Performance Malfunction in Cooling System

[msharifi]

Fixed! a BIG THANKS to OLDGUY for helping me out. I replaced the Thermostat and all is fine. I replaced first T-Stat at 108K miles Behr brand car has 145K with failed T-Stat that was opening too early. Fans were running the minute I started the car in cold temp and took very long time for temp to show normal temp at 12:00.

Hi all,

Monday when I turned on my car it took way too long for the car to reach normal on the gauge even 20 min driving it wasn't even half way couple of times it came back to middle and went down a bit. car doesn't overheat so I scanned it and got this :

18613 - Performance Malfunction in Cooling System
P2181 - 008 - Implausible Signal

Coolant sensor the green one replaced 6 months ago which I got from dealer.

I also notice my fans are not running.

Could it be lower radiator coolant sensor the black one? Fan control module? Does the black coolant sensor control fans?

I was reading this post pointed to Fan Control module but my car doesn't over heat.

http://www.audizine.com/forum/showth...rking-overheat

Ross Tech:

http://wiki.ross-tech.com/wiki/index...3/P2181/008577

Thanks

[sinistervii]

Thermostat is stuck open, causing the car to take 20 minutes to get to somewhat a hot temp. Then when you drive it the water pump it turning faster causing the coolant to cool faster through the radiator. which means it cools the coolant. there are patches I would describe or cool coolant and hot coolant. when you drive the gauge drops? when you turn on heat, the gauge drops? This would be the Thermostat failing. Our thermostats have fail safes to where they wont close causing our cars to overheat. I had he same problem lat month. I change temp sensors which didnt work and went to thermo. (if you are loosing a baby amount of coolant that you notice tke a flash light and check in between the first and second runner on your manifold and you might see a little bit of crusty pink stuff there. Thats where your thermo is located.)


If that isnt the symptoms on driving and gauge drops then check the heater core and flush. There is a DIY out there. Just Google it.

You can also have air in your system. Might need to bleed if you've had a flush latley.

[msharifi]

I'm going to change the black coolant sensor on the bottom of radiator which controls fan and temp gauge. I had replaced the Thermostat not too long ago brand new from Audi also the green temp sensor. I just did a flush cause coolant was nasty looking. After couple long drives temp gauge comes to normal. I don't get a code for thermostat which makes me think it's not the issue.

[old guy]

Sure sounds like the t-stat. Do you have reduced heat while the temperature gauge is reading low? The black sensor isn't going to cause the engine to not heat up.

There is one thing you can try to confirm that it is the t-stat. Unplug the t-stat heater and see if the engine heats up normally or if it still takes 20 minutes. If it heats up normally then we need to figure out why the ECM is forcing the t-stat open. If it still takes 20 minutes to heat up you will need to replace the t-stat.

[msharifi]

I dont have reduce heat when the gauge is reading low. If the black sensor is not reading correctly doesn't that send wrong info to the gauge and T-stat? I clear the code and didn't come back.

[msharifi]

Sure sounds like the t-stat. Do you have reduced heat while the temperature gauge is reading low? The black sensor isn't going to cause the engine to not heat up.

There is one thing you can try to confirm that it is the t-stat. Unplug the t-stat heater and see if the engine heats up normally or if it still takes 20 minutes. If it heats up normally then we need to figure out why the ECM is forcing the t-stat open. If it still takes 20 minutes to heat up you will need to replace the t-stat.

Disconnect T-Stat heater? you mean unplug harness plug from T-Stat?

[old guy]

I dont have reduce heat when the gauge is reading low. If the black sensor is not reading correctly doesn't that send wrong info to the gauge and T-stat? I clear the code and didn't come back.

The gauge gets its signal from the rear green 4-pin coolant temperature sensor. The ECM activates the t-stat heater based on input from numerous different sensors.

Disconnect T-Stat heater? you mean unplug harness plug from T-Stat?

That is correct. the t-stat harness is the connection to the wax heater embedded in the t-stat.

[msharifi]

What does the black coolant sensor do?

The car is my daily driver is it safe to say T-Stat needs replacing?

[old guy]

What does the black coolant sensor do?

The car is my daily driver is it safe to say T-Stat needs replacing?

It sends a signal to the fan control module and is used by the ECM for a rationality check. Before you replace the thermostat try what I suggested with the t-stat heater and see if it changes the warm up time required.

[customa4]

Black coolant sensor? Where is that?

[old guy]

Black coolant sensor? Where is that?

Lower radiator hose. It measures the temperature exiting the radiator.

[customa4]

I thought it was grey?

[msharifi]

Sorry gray when it gets dirty looks like black.

[customa4]

Sorry gray when it gets dirty looks like black.

Ok, I thought I was missing something. I remember someone else referring to a black coolant temp sensor and someone replying that there was a black CTS on a different model or something. Understood

[DiertyEuroSpec]

Lol yea it's the black / grey one, otherwise known as lower CTS

[msharifi]

It sends a signal to the fan control module and is used by the ECM for a rationality check. Before you replace the thermostat try what I suggested with the t-stat heater and see if it changes the warm up time required.

