Heat Issues

[dizzlesizzle]

So its been a colder and snowier then normal winter up here in New England this year, so a few mornings I went outside to warm up the car to defrost the layer of ice on the windshield and to get the inside of the car warm before my drive to work. It seems that the heat doesn't really get warm while the car is sitting in neutral (6 speed). The thermostat is sitting dead middle so the car is def warmed up, soon as i start driving the heat is plenty warm though. If i take the car out of gear and coast down a hill, i can feel the heat cut out again. I normally drive with the defrosters (which runs the AC) because i rather not have the air blowing at me. I even tried changing it back to the auto setting with 75 degrees and it still does the same thing. Anyone else have this issue while the car is sitting in neutral?

[schirm]

Someone else was having this issue the other day. I am trying to find the thread.

http://www.audizine.com/forum/showth...tio-at-low-RPM

Did you get your water pump replaced under recall.

[S4'ed]

My S4 does the same. I have the "water-running/gurgling noises behind the dash" problem, which are air bubbles in the coolant lines to the heater core. When the air pockets get big enough (at idle they are not forced thru the heatercore), it then blocks coolant flow thru the core and you get no heat. At higher RPMs, when you drive the car, the waterpump has enough pressure to push the air pocket thru the core (the gurgling noise), and the heater then puts out some warm air.

Do you have the gurgling noise?

[dizzlesizzle]

Yeah I get that water-running/gurgling noise when starting the car and making a slight turn. Not sure if the water pump has been replaced I know the thermostat has been before I purchased the car. I will have to check since its still under CPO. Any TSB for this?

[S4'ed]

The cooling system needs to be properly bled to get the air out. The water-pump is fine, it is not the cause of the no-heat and gurgling noise problem.

[schirm]

The cooling system needs to be properly bled to get the air out. The water-pump is fine, it is not the cause of the no-heat and gurgling noise problem.

I get the gurgling noise every morning when I leave my house as soon as I go on the first bend. I have no heat issues at all.

[S4'ed]

IF you have the gurgling noise AND you let the car idle for a while, your heat will go away. If you get the engine RPMs up, as in driving the car, the heat will work again.

[jlaudio]

IF you have the gurgling noise AND you let the car idle for a while, your heat will go away. If you get the engine RPMs up, as in driving the car, the heat will work again.

I have the gurgling noise on cold start up and i don't have these issues. My heat works like it should. I don't think the two are related.

[Acejam]

I've noticed this somewhat. In 14k miles, I think I've heard the "gurgling noise" maybe 2-3 times. However when I begin to drive the car, the air that does come out of the vents is nice and warm. I'm wondering if the car is simply designed to not blow any air through the vents unless the air is at the requested temperature.

[Crucible35]

^^^this sounds like you have an issue with your blower. I had to have mine replaced about a year ago when the heat wouldn't start blowing warm air into the car for about 10-15 minutes after I got on the road. The car was completely warmed up, could even feel warmth from the dash vents but wouldn't blow. Replaced the blower and all is well. The rushing water sound isn't the same issue. As mentioned above, you can get some air in the cooling system that may need to be bled, but it could also indicate you have a leak in the system. How's your coolant level?

[Acejam]

^^^this sounds like you have an issue with your blower. I had to have mine replaced about a year ago when the heat wouldn't start blowing warm air into the car for about 10-15 minutes after I got on the road. The car was completely warmed up, could even feel warmth from the dash vents but wouldn't blow. Replaced the blower and all is well. The rushing water sound isn't the same issue. As mentioned above, you can get some air in the cooling system that may need to be bled, but it could also indicate you have a leak in the system. How's your coolant level?

Coolant level is perfectly fine. Car is a 2014 S4 with 14k miles. It's in perfect condition. I'm 99% confident there is nothing wrong here - the car is simply smart enough to not blow cold air. It begins to blow warm air very quickly once I begin moving. I know BMW's and other cars do this as well. Keep in mind I'm also using "auto" mode. If i turn auto mode off and turn the blower on manually, air comes out no problem.

[dizzlesizzle]

Coolant level is perfectly fine. Car is a 2014 S4 with 14k miles. It's in perfect condition. I'm 99% confident there is nothing wrong here - the car is simply smart enough to not blow cold air. It begins to blow warm air very quickly once I begin moving. I know BMW's and other cars do this as well. Keep in mind I'm also using "auto" mode. If i turn auto mode off and turn the blower on manually, air comes out no problem.

