Coolant system code P2181

[C300]

Code came on this morning. didn't let car warm up. came on when i hit 50+, figured that it was too cool. was putting along. Background... the fans have been full speed on all the time the key is turned, till 3 min. after key is turned off. Was told it was normal by dealer and inspection shop..
So i stopped at parts store and stuck the OBD 2 on it, googled it, and erased the code. fans shut off immediately. Now i was worried that somethings wrong. went to a 3 mile steep hill and shot up it, traffic n all. 2 seconds later and i'm at the top. can't even get it warm :hahahehe: damm car don't even notice hills... sat in traffic, got home and the fans kicked on as i was opening the gate.
So what's "normal" ? when this car is warm, temp gauge sits strait up. oil temp near a quarter gauge.
Now, I'm assuming that they had the fans screaming to cover up other noises. is the recirculation pump and fans to stay on after the car is turned off when hot ?,like a turbo timer ? thank, C300

[kruat]

Your fans on all the time is not normal, as that shop told you (I'd find another shop). P2181 is cooling system performance, which most of the time is a bad thermostat. Either means it's stuck open and the car can not reach normal operating temps, or means it's stuck closed and car could overheat.

You already cleared the code, drive it around, watching your temps like a hawk, maybe it's an old stored code.

My thermostat on my RS is stuck open, doesn't throw a code btw, but when it's cold out the car struggles to get to operating temp. I plan on replacing it with my timing belt here before winter.

[kruat]

Btw, I should have elaborated, when your car has a cooling system fault/code, the ecu automatically turns all the cooling fans on as a safety measure.

[C300]

Thanks Kraus, the fans on as a safety precaution is smart ! Good info. I'm staring at the gauges. Seems to be what normal should be. Where do your oil and coolant gauges indicate in normal operating conditions? By the way, my brother nicknamed this RS6 Krauthammer!

[kruat]

My coolant gauge sits at halfway, but I did notice this last fall/winter while coasting down the back hills around my home, my needle actually dropped below the halfway mark.

With cold ambient temps out, my oil temp barely hit 180. This hot summer it sits around 200-210.

But im planning on doing a complete timing belt/thermo service. Also thinking about eliminating the extra radiators also. It doesn't get hot enough around here, and eliminate more chances of coolant leaks.

[C300]

Thanks, not knowing the "refinance point " makes it hard to understand if it's in the normal operating range. Seems like all is good. One of the sales men must have done something stupid to it. ..

[G2]

Similar symptoms have been discussed here before.

In short: Sounds like the t-stat is going bad. If stuck closed, the fans will run on high. The gauge is NOT accurate once warmed up (over 185F, but is accurate until that point). The temp gauge will not budge until about 220F, then maybe a needles width. At which point the rad fans run on High.

There is a real risk of engine damage driving it. VAG put the aux rads in for a reason. Even the V8 S4's have them. If the rads are deleted it should be quantified for one' driving habits and region. And scientific measuring of ECT (live data), IR temp gun, related effects such as IAT increases. While we don't have the autobahn to heat soak the engine with high and prolong loads, low speed driving has it's effects.

Normal ECT is 185-195 driving down the road. Fans turn on by 205F (low, as they are PWM controlled). My oil temp is 165-200 driving, depending on time of year. Up to 210F town during high heat. I think the oil t-stat opens at 160F or so.

Welcome aboard C300. Even for us pro techs (hmm, am I the only?), this forum offers a wealth of information and help.

Park the car, get it fixed, enjoy.

[C300]

Thanks G2, good info. Seems mine runs about the same, factory Guage wise. Looks like the t/stat and the fans kick on just over straight up. 205... I have no plans to delete anything. Have a place in AZ. All seems right. Does make engine ticking noises. Injectors plus kinda like a Nissan. Unless I compare side by side I can't say if it's normal. It's not just one lifter or anything. So not worried. I had a shop but never did Euro cars. This looks like it isn't for the faint of heart, C300

[lswing]

That ticking could be your cam adjuster pads starting to fail. Audi used these nice little plastic guides with a chain running over them under tension. There is a VCDS block to log to see how they are adjusting, and can indicate the issues, I need to look those numbers back up. Failing point is 75k to 150k it seems; oil, temp, driving dependent.

The drivers side is fairly easy to get to if you're taking your valve cover off to do the gasket...passenger is a bitch as it's tucked in and SAI is in the way.

