CEL P2181

[kerfuffle]

I got a CEL over the weekend drive home, so I took the car to the nearest AutoZone to scan for faults -- P2181: Coolant System Performance came up. Did a bit a reading on this forum as well as others out there, and the general consensus is that the culprit could either be one of the following (but nothing definitive):

• Coolant Temperature Sensor
• Water Pump
• Thermostat

The car currently is a little under 52,300 miles. The car does not overheat, and the temperature gauge levels at the mid-point from a cold start after 5-10 minutes of driving. Heating and A/C seemingly works fine, and the fans kick on when it's supposed to -- the car runs great otherwise.

Since it is a really time consuming and expensive job to replace the water pump and thermostat, how likely are either of these two items to blame for the CEL given the relative low mileage of the car? Does anyone have any additional tips to isolate potential symptoms so I can track down the exact point of failure?

I am not the most mechanically inclined person, so I will have no choice but to take the car in to a local mechanic to address this. The plan is to have him VAGCOM the car to confirm the fault, and to determine if there are any outstanding errors in addition to P2181. If it is the only fault logged, is it a good idea to have him clear the code to see if it comes back to determine whether it's a false positive? Any potential downfalls continuing to drive the car even with this CEL? If the code does come back, which part would you suggest I start with (probably the least expensive part to replace)?

Please let me know if you have any suggestions or recommendations.

Thanks!

[bfunk1414]

Thermostat. They tend to go bad after 85k

Edit: doubt is the thermostat. I read the post again and when it's the thermostat, the middle will either not stay in the middle and just stay below it or it'll be overheating

[Rulty]

Doubt its thermostat. Most of the time I beleive that they fail open or closed. So your would either never heat up or over heat. Not too sure on how to narrow it down to a coolant temp sensor or water pump, but my money would be on the water pump. However I'd personally replace the coolant flange ( not that bad of a job I just did mine) and replace the temp sensor with it. I think a kit on ecs is like 30 bucks or something like that. If that doesn't fix it then I'd do a full timing belt service with the water pump.

[trj]

What color coolant do you have? It's possible that you might get away with coolant flush. On phone so couldn't see your location. But with cold climates, if the correct coolant is not used, you are in for many surprises.

If there are no leaks and do not plan to change the water pump, thermostat then do a proper coolant flush and replace with vw/Audi coolant 50-50 with distilled water.

If I were going near thermostat, I would do the timing belt, pulleys, waterpump, thermostat, serpentine belt, etc. It takes almost the same amount of time/labour.

[kerfuffle]

What color coolant do you have? It's possible that you might get away with coolant flush. On phone so couldn't see your location. But with cold climates, if the correct coolant is not used, you are in for many surprises.

If there are no leaks and do not plan to change the water pump, thermostat then do a proper coolant flush and replace with vw/Audi coolant 50-50 with distilled water.

If I were going near thermostat, I would do the timing belt, pulleys, waterpump, thermostat, serpentine belt, etc. It takes almost the same amount of time/labour.

I'm just south of Boston. The coolant is orange in color and FWIW it was in the 60s during Christmas and leading into the weekend. The car is relatively low in miles, I was under the impression that those items don't become an issue at least until after 65k.

There are no leaks from the coolant reservoir as far as I can tell, because the level is steady.

I may regret asking this, but what type of surprises are we talking about here?

[wding2000]

My thermostat went bad at 54K miles (plus change), so it is not too early for 52K. In my case, temp would not come up to middle, so it was easy to guess - thermostat stuck open. Your case is peculiar.

I would clear the code and see if it comes back; then do what Member trj suggested: do a coolant flush first if car has never had one. My coolant turned brownish (7 years) - I should have flushed it a lot earlier. Then coolant temp sensor (even cheaper than 1 gallon G13 coolant). Then between thermostat and water pump, it is hard to tell. If you only do thermostat, you do not have to touch timing and water pump; but if you do water pump, you may as well change timing and thermostat.

[trj]

I'm just south of Boston. The coolant is orange in color and FWIW it was in the 60s during Christmas and leading into the weekend. The car is relatively low in miles, I was under the impression that those items don't become an issue at least until after 65k.

