2000 Bonneville SE and Heating Problems

I have a 2000 Bonneville SE.

About 6 weeks ago, I had the oil changed and it was determined the Radiator cap was 'venting'. I had the oil-changing service top off the coolent and went on my way. The radiator fluid was that good old 'pink stuff'. What they put in was the non-pink stuff but is supossed to be now able to be mixed with the pink stuff. (This is not normal prestone... but some other type). this changed my radiator fluid from the normal glowing 'pink' to a more muddy-ish color. I went to my auto-part store several days later and bought a radiator cap and some more 'fluid'. I replaced the radiator cap and topped off the fluid once again.

Now my problem is that it doesn't seem to be heating right. It was heating just fine for several days or even a week... but now it is really 'hit-or-miss'. Sometimes I turn the heat up to 90degrees for both driver and passenger and sometimes the vent gets hot... othertimes it comes out about 65-70 degrees (Not what I want during the winter time). When I put it on FLOOR it doesn't seem to even really warm the air at all (although I haven't tested it out with a thermometer or anything. I've noticed if I'm driving to or from work (a 45mile trip each way) the vent does heat up over time... and there is warm air coming out (Sometimes borderline HOT as it should normally be). Other times it is barely above the outside temp and will not warm up the car.

I thought perhaps the thermostat was 'stuck' and thought maybe this happened while the radiator cap was venting. I just went and replaced the thermostat on the car. It heats up just fine (Engine wise) but still very little heat (if any) is coming out of the Upper vents. Virtually NO heat is coming out of the floor vents. The rear vents are controlled by the driver temperature. I put my hand back to feel those vents... and it is very 'cool air' coming out.

I've also noticed when the fan is on HIGH (upper 2 levels)... there seems to be more 'sound' than air-flow. If I turn the thermostat down to 60 for both driver/passenger the air flows much stronger than when I had them up at 90degrees.

Heater core clog???? or does anyone have any thoughts where I need to go with this one?

TO me sounds like blown head gasket. It has all the symtoms."venting cap", irregular heat flow, that fills the bill....
I'll be happy for you if I'm wrong.

Blown Head Gasket.... Now there is a happy thought ... LOL. I certainly can't say that I would rule that out, but I would certainly hate to jump to that conclusion immediately (Although I'm no expert on cars as most here probably are).

My update:

I can pretty much clearly state I do not recall having any problems with the 'heating' aspect of the vehicle until I actually went and replaced the radiator cap and added the new mixture. While this might have been untrue, with the weather we had here in the northwest, I wasn't really having to run the heater much until recently.

That being said.... I made a decision to go and take the car back to the Lube Place and have them do what they call a 'flush' of the radiator system. I guess things have changed or maybe they haven't. However I do remember when I used to 'flush' my system in the past I used a concentrate to 'clean out the junk' in the cooling system. They seemed to simply suck out the old.. and replace it with the new. With me using the Pink Coolant I'm not entirely sure if it needs those old 'fushing' techniques I was so accustomed to. To replace the coolent took roughly 10 minutes and after forking over over $80 I was on my way back home.

I had to take my daughter to soccer practice (which is about 30min away so I decided to take that vehicle to see how things went. The heat coming out was 'fair'. I might have actually called it 'better' than it had been. Before it was more like a hair-dryer on high-blast but cool temp. The trip up showed the air was actually a little 'warmer' than that. Least I thought so. Maybe I was just kidding myself into believing it.

I stopped the car and went and talked with the coaches some. After about 30 minutes of watching practice in the cold (roughly 30 degrees or less outside) I decided it was too cold for me to just stand out there doing nothing so I went back to the car and started it and sat in the car with the engine running. OH MY GOODNESS. The heat started to pour out like it was on a mission. Within 5 minutes it felt like a dry sauna in my bonneville. I had to turn my fan down to the lowest setting so as to not be sitting in my car and sweating. Even with the lowest fan setting it still was too hot. I was too scared to mess around with the temperature controls and just left both the driver/passenger settings at 90degrees.

I ended up turning the car off and then turning it back on about 15min later. Same thing... HOT AIR. I pseudo thought perhaps the flush fixed it and if there was a clog to the Core it might have 'released it' or something like that.

This morning ...... disappointment. I went out and started my car (23degrees here this morning) 15min before I had to leave for work. Heavy frost to get rid of. My 45mile trip to work.... well the air was 'warm'. Back to the same as it was virtually before I had it flushed. More like a hair-dryer on high fan but cool temp. (perhaps a degree or two above that :) ). I wasn't frozen on my way to work, but I certainly wasn't really very warm. It was tolerable I guess is the way to put it.

I go from HOTTER than hell 9hrs before to 'so-so' ...... go figure.

So...... Now I have a new Radiator Cap.... New Thermostat... New coolant from the flush .... (roughly $100 so far) and not much further than I was before (with the exception of having a ultra-hot car last night sitting idle).

I can say .... I did seem to notice ... with the driving home the temp output did seem to 'go down' some. While the air was hot, it wasn't as hot as when I was sitting there idle. By the time I did get home it felt probably 15degrees cooler than what it was outputting up at the soccer field.

Blown Head Gasket..... eeeeeeeeeeeks... for some reason... that just don't sound good.... Sounds like Hours of work at a shop... and plenty of $$$ withdrawls from the old bank account. :(

...I do not like my conclusion either, but the mechanism is too close to be discarded: it is a classic. Exhaust and air gets into the cooling circuit through the gasket failure; CO2 and air do not carry a lot of heat: it is about 200 times less efficient than liquid in heat exchangers. WHen air is vented and some liquid invades the heater circuit, heat comes back, but then is replaced sooner or later by CO2/air and back to no heat.....Often one can see exhaust bubbles coming out of the surface or liquid when running engine with radiator cap opened.