B6 1.8T not getting up to temp. Please help.

[zlaja80]

Dear friends,
I posted a week ago about this issue, but I did few more things to the car and still have the same result or no result!.
The temp gauge stays at about a 1/4 after driving a car for more than 26 miles, mostly interstate miles. Never had this with the old T-stat, however had to change it because the plastic nipple broke off where it connects to the upper coolant hose.
Recent work:
New T-stat 3 weeks ago - by Hamburg Technic - I just read a post where someone is telling people not to buy their parts! Could it be the T-stat?
New CTS both upper and lower through Bap Geon - they are aftermarket OE sensors - 2 days ago
Car runs smoothly, and I tried to see if there was heat this morning, and yes there was heat coming out of the vents.


Here is the picture of my gauge



Thank you all for your help!!

[diagnosticator]

Just to clarify, the low temp indication only occurred after the t-stat was last replaced, and the new temp sensors did not effect the displayed temperature, right? Can you scan the ECU for cooling system fault codes? If you don't have VCDS, or a generic OBDII scanner, Autozone will scan the ECU.

[B6a418t]

This happened when I unhooked my Fan control Module for a day or 2 as I was sourcing another (it was cold, no fear of over heating at the time). Perhaps the root cause of your issue is Fan Control Module related.

[Charles.waite]

Doubtful. My money is on a bad thermostat.

[zlaja80]

This is all after I changed the T-stat. It ran normal for about two weeks. I had P2181 show up about a week ago. At that time I went and purchased new CTS upper and lower.
Both fans are running
I don't have any codes now

Just to clarify, the low temp indication only occurred after the t-stat was last replaced, and the new temp sensors did not effect the displayed temperature, right? Can you scan the ECU for cooling system fault codes? If you don't have VCDS, or a generic OBDII scanner, Autozone will scan the ECU.

[Let it snow]

I was thinking bad green CTS sensor giving a false reading. Could a wide open thermostat cause the engine not to reach operating temperature in Virginia summer time heat? I am curious to know.

[imnuts]

Looking at the information for the DTC you posted, it has some good information on what to look at, and seems to match your symptoms that you've listed thus far. An easy way to check the thermostat would be to take it out, put it into a pot of water and see if/when it opens, and measure the temperature of the water if/when it does open. Test the sensors with VCDS, though I'd think that there would be a code stored if one of them was providing invalid data, but possibly not.

18613/P2181/008577 - Performance Malfunction in Cooling System

Possible Symptoms

• Malfunction Indicator Light (MIL) ON
• Reduced Heater Output - Cold toes
• Incorrect Temperature Gauge Readings
• Increased Emissions

Possible Causes

• Faulty Coolant Sensor
• Faulty Coolant Thermostat
• Faulty Wiring, Connections

Note: This fault code sets when engine coolant temperature mapping is lower and out of expected range based on operating conditions of the engine.

For example: Engine warms up, thermostat opens and stays open, coolant temperature drops below normal operating range. The ECM knows the coolant temperature should stay within 80.0...110.0 °C typically after warm up. Thus a drop in coolant temperature below normal operating temperature is not possible without a Malfunction in Cooling System.

Possible Solutions

• Check G62 - Engine Coolant Temperature Sender
  
  • Inspect wiring for G62 (Coolant Migration, damage, corrosion, etc)
• Check (if applicable) G83 - Radiator Outlet, Coolant Temperature Sender
  
  • Inspect wiring for G83 (Coolant Migration, damage, corrosion, etc)
• Check Coolant Thermostat
  
  • Use Graph function in VCDS, Measuring Value Blocks - MVB
  • Start Engine cold, graph Coolant Temperature Sender (G62) Typically MVB Group-001
  • Hold RPM around 1,500rpm and watch coolant temp increase in Graph until thermostat opens, indicated by a slight drop in coolant temp
  • If coolant temp drops below minimum operating temperature (80°C) or never reaches operating temperature, (verified by external thermometer) suspect failed thermostat
• Vehicles with both G62-Engine Outlet, Coolant Temperature Sensor and G83-Radiator Outlet, Coolant Temperature Sensor
  
  • Use Measuring Value Block group MVB-130 instead on MVB-001
  • G62 should increase in Temperature before G83 increase when engine coolant is cold
  • G83 will increase when the thermostat opens and after G62 reaches operating temperature (80°C)
  • If G62 and G83 both increase while engine warms up, suspect failed thermostat

Special Notes
Check the stored Freeze Frame data with this fault code. Freeze Frame information will be found in the fault code description (if the module supports it) or in Generic OBD-II if the vehicle complies with those regulations.

