Car overheating, coolant light on, but coolant res is full?!?!

[b6Hate4]

Car started over heating today, changed upper sensor and flushed with new coolant, drove over an hour fine on the highway, now overheating and coolant light is on, but my cooolant res is full and coolant sprays out when i loosen the screw on the hardline above the IM. Halp :(

[RSicks]

How's the water pump? What codes are being thrown?

[b6Hate4]

Cant comment on either right now as im stranded. FTL.

[msharifi]

Did you mix 50/50 coolant and water?

[b6Hate4]

[QUOTE=msharifi;8785678]Did you mix 50/50 coolant and water?[/QUOTE


More like 70% coolant to 30% water

[Charles.waite]

Could be the reservoir cap isn't working. Could also be the water pump.

[msharifi]

If the cap was bad coolant would spill from the Bottom of the coolant tank. I think it wasn't mixed With correct amount of coolant and water.

[elewsader]

If the cap was bad coolant would spill from the Bottom of the coolant tank. I think it wasn't mixed With correct amount of coolant and water.

it's not necessary to have 50/50, his composition ratio should be perfectly fine for current temps; there's probably some blockage/flow issue, or failed water pump.

[jjvwg]

Did you make sure you got all of the air bubbles out of the system? I've heard these cars can be picky and throw warning just from one of those.

[b6Hate4]

Did you make sure you got all of the air bubbles out of the system? I've heard these cars can be picky and throw warning just from one of those.

Is there any way to get the bubbles out other than the bleeder screw on top of the hard line?

[RSicks]

I used to work at a radiator wholesale warehouse and what your describing briefly I would think is either water pump or clogged radiator. I have had customers flushing rads and the gunk loosens up and clogs it. Most of the time it's from power flushes. I wish I could give you the magic answer but something like that you will have to get dirty to find out.

[POPO]

Not to thread jack but I have recently been experiencing the same problem, more so when I run the a/c. When I switch to heat and blast it, the temps come back down. I need to figure out what my problem is.

[b6Hate4]

Not to thread jack but I have recently been experiencing the same problem, more so when I run the a/c. When I switch to heat and blast it, the temps come back down. I need to figure out what my problem is.

nono, threadjack away, hahah your describing my symptoms! On this 95 degree day I had to blast the heat to get home

[Tanzimur]

sounds exactly like a closed t stat not wanting to open......

[jjvwg]

sounds exactly like a closed t stat not wanting to open......

X2

[h82loze]

Is there any way to get the bubbles out other than the bleeder screw on top of the hard line?

Bleed from the upper heater core hose

[stelvio]

^ this. Make sure you bleed the system from the upper heater core beside the battery. Also thinking the T-Stat has retired..

[Rausch]

Are your cooling fans coming on?

[b6Hate4]

Are your cooling fans coming on?

now that you mention it no! they are not.

I have a new t-stat sitting at home, ill have to try and swap that out tonight.

[Rausch]

I would look into your fans not turning on before you just put in the new t stat.

[b6Hate4]

I would look into your fans not turning on before you just put in the new t stat.

Well, this would also explain why im not overheating on the highway.

[b6Hate4]

Question for probably OG, if the lower CTS (the one that controls the fans) gets disconnected, should the fans kick on?

[old guy]

According to the Mapped cooling strategy outlined below a failed lower sensor should cause the first fan to run.

Engine Coolant Temperature (ECT)
Sensor G62 and Engine Coolant
Temperature (ECT) Sensor
(On Radiator) G83

These sensors both operate as negative
temperature coefficient (NTC) sensors. The
coolant temperature set points are stored in
the Motronic Engine Control Module J220
in the form of maps.

The actual coolant temperature values
are registered at two different points in
the cooling circuit and indicated to the
Motronic Engine Control Module J220 in
the form of a voltage signal.

