I have a 94 Sedan Deville w/170000+ miles on it. About a month ago I had a problem with the heat sometimes working and sometimes not. One day the car overheated and I replaced the thermostat, and the heat all of a sudden started to work. Fast Forward a couple of weeks and the heat doesn't work again. Before it completly stopped working, I noticed it would blow hot air while i was moving and cold while i was standing still. Fast forward again to this week, still no heat, but i deal with it because its getting warmer(chicago area), and i also noticed that when i get to my destination that the antifreeze inside the reserve tank is bubbling and the radiator cap is steaming. I havent had an engine overheat warning while driving since i noticed the steam and bubbling, but today i looked under the hood w/ the engine running after driving about 10 miles and seen the fans werent working +(steam and bubbling from reserve). Any suggestions as to what can cause these problems at once.
Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
Re: no heat in cab + overheating
My first thought reading your thread is that the system is low on coolant. When the engine is cold, remove the radiator cap, should find the radiator full to the top? If not either theres a leak or the system has air in it. The heater blowing cold or not warm enough generally means low fluid level. The way I fill the radiator is to raise the engine speed to apprx. 1500 rpm then fill the radiator. Holding the rpm up, and the radiator full, I reinstall the cap. Top off the recovery tank. I would also pressure test the radiator cap, making sure it holds proper pressure. Or just replace it with the proper cap. I would also pressure test the system to verify no coolant leaks. usually its more efficient to pressure test with the system almost or completely empty, you can hear the hissing from a leak rather than see the coolant dripping. Post back with what you find. The fans wont work if there is air, not antifreeze for the sensor to read. The system will boil if the radiator cap wont hold proper pressure. Water will boil at 212 at sea level , but under pressure , it wont boil till approx 220 degrees. Good luck, Bill.