Yeah mine is a different issue. I know the car if warmed up to proper temp and heat only goes away when idle. I will have to agree with the air in the line. I am bringing it in for oil change next week and let them know.

[sangaroo]

Yeah mine is a different issue. I know the car if warmed up to proper temp and heat only goes away when idle. I will have to agree with the air in the line. I am bringing it in for oil change next week and let them know.

Did you end up finding out what happened?

[dizzlesizzle]

Did you end up finding out what happened?

So actually just got around to bringing it in for this issue. So here is the update, they originally fixed some hose or vacuum line they thought was the issue...that didn't fix it. I told them about the gurgling noise and possible air bubble and should bleed the system...well they did that and still cool air at idle. They contacted Audi, they told them that it could be the thermostat and should be replaced. That's where we are now, still no call back or update if that was the fix. I will let you know. Just to add, the thermostat was replaced for the recall, so I dunno...maybe it could be that, they said it is getting stuck at low RPMs.

[cW6mT mKviGLi]

I'm not sure if the water pump on these cars are mechanical or electrical. If it's mechanical it will have a higher flow rate as the motor rpms increase. If it's electrical I'm assuming there's some sensor in which input is measured and you have a process output to speed up or slow down the flow rate of the pump resulting in the required coolant flow rates.

I'm thinking there is a possibility that the water pump could be failing and/or if it's electrical the input parameter/sensor responsible for the output value. At idle your not circulating enough coolant through the heat exchanger to extract heat for the blower to displace warm air into the cabin.

I'm also thinking it could be an issue with the climate control air mix valve but it only happens at idle so I'm thinking not.

So as soon as the motor revs beyond idle the vents blow warm again?

[BernanksBeard]

CW brings up a good point. The study guide shows an electric pump for the heater loop.
There is still a belt driven water pump, right under the front of the supercharger, but there is an Auxillary pump for every coolant loop in the car.

[Acejam]

^^^this sounds like you have an issue with your blower. I had to have mine replaced about a year ago when the heat wouldn't start blowing warm air into the car for about 10-15 minutes after I got on the road. The car was completely warmed up, could even feel warmth from the dash vents but wouldn't blow. Replaced the blower and all is well. The rushing water sound isn't the same issue. As mentioned above, you can get some air in the cooling system that may need to be bled, but it could also indicate you have a leak in the system. How's your coolant level?

Coolant level is perfectly fine. Car is a 2014 S4 with 14k miles. It's in perfect condition. I'm 99% confident there is nothing wrong here - the car is simply smart enough to not blow cold air. It begins to blow warm air very quickly once I begin moving. I know BMW's and other cars do this as well. Keep in mind I'm also using "auto" mode. If i turn auto mode off and turn the blower on manually, air comes out no problem.

I'm at 23k miles now and my coolant level is down a bit below the "low" line - a solid inch or so. I'll be taking the car in for service soon for my 25k, and I'll be sure to mention it to them as well.

Now that it's cold - I start my car and let it warm up for up to 1 minute, but no longer than that. Occasionally I will still get the water gurgling noise behind the dash.

[rcz22]

I also have the same issue - the dealer has been good at helping me although I think they are following a troubleshooting script. First time in they replaced the thermostat, that was not the root cause. A week later they replaced the water pump actuator, which again was not the root cause. On Monday I'm bringing it back to have the whole water pump replaced. If that doesn't work I maybe a coolant flush? That seems to work from some of the posts here.

The service adviser I'm working with has been great, I'm confident it'll get fixed...for now I do the same thing, when cold air starts blowing - rev till about 3500rpm for 10seconds and that usually gets the heat flowing again.

[hotleadsingergu]

IF you have the gurgling noise AND you let the car idle for a while, your heat will go away. If you get the engine RPMs up, as in driving the car, the heat will work again.

That's a generalization. Coincidence, not causation.

The gurgling noise in cold is a well-known thing that Audis do, even brand-new and working perfectly. It doesn't necessarily mean there's air in the lines as much as "liquid is moving". My car is 6 months old, has the occasional water-rushing sound, and the heat works perfectly both idling and not. I let my car sit in my grandparents driveway warming up for 15 minutes last week and the heat was coming out nice and hot when I got in.

