RPE1992GPSE Posted October 26, 2013 Report Share Posted October 26, 2013 I have a 1992 Cutlass Supreme with the 3.1L LH0 engine. I just replaced a thermostat because the engine coolant temperatures were topping out around 145*F. The coolant temperatures are now normal after the replacement. One problem that remains is the fact that I am not getting any hot air inside the cabin. The heater inlet hose is getting hot, but the outlet hose is not. I also backflushed the heater core and observed a good, steady flow. There are no flow restrictions in the cooling system. Still, no heat. Yes, I have the temperature setting on full hot and I can hear the sound of the air flowing through the ducts change slightly with the adjustment of the temperature setting from hot to cold and vice versa. Any ideas as to what the fuck is going on? Thanks. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted October 27, 2013 Report Share Posted October 27, 2013 Air pocket in the heater core or plumbing? Did you properly bleed the cooling system? The DOHC 3.4L has two bleeder screws, I don't know about yours. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted October 27, 2013 Report Share Posted October 27, 2013 sounds like you have your bases covered. here's my take: You could have a restriction in the heater core still. I blast heater cores at full blast with a garden hose in both directions a few time when i flush them. It could also be that the clog that is restricting the heater core is in the piping, such as the pipe that follows and run on the passenger side of the engine, or the threaded fitting near the thermostat (new ones cheap and available at most part stores) Blend door motor could be fouled up, I have actually seen a motor that switch directions when operated, such that it turned the heat back on when run to the cold end of the range. You can find it under the passenger side of the dash and unbolt it (after unbolting the vaccuum selonoid by it) and visually inspect it's operation. I've seen all these happen. good luck! Quote Link to comment Share on other sites More sharing options...
l67ss Posted October 27, 2013 Report Share Posted October 27, 2013 I didnt think of that Air pocket in the heater core or plumbing? Did you properly bleed the cooling system? The DOHC 3.4L has two bleeder screws, I don't know about yours. Quote Link to comment Share on other sites More sharing options...
RPE1992GPSE Posted November 5, 2013 Author Report Share Posted November 5, 2013 I found out what happened. The heater inlet hose felt warm because of the heat transfer from the bracket that holds it to the intake. The pot metal quick connect nipple that threads into the lower intake manifold corroded shut. The slightest bit of torque with a wrench broke the nipple off. We tried to tap the exposed remnants out with a screwdriver and hammer, but we couldn't get all of it out of the threads in the lower intake. An "easy out" proved futile as well. Once we got the upper and lower intake manifolds off the motor, a little heat from an acetylene torch flaked the remnants up very quickly and they scraped right out of the threads with a hardened "dental pick." The lower intake was leaking anyway, so was that damned oil pump drive shaft seal, then I found a partially broken plug wire, compression leaks at some of the spark plugs...yadda yadda yadda, so it wasn't a waste of time. But it was a HUGE pain in the fucking ass! Quote Link to comment Share on other sites More sharing options...
Schurkey Posted November 5, 2013 Report Share Posted November 5, 2013 As far as I can tell, that fitting is made of zinc. Zinc winds up being a "sacrificial anode" that protects the rest of the metal in the cooling system from corrosion. The other benefit is that it's not hard to remove the corroded remnant from the aluminum of the main casting. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted November 5, 2013 Report Share Posted November 5, 2013 I believe the stock fitting is made of aluminum on earlier cars. I think 93 or 94 up went to steel. New ones from Dorman are steel. Quote Link to comment Share on other sites More sharing options...
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