jje1953 Posted January 21, 2012 Report Share Posted January 21, 2012 What would explain a heater that blows ice cold to start (ambient temp of 10-15 degrees outside), then after the car has been running at normal temps for a 20-30 minutes, it begins to warm? Please note, I'm not talking about the usual warm up time for a heater in cold weather, where once your temp gauge begins to move, you have some heat. This is a much delayed situation. Also, the degree of heat you attain seems to vary from drive to drive. Here a few potentially related issues: *If you put the climate control on "Auto" it will begin boosting the fan at about 120 degree engine temperature, as if it senses the heater core is warming, even though it apparently isn't. *The car consumes coolant, even though there are no obvious leaks and tests negative for head gasket leaks (pressure and exhaust in coolant tests both done). No coolant leaking into cabin, no coolant puddles under car after driving. *There are noises in the dash that seem to indicate problems with the air flow controls. For the amount of sound you hear when the fan is at medium level, there really isn't that much air coming out anywhere. I guess I'm baffled by a heater that will eventually blow some warm air (though not as hot as it probably should be), but takes 30 minutes to start doing so. I imagine the heater core is shot, and has restricted flow (coolant tablets, gunk), but I do find it odd that it takes so long to get warm. Link to comment Share on other sites More sharing options...
Texas Jim Posted January 21, 2012 Report Share Posted January 21, 2012 The BCM will turn on the blower at around 120 "ENGINE COOLANT" temp... not heater core temp... I would suspect an air mix door problem from your description... Do you have any codes??? Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 21, 2012 Report Share Posted January 21, 2012 YES, check for codes, as Jim noted the blower will not normally come on until the coolant temp reaches 120 degrees You DO have a thermostat in correct? Could it be stuck open? 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...
Texas Jim Posted January 21, 2012 Report Share Posted January 21, 2012 YES, check for codes, as Jim noted the blower will not normally come on until the coolant temp reaches 120 degrees You DO have a thermostat in correct? Could it be stuck open? He said the "ENGINE" gets to normal temps... just that it takes the "HEATER" 20 minutes or so, to start blowing warm air... Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 21, 2012 Report Share Posted January 21, 2012 Good point Jim! This could be low coolant, or a clogged heater core also. Reverse flushing the heater core would help if there are no actuator or control problems, found in the codes 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 January 22, 2012 Report Share Posted January 22, 2012 The car consumes coolant, even though there are no obvious leaks and tests negative for head gasket leaks (pressure and exhaust in coolant tests both done). No coolant leaking into cabin, no coolant puddles under car after driving. Impossible. If it is consuming coolant, it is either leaking or burning it. How much does it consume? Do you smell coolant when you open the hood? You need to figure this out before you go any further as it will tell you what direction to go. Link to comment Share on other sites More sharing options...
jje1953 Posted January 22, 2012 Author Report Share Posted January 22, 2012 The car consumes coolant, even though there are no obvious leaks and tests negative for head gasket leaks (pressure and exhaust in coolant tests both done). No coolant leaking into cabin, no coolant puddles under car after driving. Impossible. If it is consuming coolant, it is either leaking or burning it. How much does it consume? Do you smell coolant when you open the hood? You need to figure this out before you go any further as it will tell you what direction to go. I'm with ya' that it seems "impossible", but my problems with this car never seem to lead to a logical conclusion. No, I do not smell coolant when I open the hood. Have made a few posts here about this car's past overheating problem. That led to no fewer than 6 different pressure and exhaust tests done over a 2 week period, all of which proved negative for a head gasket leak. The engine "off" tests held steady pressure with no obvious leaks. The engine "on" pressure tests never went over 9psi. Two exhaust tests by a certified mechanic proved negative. Yet, every 100 miles of city driving, I have to add 1-2 pints of coolant back. It would certainly appear it's going out through the head gasket, but how could the car repeatedly pass the tests if that were the case? BTW, the car is not overheating at all these days. Runs a steady 197, with maybe a bump to 210 on extended stops or slow going. Did a major flush job a while back, and it seemed to get out the gunk that was causing the overheating. As an older car, it does drip some fluids overnight. Nothing out of hand. I presumed the spots to be engine oil leaking from (?), but I did note a while back that one of the spots smelled and tasted on the tip of my tongue like coolant. It does not drip down in an obvious leak under pressure, but rather, very slowly over night, and seemingly not enough to account for the coolant level usage. I've always looked for obvious coolant leaks after a drive with this car, and you never see one. To me, a "slow" coolant leak seems almost contradictory. I would think any leak would be pretty obvious after the car was up to temperature. So, the car continues to baffle everyone I take it to and everyone I ask about it. As far as the heater goes, my guess now is that there is flow "into" the heater core, but not "out of" the heater core. This causes the coolant loop going to the heater to be a "dead end" for coolant flow. The "dead end" line eventually warms from the main flow back at the junction, but that takes quite a while since the heater is out of the main flow. Just a guess. Still no clue where all the coolant goes. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 22, 2012 Report Share Posted January 22, 2012 You can loose coolant and never see it being lost. Coolant under pressure and hot evaporates immediatly upon escaping to the atmosphere as it leaks out in cracks and bad seals. But typically you can smell a mild smell of coolant, and I mean MILD, and only when you lift the hood and get your nose in there. That said, that you don't smell coolant is odd and that a pressure test did not turn up a slow leak is odd. The radiator end tanks, coolant tank, radiator cap blowing off prematurely, water pump body seal and crossover seals are famous for seeping coolant under pressure. Was this cooling system pressure test done by someone who knows the Northstar? If you can feel the heater core input hose HOT and the output hose COLD, it would confirm that the core is blocked or clogged. Simply detaching the two hoses and flushing in both directions until the stream of water runs clear would solve that problem. That is where I would start to get some heat. I would also check the purge line to make sure it is clear by removing the bolt with a hole in it and making sure it is clear by pushing a pipe cleaner or drill bit through it, if you are not getting all of the air out that can cause heat problems also These are easy things to do 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...