* Coolant actual value 1 is measured at
the cylinder head coolant outlet by
Engine Coolant Temperature (ECT)
Sensor G62 located in the upper level of
the coolant distributor housing.
* Coolant actual value 2 is measured at
the radiator by Engine Coolant
Temperature (ECT) Sensor (On Radiator)
G83 before the radiator coolant outlet.

Signal Utilization

Comparison of the specified temperatures
stored in the maps with the coolant actual
value 1 temperature gives the pulse-width
modulated signal for the application of
voltage to the heating resistor in the Map
Controlled Engine Cooling Thermostat F265.
Comparison of the coolant actual values
1 and 2 is the basis for activation of
the electric Coolant Fan V7 and Coolant
Fan -2- V177.

Effects of Failure

If Engine Coolant Temperature (ECT)
Sensor G62 fails, a defined substitute value
of 203°F (95°C) is used for coolant
temperature control and the first fan speed
stays activated.

If Engine Coolant Temperature (ECT)
Sensor (On Radiator) G83 fails, the control
function remains active and the first fan
speed stays activated.

If a certain temperature threshold is
exceeded, the second fan speed is
activated.

If both sensors fail, maximum voltage is
applied to the heating resistor in the Map
Controlled Engine Cooling Thermostat F265
and the second fan speed stays activated"

[b6Hate4]

OG you do too much for these forums, thank you.

I scanned my car, although not with vag-com, and got no codes for the fan control module..I guess a course of action should be..

-unplug lower CTS and see if either of the fans come on
-change thermostat
-measure voltage at the fans with my trusty fluke clamp meter....

[old guy]

If the thermostat fails to open it doesn't matter if the car is on the highway or sitting still. There will be no circulation through the radiator and the block is going to overheat. If the car is only overheating at idle or low speed but doesn't overheat on the highway that is an indication of a problem with the cooling fans and not the thermostat. If it only overheats when there is low airflow through the radiator I would look at the fans/lower CTS/fan control module first.

[b6Hate4]

Okay UPDATE with a little more info:

- Fans come on only when I turn on heat/AC
-I unplugged lower temp sensor and fan 1 did not come on.
-Monitoring actual coolant temp on the HWY on the way home I saw between 173* and 193*, once i got off, and slowed down I saw temps as high as 210*

-Before getting on the highway, the car died. Coolant temp was normal, car just shut off, but started right back up.
-No codes related to any modules but again this has not been confirmed with vag-com.

[old guy]

Do both fans come on with the AC or only 1?

How and where are you monitoring the coolant temperature? Your highway temps actually sound a bit low. Clicky click (Some informative stuff on mapped cooling systems). If I check the temperature on the upper hard pipe of my motor at idle it typically reads around 220°

[b6Hate4]

You know what? I take that back. I just went outside and started my car to be 100% sure the information im putting in this thread is accurate. Right now, neither fans are coming on, heat OR ac, nothing.

Should also add while I was monitoring my highway coolant temps I had the heat running full blast.

I was monitoring the coolant temp via the obd2 with a hand scanner that has the ability to display real time information of my maf, engine temp, Iat's ect..

[old guy]

You know what? I take that back. I just went outside and started my car to be 100% sure the information im putting in this thread is accurate. Right now, neither fans are coming on, heat OR ac, nothing.

Should also add while I was monitoring my highway coolant temps I had the heat running full blast.

I was monitoring the coolant temp via the obd2 with a hand scanner that has the ability to display real time information of my maf, engine temp, Iat's ect..

So it sounds like your overheating is being caused by a lack of air circulation (no fans) at idle. Have you checked your fuses? Could also be a problem with the fan control relay or fan control module.

[b6Hate4]

So it sounds like your overheating is being caused by a lack of air circulation (no fans) at idle. Have you checked your fuses? Could also be a problem with the fan control relay or fan control module.

My voltage meter right now is at work, I think I need to leave the Audi at home tomorrow and take the truck, once I get my meter I can test the continuity of my fuses. If not that, the I guess I'll just have to replace the relay and control moule, starting with the cheaper of the 2 first.

