JackAysJake

98 Navigator that will not blow heat from front or rear. Took it to 2 different shops today. #1 says it is a stuck thermostat and bad water pump. #2 went ahead and replaced the thermostat and took 6 hours trying to figure out why the backflush didnt help. The lines going to both heater cores are cold. Even if the heater cores are both clogged up, the lines should still get hot. While they flushed the cooling system, they said it had junk in it and was obvious that it had stop leak run through it. I dont think we should go check out the blend air doors, Im thinking I need to start with why the heater core hoses are staying cold...Right? Thanks!

Jake

Bert

If water can't flow through the hoses due to a plugged core, the hose can't get hot. The only heat you'd get would be the transfer of just being close to the engine. If he found that much stopleak in there, it's almost certain the cores are plugged. Take the hoses off and try to run water with a water hose.

CaptJack

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.