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Danny, ASE Certified Technician
Category: Audi
Satisfied Customers: 4004
Experience:  ASE Master Certified with L1 Certification, Volkswagen Certified, VW and Audi repair shop owner
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2001 audi a4 quattro: 1.8t..Ive replaced the thermostat and that

Resolved Question:

2001 audi a4 quatro 1.8t. I have no heat. I've replaced the thermostat and that did not work. I've flushed the heater core and did see debris coming out of the hose. The flow from my garden hose through the heater core was slow. Perhaps the core needs flushed with higher pressure??? That produced little heat for short time. My engine temp guage reads COLD (C)95% of the time and occassionally the needle will move between the C and H. I checked to make sure the resevoir cap was tightly on. I thought this coolant system was vacume type and might have a leak somewhere. I've also thought the heater core needs to be replaced but seems to be an extensive job. Any thoughts as to my next step?
Submitted: 7 years ago.
Category: Audi
Expert:  Danny replied 7 years ago.

Ok, so you're having two seperate concerns here. The temp needle not moving is because the temperature sensor on the back of the head in the coolant flange is faulty. Replace that and it will fix this problem. The easiest way is to remove the coolant bottle cap then reinstall it to create a vacuum in the system. Maybe pick up an extra temp sensor clip and a couple extra seals because it's pretty easy to drop the seal and lose it on top of the transmission.

Alright, as far as the core goes, it is common of them to plug up like this. All you can do is flush it like crazy with the garden hose or compressed air from an air compressor. When you refill the system you often need to loosen the coolant bottle and elevate it so it's higher than the heater core by bungee cording it to the hood and then remove the cap and run the car. One of the heater core hoses should have a small hole molded into it so you can loosen the clamp and then pull it back to expose the hole and that will push most of the air out.

At VW/Audi repair shops we use a special vacuum machine to pull a vacuum on the system and then flip a lever to replace the air with coolant. Often this is the only way to get all the air out.

So to sum it up.

1. Replace the temp sensor.
2. Try bleeding the heater core of air as described.
3. Maybe have a shop vacuum fill it as a last ditch effort.
4. Try flushing it again or you'll end up replacing the heater core which you are right is a giant pain on this car.

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