Re: 98 Navigator: No Heat...
I agree with what RTG143 said in his response to your problem. I had the same problem with my front core and had to flush it out with water 3-4 times over a few months to clear the core and alow hot coolent to enter. Try detacting the coolent lines on the engin side of the fire wall (its easier this way), should be located to the right of your battery and behind the Automatic transmission dipstick very cloes into the firewall. You will notice that there are four lines, two going to the front core and two going down and under the seating compartment to the rear core. (The top two should be the front and the bottom two the rear unite) Disconect the two top lines (you will get draining of coolent so be ready for that) and insert a narrowing nosle of a garden house. Hold it in place or tape it, then turn the water on and stand back! The water will run yellow/brown/green when it starts flushing but then should run clear when it is done flushing out. I had to do this several times and connecting to both lines because I had a clot deep in the core that I had to loosen up from both sides before it came out. The water flow coming out of the core threw the coolent line should match the level of flow going into the core from your garden house. If you are only getting a trickl, try coming at it from the other side of the core by attaching it to the other line. Hope this helps.