- Jul 22, 2019
- Reaction score
- Ram Year
Thank you. You gave me a lot to cover. Im getting into it later today.By top 'motor area' ...are you referring to the engine, or blower motor? I assume engine. First make sure the engine is operating at it's rated temperature. I had a diesel that was running at 160 and the difference in heat output in the cabin between 160 and 185 was enormous. Like night and day. There could be a cooling issue to iron out (T-stat or another).
Well, track down that hissing area. If your defrost was on prior to shutting the vehicle off, it could be the A/C pressures equalizing out and mimicking the sound of leaking antifreeze ...because usually A/C comes on when the defrost is on. Or you could have a leak to track down. Is there a 'film' on the inside of your windshield? I mean the possibility of a heater core leak? Or 'girgling' (air bubbles) inside the heater core after you start the vehicle in the morning? That could point to a heater core leak. Even if your truck's heater core is leaking it should still provide heat, unless it's plugged. If they used tap water after replacing the engine's, yeah, that helps create mineralization inside the tiny passages of the heater core vanes. A guy should use filtered/RO water only (ideally). A plugged heater core can also cause a no-heat situation. Just because the hoses are warm doesn't mean you have proper flow through the heater core. The outside passages could be open, and the middle ones plugged.
If you knew someone who had a 'good' scanner, it would be real helpful to get into the HVAC control module and check for HVAC codes. Then perform an HVAC doors sweep test to test the blend door motors and full range actuation. During normal operation, the blend doors cycle and the computer notes when they reach full open and full closed ...so the computer know's the position of the blend doors (ie 30% or 72%). Motors can fail, and so can the hinges of some doors ...or where the motor connects to the door itself. Also, an outside air blend door or motor (to the cabin or the hvac box) failed (or the hinge busted), the heater can still provide heat, but not enough to overcome very cold 'fresh' outside air on a cold day. In other words there 'could' be more cold air entering the cabin entering the cabin than the heater can overcome (making it 'feel' cold inside). Or, if it was like our Jeep when we got it (used), it had multiple blend door issues the previous owner had not addressed ...and was a mess till we got it sorted out. Some of these blend door issues I've outlined may vary depend on the model truck you have (basic or dual-zone hvac). The dual-zone and more complex units tend to have more possible fail points.
Another thing you could do if you suspect a heater core leak, is pry up your pass door's sill plate and put your hand under the carpet (or matt) and feel for wetness under there. That's a pretty good sign of a heater core leak.
My truck also got hot today. I was idling in my car waiting to pick up my kid and it pegged the temp gauge. Nothing leaking. Still hissing. I will find the hiss and reprt back. Thank you for all your input here.