DA8

I e got a bit of a head scratcher. I'm getting the 3 beep overheat warning. It happens when car would normally be hot. Example, I drove on the freeway to Tacoma yesterday 60 miles 70+ mph outside temp was 70F and no problem until traffic stopped in Tacoma and the Beep-Beep-Beep. I turned off the AC and drove gingerly at moderate speeds 55mph about another 5 miles and it went off and back to normal. On city streets with stop lights it came back on. The temp gauge stays right at the middle line, maybe a half a line higher but hard to tell. I heard no jet engine fan, I never heard the fan.

Now a month ago my coolant reservoir outlet tube connection broke, so I replaced the reservoir. I put in a hot mixture of G12 roughly 80/20 because while the reservoir had been leaking the last few months I'd been adding just water so I wanted to restore the mix. After replacing the reservoir everything seemed to be fine. So I suspected too much G12 and not having proper cooling capability. I added strait water to the reservoir in Tacoma by squeezing plastic water bottles into the reservoir and ejecting some of the mix. This did not help and the warning continued to come on in the same warm circumstances driving home.

I have a Bluetooth scanner so I plugged that in while driving. It showed no codes. It can monitor the coolant temperature and it was showing 90C, 194F. That temp and above is about where the warning comes on. It never got above 199F and got as low as 185F while driving home. Any ideas?

Panelhead

I had the temp gauge peg out while on the freeway. Expected a boil over. The nipple on the reservoir had cracked. The tank was low. Topped off and it went back to normal.
The fan controller may be your issue. If it is hot the fans should be running. The thermostat sticking would cause a boil over quickly.
The gauge does not reflect temperature on D3 and other European cars. Goes to the middle and stays there. When it moves it goes to max and it indicates a serious issue.

DA8

Yea the gauge seems to go to the middle and stay there. It has never gone to peg mode thankfully. I haven't been able to determine if the fans are working. I did not hear them. Any suggestions how to check the fans for proper operation? I have vag-com at home and will hook it up tonight. What is this fan controller? I assumed the fans were controlled by the ECU.

The.aviator2

Could it be that your coolant level is getting low?


I've had a similar problem to yours and discovered that my coolant level was getting low slowly as a result of small leak that I barely noticed.


If you have access to VCDS you can try a scan to see if your coolant temp sensor is ok.

DA8

OK guys come on, I need some help here. I checked it out more this afternoon with vag com to verify fan operation. BTW coolant level is fine, as I mentioned in my post my one theory was that coolant had too strong a G12 mixture.

So on vag there is NO ERROR CODES

Under test blocks group 135 monitors fans 1 & 2. I warm up driving around block till normal temp 90C with no accessories on. Fans show 10.2% activation, but I physically looked at them and there is no movement. Park and idle the temp rises 92-93-94 then warning light comes on on dash. Then fans come on but not much if at all. They will go up to 14.9% which when physically checked means decent movement from the zero movement at 10.2%. I saw fan 2 bump up to 49% for a minute, but did not really stay there. Temps still kept up around 93-96.

Now turn on the cabin heater on high and whamo! the fans come on 60-70% jet engine wind up. They calm down and stay on around 40-50% with heater on until the coolant temp goes down to around 87C, that is where the warning light on mini mmi goes off.

It seemed weird to me that the fans only really are working when the heater is on, they should be coming on before the warning light ever gets triggered and keep the coolant temp steady. The heater is a fan in itself on the cooling system which only cools coolant more. But the fans don't seem to be working much with the heater off. Indeed when I turn the heater off the fans stop and go back to the 10.2% value.

And why does group 135 fan activation say 10.2% but there is no fan movement at that value?

Any ideas? I read the post about the coolant sensor going out and symptoms were fans in jet engine and temp gage in peg hot mode. I do not have those symptoms.

This just seems like a mild case of getting too warm. I am concerned for when it gets hot out (right now 45 and rain in Seattle) and I just want to fix the annoying beep! mini mmi. Could my G12 mixture be faulty? I don't have much faith that a rich mixture of G12 would cause slight overheat or fans only working significantly when heater on???

Shamoye Lewis

Put on ac and see if the fans go fast, also if you think at 10% the fans not spinning try sticking your finger in the fans for a minute or two, don't think you will be happy, D3 don't give fan issues normallyou, could just be your have a liquid circulation issue, vag can't detect that, you will need to let the car cool and drain the system, maybe your radiator cores blocked or thermo ceasing...anything mechanical needs physical inspection....

MP4.2+6.0

Basic missing fact: miles on car. Read on.

When you are turning on "heater" you are turning on HVAC, unless you go in and specifically switch on Econ mode with controls shown in display. Thus fans probably kicking up because you basically turned on AC, even if elevated temp. Try switching to Econ mode and see if they back off.

