vincemoran

So, my car used to have this overheating issue that's beginning to occur again. I thought it just wasn't ran enough (I recently purchased my IS300 a little over a month ago), or at least that's what my Dad had told me when he's brought the car from an Auto Auction. He would tell me that when the engine overheats, to turn on the heater and run it on high. And I've never had a problem running the heater. At all, actually.. And now, with the temperature being a surprising 18 degrees in Denton, TX., I haven't had a problem with my heater turning on until now. My A/C / Heater isn't producing any kind of heat. It's producing air about as cold as it is outside. Is there anything else I can do to fix this? Is there something I'm missing? Anything I should have checked out? Because I can't go more than a mile without the Temperature Gauge going above red.

Meatball

Check your coolant level.

MURPHY660

Very large air bubble in the coolant system, will take some work to get it out.

It's cold enough outside that the thermostat shouldn't be of issue.

Google how to bleed a pita coolant system. If not just ask, I'll explain

BoughtanIS

Heatercore could be blocked as well. It's easier to burp it though and it usually fixes the issue.

Jack up the front of your car (or park on a steep hill), remove the radiator cap and just idle it. Have the heater on full blast as well. As it heats up, you should see bubbles come out. Keep an eye on your temp gauge and just add more coolant as bubbles appear. Top off reservoir, replace the cap and you're good to go.

Supraguy88

Could also be the 2 different problems, fan not working, thermostats sticking, heater control panel not operating the servo that regulates the air. Or the servo gone bad. Had to replace several of these of 02-06 toyoas

PIONEER

iTrader: (2)

Check the heater control valve on the firewall in the enginer bay. This allows hot coolent to travel from the engine to the heater core behind your dash. The heater control valve is usually controlled via vaccum. See if the vaccum hose has a puncture now allowing for sufficient vaccum. You can operate the control valve by hand just to test this theory.

Start the car, allow car to get warm, Turn the heat on full, Operate the heater control valve by hand, which will allow coolent to go in the heater core. This should produce hot air in the cabin, unless the core itself is clogged.

mitsuguy

iTrader: (2)

There is no heater control valve on our cars...

PIONEER

iTrader: (2)

There is a hot/cold actuator behind the glovebox. Is that the replacement for the heater control valve? Something's gotta open to allow for hot water to get in the core.

You the HVAC guy, help the man out.

mitsuguy

iTrader: (2)

Heater core is always hot so long as the engine is warmed up - the only change when going from hot to cold is a blend door...

I didn't really go any further as I believe the answer has already been found by others - most likely cause for overheating and no heat is an air pocket in the cooling system - as has already been mentioned, park on an incline or jack the front of the car up only, run it, and add coolant as necessary with the radiator cap off... make sure we're adding to the radiator, not the reservoir...

If thats not it, then water pump would be my next best guess - coolant will actually flow through the heater core before the thermostat ever opens (it uses the heater core as a bypass essentially), so thermostat is unlikely... Only other weirdo combination would be a plugged up heater core and thermostat so its overheating and no heat... lets stick with most obvious / most common first though...

MURPHY660

^ ehhhhh. I completely agree with the whole stick to the basics

Buttttt the heater core could be "clogged/blocked" what have you even with the engine being warm/hot and not blowing hot air, in cabin

I just like to debate

redsx

iTrader: (1)

Add coolant and pressure test the system. Possible coolant leak, headgasket, thermostat sticking.

Jaybeck860

I haven't had this problem with my is300, but i had the same problem with my last car, a toyota camry, and it happened to be a blown head gasket.. Like you said, the heat didn't blow hot air at all, and just driving down the road overheated the car, so it could definitely be the same thing. but obviously try the smaller problems first.