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2001 buick century windows fogging up

Hello again! My current issue is as such: I started my car the other evening after a long day at work to find that when I started the car(i always leave the heater/AC control in bi-level mode with the a/c on with the fan at low or not on at all, unless I need the floor heater or the defroster) the interior of the windshield as well as the side windows instantly became fogged up. It took close to 10 minutes for the windshield to defog. Upon arriving home from work, I checked the reservoir where the coolant is recirculated and found that it was bone dry. After the vehicle had cooled down, I popped the radiator cap and indeed the radiator fluid level was down. I replaced close to a 3/4 gallon if not a tad bit more of 50/50 mix. The next morning I started the car and the problem was still there and it took a few minutes for the heater to heat the car. Last evening and then again this morning, after the engine cooled to ambient temp, i squeezed the upper and lower hoses and there was still coolant in both hoses and thought this was odd, but I started the car w/o the fan on and the problem seemed to go away, but I noticed it didn’t take any time for the car to heat up. Taking all of these things into account, is this a heater core(no coolant in cabin) or water pump problem or simply a bad thermostat? Any help is greatly appreciated!

You may have a heater core leaking into the interior of the vehicle.

You want to have someone pressure test the cooling system to detect the leak. And once it’s found and repaired, have them flush the Dexcool out and introduce one of the universal coolants.


The fact that it was low and you topped it off i’m sure you had an air pocket in the system which would explain your no heat issue. Having changed probably a 1000 of these, maybe not a thousand but a hell of alot of them my first guess would be you have a leaking intake manifold gasket. Very common on these engines, if you know where your throttle body is take a flashlight and look below it on top of the transmission and look for a puddle of coolant if you see it odds are the intake is leaking. probably about a 300-400 dollar repair depending on the shop.

@g-14classified I have to agree with Tester on this one. Windshield fogged over on the inside is a very classic example of heater core leaking. These are not hard to replace on most of the GM front wheel drives W type body platforms since it is typically below the radio in the lower part of the dash.
I’m not saying this GM doesn’t have an intake leak also but the window fogged over is a sure bet the heater core is leaking. I believe a 2001 dumps it outside about where the AC condensor run-off would dump out water but I’m not sure when they changed back over to dumping it in the floor on the passenger side like my 2004 Monte Carlo.

well it could be heater core,water pump,radiator or hoses but the op did say no coolant on floor so i kind of dismissed the heater core. you would think if it was 3/4 of a gallon low some would have showed up. the windows fogging over, well i have seen on a cold morning with no heat the mere act of breathing while sitting in the car fog windows over pretty quickly. and i’m not saying it is one thing or the other just throwimg it out there as an option.