Hi all,
I recently changed the thermostat and flushed the coolant system in my Sebring. It appears that I removed all of the bubbles from the system and coolant/water mixture is at approximately 60/40 (-37 degree F). While purging the system of air, the heat worked very well at idle and high RPM at normal operating temperature. I lost the heat when sitting at a traffic light after driving for 15-30 minutes later in that day. The coolant level was between the min and max lines and I topped it off. The inlet hose to the heater core was very hot and the outlet hose was slightly warm. Car does not overheat. Any advice would be much appreciated!

 

I hope you didn't bleed the air out of the system by opening the bleed screw in the outlet manifold on top of the engine. If you turned that screw you almost certainly stripped out the insert it screws into from the plastic housing. If that occurred, you are leaking coolant there and your coolant will be low, and not getting to the heater coil at low RPM. If you are sure that that did not occur and that the coolant level is not low, your heater coil could be clogged and not allowing coolant to flow through fully. Or the blend door, which mixes cold outside air with heated air passing over the heater coil may not be operating properly.

 

Thanks for your reply and advice! I didn't realize opening the bleed valve would cause that kind of problem. I don't see any liquid exiting the system there after tightening the valve. However, I understand it could be leaking as steam. I don't think it stripped out. Hopefully, I didn't damage the system by using a valve placed there for bleeding the system. 😑 I plan to flush the heater core and if that doesn't work, I'll test the system by pressurizing it. I guess if it leaks.....I'll look at the bleed valve first.....

Thanks for mentioning the blend door because I would have never thought to check that.

 

if one heater hose is hotter then the other you have a clogged heater core.
same goes with a radiator hose they work the same principle

 

The symptoms you describe, heat while driving - no heat at idle, are what I experienced when I had low coolant due to a cracked water outlet housing (bleeder screw is part of this). Is there any staining on the housing maybe below where the hoses attach? You may not see any liquid but the staining is obvious.

 

"Hopefully, I didn't damage the system by using a valve placed there for bleeding the system."

The bleed screw is there for allowing air to escape when filling the system with coolant at the factory. They need to get the air out immediately, and the bleed screw allows that to occur. The problem is that with time, now some 18 years, the screw seizes to the insert, and if you turn the screw, you spin the insert in the plastic. (Been there; done that.) Aftermarket parts have flats on the insert which you can use with a wrench to prevent the insert from turning. Alternatively, you can just let the air work its own way out over a few warm-up and cool-down cycles and top up afterward.