Heating issues.

So i posted earlier and have had little response. So I’m going to retry. Friday driving to work I had no heat. I had heat a few days before that no issue. Replaced the Thermostat. And coolant T almost a year ago. Never had any issues with heat. Used the proper antifreeze and distilled water. Again no issues till Friday. Today I flushed the system. Used CLR and flushed and back flushed. Then rinsed with water. Flushed and backflushed again with just Distilled water. Turn the car on let it get up to temp. Drove up and down the block and I was getting warmish air. It seemed to vary as I drove. If I was in park and reved the motor I got hot air. If I was just idling it was warm. I took it for an actual drive this evening and what do you know cold air. I heard a weird spitting noise from behind the dash. And a little bit of gurgling. Got home tried to bleed the air out. Took the passenger side hose off a bit to get to the bleed hole raised the tank and just antifreeze came out. No air. Got back in the car had warm air for about 10 seconds then back to cold. Tried bleeding again. Got warm air for a little while. It stayed. So I drove up and down the block and back to cold. Do I just have a bunch of air in the heater core or could it be my water pump.

Please help out. Winter is coming. I would rather replace the water pump then the heater core. But I’m hoping it is just air. And if the water pump was bad wouldn’t my car overheat. I don’t have over heating issues.

If it was the water pump the engine would overheat. The problem is air in the heater core area.

Based on my experience, an auto air conditioning shop can flush the heater core better than you can. They have succeeded when I didn't. It shouldn't be very costly just for that.

Never had an issue bleeding my Passat but my C5 Allroad was a different story. It has the same setup for bleeding, with a weep hole in the heater hose. I had all the same issues you have even after getting the heater core back flushed with a pressurized tool. What ended up working for me was to pull the heater hoes off till the weep hole was open. Then had someone hold the engine rpm at 2000. Coolant did NOT come out of the weep hole the whole time. After about 2 min I had him let off the throttle. Immediately coolant came out of the hole and I quickly pushed the hose back on. Now the heat works great.