Hi all

I have a 1995 Eagle Talon TSi.
I am not getting heat, just a little at 0 C., none at -10 C.

So far the thermostat has been changed, the coolant changed and the system flushed, the heater core flushed until the water coming out is clean. Still no heat. The fan works, air comes out, but it barely warmer than the outdoor air.

My mechanic put a valve on the output hose from the heater core to check for air in the system. There is no air in the system, sometimes the pressure is good (coolant sprays out if the value is opened), sometimes the pressure is low (no spray). It can change from minute to minute. Also, the coolant level at the rad cap can be up or down from minute to minute. No collant leaks. The blend doors are working OK.



The mechanic has no idea what is going on and has given up.
If anyone knows what the problem is and how to get heat I would really appreciate it.

Thanks,
Brian Monk

Have you checked the actual dash controls?

Maybe somehow the knob on the HVAC controls is stuck on the 50% cold / 50% hot?

Yes, that was checked.
Thanks

Yes, that was checked.
Thanks

Do the heater core hoses get hot?

Was the thermostat replaced with an OEM or aftermarket?

Also, I would double check your dash controls again for the outside air / inside air recirculation. Something tells me the problem lies there. I had an issue similar to yours a few months ago and I yanked my hair trying to figure the problem out, only to find out the cables / doors was the problem in particular the center dash vent that has a wheel that opens and closes the air door. I had a bit of heat come through it once in a while and after I fixed it, I got my warm air back

Good luck.

check the temp on both heater hoses in and out going to heater core.

other than that you can have a faulty thermostat (even new)
Stant thermostats are really cheap and fail any time.

you also may have a failing waterpump. If there is no water flow from the pump then you have no circulation to the heater core.
(this is probably very uncommon on the 4g63 because it has a metal impeller but if it's rebuilt it could spin on the shaft)

some cars come with plastic impellers which break down and fall apart when they get old and brittle or the split and spin on the shaft which can give erratic coolant flow (which you described)


another issue could be that if you have foam seals around the doors/flaps and air ducts of your heating system;
They could with age fall apart and/or become dislodged and you will not have the proper airflow past the heater core to get hot air. It has happened on some vw's.

Just happened to me. The metal sleeve on the cable ended up getting bent and wouldn't go into the plastic sleeve. On the controls it would close all the way (cold) but wouldn't go to full warm because the cable wouldn't be pushing. The deceiving thing was the knob would still rotate all the way over to hot.

One quick way to check for it is: pop the center vent out (grab between the two vents and wiggle and the entire thing will come out) disconnect the wiring to let it swing away so you can see. Once that center vent is out, you can see all the inner workings of the HVAC (other than the blend door itself).