There are no leaks from the coolant reservoir as far as I can tell, because the level is steady.

I may regret asking this, but what type of surprises are we talking about here?

Orange is throwing me off now. VW/Audi G13 coolant should be pink, not orange. But who knows what has been mixed to it. As I said earlier, flush the cooling system and fill it with proper coolant and distilled water. And clear the code as wding2000 mentioned and see if it comes back.
There is not much to cooling system than coolant, thermostat, water pump and sensor, and pipes connections if its leaking. Thermostat is difficult to look at for the leaks, so get a mirror and flash light and go under there. I don't know the year of your car, but the miles are only one parameter. If its a 05/06 car then its time for new water pump, thermostat and timing belt anyway.
I replaced timing belt, serpentine belt, water pump, thermostat, coolant, pulleys all at once at 85k miles (05.5 year). No CELs, but after the thermostat change I noticed my temp goes to 12 o'clock position much quicker (5 minutes in cold cold Colorado temps) and within 3 minutes in normal non sub zero temps and the needle doesn't drop slightly to left side when doing extended highway driving. No leaks, no coolant loss. So, its not necessary to have a leak for thermostat to go kaput. Its a simple mechanical device that is set to open at certain temperature. The temperature depends on the coolant you use, as to what is the boiling point of the coolant right now. Either the coolant you are using is not in proper ratio or thermostat is going bad. With colder temperatures coming your way this week (I have relatives in Boston), I would keep a close eye on the temp needle. Usually thermostat remains open when its bad, giving you full coolant flow even when not necessary. Results in longer heating time, heater not heating enough, less gas mileage because the engine burns more fuel, needle going slightly to the left on extended highway driving.

As for DIY, its not very difficult. Make sure you have triple square #5 for the hard pipe to the thermostat. Thats the only special socket you will need. All other normal metric tools will work.

As for the surprises, non VW/Audi coolant on this engines have corroded the engine internals and pipes. You really don't want that to happen. So, I would never put anything else than Audi/VW approved fluid in the car. That goes for all the fluids not just for coolant.

[kerfuffle]

Orange is throwing me off now. VW/Audi G13 coolant should be pink, not orange. But who knows what has been mixed to it. As I said earlier, flush the cooling system and fill it with proper coolant and distilled water. And clear the code as wding2000 mentioned and see if it comes back.
There is not much to cooling system than coolant, thermostat, water pump and sensor, and pipes connections if its leaking. Thermostat is difficult to look at for the leaks, so get a mirror and flash light and go under there. I don't know the year of your car, but the miles are only one parameter. If its a 05/06 car then its time for new water pump, thermostat and timing belt anyway.
I replaced timing belt, serpentine belt, water pump, thermostat, coolant, pulleys all at once at 85k miles (05.5 year). No CELs, but after the thermostat change I noticed my temp goes to 12 o'clock position much quicker (5 minutes in cold cold Colorado temps) and within 3 minutes in normal non sub zero temps and the needle doesn't drop slightly to left side when doing extended highway driving. No leaks, no coolant loss. So, its not necessary to have a leak for thermostat to go kaput. Its a simple mechanical device that is set to open at certain temperature. The temperature depends on the coolant you use, as to what is the boiling point of the coolant right now. Either the coolant you are using is not in proper ratio or thermostat is going bad. With colder temperatures coming your way this week (I have relatives in Boston), I would keep a close eye on the temp needle. Usually thermostat remains open when its bad, giving you full coolant flow even when not necessary. Results in longer heating time, heater not heating enough, less gas mileage because the engine burns more fuel, needle going slightly to the left on extended highway driving.

As for DIY, its not very difficult. Make sure you have triple square #5 for the hard pipe to the thermostat. Thats the only special socket you will need. All other normal metric tools will work.

As for the surprises, non VW/Audi coolant on this engines have corroded the engine internals and pipes. You really don't want that to happen. So, I would never put anything else than Audi/VW approved fluid in the car. That goes for all the fluids not just for coolant.

Thank you very much for that informative response. It's a 2008 that had the orange coolant since it was first purchased, but I'll take a picture of it to give a better visual. I will proceed as suggested -- clear fault code first, then move forward with a coolant flush if it returns.