• Freeze Frame data stored at -40*C is generally an indication of a faulty ECT or wiring.
• Freeze Frame data stored at +140*C is generally an indication of a faulty ECT or wiring.
• Freeze Frame data stored with in the 68*C ~ 80*C range is an indication that the vehicle was close to, but not within, the cooling systems normal operation range. The Thermostat itself or Cooling system components may be at fault.

[zlaja80]

Have no access to VCDS, Would it be better to take it to a Audi shop - not a dealership and have them run a diagnostic. Once they tell me than I could possibly try to fix it myself. I hate to spend money on diagnostic when I can use that same money for a possible purchase of another part.

As I stated earlier. Once I installed a new T-stat, the car operated at a normal temp, and all of a sudden the P2181 came up and the gauge started misbehaving. I wish I knew someone with the VCDS. Thank you all for your help!

Looking at the information for the DTC you posted, it has some good information on what to look at, and seems to match your symptoms that you've listed thus far. An easy way to check the thermostat would be to take it out, put it into a pot of water and see if/when it opens, and measure the temperature of the water if/when it does open. Test the sensors with VCDS, though I'd think that there would be a code stored if one of them was providing invalid data, but possibly not.

[Charles.waite]

The only sure way to test the thermostat is to pull it out and do the by water test.

This a sadly a common occurrence with non-oem thermostats.

[Let it snow]

You said you don't have codes any more. Which should mean your coolant system is operating normally. The green CTS sensor has 2 functions. One goes to the ECU and the other goes to the dash display. I would get an OEM sensor and try that. I find it hard to believe an open thermostat would keep your coolant that much below operating temperature in Virginia summer heat.

[Charles.waite]

You said you don't have codes any more. Which should mean your coolant system is operating normally. The green CTS sensor has 2 functions. One goes to the ECU and the other goes to the dash display. I would get an OEM sensor and try that. I find it hard to believe an open thermostat would keep your coolant that much below operating temperature in Virginia summer heat.

It definitely will. My current b7 uses a similar design thermostat and it's been stuck open for a few months now, my old b7 had the same issue at the same mileage. Basically it gets to about 3/8ths in the dial (10 o'clock) then sits there. Sometimes moves up to the middle then drops down again to almost 1/4. When I replaced my old b7s thermostat I tested it in a pot of water and it began opening around 50°C. The Bentley specifies it shouldn't open until 80°C. Even yesterday when it was around 100° at my house the temp wouldn't go up to the middle of the gauge.

Long story short, even in hot ass weather in the dead of summer the open thermostat can prevent the coolant temp from reaching the 80°C target (or 90°C in the case of the b6).

[Let it snow]

It definitely will. My current b7 uses a similar design thermostat and it's been stuck open for a few months now, my old b7 had the same issue at the same mileage. Basically it gets to about 3/8ths in the dial (10 o'clock) then sits there. Sometimes moves up to the middle then drops down again to almost 1/4. When I replaced my old b7s thermostat I tested it in a pot of water and it began opening around 50°C. The Bentley specifies it shouldn't open until 80°C. Even yesterday when it was around 100° at my house the temp wouldn't go up to the middle of the gauge.

Long story short, even in hot ass weather in the dead of summer the open thermostat can prevent the coolant temp from reaching the 80°C target (or 90°C in the case of the b6).

Good to know. Thank you Charles.

[zlaja80]

I guess now I will become a true expert in changing a t-stat on this car. While I am in there again I will change the J plug. Should I go with the ECS one or genuine OEM audi? Thanks guys on all of your help!