Heater not working correctly

Do you have heat when you rev it up? You could have a blocked/clogged heater core. Try back flushing the heater core in both directions to try and clear any deposits. Also if there has been any kind of stop leak added it can clog heater cores right up. Also verify that temp blend door stays in proper position.

You probably have a plugged heater core. If one hose is hot, and other one is quite a bit cooler or cooler, then you have a problem with flow through heater core. Try flushing it. I hope that will help.

Good Luck!

There are two possibilities, one is the thermostat. Many people remove them which spoils the whole heating / cooling system. Since you changed the thermostat, I would check the heater valve on the heater which allows the hot water to circulate through the heating system.
It may be necessary to remove the heater box and flush the heater core since you talk about a lot of rust, which could have clogged the heater core and / or the pipes leading to the heater.

Regarding this types of problem,i suggest you to go through this help links.Click the link below to go through the procedure and troubleshoot the problem :----HOW TO REPLACE AN UPPER RADIATOR HOSE

http://schematicsdiagram.blogspot.com/2011/07/how-to-replace-upper-radiator-hose.html

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HOW TO REPLACE A LOWER RADIATOR HOSEhttp://schematicsdiagram.blogspot.com/2011/07/how-to-replace-lower-radiator-hose.html
----------How to Flush Heater Core?http://schematicsdiagram.blogspot.com/2011/12/how-to-flush-heater-core.html
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For heater core replacing procedure. I suggest you to go through this related help links.Its all complete step by step procedure: ----How to replace heater core for All car models?

Click the link below: ---

http://technoanswers.blogspot.com/2011/11/how-to-replace-heater-core-for-all-car.html

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How to Flush Heater Core?

http://schematicsdiagram.blogspot.com/2011/12/how-to-flush-heater-core.html

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How to Remove Heater Core ?

http://howtobyme.blogspot.com/2011/12/how-to-remove-heater-core-on-2008-honda.html
Heater Core Replacement?

http://howtobyme.blogspot.com/2011/12/honda-heater-core-replacement.html

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To replace heater core?http://technoanswers.blogspot.in/2012/02/how-to-replace-heater-core-on.html------

How to replace heater core?http://technoanswers.blogspot.in/2012/02/how-to-replace-heater-core-on_10.html
How to replace heater core on Buick Regal?

http://howtobyme.blogspot.in/2012/02/how-to-replace-heater-core-on-buick.html
----------This will help.Thanks.

Did you try back flushing the system?

flush the heater core out with a garden hose and try that

check to see if both heater hoses are same temp when engine is at normal running temp if not heater core not flowing coolant may need to flush also make sure it does reach normal temp around 200

You need to flush the heater core or verify that the valve to it is actually moveing with the selector in the dash.

You probably just need to backflush your heater core. You can use a hose to flush it back and then forward. You'll be surprised at how much sludge and gunk will come out.

Your heater core is starting to go out.