Here is my issue with doing that the gauge showing cold at start up to 40 min it starts up back to normal city driving and if I turn off car turn it back on its back in middle. removed the harness from T-Stat didn't do anything beside throw a code 17700 Map controlled engine cooling thermostat (f265) open circuit P1292-004 no signal/communication intermittent.

I don't get the code 18613 - Performance Malfunction in Cooling System P2181 - 008 - Implausible Signal anymore after I erased it.

Once the car is warm enough tempt stays in the middle and doesn't go down.

[old guy]

Let me make sure I understand what you are stating. The gauge takes 40 minutes to reach the 12:00 position. but if you turn the key off and back on when it is reading low that it will go straight to the 12:00 position. Is this correct?

Do you have any way to read temperatures? Any type of temperature probe or IR scanner?

Are you getting adequate heat even though the gauge reads low?

Are your cooling fans running at any time when the gauge is reading less than12:00?

did you try driving the car from a cold start with the t-stat unplugged to see if it heated up faster? Unplugging the heater will give you a code but just reset it when you are through with the test.

[msharifi]

In the morning from my house getting on 3 freeways to my final stop temp gauge is in first white line from cold. as I start to do more city driving gauge comes back to normal. When the gauge comes back to normal it will not act funny until couple hours from engine shut or the next day.

When I turn on the heater its blowing hot air.

On VAG com block 131 it showed 91-93C first box and 80c on second box I was following the troubleshooting from Ross tech to see if T-Stat was stuck open

My cooling fans are not running when its reading less 12:00 nor does it come on when its at 12:00.

[old guy]

Are you sure you were looking at block 131? Your readings sound like block 130. Even if the block isn't fully up to temperature you can still get heat in the cabin. Coolant always circulates through the heater core regardless of the thermostat being open or closed. The needle hits the first white line somewhere around 165°f so that is enough to start giving you cabin heat even without the block being fully up to temperature.

Sure sounds to me like your thermostat is opening early.

[msharifi]

Are you sure you were looking at block 131? Your readings sound like block 130. Even if the block isn't fully up to temperature you can still get heat in the cabin. Coolant always circulates through the heater core regardless of the thermostat being open or closed. The needle hits the first white line somewhere around 165°f so that is enough to start giving you cabin heat even without the block being fully up to temperature.

Sure sounds to me like your thermostat is opening early.

Sorry 130 I have a cold my brain is not working right... I just need to replace the T-Stat? I can get it from VW dealer for $124 the second one which had leak I replaced when my car had 90 or 100k. it has 145k I got the brand Bahr sucks it didn't last long.

[old guy]

Sorry 130 I have a cold my brain is not working right... I just need to replace the T-Stat? I can get it from VW dealer for $124 the second one which had leak I replaced when my car had 90 or 100k. it has 145k I got the brand Bahr sucks it didn't last long.

That is unusual for a t-stat to go out that soon. But all your symptoms are pointing toward the t-stat. Can you pick up some type of temperature probe to check the temperature of the upper hard pipe return line? I use a Craftsman Professional 81079 Multimeter. It has a built in temperature probe and an IR scanner. Excellent tool for a lot of things. Clicky click

[msharifi]

How come my fans are not running?

[old guy]

How come my fans are not running?

Because the lower coolant temperature sensor is not getting hot enough to require additional cooling from the radiator as a result of the t-stat opening early.

[msharifi]

Coolant temp is 194 f on the coolant tank.

[old guy]

Coolant temp is 194 f on the coolant tank.

Was the temperature gauge reading at 12:00 when you took that temperature on the coolant reservoir? The coolant doesn't circulate through the reservoir until after the t-stat opens. If the gauge was up to temperature the coolant reservoir at 194°f would be normal. If the gauge was below 12:00 and you read that temperature at the reservoir the issue is either with the gauge or the green CTS.

[msharifi]

Yes temp was reading at 12:00 and I checked the coolant reservoir.

Green coolant sensor was replaced not too long ago which was acting up gauge going up down which was leaking so I replaced new sensor/ o ring and clip.

[old guy]

One more thing you can check. Normally the coolant doesn't circulate through the radiator until the thermostat opens. That means the top of the radiator will remain cool to the touch or maybe slightly warm at most until the temperature gauge is at the 12:00 position. Once the t-stat opens the top of the radiator will become hot as the coolant starts to flow down through the radiator and out the lower radiator return hose to the t-stat housing.

If the top of the radiator is getting hot before the temperature is all the way to the 12:00 position that would indicate a premature opening of the t-stat.

[msharifi]

I guess that would have to wait until weekend as I don't have time during weekdays since the testing can't really be done when im on the move. I just don't want the car to over heat and get stuck somewhere.

If the t- stat is in open position any hard to the engine?

If the temp gauge is at 12:00 why doesn't the fan turn on?

