I just purchased a 2007 IS 250 and it has an issue with the heater. It only blows cold air unless the engine is revved fairly high (2500 rpm plus) so no heat in normal cruising speeds. It sounds like a vacuum hose issue to me, assuming that is what diverts the heat through the fan. Has anyone encountered this? Thank you.

 

Having this problem in my 07 is350. Idk what's the cause.

 

I'm hoping someone has seen this before and will have some advice. If not I will likely have to take it to a mechanic friend. If I do I'll let you know what he says.

 

Water pump.

 

thanks. I hadn't considered that.

 

You sure? Had my Waterpump replaced 2 years ago.

 

Did you check the level of the coolant in the reservoir?

 

Not the same car, but I had a very similar issue with my old e36. The cause was the heater core. Other areas to look into would be your cooling system. Is it bled properly? If there are air pockets it'll cause what you're describing.

 

Antifreeze level may be low in the radiator. Thermostat could be stuck or bad. If the vehicle has overheated it may have a blown the head gasket, your oil will be milky white and the car may have white smoke coming out of the exhaust....and the coolant level will be low.

 

This is a telltale sign of a thermostat. Does the engine take longer to get warm? Does it stay below middle when you've warmed the car up?
-The thermostat stays closed until the the coolant surrounding the engine block is warmed up, and attached to that is the heater core. So the thermostat opens up once the coolant inside the block hits a certain temperature, and once the coolant starts to cool down, the thermostat closes to warm the coolant back up. If the thermostat is bad and is staying open, it's allowing coolant to flow into the radiator at all times, which means the coolant that's entering the heater core is not hot coolant but warm coolant. When you rev up the engine, you're creating extra heat inside the engine block which is why your coolant is hot entering the heater core and giving you hot air.

Could definitely be air in the system if you've done work on it recently.

Could be the water pump but not likely, the only way it could be the water pump is if the impellers were worn out, or if the pump wasn't being spun (as long as your water pump is attached to the serpentine belt you're okay on this front.)

I assume your coolant level is topped off, you certainly don't want it low regardless of issues or not.

Of course, if your heater core is the problem you'd have to find that out in other ways...Get the Torque App and check the engine temperature with an OBD2 dongle, if it's at operating temperature when it's idle and warmed up, then your heater core is the problem. If the temperature is lower than normal while your car is idle and warmed up, it's your thermostat.