I need the replys from people who drive their car in the cold weather. Does anyone else experience their heater blowing hot when the car warms up, but as you drive and the cold air blows over the radiator, the heat gets cool again? If so, is there a way to keep it from doing this? What if I install a heater control valve? My 93 Buick Roadmaster does not have this problem, nor did ANY of my other vehicles. What makes the heater in my Camaro go cool as the car drives? The only difference between the Camaro and all the other cars I've had or driven is the heater control valve. Could this be the answer? Thanks for any and all suggestions.

could try the old trick of shielding the rad from the air flow

could try the old trick of shielding the rad from the air flow

Yup, congratultions, your cooling system is very effective. A sheet of cardboard over half the radiator will calm it down.

First make sure the cooling system is actually full (to the full cold mark on the pass rad tank when cold.) as low coolant can cause this behavior too.

Jim M, The radiator is full. I just checked it yesterday. You say this shows an efficient cooling system? Why doesn't my other car do this?

Todd, Have you had experience with cardboard? How well does it work?

ive never done it with my camaro as it never sees winter - im just speaking from 40yrs experience of living in michigan - and yes sometimes its all you can do

What I can't understand is why EVERY other car I have ever had or driven in cold weather has not done this. Once the car heats up, the heater blows HOT. Most of the time I have to turn the heat down because it's too hot and this was driving at 65mph in 30* weather. If ever a time when the heat should blow COLD, not cool, it's then. 65mph in 30*, but it was so hot I had to turn it down. The only thing different with the cars of today and yesterday are the heater control valves. We don't have them.

sounds like any other 60s/70s vehicle i drove in the 80's

Are you sure you don't have an air leak into your passenger compartment? Like maybe around one of the floor air vents... or around the heater box... or somewhere else around something connected to the firewall that's covering a leak path to the inside of the car? That could do the same thing you're describing... so the faster you go, the more cold air is creeping inside through some hole or poor seal.

I had this happen once on an old Impala I had. The floor vent seal around the driver's side vent door actually came partially off and was leaving a gap when the vent door was closed. When idling or going slow (when there was no wind blowing on it) everything seemed fine, but as soon as I got the car moving a bit, I was like... "Why is my heater blowing cold air the faster I go!?" It drove me crazy for a while until I finally figured it out. Yeah, high speed + cold weather = the worst time for cold air to be blowing on you (I lived in N.E. Ohio most of my life, so I feel your pain).

Just a thought... might be worth looking around a bit.

~Bob

Charlie do you have A/C ? If so, the cowl flapper valve might be sticking open and letting cold air into the system?

Does the car have a temperature gauge? and where is it when the heater is blowing cold?

Will the heater blow hot all the time when it's warmer out?

I suppose it's possible your thermostat is stuck opne or paritally open, and the motor is not warming all the way, but really, it's not that unusual to have to block part of the radiator to build some heat in the winter. The newest car I've had that I needed to do this was an 86 monte SS. Also had a 75 Monte 454 with an overactive cooling system, and many older cars.

Modern cars that have to comply with modern emissions laws are put together pretty carefully to be able to achieve normal operating temp quickly and maintain it no matter what. Temperature variations are hell on emissions. These are a totally different animal.

Bob, The car does not have a leak. At least I don't feel one. The air that comes out of the floor vent itself is cool. The air blows cool when I am sitting still. If I let the car warm up, the air will blow HOT, but as I drive and the cold air flows over the rad., it turns cool.

Jim, the car does have a temp gauge and it warms up to 200*, the air blows HOT. As I am driving the gauge drops to 160 or so and the air gets cool. Just let me say that I just got back from a drive after placing a piece of cardboard in front of the rad and the air stayed HOT so that tells me that it is definately to do with the coolant temp. Emissions or not, an engine runs the same. I don't think that has an effect on temperatures. The only major difference between new cars and old cars are the use of a heater control valve. The name alone should stand for something. What about people that have installed fuel injected engines in their cars and had to install O2 sensors along with catalytic converters? They have emissions controls on their cars and I am sure they still experience the same situations as me. You said you had an 86 Monte. They have emissions controls on them and you still had to block the rad. There has to be an underlined issue with this.