[old guy]

It sounds like yours is just opening a little too soon. No it will not hurt anything but it may reduce your gas mileage slightly.

[msharifi]

So once the temp gauge is at 12:00 it's fine even if the fans are not running? Poor mpg all the time or until temp gauge is at 12:00?

[old guy]

The fans are not going to run until the lower hose sensor gets hot enough to require additional cooling. The ECM is going to run the A/F mix on the rich side until the engine is up to normal operating temps. Once the block is up to temp the A/F will return to normal.

[msharifi]

Is Bahr t-stat oem or after market? Audi/vw is $124 at vw dealer. Is 06B121111K the correct part number? I. Going to order so I can replace it weekend.

[old guy]

Behr is an OEM supplier. That part number look correct. I picked one up for $85 from AZautohaus.

[msharifi]

Thanks just ordered from them plus the j plug I never replaced it when I changed the t-stat paid external to get it by Sat. I will update the post once I installed.

[msharifi]

So my fans came on the minute I turned on the car this morning but temp gauge acting same does that mean gray coolant is going bad?

[old guy]

So my fans came on the minute I turned on the car this morning but temp gauge acting same does that mean gray coolant is going bad?

This is worth a read: Clicky click I realize that you already replaced your rear CTS. Personally, with your current symptoms I would replace both sensors before doing anything else. If either sensor fails the default is to run the cooling fans. I am surprised that you haven't had the fans running at start up sooner. But since you didn't it pointed more toward a defective t-stat than a bad sensor.

Good luck!

[msharifi]

The Green coolant sensor was replaced not too long about that I got from Audi and gray one is original. So if the fans are running when car is cold its not T-Stat? Sorry if I'm repeating but if the gray sensor is not reading temp its not turning on the fans but coolant sensor has no control over T-Stat opening/closing even its electronic?

[old guy]

Go back and read the link that I provided above. The default action from the ECM is to run the radiator fans if it is getting readings that are outside of the expected map values. The ECM knows that there is a problem but it doesn’t know which sensor is causing the problem. The other thing the ECM can do is to apply full power to the thermostat to help prevent the engine from overheating.

The thermostat is not electronic. It is a mechanical thermostat that is fitted with a wax heater. If there is no input from the ECM the thermostat will open at its normal temperature. If the ECM wants to bring the temperatures down (based on input from several other sensors) it will apply power to the wax heater in the thermostat thus making it open sooner than it would normally open.

Up until your recent post you have not indicated that the coolant fan was running immediately upon start up. You just indicated that the car was taking a long time to heat up. There are numerous possibilities.

One possibility is that your car is heating up normally but you have a defective 4-pin sensor and the signal going to the display is incorrect. That’s probably not the case here since the display portion of the 4-pin sensor doesn’t provide feedback to the ECM and you were picking up a code for a cooling system malfunction. The 4-pin sensor is actually two sensors incorporated into one housing. One signal goes to the gauge and the other signal to the ECM.

A second possibility is your thermostat is opening prematurely and the thermostat needs to be replaced.

A third possibility is that the ECM portion of the 4-pin sensor or the lower 2-pin sensor is sending incorrect information to the ECM. This information falls outside of the expected mapped values so the ECM applies heat to the wax heater in order to make sure the block doesn’t overheat since it really isn’t sure what is going on to cause the values to be outside of the map.

[msharifi]

Thanks for the info I didn't hear the fan turning other days but this morning it turned on and right now it turned on full blast but would turn off after less then a min.

Should I try replacing gray sensor or both green and gray? I don't want to spend $$$ since I ordered t-stat coming sat.

[old guy]

What I would do is to first determine whether or not the block as actually heating up during the 20 minutes or so that it takes the gauge to reach 12:00.

First I would disconnect the thermostat heater to eliminate the possibility of the ECM forcing open the t-stat. Yes you will get a code but you can reset that when you are through testing. Then I would check the temperature of the upper coolant return hard pipe as well as the lower radiator return hose during the 20 minute interval.

If the upper return hard pipe is reading 175°f or higher and the gauge is below 12:00 I would replace the green CTS. The gauge should read 12:00 somewhere around 175-180°f. If it doesn’t and the coolant is the proper temperature the sensor is not sending the correct temperature.

If the upper return hard pipe is reading less than 175° f and the lower radiator return hose is getting warm then I would replace the thermostat. This would be an indication that the thermostat is opening before it is supposed to and consequently the block will take a lot longer to get up to temperature.

If disconnecting the thermostat heater returns the operation to the normal 4-5 minutes to 12:00 on the gauge then I would replace the lower 2-pin gray sensor. This would be an indication that the lower sensor is sending an erroneous signal to the ECM and consequently the ECM is applying heat to the thermostat heater and forcing it to open prematurely. By disconnecting the heater the thermostat will function as a simple mechanical t-stat. *

*Edit: In this scenario it can be either sensor causing the problem. Since you already replaced the green sensor I would go for the gray 2-pin one first.