Fixed my "no heat" problem.

[JMRQuattro]

Wow...so I spent an hour trying different methods and finally have heat <crosses fingers> This method was bleeding from the hose that comes from the firewall with the coolant cap off, coolant cap on, heat on, heat off, tried from the bleeder screw, shop vac and just about got the 5lb sledge...What finally worked for me was having the coolant cap closed, hvac completely off, hold rpm around 2-3k for 30-60 seconds, run to the hose and slightly pull back until bubbles then coolant. Did this 15 times before I coolant only came out!!!!!!!!!! Did not drive the car afterwards since I was scared of the results but will post tomorrow.

Did you fix a coolant leak at any point leading up to this? Because if you had that big of an air bubble in there it's probably going to reform again unless you make sure you don't have any leaks.

[dewey527]

No friggin heat again...I am so frustated at this point I am ready to take it to the dealership. I have had these codes for some time but haven't gotten time to look into them. Could any of them be in direct relation?

3 Faults Found:
01274 - Air Flow Flap Positioning Motor (V71)
41-10 - Blocked or No Voltage - Intermittent
00604 - Potentiometer Positioning Motor for Air Flow Flap (G113)
30-10 - Open or Short to Plus - Intermittent
01592 - Air Quality Sensor (G238)
37-10 - Faulty - Intermittent

[old guy]

Absolutely. The flaps control the airflow through the heater core.

[dewey527]

So in another thread I remember you explaining how to remove the motor. But yesterday after burping the system I had heat...why not today?

[JMRQuattro]

Air bubble reformed just like I thought haha. You have some sort of a leak somewhere in the system. Maybe from the flaps like Old Guy said. Either way, air is getting back in there somehow.

[old guy]

So in another thread I remember you explaining how to remove the motor. But yesterday after burping the system I had heat...why not today?

Possibly your flaps are sticking. Another possibility is that you are getting air into the coolant from a leak somewhere. As someone previously posted in this thread the "J" plug can seal under pressure but let air in as the block cools and the coolant decreases in volume, creating negative pressure on the coolant system. If this is the case you can check to see if there is an air bubble by following the procedure in the original post:

Here's any easy way to tell if you have air trapped somewhere. Get your motor up to temperature. Then SLOWLY crack open the reservoir cap. If you have an air entrapment you should be able to hear the coolant gurgling and the coolant level in the reservoir will noticeably increase as the entrapped air is allowed to expand. The bigger the bubble the more the tank level will increase. If the bubble is big enough it will push coolant out of the overflow port on the bottom of the reservoir so be careful that you don't burn yourself. Even if you don't have any entrapped air the level will rise just a little as the coolant hoses contract back from the pressure release. However, you probably won't hear the gurgling noise that accompanies the bubble as it expands.

If no air bubble is present I Would suspect a flap issue. One other thing to check: With the motor up to temperature reach under the hood and feel the heater supply hose coming out of the rear coolant flange and compare it to the return heater hose connecting to the lower coolant return hard pipe. If the temperature is essentially the same you have a flap problem. If the temperature is significantly different you have a heater core issue.

Good luck!

[tommy782]

so I go to my friend house tonight and I see that my car overheat when I run the car in 4 or 5 gear over 3000rpm. when I go over this rpm, the temp gauge show an overheat coolant and I check under the hood and the coolant overflowon the ground. this seem like the thermostat is not wide open an have just a small flow ofcoolant. someone have already have this problem? this is a serious problem and I want to solve it the fast as possible!!!

[dewey527]

Did you fix a coolant leak at any point leading up to this? Because if you had that big of an air bubble in there it's probably going to reform again unless you make sure you don't have any leaks.

Just finished a timing belt a few weeks back. This has been an on going issue for close to two years...flushed the system last summer, had my indy shop flush and change t-stat. So I am stumbed.

[dewey527]

Possibly your flaps are sticking. Another possibility is that you are getting air into the coolant from a leak somewhere. As someone previously posted in this thread the "J" plug can seal under pressure but let air in as the block cools and the coolant decreases in volume, creating negative pressure on the coolant system. If this is the case you can check to see if there is an air bubble by following the procedure in the original post:

Here's any easy way to tell if you have air trapped somewhere. Get your motor up to temperature. Then SLOWLY crack open the reservoir cap. If you have an air entrapment you should be able to hear the coolant gurgling and the coolant level in the reservoir will noticeably increase as the entrapped air is allowed to expand. The bigger the bubble the more the tank level will increase. If the bubble is big enough it will push coolant out of the overflow port on the bottom of the reservoir so be careful that you don't burn yourself. Even if you don't have any entrapped air the level will rise just a little as the coolant hoses contract back from the pressure release. However, you probably won't hear the gurgling noise that accompanies the bubble as it expands.

