micahdaniel Posted December 6, 2007 Report Share Posted December 6, 2007 Some background: I changed my spark plugs this summer and in the process cracked open the brittle plastic housing that covers the blower / heater core area. I have taped the opening with duct tape, but that doesn't change the problem. I don't think this could be the problem, but it's worth mentioning. My a/c didn't have any problem keeping me cold in the hot weather. I noticed that one side of the lines going to the heater core is hotter than the other, but the other is not cold. One side gets so hot that I can't keep my hand on it. The other side is hot but I can hold it. I disconnected both sides and blew 100psi through it hoping that might blow any obstructions out, but I don't know if that is the problem or the best method of removing obstructions if there are any. The other day the outside temp got into the 60's and the heater began blowing hot air. This was while it was parked in the garage. Now the temp is back into the 30's and I'm back to freezing again. I read in some other thread that there might be an issue with the mechanical door/flap that controls how hot the air being blown is. It sounded like there is a way to exercise this using the onboard computer, but no details were given. Any ideas on how to rule this out? Also, I'd be curious to know how to read the coolant temperature. Any help would be greatly appreciated. Meanwhile, my portable seat heater is getting a workout. Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 6, 2007 Report Share Posted December 6, 2007 Reverse flush your heater core until it flows clear and a good stream of water. We have seen the 4.9 heater core need flushing. That said, make sure your coolant level is up to the correct mark... Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Ranger Posted December 6, 2007 Report Share Posted December 6, 2007 First off, flush the core with water, not air. If there is any sediment in there it will be carried away by the water. Secondly, have a good look at the HVAC housing again. They are known to get brittle and crack. All your heat may be going out under the hood. Where there is one crack, there may be more. Perhaps on the bottom. Did you remove the "T" when you blew out the heater core lines? There is a restrictor in one leg that must go in the proper position. If you reinstalled it wrong, it will affect your heat. Link to comment Share on other sites More sharing options...
micahdaniel Posted December 6, 2007 Author Report Share Posted December 6, 2007 First off, flush the core with water, not air. If there is any sediment in there it will be carried away by the water. Secondly, have a good look at the HVAC housing again. They are known to get brittle and crack. All your heat may be going out under the hood. Where there is one crack, there may be more. Perhaps on the bottom. Did you remove the "T" when you blew out the heater core lines? There is a restrictor in one leg that must go in the proper position. If you reinstalled it wrong, it will affect your heat. I didn't remove the T. I'll try flushing with water and post back. As far as the HVAC housing, I'm sure I probably have a few exposed cracks still. What I covered up were the huge chunks that were missing. But if this were the problem, wouldn't my a/c have had problems keeping cold during the summer? Link to comment Share on other sites More sharing options...
Ranger Posted December 6, 2007 Report Share Posted December 6, 2007 But if this were the problem, wouldn't my a/c have had problems keeping cold during the summer? Probably so. Link to comment Share on other sites More sharing options...
micahdaniel Posted December 12, 2007 Author Report Share Posted December 12, 2007 OK, I flushed the heater core and it seemed to heat right up. However, the car was, and had been, sitting in the sun in my driveway. Since then, I've noticed how that when the car is parked or I'm driving in the city, the heater works good. When I take it above 55 on the highway, the heater cools and eventually blows cold. I think I've done a fair job of duct taping over all the missing plastic over the hvac, but I suppose it may not be enough. However, I remember reading another thread where somebody else had installed an aftermarket thermostat and had resultant heater issues like mine. I haven't changed my thermostat, but could this be my issue. How can you display the actual temp on the dashboard. To make things worse, I overtighted the hose onto the T behind the engine. It broke in a parking lot causing me a fair amount of embarrassment. Anyway, all the nearby autozone had was a generic T. The original T had constriction going to the heater core. The new one is wide open. Will that matter? Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 12, 2007 Report Share Posted December 12, 2007 Go to the dealer and purchase the correct T Check your thermostat for it being stuck open, if it is NOT IN or stuck open you will not get heat Check your coolant level also When you put the new T in, you will need to put it in the correct orientation, Mike Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Ranger Posted December 12, 2007 Report Share Posted December 12, 2007 The original T had constriction going to the heater core. The new one is wide open. Will that matter? You bet. That is your problem. Follow Mikes advice. Link to comment Share on other sites More sharing options...
micahdaniel Posted December 13, 2007 Author Report Share Posted December 13, 2007 Any ideas on how to find the tee on rockauto? the cooling section doesn't list anything that sounds like what I'm after: Coolant Hose Coolant Temperature Sender Coolant Temperature Sensor Cooling System Adapter Engine Cooling Fan Assembly Radiator Radiator Cap Radiator Cap Adapter Radiator Drain Petcock Radiator Fan Assembly Radiator Fan Motor Radiator Lower Hose Radiator Upper Hose Thermostat Thermostat Housing Gasket Thermostat Housing/Water Outlet Thermostat Seal Water Outlet Gasket Water Pump Water Pump Gasket Those are the choices under the cooling system menu. Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 13, 2007 Report Share Posted December 13, 2007 I like Rockauto but sometimes there is not enough detail to find what you are looking for, call Gmotors.com's 800 number and talk to one of the guys, they should help you out, Mike Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
KHE Posted December 13, 2007 Report Share Posted December 13, 2007 The tee shouldn't be that expensive at the local dealer's parts counter. In fact, the total cost will probably be cheaper as the shipping cost from rock auto or other online parts outlets may exceed the cost of the part. If you buy the tee at the dealer, you can ask them to provide the orientation of the restrictor. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 13, 2007 Report Share Posted December 13, 2007 The tee shouldn't be that expensive at the local dealer's parts counter. In fact, the total cost will probably be cheaper as the shipping cost from rock auto or other online parts outlets may exceed the cost of the part. If you buy the tee at the dealer, you can ask them to provide the orientation of the restrictor. Very true Kevin, this post makes me wonder why I didnt think of that, Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
adallak Posted December 13, 2007 Report Share Posted December 13, 2007 Get a T at NAPA. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Ranger Posted December 14, 2007 Report Share Posted December 14, 2007 I'm with Kevin. Go to the dealer. Can't be very expensive and you'll be sure to get the correct "T". Link to comment Share on other sites More sharing options...
micahdaniel Posted December 18, 2007 Author Report Share Posted December 18, 2007 I decided to go buy the thermostat and tee from the dealer. Thermostat and seal were $20 together. They want $29 for the Tee (I'm not buying that). When I took the old stat off, it was obviously stuck open. With the new stat in, I now have heat a' plenty Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 18, 2007 Report Share Posted December 18, 2007 I decided to go buy the thermostat and tee from the dealer. Thermostat and seal were $20 together. They want $29 for the Tee (I'm not buying that). When I took the old stat off, it was obviously stuck open. With the new stat in, I now have heat a' plenty Ahhh just as I suspected... cool, get that T someplace, find a scrap yard, and pull one off Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
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