Is the car still safe to drive in this condition (assuming P2181 is the only fault)?

Cheers

[trj]

Thank you very much for that informative response. It's a 2008 that had the orange coolant since it was first purchased, but I'll take a picture of it to give a better visual. I will proceed as suggested -- clear fault code first, then move forward with a coolant flush if it returns.

Is the car still safe to drive in this condition (assuming P2181 is the only fault)?

Cheers

I wouldn't say whether car is safe to drive or not. Its up to you. If you keep a close eye on the temp gauge then I think it will be safe to drive, but there are many "what if"s. Say, what if it overheats and ruins the engine. Not saying it will. I drove with a open thermostat for 3 months in my other car because I was busy. Nothing happened, but its not to say nothing will happen in your case. I would first clear the code and see if it returns. Post in the local section and someone can definitely help you out on diagnosing the problem with VAG COM and probably say what kind of coolant you have in your car. Pictures can be deceiving on the screen, its always better to have someone look at in person.

[KJack]

It's a 2008 that had the orange coolant since it was first purchased, but I'll take a picture of it to give a better visual. I will proceed as suggested -- clear fault code first, then move forward with a coolant flush if it returns.

If it still has the original, 7 year old coolant it wouldn't be a bad idea to flush it anyway and replace it with some fresh G13 coolant.

[kerfuffle]

If it still has the original, 7 year old coolant it wouldn't be a bad idea to flush it anyway and replace it with some fresh G13 coolant.

Agreed. Slight correction on my previous statement, it's a 2008 that had orange coolant (as far as I can tell) in the reservoir when I purchased it pre-owned.

[wding2000]

Agreed. Slight correction on my previous statement, it's a 2008 that had orange coolant (as far as I can tell) in the reservoir when I purchased it pre-owned.

Audi G12 or G13 should be pink color. It is either original 7-year old coolant degraded, or previous owner put in wrong coolant. Either way, not a bad idea to flush it fresh.

[kerfuffle]

This is what the coolant currently looks like.





Called a few local shops to get a quote on flushing the coolant, and they're mostly quoting in the upper $200 range -- thoughts?

[Alucard136]

Flush it yourself. Its a 20 min job and it requiers a screwdriver and a piler. Here are guides at the zine.

[drmonkey]

I'm getting the same code on my 2008. Pretty sure it's the Thermostat though since my temp is always at the 10o'clock dash when I'm driving and goes to normal when coming to a standstill. Also the heat isn't as hot either. How hard is it to replace the thermostat? Is it just better to do it with the timing belt and all that?

[swaggerwagon]

Here is a question for you about the thermostat:

Does the car run "cool" at highway speeds? IE: Does the temperature gauge drop when driving highway speeds? I too had a bad thermostat that I diagnosed with some temperature logging through VCDS.

[drmonkey]

Here is a question for you about the thermostat:

Does the car run "cool" at highway speeds? IE: Does the temperature gauge drop when driving highway speeds? I too had a bad thermostat that I diagnosed with some temperature logging through VCDS.

Yeah, that's when it drops down to the 10o'clock dash on the gauge. During idle it sits at normal or under. So I'm fairly certain it's just stuck open.

[trj]

This is what the coolant currently looks like.


Called a few local shops to get a quote on flushing the coolant, and they're mostly quoting in the upper $200 range -- thoughts?

That looks like OE coolant. But pictures can be deceiving on the screen. $200 is way too much for a coolant flush. About $30 for the coolant and $2 for distilled water. A long nose plier is all you need for coolant flush. Get some local member to help you. Give him a 12 pack beer. No need to pay $200 for a coolant flush.

PS: I removed the pictures in the quote

[trj]

I'm getting the same code on my 2008. Pretty sure it's the Thermostat though since my temp is always at the 10o'clock dash when I'm driving and goes to normal when coming to a standstill. Also the heat isn't as hot either. How hard is it to replace the thermostat? Is it just better to do it with the timing belt and all that?

Depends on if the timing belt was ever changed or what mileage are you at. If not changed and you are nearing 70k miles, I would do it at the same time.