If no air bubble is present I Would suspect a flap issue. One other thing to check: With the motor up to temperature reach under the hood and feel the heater supply hose coming out of the rear coolant flange and compare it to the return heater hose connecting to the lower coolant return hard pipe. If the temperature is essentially the same you have a flap problem. If the temperature is significantly different you have a heater core issue.

Good luck!

Can the J plug leak but only let air in? I looked at it last night to make sure it wasn't leaking and no undue wetness was around it.

[old guy]

When I run the car in 4 or 5 gear over 3000rpm. When I go over this rpm, the temp gauge show an overheat coolant and I check under the hood and the coolant overflows on the ground.

Tommy,

It sounds to me like you have a defective water pump. The OEM pump has a plastic impeller and it tends to crack. As long as you are running at low speeds/ low motor loads it can circulate enough water to keep everything under control. As you pick up motor speed / cooling load the impeller slips and the motor overheats.

Good luck!

[old guy]

Can the J plug leak but only let air in? I looked at it last night to make sure it wasn't leaking and no undue wetness was around it.

Yes it can. As the plastic deteriorates the plug deteriorates from the inside. The coolant pressure pushes out on the sides and makes a seal with the "O" ring. However when the coolant cools and contracts the plug can collapse in on itself and suck air in. But before you replace the "J" plug you need to confirm that the air bubble is returning after you bleed the system. I'm leaning more toward a defective flap servo. If you clear the potentiometer codes do they return?

[tommy782]

I replace the timing belt in mai last years and the water pump have a metal impeller... a new water pump with a metal impeller can slip??? when I stop the car I check under the hood and I heard a noise on the coolant cap. a small pressure. the problem is all the time in the first 10 min.

[JMRQuattro]

Just finished a timing belt a few weeks back. This has been an on going issue for close to two years...flushed the system last summer, had my indy shop flush and change t-stat. So I am stumbed.

You really should check to see if you have another air bubble.

I checked online for more information about the flaps, and the code you have is for the air flow flap positioning motor (V71) which directs air flow to either the defroster, center vents, or floor vents. So that wouldn't necessarily effect your heat. And a potentiometer controls voltage (but rarely more than a watt) and is used to adjust the level of analog signals. But with respect to your heater core, I don't know exactly what the potentiometer controls. But it would make sense that your heat doesn't work if it controls temperature, but it's also likely that it doesn't because apparently there is a temperature control flap positioning motor (V68) and you don't have a code for that one.

Old Guy, do you know what the potentiometer controls?? Is it just the positioning of the flaps?

[old guy]

Old Guy, do you know what the potentiometer controls?? Is it just the positioning of the flaps?

Flap position only. The heater core circulation doesn't change, just the air being directed through the core. I'm pretty sure that the G113 is the one that directs flow between the A/C evaporator coils and the heater core. I will check the Bentley tonight.

[old guy]

I replace the timing belt in mai last years and the water pump have a metal impeller... a new water pump with a metal impeller can slip??? when I stop the car I check under the hood and I heard a noise on the coolant cap. a small pressure. the problem is all the time in the first 10 min.

If you have a metal pump you should be OK. I have never heard of a metal one slipping. Something is causing the pressure to build rapidly in your cooling system. You may still have a very large air pocket somewhere or another possibility is blow-by from a leaking head gasket. Thermostat could also be sticking causing an overheat condition.

[mister_tu]

It's funny to see that the same people post in this thread that has posted in the same "no heat" thread a couple of years ago.

I've only tried burping the system (doublezero's method) and so far this winter, I've been good with heat. However, last year the same thing happened - the beginning of the winter seemed to be ok, but in the middle of the winter (the coldest time of the year) I would have problems with low coolant and minimal heat. If it's only air in the system, would I still lose coolant?

[tommy782]

I write that I use the doublezero30 method. I start the car and run at 2000rpm. after 1 or 2 min, the coolant up in the coolant reservoir( when the cap is off) and boiling out. this thing arrive at every 1 or 2 min when I try to ouput the air bubble of the system. it is normal?? and before he do that, the level coolant is the same and no flow in the reservoir. after the symptom, the coolant drop in the reservoir and am obligate to refill... I have this problem since 3 or 4 week and here the temperature is cold about -15c so is not suppose to heat!!!.

-I try the doublezero30 method to output air bubble and now I have heat
-the car heat sometime in the first 10 min and I my rpm and the temperature return to 90
-I have a water pump with metal impeller
-the 2 sensor are change since 1 or 2 years
-no misfire
-no thermostat code(I see that is an lectronic thermostat(b6 2003)
-I drive the car in the highway and its O.K(30 40 min) but just in the first 5 min, if I push the car a little bit, the temp rev.

I see a ton of thread but no person have this exactly simptom.