[ECS Tuning-Audi]

When was the last time you bled the system? Air bubbles will cause your temp to fluctuate. Both fans should be on high at idle when the thermostat opens.

Jason

[b6Hate4]

When was the last time you bled the system? Air bubbles will cause your temp to fluctuate. Both fans should be on high at idle when the thermostat opens.

Jason

Both fans are dead, not coming on (on their own). They come on and shut off at random and do not operate when i turn on the AC or when fan switch is pulled.

1 more update. I pulled the ECU out and looked at the fan relay 219, dry as a bone. Other than water damage do these really go bad? I know anything is possible but a relay would easier then the FCM! I guess Ill just have to do them both.

[old guy]

Relay 219 in the ECM box is the ECM power control relay. The fan control relay is located underneath the dash on the drivers side. The 219 is often called the fan control relay because when it gets wet it powers up the circuit that supplies power to the fan control relay and causes the fans to run. Unfortunately my daughter currently has my notebook that has the Bentley loaded on it. I don't recall for sure which one is the fan control relay. Hopefully someone with a Bentley will chime in. If not I will have her bring the notebook by tomorrow so I can look it up for you.

[b6Hate4]

Is it fused? I checked the fuses in the door jamb and all rang out with continuity, but tomorrow I could drop the dash and continue testing if there is anything to be tested with a multimeter.

If you could check that you would be going above and beyond O.G.... Always appreciate your efforts

[CardFan]

Not for sure which one OG is referring to, so here's some info from the Bentley. Hope this helps.

[b6Hate4]

Not for sure which one OG is referring to, so here's some info from the Bentley. Hope this helps.

Thanks! Unfortunately what you posted is more complex than what my brain wants to comprehend at the moment hahah, Ill have to wait untill tomorrow to dive into schematics.

[diagnosticator]

Well, this would also explain why im not overheating on the highway.

Correct. If it does not overheat on the highway, but overheats in stop and go traffic, then the rad fan is not working. Not a t-stat problem. The fan on the driver's side is the radiator cooling fan. The fan on the right side is the A/C condenser cooling fan and only runs when the A/C is in cooling or AUTO mode. If coolant overflows from the expansion tank when the cap is loosened, then there is air still trapped in the cooling system. I don't understand why so many guys have trouble purging air from the cooling system after maintenance, and repairs. I just fill the system and allow time for the coolant to slowly drain into the system may take half an hour. With the bleed port plug removed, watch for coolant to appear and rise in the hard pipe. when the coolant fills the pipe, replace the bleed port plug then top off the tank and replace the tank cap. Start the engine and increase idle speed to ~2000 RPM for two min. Turn the engine off and allow the system to cool down for 1/2 hour. Top up expansion tank, replace cap and drive car.

[ECS Tuning-Audi]

It could also be your cooling fan sensor. If I remember correctly its located on the driver side lower radiator hose.

Jason

[b6Hate4]

It could also be your cooling fan sensor. If I remember correctly its located on the driver side lower radiator hose.

Jason

That is correct, but when this sensor is disconnected, the rad fan should automatically come on, such is not the case.

[old guy]

I guess my memory isn't what it used to be. The B5 has a high speed and low speed fan control relay underneath the dash on the drivers side. The B6 does not. The B6 fans are controlled completely by the fan control module. There are two fuses associated with the system. there is a 5 amp control voltage fuse on the fuse panel located on the drivers side of the dash and there is a 40 amp fuse located underneath the drivers side dash that provides power to the fans. The fan control module gets activated with the ECM power control relay via the 5 amp control voltage fuse. Input is also required from the lower CTS. I don't think fuses are your problem.

You mentioned that your fans now come on and off at random intervals. That sounds more like a frayed/broken wire than a relay control problem. Take a very close look at the connections on the fan control relay for any signs of damage. Another possibility is that the fan control relay is defective.

Good luck!