[dizzlesizzle]

well just got the car back, it was a faulty thermostat. Plenty of hot air now at idle once they replaced it. Guess it wasn't opening or closing correctly at idle, but once moving with higher RPM's it functioned fine.

[BernanksBeard]

Engine thermostat? Or a thermostat for the HVAC system?
If the engine thermostat was stuck open, the coolant wouldn't get up to full operating temps (which u said it did) and stuck closed wouldn't bother the HVAC system...

[dizzlesizzle]

I believe the engine thermostat since they had to remove the supercharger to replace.

[S4'ed]

Your problem was fixed because they had to bleed the air out of the coolant system when they refilled it, after the thermostat was replaced. A stuck closed thermostat will give you all the heat you can handle.....if the thermostat is stuck open, the engine temperature would drop below normal. There was nothing wrong with your old thermostat......

[dizzlesizzle]

Your problem was fixed because they had to bleed the air out of the coolant system when they refilled it, after the thermostat was replaced. A stuck closed thermostat will give you all the heat you can handle.....if the thermostat is stuck open, the engine temperature would drop below normal. There was nothing wrong with your old thermostat......

I hear what your saying...i was thinking the same thing. But they said they tried bleeding the system before replacing the thermostat, I had asked them to do that first...I even copied and pasted your reply on post #3 and emailed them...which they did and still no joy.

[dizzlesizzle]

The only thing then I can think of, is when said they bled the system before replacing the thermo, that did they didn't actually bleed it right maybe?

[S4'ed]

There are two ways to bleed this system :
1) Use the 2 bleeder screws on the supercharger, and the bleed at the heater hose (under the cowl cover). This method does NOT always get all the air out.
2) Use a vacuum coolant refill tool (like how the factory fills the coolant), but you have to dump all the old coolant out first, before you vacuum refill it.

My guess is that they tried method #1 first, which perhaps did not get all the air out, and that's why it didn't solve your no-heat-at-idle problem.
Then, later, the tech decided it must be the thermostat, and dumped all the coolant out, and successfully refilled the system, air-free, with the vacuum refill tool....and now solved your no-heat problem.

[dizzlesizzle]

My guess is that they tried method #1 first, which perhaps did not get all the air out, and that's why it didn't solve your no-heat-at-idle problem.
Then, later, the tech decided it must be the thermostat, and dumped all the coolant out, and successfully refilled the system, air-free, with the vacuum refill tool....and now solved your no-heat problem.

I'm going to have to agree with you, I was thinking the same thing. I've had nothing but problems with the dealership I brought it to...I actually have AoA involved with another matter, still waiting to see the outcome of that issue. Don't think I will be returning to them after all this.

[BernanksBeard]

I haven't seen the thermostat in person nor do I know how they typically fail, but the self study guide shows that heater core coolant returns to the thermostat. So it's not impossible that a failing thermostat could effect the heater circuit only. I would say unlikely but possible.

[jygesq]

Your problem was fixed because they had to bleed the air out of the coolant system when they refilled it, after the thermostat was replaced. A stuck closed thermostat will give you all the heat you can handle.....if the thermostat is stuck open, the engine temperature would drop below normal. There was nothing wrong with your old thermostat......

if thermostat stays open too quickly you get no or little heat, if it stays closed car overheats. Replacing thermostat on the car was the right call, you do not want it to stay closed. Early b8's had thermostat problems , his is 2010. Just be thankful thermostat did not stay stuck closed.

[S4'ed]

His thermostat was fine, he said had normal engine operating temperatures when his heater output was weak.

[dizzlesizzle]

Here are the notes on my invoice:

Heat at RPM but at idle the temp from center vents drops to 70 degrees. GFF to test climate vent motors, checked coolant level and checked DTCs. Tried bleeding the system, same result. Coolant house leaving heater core is cooler than input. Removed heater core hoses and flushed heater core for 30 min in both directions. Refilled cooling system, retest, still cool at idle...even after highway test drive to help bleed system. (TAC 1540112 made)

Advised to test if combustion gasses are entering cooling system. used block tester, negative for pressure spikes and combustion gasses. TAC then advised to replace thermostat. Removed supercharger and replaced thermostat. Refilled cooling system and retest. System is better after bleeding - idle heat temp is around 115 degrees. System is now working to spec.

[jygesq]

His thermostat was fine, he said had normal engine operating temperatures when his heater output was weak.

guess it was not