97 Integra – heater not blowing hot air (w/pics)

I realize it’s summer and temperatures in some places are quite high; nonetheless, this symptom has been plaguing my Teg since winter. I had to finally address this because of an overheat condition yesterday. This symptom is persisting and I’m concerned that something is not right.

After some troubleshooting, I’m concerned that I may have a partially obstructed heater core, and welcome suggestions that I may have overlooked something in my troubleshooting.

The car is a 1997 LS with mods including I/H/E and a 95 B18C1 long block. The thermostat was replaced (with OEM t-stat) some time last fall. It was replaced because my temp gauge was always reading cold and I thought it was from a stuck open t-stat. It turned out I had a defective ECT sending unit on the block. After that event, my heater did not [B]reliably[/B] blow hot air while driving.

I emphasize reliably because there were times when it blew hot air, however this was unpredictable. If I drove the car for quite a while and switched on the fan, sometimes I did get warm air, while other times I would not. The usual cause of this is air in the coolant system.

[URL=”http://www.team-integra.net/forum/11-generation-three/257106-overheat-diagnostic-help.html#post2850170″%5DThis post[/URL] on TI provides a background to my process for bleeding the block. I also use the Lisle coolant funnel ([URL=”https://www.youtube.com/watch?v=zUpXgAJ1gjU”%5Ddescribed here [/URL]courtesy of ETCG), and therefore do not perform step 3 in the first link. In the past, this process has worked extremely well at getting all the air out.

My overheat condition yesterday may have been triggered by using the air conditioning. That was the only anomaly. There are some issues with my AC not blowing cold air, but that may be a separate thread (I will gladly provide more details if anyone thinks it’s germane). Part of the lower radiator hose came loose and I lost some coolant. If my suspicion of an obstruction in the heater core is right, then clearly not all of the air is getting out of the coolant loop. The added stress on the engine from running the AC increased the coolant pressure, and overloaded the seal between the lower radiator hose and radiator.

During my efforts today at bleeding the coolant loop, I can confirm:
[LIST]
[*]The radiator fan is turning on and off.
[*]The upper rad hose is hot, the lower rad hose is warm (but cooler than the upper hose)
[*]I’ve cycled the heater slide lever back and forth several times in case it’s getting stuck (see pics below to confirm it moves correctly)
[*]Since the block is a 95, it does have a bleeder screw. I’ve loosened the screw and verified that coolant comes out.
[*]Since the car is raised and on stands, I can see underneath the engine. The ground is dry… i.e. there are no leaks.
[*]After the bleeding process, I turn the heater fan on and do not get any hot air.
[/LIST]

Some photos to provide visual assistance:

Using Torque, I monitor the coolant temperature. The engine reaches normal operating temperature, and the radiator fan [B]does [/B]turn on in the 180-195F range.

[URL=http://s810.photobucket.com/user/soigne95035a/media/2014_05_17_cooling/Screenshot_2014-05-17-16-20-49_zpsqghb7nnh.png.html][IMG]http://i810.photobucket.com/albums/zz22/soigne95035a/2014_05_17_cooling/Screenshot_2014-05-17-16-20-49_zpsqghb7nnh.png[/IMG][/URL]

There are no air bubbles coming out of the funnel:

[URL=http://s810.photobucket.com/user/soigne95035a/media/2014_05_17_cooling/20140517_150248_zpsz0sp0frm.jpg.html][IMG]http://i810.photobucket.com/albums/zz22/soigne95035a/2014_05_17_cooling/20140517_150248_zpsz0sp0frm.jpg[/IMG][/URL]

The ECT dash-gauge has reached a normal point:

[URL=http://s810.photobucket.com/user/soigne95035a/media/2014_05_17_cooling/20140517_150326_zpsmg4ceio5.jpg.html][IMG]http://i810.photobucket.com/albums/zz22/soigne95035a/2014_05_17_cooling/20140517_150326_zpsmg4ceio5.jpg[/IMG][/URL]

The heater air-mix cable is installed and moving correctly. The following four pictures should illustrate the cable movement in the cabin and engine bay.

In the cabin –
Set to HOT:
[URL=http://s810.photobucket.com/user/soigne95035a/media/2014_05_17_cooling/20140517_155959_zps1qjjnrof.jpg.html][IMG]http://i810.photobucket.com/albums/zz22/soigne95035a/2014_05_17_cooling/20140517_155959_zps1qjjnrof.jpg[/IMG][/URL]

Set to COLD:
[URL=http://s810.photobucket.com/user/soigne95035a/media/2014_05_17_cooling/20140517_160008_zpsbstdiwxo.jpg.html][IMG]http://i810.photobucket.com/albums/zz22/soigne95035a/2014_05_17_cooling/20140517_160008_zpsbstdiwxo.jpg[/IMG][/URL]

Inside the engine bay –
Set to HOT:
[URL=http://s810.photobucket.com/user/soigne95035a/media/2014_05_17_cooling/20140517_160242_zps7ruivf1n.jpg.html][IMG]http://i810.photobucket.com/albums/zz22/soigne95035a/2014_05_17_cooling/20140517_160242_zps7ruivf1n.jpg[/IMG][/URL]

Set to COLD:
[URL=http://s810.photobucket.com/user/soigne95035a/media/2014_05_17_cooling/20140517_160305_zpsraclcdxy.jpg.html][IMG]http://i810.photobucket.com/albums/zz22/soigne95035a/2014_05_17_cooling/20140517_160305_zpsraclcdxy.jpg[/IMG][/URL]