hjb981 Posted January 22, 2012 Report Share Posted January 22, 2012 Maybe the coolant only leaks out when the engine is warming up (when the pressure increases), and that is why there are no big puddles (the leaking takes place during the beginning of each trip, and has stopped when you park again. I have seen a case like that before on the '88 DeVille I used to have. Some of the coolant would accumulate on parts of the frame of the car, and sometimes drip a little after parking, but most of it probably got scattered in the wind during driving. It also makes sense if you experience quicker loss during city driving, because you probably have more warm-up cycles then (and also higher max temps, perhaps). Have you felt the upper radiator hose when the engine is warmed up? It should be pressurized. You could also try idling the car from a cold start until it is warmed up (enough that the upper radiator hose gets hot), and maybe then be able to locate the leak, since it would take place while the car was standing still. If your heater core is plugged for some reason, I would guess that that would disturb the coolant flow in the engine, but I don't exactly how and by know by how much. If you end up wanting to change your heater core (and have a look at the actuators also, btw), you can read this thread: http://caddyinfo.ipbhost.com/index.php?showtopic=28646&st=0&p=167025&fromsearch=1entry167025 In post #9, I described how I changed the heater core on my '97 DeVille (should be identical to your '98 DeVille, as far as I know). Be sure to click the link to the Picasa album (the link is in post #9, just before the step-by-step instructions) to see pictures of all the steps. The pictures are referenced in the instructions. I am not saying that you need to change your heater core, just posting the link in case. Hope it helps. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 23, 2012 Report Share Posted January 23, 2012 A clogged heater core circuit will not cause overheating 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 January 23, 2012 Report Share Posted January 23, 2012 I agree with BBF. Sure sounds like a VERY small external leak, more like seepage that evaporates before it drips and is so small that even the evaporation is hard to smell. I do not like the sealant tabs. Don't use them or recommend them, but this may be the perfect case to use them. Link to comment Share on other sites More sharing options...
KHE Posted January 23, 2012 Report Share Posted January 23, 2012 Sounds like there is an issue with the blend doors in the ducts. As far as the coolant goes, you will get a negative result with the block test if new coolant has been added. Not sure how many miles are on your car but the radiator inlet tank can develop a crack and leak coolant. Check the tank that the upper radiator hose connects to for bulging/cracking. If you find the tank is cracked, a radiator shop can replace the tank for less than $100.00 - no need to replace the entire radiator. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
hjb981 Posted January 23, 2012 Report Share Posted January 23, 2012 Sounds like there is an issue with the blend doors in the ducts. As far as the coolant goes, you will get a negative result with the block test if new coolant has been added. Not sure how many miles are on your car but the radiator inlet tank can develop a crack and leak coolant. Check the tank that the upper radiator hose connects to for bulging/cracking. If you find the tank is cracked, a radiator shop can replace the tank for less than $100.00 - no need to replace the entire radiator. How much would one have to drive the car after coolant has been added, in order to perform a correct test of the coolant? Should one warm-up cycle be enough, or is more needed? Just asking out of curiosity/general interest. Link to comment Share on other sites More sharing options...
KHE Posted January 23, 2012 Report Share Posted January 23, 2012 How much would one have to drive the car after coolant has been added, in order to perform a correct test of the coolant? Should one warm-up cycle be enough, or is more needed? Just asking out of curiosity/general interest. I'm not sure in this case. When dealing with a car that is overheating, it would need to overheat/puke out some coolant. In this case, it seems like it would need to be driven enough to have the level go down in the surge tank. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
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