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Thanks for choosing Just Answer . I'm Wolfgang here to help!!Below is my first answer or request for more information. If you do not understand it, or you need more information from me, or need me to go in more detail. Do not rate yet, just reply. Put yourself in my shoes, I can not see, smell, hear, feel or touch your car, nor do I know any history on it. So take into consideration I am doing my best based on what you tell me. Also understand fixing cars often requires sophisticated tools, that you may not own. So even if you can not do what is outlined in my answer, that does not mean my answer is wrong deserving to be rated negative.
On your issue the heater core will need to be replaced . of how it is designed and located the sediment gets trapped and clogges the heater core. you will also need to do a chemical flush to the cooling system to prevent this happening again. you take the heater core out of the loop and connect the 2 hoses together and then add the chemical flush and get the engine to operating temperature . then drain and flush the entire circuit with water. then replace the heater core and use new vw coolant. 50/50 mix. bleed the air and you will have heat again .
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