[old guy]

I've only tried burping the system (doublezero's method) and so far this winter, I've been good with heat. However, last year the same thing happened - the beginning of the winter seemed to be ok, but in the middle of the winter (the coldest time of the year) I would have problems with low coolant and minimal heat. If it's only air in the system, would I still lose coolant?

Sounds like you are dealing with a slow leak. It is possible for air in the cooling system to cause you to loose additional coolant. If the air pocket is in the block area you can end up creating superheated steam. The bubble expands and the resulting pressure exceeds the reservoir cap capacity and you blow coolant out the overflow.

[old guy]

I write that I use the doublezero30 method. I start the car and run at 2000rpm. after 1 or 2 min, the coolant up in the coolant reservoir( when the cap is off) and boiling out. this thing arrive at every 1 or 2 min when I try to ouput the air bubble of the system. it is normal?? and before he do that, the level coolant is the same and no flow in the reservoir. after the symptom, the coolant drop in the reservoir and am obligate to refill... I have this problem since 3 or 4 week and here the temperature is cold about -15c so is not suppose to heat!!!.

It sounds to me like you still have air trapped in your cooling system. As your motor heats up the bubble expands. That would be what is forcing the coolant out of your reservoir when you heat the car with the cap off.

[tommy782]

ok so can I extract all the air bubble with the method I describe?? or I'm obligate to use other method on something else?

[old guy]

ok so can I extract all the air bubble with the method I describe?? or I'm obligate to use other method on something else?

Tommy here’s is what I would recommend for your problem. Instead of trying to bleed your cooling system try to fill it instead. Get a funnel and a 6” piece of clear tubing the same size as the hoses running into the heater core. Remove the rain tray that covers the Battery/ECU/Cabin filter etc. Disconnect the upper heater hose. Use the clear tubing and funnel to completely fill the heater core. You will be able to see the level through the clear hose. Quickly plug the heater connection and then use the funnel to make sure the outfeed hose is also completely filled. Hook everything back up and see what happens.

[Dan[FN]6262]

^^^ Listen to Fletcher


you need 3/4" ID hose, any hardware store should sell it

[old guy]

Flap position only. The heater core circulation doesn't change, just the air being directed through the core. I'm pretty sure that the G113 is the one that directs flow between the A/C evaporator coils and the heater core. I will check the Bentley tonight.

I was wrong. the G113 position sensor controls the flap motor as SeatownB6 pointed out. Probably not related to your no heat condition. I assume you are getting plenty of air flow through the vents, just no heat. correct? If so I'm back to thinking you still have air present in the heater circuit.

[diagnosticator]

so I go to my friend house tonight and I see that my car overheat when I run the car in 4 or 5 gear over 3000rpm. when I go over this rpm, the temp gauge show an overheat coolant and I check under the hood and the coolant overflowon the ground. this seem like the thermostat is not wide open an have just a small flow ofcoolant. someone have already have this problem? this is a serious problem and I want to solve it the fast as possible!!!

When this happens, feel around to see if the radiator is hot or not.

[tommy782]

ok today I try to fill the heat core and I come back with some news thanks

[tommy782]

tonight I take off the pipe fixed to the heat core. the first try(why the cap on) some air go out of the heat core and after this coolant begin to go out. after this I start the car to the normal temp and I bleed it with the bleeder valve. I take off an other time the pipe fixed to the heat core. now no air and no coolant go out. I try to fill the heat core and the pipe with coolant and replug all this. the car stay in the garage about 2 hours. after this, I start the car and I go at my friend house (about 25min of highway). when I start the car the temp gauge was at 1/4. after 3-4 min when I take the highway, crazy hot heat during all the travel with no variation of temperature and the gauge not try to overheat.

the real test is tomorrow morning when the car was no running during all the night.

[juttin3]

Ok I have similar issue on b5 I mighta asked before but no heat when econ button is off. So no heat using defrostrer. What section do u look for heating and ac errors in vag. I just recently got econ heat working using Clr like someone mentioned. Also on my b5 it overheated and possibly busted head gasket or cracked the head. I used a sealer in coolant n that fixed leak. But clogged heatr core.

[tommy782]

sorry I don't no where is the section in vagcom for the econo. so this morning I try the car. in the first 10 min I have hot air only if I run. when I'm stop to a red light, slowly the air change to hot from cold. afternoon I output an other time the hose to the heatcore and still have air in the pipe... when I stop the car I heard the coolant and air in the piping behing the block.... what is the real thing to do to output all the air.... I think this is the problem because before the heat was coldest than now. now when I have heat, she is very hot!!

[SEATONE]

Man I did my car about a week or so ago. I bleed the system after filling the core and got some really hot air going, unfortunatly twas temporary. LOL... I will be attempting it again this week.

