Why no heat to speak of?
09-30-2008, 10:08 PM
#1
Burning Brakes
Thread Starter
Why no heat to speak of?
Ok - I'm puzzled and need a bit of help on this one. I've always had a problem with my heater - or lack of a heater to be more specific - it works but it just doesn't throw much heat. So I thought maybe it was a blockage in my heater core... I decided that this would be a good time to do a complete coolant drain/flush/backflush/refill and did it all according to the FSM. No problems. Everything worked out well. I even disconnected the heater hoses and hooked it up to my garden hose and flushed that out. Lots of flow through the heater core; no blockage there. The car runs well and I can't get it higher than about 211 degrees under normal conditions - so I think it's all good and working as it should. But I still don't have any significant amount of heat coming out of my heater! What's going on here? I'm quite certain that the system itself is working as it's intended - and there was hardly any crud in my entire coolant when I drained it (including the block), so I don't suspect a blockage anymore especially when there's lots of flow going on. Am I missing something here? Where do I look next? Ideas anyone? Anyone else had this problem? 
09-30-2008, 10:45 PM
#3
Le Mans Master
When the core is plugged, coolant flows over the top but not through it - can you imagine what would happen if it didn't? There are a couple of other things: 1. I believe there is a checkvalve on your Year from the expansion tank to the core inlet - make sure it's not plugged up. 2. The temp door may be sticking or the motor that controls it (assuming that it's Electronic Air) may have a stripped gear. Remove the Blower Module on the left side of the Evaporator Case and look inside to see the temp door. Have someone operate the controls and that door should move between 60 and 90. At 90, you should be able to see that the door is blocking air flow to the Evaporator. If it isn't, try pushing on it with a screwdriver and if that closes it and you get heat, you'll need to see what's up with the motor. It's accessible from the passenger compartment. Remove the hush panel to get to it. On your Year, it's directly connected to the door with a plastic gear and that often strips. Someone around here found that gear, but I can't remember where.
If the checkvalve is good and the temp door works, the core is plugged and should be replaced. I did unplug one once be putting my thumb over the outlet and pressurizing it with 125 psi before letting my thumb go. There was a loud pop and when I ran hot water through it, the sides got nice and toasty again. I did have it out of the car and since system pressure is only 15 psi, I don't recommend subjecting it to that much pressure - put a hole in it and it will create a huge mess.
If the checkvalve is good and the temp door works, the core is plugged and should be replaced. I did unplug one once be putting my thumb over the outlet and pressurizing it with 125 psi before letting my thumb go. There was a loud pop and when I ran hot water through it, the sides got nice and toasty again. I did have it out of the car and since system pressure is only 15 psi, I don't recommend subjecting it to that much pressure - put a hole in it and it will create a huge mess.