Hi,

I have a 2002 RSX Type-S. This morning it's -30 in Montreal , so I gave myself a few extra minutes to let car warm up. The fan was blowing stong but only cold air was coming out. Eventually when the car was moving I think I could feel the heat from the engine. Does anyone no what could be wrong?

Thanks in advance!

 

My '05 Civic Si does the same thing. It blows cold air when stopped but when you start driving it gets HOT. Maybe the system works this way on purpose to improve efficiency?

 

I don't know because my car takes like 5 minutes in the morning before I start feeling heat, but it doesn't matter if I'm driving or not it still blows warm air even if I leave it sitting there to warm up.

 

Most of the time it means your low on coolant. Our work trucks do it. And my RSX just did it after the engine swap. Check your overflow tank and fill her up and see what happens.

 

Low coolant? Broken Thermostat? Blower motor?

 

While letting the car warm up with the heat and the fan on, you are introducing the heater core as an extra radiator and it takes the car longer to heat up.

Turn the heater to cold and the fan off while the car is warming up. That way the motor warms up so much faster. You will notice that the car warms up faster and when you do turn the heat on, it will be hotter.

I do this with my rsx in the moring here in WA state. 2-3 min's of warm up and driving the car out of my neighborhood the engine temp is at normal, and the heat blows nice and hot.

 

So if the motor is already up to temp and the fan blows cold when stopped, does that mean the radiator/cooling system is being "too efficient"?

 

that might mean that your thermostast is bad or your fan switch is keeping your fans on too long.

 

Good info. Myrsx does that too and i always thought it could be the thermostat too.

 

The same thing happed to me when I got the car a year ago!!! So I took it back to the dealer cause its in warranty, nothing to tell me but "sir , it works fine " but I knew I wasn't crazy lol, ui noticed that there's a small rattle too when the heater fan is on!!!has that happened to n e one!??

 

This question comes up every winter. If you search "heater" you'll see there are several threads on point.

Short answer: I seriously doubt there anything wrong with your car's heater or the cooling system (radiator, hoses, etc.). There is a mechanical (mostly plastic) valve on the firewall in the engine compartment that diverts heated water from the car's water radiator to a smaller radiator inside the car. As you turn "blue/red" **** on the dash, a wire "arm" pushes the valve open. The "fix" is to ensure it is fully open when you rotate the **** on the dash. People often replace the valve, but it's rarely necessary.

 

^^ This still doesn't explain why it blows cold air when stopped, but gets hot when the car is moving. :confused:

 

So for the hell of it, I tested my rsx today while I was driving around.

It does the same thing. It will blow really hot air when I drive but then when I stop at a light it will blow cold.

I did notice that if I rev the engine to about 2000 rpm will start blowing hot again.

So my thought about it now is that the k series thermostat housing has two springs in the thermostat housing.

One allows water/coolant to flow to the head and radiator

Second allows water/coolant to flow to the heater core

So with that in mind, when the car is at low rpm and the coolant in the radiator gets hoter because the water pump is turning really slow (relative to the rpm) then the thermostat spring closes the part that goes to the heater core to allow more coolant to the head/motor to keep it from over heating.

As soon as the rpm raises and the water pump produces enough volume to keep the engine at the right temp, then it opens way for water to go to the heater core.

So I really think that there is nothing wrong with the car, just normal operating procedure.

 

^^ I concur, dear Watson.

I didn't know that's how the DC5/EP3 thermostat worked, but it makes sense in theory.

 

So what about EPs? My heat works all the time when it's on. Does this mean that there's something wrong since most people are noticing that it cools down when the cars not moving.

 

I usually close the fan and leave **** turned to hot... so i tried your way and I must say it did warm up the engine much quicker but it was a little colder in the car during the warm up period but i was able to get more heat quicker in the end!

Good tip!