing a coolant pressure test on my vehicle listed above it is a K1500 (5.7L 350 Vortec). I know I was supposed to disconnect the battery beforehand but I have had issues with the terminals connecting properly in the past so I left it alone because I figured the vehicle was off and had not been driven in hours. I disconnected the two sensors attached to the air intake and removed the air cleaner assembly box so I could get a better view of my hoses.

About ten minutes later I got in and turned the key, not to start the car, just to turn the lights on, but I immediately noticed my heater was on and blowing (the sensors and assembly were still disconnected at this time). I quickly turned the heater fan off and turned the key back to the off position and removed it from the ignition. At that point I heard three or four very quiet popping sounds coming from inside the dash behind the steering wheel. I also noticed that I was able to remove the key from the ignition with it being in the back position (radio clock light still on), which usually is not possible (I think?).

My question is, do you think the quiet pops were related to not bleeding the coolant system yet, an electrical short, or just air sounds due to the heater running briefly with the air intake assembly detached? I am hoping I did not inadvertently cause some damage to the electrical system. Based on the scenario I described above, would you be concerned about that? If so, what tests/troubleshooting should I do to double check?

1 Reply

HARRY P

MECHANIC
2,292 POSTS

The sounds you heard were not anything to worry about. It was just the sound of plastic vent doors, blend doors, and actuators, all part of the HVAC system. Usually you do not hear them because the truck is running or the fan is on.

The part with about the key coming out with the switch still in the back (ACC) position is a problem with the ignition lock cylinder. Pretty common in many GM vehicles. There have been some recalls. Check at http://www.safercar.gov to see if your truck is under a recall.

It could also be just a worn out key and a worn out lock cylinder. If the key that came out is old and worn, try it with another key and see if it comes out.