Coolant boiled over trying to bleed after flush, now no heat

[Avylon]

Hi everyone. I just replaced my heater core on my 2004 A4 1.8t because my heat wasn't workin and it's cold as hell out now lol. Anyways, I did a few flushes, swapped out the heater core, then flushed again. Heat was working MUCH better, but still wasn't 100%, so I figured I just had to bleed it. I had the car running with the reservoir cap off and to get any air to rise up and come out, all of sudden the resevoir boiled over! Now the heat is almost non existant as it was before. I'm thinking a lot of air got sucked in when it boiled, idk I'm just going to wait until tomorrow when car is cold and try bleeding again.


I'm not sure if I had too much water in the mix, was following this DIY. After the last flush when just clear water came out, I filled with undiluted coolant. Anyone got any thoughts?

[a4lownslow]

Sounds like your process is good. Coolant will overflow if cap is left off long enough and coolant gets got. Just go drive the car and get the revs up. 4-5k. It will bleed itself. Top off as necessary once cooled.


Sent from my iPhone using Audizine

[inliner311]

Hi everyone. I just replaced my heater core on my 2004 A4 1.8t because my heat wasn't workin and it's cold as hell out now lol. Anyways, I did a few flushes, swapped out the heater core, then flushed again. Heat was working MUCH better, but still wasn't 100%, so I figured I just had to bleed it. I had the car running with the reservoir cap off and to get any air to rise up and come out, all of sudden the resevoir boiled over! Now the heat is almost non existant as it was before. I'm thinking a lot of air got sucked in when it boiled, idk I'm just going to wait until tomorrow when car is cold and try bleeding again.


I'm not sure if I had too much water in the mix, was following this DIY. After the last flush when just clear water came out, I filled with undiluted coolant. Anyone got any thoughts?

The proper way to bleed these cars is to take the screw off the coolant tank, take it off the mount, and prop it up vertically. Have the top of the coolant in the tank higher than the upper heater core hose at the firewall. You need to make it the highest point, the normal position isn't the highest point. Then open up the other bleed points which are the little hole on the top of the upper rubber hose that connects to the heater core at the firewall and the other one is a 5mm allen under the engine cover. No need to have the car running, gravity will push out the air if the bleed points are open. You can loosen the cap on the coolant tank or have it completely open when its propped up.

Depending on how much coolant it needs, the coolant tank will burp when the car is bleed. You can do each bleed points one at a time. The one under the engine cover, you should have the Allen key/socket on the bleed screw ready to close it, it would bleed out the air and start leaking fluid fairly quickly. The little hole can be harder to know if it's bleed, I've used coolant hose pick to pull it open from the top and let a little fluid out a couple times. You have to listen carefully and watch for coolant.

[Fast4esT]

It takes a while to bleed these systems. After propping the tank as high as you can and make sure it’s full, let it sit there for at least 30 minutes before opening the first bleed screw. Keep the tank full. After the second hole is opened and closed I still let the tank sit up high for half hour or so. Engine cold. Once done bleeding turn car on, fans low, heat high and let it come up to temp. Checking for heat and also also watching temp gauge so to not overheating.
I’ve driven my car after incorrectly bleeding it with engine running and the temp gauge rises and coolant spits out.

[Turbo510]

Key points: don't run the engine, and keep the reservoir as high as you can.