Vapor from defrost vent after changing heater core. No coolant leak or smell.

[Motor City Impala]

The car in question is a factory fresh 1987 Chevrolet Caprice Classic Brougham. I recently changed the heater core due to a vapor coming from the defrost vent . I DID NOT HAVE coolant leaking into the interior nor was the h/c area wet with coolant. I never noticed the smell of coolant in the car nor when i opened up the HVAC in the engine compartment. On several occassions I noticed a BLACK stain on the windshield.

When I bought the car, the HVAC upper half had an ugly repair job from some previous work. I went to the Clearwater, FL LKQ and pulled another upper half in great shape. When I pulled my HVAC case apart I noticed that there was no foam sealing tape around the majority of the perimeter and that 3M strip caulk had been used. Certain sections of this caulk had turned runny and started sliding down the insides of the case. I cleaned up the caulk as best I could and did a real good job of only using just the correct amount of strip caulk to reseal the perimeter. I used the strip caulk as it appears as if thats how the factory sealed the unit. The preimeter of the housing had small chanels as if they were designed just for strip caulk.

I never did do a pressure test on the old heater core and now I am wondering if I spent $50 when I didnt need to. I have the same issues as before the change... only now the vapor is more noticeable.

I did not touch the EVAP core. I did vacuum all the small leaves and debris laying inside the case. There was some mold on the fresh air door and I did clean the door.

What I am wondering is if the caulk is the cause and maybe I need to take more of the case apart to clean more??? Mold???? Thoughts and directions are very appreciated. North central Florida is brutal in the summer and I want to make sure that my heat and a/c are up to the task.

Although my car wouldnt be considered a P/T car; it is what I have to work with and as such will see considerable suspension and brake upgrades.

Todd

[MonzaRacer]

I hope you didnt seal up the drain hole on the evaporator case. This will be a certain cause for condensation blowing out from the defroster vents.

[absintheisfun]

I hope you didnt seal up the drain hole on the evaporator case. This will be a certain cause for condensation blowing out from the defroster vents.

x2.

A good way to rid your A/C box of any residual moisture is to first clean out the drain hole (hangers work great for this!) After you are sure that it is clean, crank the heater on and turn it to defrost. This will cause the air to pass over the evaporator and heater corre-both heating it and drying it. Barely crack the windows so the moist air can escape and leave the car running for about 15 or so minutes.

There are some products out there that you can spray into the evap housing that kill any bacteria and mold that have grown due to the moisture being tapped.