Cooling Issues 92 XLT

[acschilling]

Hey guys any of you first gen owners heard that loud pop/thud coming from the glove box? That is where the heater core is...my truck runs pretty warm while idling in traffic (gauge never goes past half) but cools down while driving. I've only been able to get the truck to make the "popping" noise after I get to work in the morning and idle for about 60 seconds. Heat does not work while popping, but it works great when not. After turning the truck off, it pops from the glove box for another 60 seconds then will stop...I recreate the noise any other time. i figured I'd start with the thermostat and heater core? Can anyone tell me if they ran into this problem and what they did to fix it? I'm trying to think of as many details as I can about this ****...I appreciate the input 92 XLT 4.0 V6 OHV

 

[tweakedlogic]

Are you sure the noise isn't the vacuum operated vent flap?

 

[acschilling]

To be honest I'm not really sure...this is all just speculation. What does that door look like and where is it? It must be right next to the h. core right? Can you tell me what I'm looking for tweak?

 

[tweakedlogic]

From your right front door, look up under the glove box. Just behind the box is a grate with about 2" squares, if your vent is open, you will see the door closed. Mine has thin foam on the door for a seal, so you will see a rectangle grate with a sponge pressed against it. If your vent is closed for recirc, the grate will have nothing directly behind it. (Use a flashlight)
The vacuum solenoid is mounted on the right kick panel directly behind the lower right hinge for the glove box. If your switch is working, when you slide it over to Max A/C it (with the engine running) it will pull vacuum on the valve and the door (behind the grate) will move toward the firewall. If your valve or hose is leaking (I don't think it is) you will hear a hissing noise under there.
On my truck, my vacuum switch is bad and always holds vacuum. So even after switching to floor or defrost, the vent will stay closed for many days until the vacuum finally bleeds off. So be aware that can happen. It isn't as common as not holding vacuum at all.

 

[acschilling]

Update: A couple days ago I replaced the thermostat and heater core. So far my problems of popping noises and crazy temp needle seemed to be solved. As far as the blend door everything seemed to be fine under there. When i moved the switches on the dash everything behind looked to move normally. I do though hear a sizzle by the temp controls on the dash after shut down...what's that?