I have a 2003 montero with a heater that blows cold on the passenger side and warm on the driver's side. I've heard this could be a possible air bubble in the heat exchanger. Any ideas, and should I bleed the cooling system?

Thanks for your time - Todd

 

You can purchase a cooling system bleeder kit to get rid of any air pockets in the system. Another way is have the vehicle on a slight include (Nose facing upwards) and run the vehicle with the radiator cap off. Cooling system circulating and gravity will have the air bubbles move to the highest point.

Good luck.

 

if you have heat working on one side only, the most likely cause is a failed (stuck) gate inside the dash. The heater core is obviously working, but you may not be getting the airflow to the passenger side. Check the following: do you have air flowing to the passenger side if you run fan on High? Does the air flow appear to be the same amount/speed as on driver side? If you run AC (this is hard to test in the winter), do you have cold air getting to passenger side, or to driver side only? When you turn system to windshield defogger, does it blow and heat evenly across the entire windshield, or one side is warm, the other is cold? Doing these tests, will let you know if you have an airflow issue or actual heater core problem.

 

One more thing - do you have Auto Climate control with dual zones?

 

Thank folks I'll give the suggestions a try. The does flow evenly across the vents so I'm suspecting an air bubble. Will try today and advise. Thanks again!! Good old Montero with 260,000 and running good.

 

I don't have dual control, and air pressure is equal on both sides. Yesterday I took a look and discovered low coolant, so I filled it up and still have the issue. So this weekend I'm crawling underneath and above to see if I can find the leak. I don't think it's a head gasket issue, but will see. But still assuming air is trapped in the heater core . Will see and advise.