[tommy782]

me I think I found the veritable problem...... after each time I bleed the car, I drive it and everytime I have air bubble. I overheat too... and my plug on the cylinder #2 is stick in the head and I have misfire on the #2 cylinder... I think my head gasket is broke...

[42no_B6]

Hey wassup guys! I just bought an 02 a4 1.8t a week ago and discovered I had this problem along the drive home. I've read several forums about this heat thing and think this may have the fix, although I'm unsure if I'm doing this correctly. My air blows cold except when driving on the freeway at 3k rpm, which at this point only gets warm. I also noticed at times, intermittenly the temp gauge goes hot, then immediately returns to normal. Beliving this may be an air bubble I took the resevior cap off and cracked open the bleeder screw. At first there was air, but then came coolant. I noticed the coolant kept bubbling though and wondered if this was normal? I used to work on Honda's, and found that they do not bubble once all air is out. I also attempted Old Guys procedure of filling the outlet hose, but from the firewall. I then re bled and found the temp to only get warm, not hot. Thanks and sorry for the long reply!

[dewey527]

glad to hear you fixed it fletcher! another way to bleed the system is to just fill the resivoir with coolant, leave the cap off, and let the car run and get up to opporating temp. when it gets up there, the fans will start and thermastat allows the coolant to flow. keep the resivior at the full mark while its cycling through. youll also want to monitor your temp gauge to be positive you dont overheat. you can hold the rpms at about 2000 to help it get up to temp faster. do this for about 20-30 minutes and you should be golden. thats how a tech at my work did it for me when my turbo burnt through a coolant hose that was installed incorrectly.

I am assuming this should be done with the hvac completely off...Tried this process again this morning and had a lot of coolant bubbling out. Still only luke warm air with econ and recirc on. Here is a list of what has been done. Flushed system twice over the summer, just changed timing belt/coolant pump a month ago, tried filing the core directly like old guy stated, very hot lower hose only warm upper hose coming from heater core, tried the bleeder valve and a whole bunch of G12! I have yet to check the flap motor due to these codes

3 Faults Found:
01274 - Air Flow Flap Positioning Motor (V71)
41-10 - Blocked or No Voltage - Intermittent
00604 - Potentiometer Positioning Motor for Air Flow Flap (G113)
30-10 - Open or Short to Plus - Intermittent
01592 - Air Quality Sensor (G238)
37-10 - Faulty - Intermittent

but I would think there should be heat since I get a change from cold to luke warm. But I also hear a clicking sound behind the vents that happens about every second or two. So could it be a bad heater core or sensor motor or still a pesky air bubble? Sorry for bringing this up again and again, but my hands were pretty cold when we had temps in the teens a while back.

[GeoergeA402]

So if my line looks like this with the white crap all over it, it means what? Air in my coolant system? I'm already gonna have work done at the shop so might as well have this added to it.

[GeoergeA402]

^^^^BUMP, any help, anyone please!!!!!!!!!

[old guy]

^^^^BUMP, any help, anyone please!!!!!!!!!

If you aren't having any heating problems then don't worry about. That pink crusty stuff is just the result of a very slow leak coming from the bleeder valve. Clean it up, tighten the bleeder a little and you should be good to go. If you have a plastic bleeder valve consider replacing it with a metal one. The dealer "should" be able to help you with that.

[GeoergeA402]

could you possibly tell me how to tighten it? Its dark and cold outside and wont be able to see it.

THANKS

[old guy]

could you possibly tell me how to tighten it? Its dark and cold outside and wont be able to see it.

THANKS

5MM Allen wrench. If yours is a plastic bleeder be careful that you don't break it off.

[GeoergeA402]

Thanks a million "old guy" as that crusty crap has been driving me nuts for a LONG time now.

[walky_talky20]

Nevermind.

[old guy]

dewey527,
Sorry to hear that you still don't have any heat. I kinda skimmed through the thread again and have a few comments for you. In the pic you posted below you mentioned that you removed the top hose to expose the vent hole. Did you try removing the hose completely and filling the heater core with a piece of hose and a funnel? If not, try it. then use the funnel to fill the outflow hose.

If you want to check out the flap valves the easiest way to do it is to remove the glove-box. After you take the glove box out you can see the various control solenoids that control the flow between the upper/center/lower vents as well as the flapper that directs the air between the AC evap coils and the heater core. You can watch the actuating levers move as you change the settings on the HVAC. It is pretty intuitive. If you look at the components and watch the movement you can quickly figure out what controls what. You can also disconnect the plastic control arms and operate the flappers manually. Once you figure out what does what you can set the flapper manually to give you permanent air flow through the heater core. Then you can control the heat with the fan until you replace the defective actuating solenoid.

Good luck!