Fixed my "no heat" problem.

[dewey527]

Possibly your flaps are sticking. Another possibility is that you are getting air into the coolant from a leak somewhere. As someone previously posted in this thread the "J" plug can seal under pressure but let air in as the block cools and the coolant decreases in volume, creating negative pressure on the coolant system. If this is the case you can check to see if there is an air bubble by following the procedure in the original post:

Here's any easy way to tell if you have air trapped somewhere. Get your motor up to temperature. Then SLOWLY crack open the reservoir cap. If you have an air entrapment you should be able to hear the coolant gurgling and the coolant level in the reservoir will noticeably increase as the entrapped air is allowed to expand. The bigger the bubble the more the tank level will increase. If the bubble is big enough it will push coolant out of the overflow port on the bottom of the reservoir so be careful that you don't burn yourself. Even if you don't have any entrapped air the level will rise just a little as the coolant hoses contract back from the pressure release. However, you probably won't hear the gurgling noise that accompanies the bubble as it expands.

If no air bubble is present I Would suspect a flap issue. One other thing to check: With the motor up to temperature reach under the hood and feel the heater supply hose coming out of the rear coolant flange and compare it to the return heater hose connecting to the lower coolant return hard pipe. If the temperature is essentially the same you have a flap problem. If the temperature is significantly different you have a heater core issue.

Good luck!

Can the J plug leak but only let air in? I looked at it last night to make sure it wasn't leaking and no undue wetness was around it.

[old guy]

Can the J plug leak but only let air in? I looked at it last night to make sure it wasn't leaking and no undue wetness was around it.

Yes it can. As the plastic deteriorates the plug deteriorates from the inside. The coolant pressure pushes out on the sides and makes a seal with the "O" ring. However when the coolant cools and contracts the plug can collapse in on itself and suck air in. But before you replace the "J" plug you need to confirm that the air bubble is returning after you bleed the system. I'm leaning more toward a defective flap servo. If you clear the potentiometer codes do they return?