I don't think coolant mixture has anything to do with it. Get to a cold enough part of world and they can run at ⅔. All it really does is in high concentrations is reduce the ability of the system to transfer heat from a metal surface to the mixture. Might get slight hot spots in heads under very extreme conditions (like Autobahn flat out, 100F), but at idle or even regular running you are usually using a small fraction of motor rated power.

1. Confirm fan operation. Some fan movement just based on operating temp car. 50 % gauge may have none at times. By 60% or ⅔ typically running. A lot of fan when you kick on HVAC.

2. Once you do #1, my guess is thermostat. No real way to be 100% sure. Indirectly if it has never been changed, or was changed 70-100K ago or more, pretty likely. So what is history? Was timing belt ever done? Was it the full job, or just a belt?

Could be other lower probability guesses. Sensor, but description sounds like it basically reads. Blown radiator core maybe. Fans themselves if both not spinning up (make sure you see both go when AC on and it is at full operating temp). Thermostat would be the more likely answer here, particularly if confirmed by decent miles on it already.

DA8

Fans are definitely not spinning at 10.2%. That is the standard low value on VCDS group 135. I physically checked multiple times looking down into fans with a flashlight. I can see the blades are still. When it bumps up to 14.9% the spin moderately, but not at all at 10.2%.

They spin when cabin heat is turned on well. I have not tested with AC, but the problem occurred (warning on mini Mimi) with AC on after traffic stopped after driving 60 miles at freeway speeds.

I've no reason to suspect a buildup or bad thermostat. Circulation seems fine with good heat blowing from heater and by monitoring exact temp with VCDS I can observe incremental cooling changes by degrees when air flow is applied be it cabin heater fan, moderate vehicle speed air flow or when the fans do actually work.

I changed the thermostat and water pump with Tbelt at 90K, 143k now. Everything was clean inside, I've flushed, and keeps it all clean with good G12. When I just replaced the reservoir a few months ago I also replaced the hose that goes out bottom reservoir to bottom engine by dipstick. Interior of hoses and reservoir are clean with no buildup.

I do not suspect thermostat because to my understanding it would fail closed or open. If closed it would have a rapid overheat which I do not have. If open it would run cold or not heat up fast enough which I do not have.

I am most suspicious of why the fans do not run with 10.2% signal and why fans only seem to run when cabin heater is on. It seems like everything would be fine if the fans ran in a more controlled manor to keep the temp constant.

MP4.2+6.0

Thermo can also fail mid way, especially if supporting frame to center portion cracks and it can't mechanically move correctly. Been there, seen that specifically on prior Audis with original or quality/OES (Behr, etc.) parts. A good percentage of thermos I have had issues with over the years turn out to be mechanical in some way, rather than the old tired bimetallic issues. Also when thermo is closed, heat circuit still circulates/runs, so any diagnostics related to that aren't very relevant as far as lots of heat inside cabin or water temps in heater circuit. Heater related sense of temp only really relevant if acting cold blooded/slow to warm--when you then suspect failed open.

Simple test. Get to op. temp. Turn on AC. If both fans kick up to decent speeds, and especially if you can ever heat it to jet engine mode (such as covering front of car with plastic like a big trash bag), issue isn't in basic fans. Could still be in fan control but not a big failure area for D3's like it used to be on Audis years ago. Once confirming basic physical fan function I would return to thermo or to blown radiator core scenario. Coolant sensor is cheap so you can try that, though nothing really says it has an issue; just obviously way easier than radiator or thermo and the sensors are a known fail point over time.

Last/edit: you are testing it with A/C. You have to turn it off in controls to not be. Remember it typically still runs a bit even if just to dehumidify, while "heater" is warming air. Basic theory of "climate control" where the two are integrated. Running defrost function with heat is where it is most obvious, but it is the typical design. Turn off A/C w/ Econ setting to see if then fans turn off, which I think you are probably confusing with the "heater."

DA8

Thanks MP, I hear what you are saying. My instinct is not telling me it is the thermostat or radiator, but I am open to where the basic evidence points.

Problem is cooling function seems fine when there is air movement. I.E. HVAC on not in econ mode fans go to 60-70% and water temp goes from 96 to 87 and warning light goes off. Freeway driving 60 miles at 70 degrees ambient no problem until I come to a stop.

My thought is that if the ECU gets a signal from the temp sensor that the temp is +90 that should trigger the fans to come on or up in speed and cool. I'm sure the ECU even knows when you are not moving and also increases fan rate based on lack of motion air movement.

Let's just say the thermostat was stuck closed a bit or the radiator was having some blocking issues. The ECU would not know that, but it would know temps were getting hot and increase fan speed.

The warning light is coming on and the temp is rising above 90 and the fan is not coming on. It says 10.2% but it is not moving. It moves only when HVAC is turned on. Isn't the obvious problem that the fan is not coming up to speed properly? Why would that be?