Here is a question for you about the thermostat:

Does the car run "cool" at highway speeds? IE: Does the temperature gauge drop when driving highway speeds? I too had a bad thermostat that I diagnosed with some temperature logging through VCDS.

The classic symptom of stuck open thermostat. The system is always cooling the engine resulting in less heat from heater and engine having to burn more fuel to get to operating temperature. Unless someone messed up the ratio of coolant to distilled water.

[kerfuffle]

That looks like OE coolant. But pictures can be deceiving on the screen. $200 is way too much for a coolant flush. About $30 for the coolant and $2 for distilled water. A long nose plier is all you need for coolant flush. Get some local member to help you. Give him a 12 pack beer. No need to pay $200 for a coolant flush.

PS: I removed the pictures in the quote

If there any experts comfortable with doing a coolant flush in the Boston/South Shore area, PM me. Food and beverages of your choice included.

[trj]

I'm getting the same code on my 2008. Pretty sure it's the Thermostat though since my temp is always at the 10o'clock dash when I'm driving and goes to normal when coming to a standstill. Also the heat isn't as hot either. How hard is it to replace the thermostat? Is it just better to do it with the timing belt and all that?

Here is a question for you about the thermostat:

Does the car run "cool" at highway speeds? IE: Does the temperature gauge drop when driving highway speeds? I too had a bad thermostat that I diagnosed with some temperature logging through VCDS.

If there any experts comfortable with doing a coolant flush in the Boston/South Shore area, PM me. Food and beverages of your choice included.

Lol. Post in the regional local section my friend.

[kerfuffle]

Lol. Post in the regional local section my friend.

Done.

[bfunk1414]

Done.

Hoping to see the results. I know I definitely need some thermostat. I have it in hand but just need to install it. Been wanting to do a flush as well.

[bfunk1414]

Lol. Post in the regional local section my friend.

Dumb question; how does one post 'local'?

[kerfuffle]

Went to an indy shop over the weekend, and they were able to clear the fault (thankfully, it hasn't come back yet after 30+ miles of driving). They VAGCOMed the car, and P2181 was the only fault that was on there. The temperature gauge does seem to fluctuate a bit from the 12 o'clock position to maybe the 10/11 o'clock position during highway driving, but it's intermittent for the most part.

The shop was pretty confident that the thermostat needs replacing. I asked for a quote which came out to be $470. If the CEL comes back, I will likely move forward with replacing the thermostat through them. Thoughts on the quote for the job?

Thanks!

[swaggerwagon]

Went to an indy shop over the weekend, and they were able to clear the fault (thankfully, it hasn't come back yet after 30+ miles of driving). They VAGCOMed the car, and P2181 was the only fault that was on there. The temperature gauge does seem to fluctuate a bit from the 12 o'clock position to maybe the 10/11 o'clock position during highway driving, but it's intermittent for the most part.

The shop was pretty confident that the thermostat needs replacing. I asked for a quote which came out to be $470. If the CEL comes back, I will likely move forward with replacing the thermostat through them. Thoughts on the quote for the job?

Thanks!

Do it yourself. There's a guide on here. Thermostat is like a $75 part if I remember (OEM). Add some coolant to that, you might at most be out $100 vs $470.

[kerfuffle]

Do it yourself. There's a guide on here. Thermostat is like a $75 part if I remember (OEM). Add some coolant to that, you might at most be out $100 vs $470.

I have zero experience working on cars unfortunately, otherwise I'd do it in a heartbeat. :(

[swaggerwagon]

I have zero experience working on cars unfortunately, otherwise I'd do it in a heartbeat. :(

Then do the timing belt while you're at it. Shouldn't be more than 850-900 at $85/hr rate

[oVeRdOsE]

Here is a question for you about the thermostat:

Does the car run "cool" at highway speeds? IE: Does the temperature gauge drop when driving highway speeds? I too had a bad thermostat that I diagnosed with some temperature logging through VCDS.

I have this, and the check engine with it ( same code as op).

I believe it stuck open, this is one of the ''must have issue'' on the b7 ...

I'm running like this since a while now, no issue. heat is ok, even @ -15°c .

I'll repair it with my timing belt next spring.