Bob, your vent door seal. Do you mean the one on the kick panel? If so, did that let air into the heater system or just blow cold air into the car? I am having my heater change from hot air to cool air. Not cold, but cool. As soon as I blocked the radiator with cardboard the problem stopped. I just can't see us having to use cardboard. There must be something else causing this. I just can't believe the manufacturer would make a car this way.

An engine is an engine is an engine. No matter if has emissions or not, it still fires and run the same. You may be right, but I can't see how emissions has a hand in this. The only thing that comes in contact with the coolant system as far as emissions is concerned are ported vacuum switches to operate EGR.

Would the fact that I have a high flow thermostat in it make a difference? I have a Stewert performance balanced thermostat that has three little holes drilled into it. I use that for summer and forgot to replace it with my other one without the holes.

My vent door seal problem was the kick panel vent, and it would just blow air into the cabin... but in a big 'ole Impala it sort of blended in with the heater air by the time it hit me, so basically all I could feel was a cold draft coming from somewhere.

If you've verified it's indeed coming through the heater system and there's no air leaks anywhere, then yeah, I'd have to wonder if that high flow thermostat has something to do with it. I've never been a fan of things that are designed to speed up coolant flow. Faster isn't always better, especially when you're talking about coolant system containing two heat exchangers that ideally should operate at a fairly constant temperature when the car is warmed up.

Maybe it's just me, but I've had a whole lot of cars with big engines and big radiators, and I've never experienced what you're seeing happen.

~Bob

The faster you can get the coolant to flow the faster the heat exchange takes place. That's the reason for the high flow thermostat and the high flow water pump. I have since changed out the high flow thermostat and replaced it with the standard one I normally use in cold weather. We will see if this has any effect. I have also removed the cardboard from the front of the radiator so I don't mistake one for the other as far as remedies are concerned.

My father has said the same thing. Once the car is warmed up the heater system should remain stable. He has never had a vehicle do this either. He has had some OLD cars and none have had this symptom. I am hoping that the three small holes in the thermostat are allowing enough coolant through to allow it to be cooled by the air and circulate through the system. With the solid thermostat it should keep any coolant from entering the radiator until it reaches the opening temp of the thermostat. We will see how it does when I go to pick up my son from school.

One thing I forgot to mention is that I am running a BeCool aluminum radiator w/22" core, a Weiand high flow water pump, and a 180* thermostat.

Well after going for a drive with the solid thermostat installed, it runs much better now as far as maintaining heat is concerned. The car never drops below 170* now and the heat is always hot. It must have been because the holes in the high flow unit were allowing just enough coolant to pass through and circulate through the system. It never fully stopped the coolant flow. The car seems to run a little better now as well.

There is also a big difference between a 180 degree thermostat and a 195. I tried a 180 in my old pickup and had to go back to a 195 to get enough heat in the winter.
David

I was thinking about a 195 David, but I have an electric fan and I haven't been able to find a kit that has the correct fan switch for a 195 thermostat. My 180 uses a 200 on and a 185 off. The 195 thermostat would need something like a 215 on and a 200 off. If I stayed with my current switch the fan would never turn off once it came on. That was the problem I was having until I switched to the 200 on 185 off. I was using the 185 on and the 170 off. I was thinking of trying to find a switch from a newer car that uses the same thread and is set for a 195 thermostat, but now that the problem seemed to be the high flow thermostat, I don't see the need. The heat get plenty hot, NOW.

Maybe your thermostat is not working properly and for some reason is sticking open. Change the Thermostat and see what happens.

I realize this thread is probably done with but, I just wanted to give some info on heater control valves.
A heater control valve just stops hot coolant from flowing through the heater core so that the A/C can work. With out the heater control valve, the A/C would be cooling down the air just so that the heater could heat it back up (or heater first then A/C depending on the car)

So adding a heater control valve shouldn't help you heater work any better, but it will help your A/C on the other hand...

Mike, I got the problem corrected. In a way it was the thermostat. It was opening and closing fine, but in the summer I run a Stewert's high flow/balanced thermostat that has three holes in it to allow constant flow. I neglected to remove it and replace it with the stlye without the holes. I have since done this and the heat works. The car still doesn't get over 165*-170* when it's cold, but the heat works. Thanks for the suggestion.

400bird, thanks for the info on heater control valves. I wasn't 100% clear on their operation.