Please help! Heater core or Air Bubble in the cooling system

[zlaja80]

Heater core or Air Bubble in the system? Researched around and tried a lot of different things

I have a 2003 Audi A4 1.8t Front wheel drive. Just finished changing the T-stat (old one was stuck open) and flushing the coolant. Added an new mixture of coolant to the system, turned on heat to HI and fan to Low. Results:
• Temp gauge finally started working
• Radiator fans turned on
• Car reached proper operating temperature
However heat that was coming through the vents was lukewarm.
Burped the car through expansion tank at least 6 times by running the car for 4-5mins with RPM at 2500 to 3000 and then slowly opening the cap to burp it.
Nice heat finally started to come out of the vents.

The next day heat issue again. Very mild air coming from the vents. At that point I started purging the air through a little hole on the hose connected to the heater core. I would let the air bubble out and then let stream coolant out as well. Heat came back, however only when the RPM were higher 2500 to 3500, and both hoses going to the heater core were hot, bottom one too hot to touch, while the upper one with the breather hole was hot, but I could hold it.

While at lunch I drove the care today for about 15min on the interstate with heat on, mild air coming out. I parked and checked the hoses going to the heater core. Same results, bottom one extremely hot, while upper one was hot, but I could hold it with my bare hands.

Any help would be appreciated or pointers if this is the air bubble in the system or heater core issue. I flushed the heater core about 1.5 years ago.

Thank you.

[lyates1987]

Pull off the rain tray that goes over the battery, brake booster, etc. There are 2 coolant hoses that go into the firewall. The higher one should have a hole in the top of it. With the car off loosen the clamp and pull the hose out but not all the way off, just enough to where the little hole can breath. Start the car and let it warmp, eventually coolant will start to come out of the little hole. When you no longer see air blasting out of it then put the hose back all the way on and reclamp. Should be no more air in your heater core.

[zlaja80]

See I did that while the car was running. I will try it when it is cold. Thanks.

Pull off the rain tray that goes over the battery, brake booster, etc. There are 2 coolant hoses that go into the firewall. The higher one should have a hole in the top of it. With the car off loosen the clamp and pull the hose out but not all the way off, just enough to where the little hole can breath. Start the car and let it warmp, eventually coolant will start to come out of the little hole. When you no longer see air blasting out of it then put the hose back all the way on and reclamp. Should be no more air in your heater core.

[MikTip]

This has been already posted here soooooo many times in the past that its rediculious!

http://www.audizine.com/forum/showth...ht=air+coolant

[jonan]

so, out of curiosity, all of you that have had or currently have heater core problems...do you fill your coolant system with a mixture of coolant and DISTILLED water? or do you just use water from a hose, tap, faucet etc???

it doesn't matter how cold it is out, my heater is blazing hot even when the car isn't fully up to operating temps...i've always used distilled water when refilling my coolant and never had problems with the getting heat...

[lyates1987]

so, out of curiosity, all of you that have had or currently have heater core problems...do you fill your coolant system with a mixture of coolant and DISTILLED water? or do you just use water from a hose, tap, faucet etc???

it doesn't matter how cold it is out, my heater is blazing hot even when the car isn't fully up to operating temps...i've always used distilled water when refilling my coolant and never had problems with the getting heat...

You're suppose to mix distilled water. Tap water has impurities in it that would be bad for the engine.

[Pothole]

/\ especially with the all the tight passages and all aluminum cooling system in these cars. You should always use distilled water.

[jonan]

/\ especially with the all the tight passages and all aluminum cooling system in these cars. You should always use distilled water.

right, i've always used distilled water and i don't have any of the buildup that i've seen in these types of threads, which is why i asked to begin with...maybe i'm just lucky...

i even cut my radiator up when i replaced it with a new one and it was relatively clean even though it had 140k+ miles on it...