[hahnmgh63]

Let's get back to the Aux radiator discussion as it has been covered multiple times. The Aux radiators were not installed on all RS6's! All cars in N. America were delivered for them because: We drive slow, drive in heavy traffic compared to Europe in many areas, and have a wide variety of climates. Very few of the RS6's delivered to the ROW except those destined for the mideast had the Aux Radiators. Many of us have been without them for years ( I live in the NW and might not do it if I was in Arizona or Texas or did stop and go in the city a lot), I do have a chipped car that see's triple digits almost every day it's driven and the occasional DE event and it has always ran normal. Now normal on the ECU damped gauge can be anywhere from 90'F to 220'F so to really know what your engine temp is you need to hook up Vagcom or I think two of us now are running the P3 gauge so we can see a myriad of sensors (Boost ECU or analog sensor, Coolant temp, intake temp, Voltage, 0-60, don't remember the rest but there is a couple more). I normally leave mine on the Coolant temp as I'm anal about not driving my car agressive until the Coolant temp is close to normal and the oil temps are above 50'C as a minimum. Interesting to watch as it can be erratic (have replaced my original coolant sensor but might do it again to see if it is just the way they read or the current sensor.

[Other_Erik]

Sounds like exactly the issue I've been fighting for 15 months or so. I logged, logged, logged - nothing to indicate why the P2181 ever popped up. Mine was the opposite of yours, though - would happen when it was ridiculous cold out (+10 to -18F this winter). As soon as early morning temperatures got above 20F, stopped having the problem. I replaced my thermostat, that did no good. I checked every relay, fuse, wire, etc... that I could find from the radiator fans all the way back to the ECU - no problems on any of them. The only 'problem' I found was the ambient air temp sensor, the wire had been pinched almost clean through - replaced that and it fixed the outside air temp display on the DIC, but that was it.

Imagine -18F outside, you start the car to let it warm for a few minutes, come outside and fans are full blast 747 takeoff mode. Check logs, and engine coolant temp pinging around 120F. Even with some moderate to harder driving, temps get up to ~190F, then the freezing-ass cold coolant from the radiator loop makes its way into the engine, drops temps back down to ~100F. Lather, rinse, repeat. I had no heat in the RS on the days I needed it most, and the fans running full blast dropped voltage to 11.2-12.7V depending whether I had heated seats all on or just driver seat (running should be ~14.3). Made for some very uncomfortable morning commutes - even the '95 Jeep Wrangler I had at the time was warmer on the days I drove that (heavy/deep snow drifts on the road, non-drivers everywhere thinking they're invincible because they drive an SUV)

I think next step is going to be full-on coolant flush, replace with the spec for Canada RS6's (good to -55F), cut with 40% distilled water and a 12oz bottle of water wetter. Fun part is going to be trying to flush the heater core - run temp has to be above 185, but if I start flush with garden hose, cold water closes the thermostat and heater core bypass loop.

HTH
O_E

[C300]

Other_Erik (http://www.rs6.com/member.php/20490-Other_Erik) , the other Night I was over a friends garage. A group of us work on our classic cars and Hotrods together and tell lies. I just stopped in for a minute and one of the guys was an Audi tech in the past. Didn't know I had one. He was all over the car and asked if there were any issues. I told him about the P2181 code. He said that code was the Inlet air Temp. sensor 90% of the time. In my case it's definitely the T/stat. He agreed. Hope that helps, C300

[C300]

Since I'm about to replace the T/Stat. I want to have all the all the parts I need before tearing into it. The two questions I have are, what brand of T/Stat. to get ? OEM ? It only lasted 60k... Also Assuming the 82c is the correct temp. one to go with. Second is the parts list. gaskets n o-rings, other necessary stuff while i'm in there. And preferred Brands. Like Felpro gaskets, Ect. will be doing the T/belt next summer. 65k currently. Possibly the T/converter n trans. at that time also. so just crutching it till then. T/Stat. can't wait. Thanks, C300

[Turbowned]

Try testing/replacing the coolant temperature sensor before you do anything drastic. The sensor and clip are less than $30 from the dealer and easy to access once you remove the airbox. I had similar, if not the same symptoms with my car, and that fixed my fan after-run problem.

[C300]

Turbowned, on cold days mine doesn't get fully warm. If I let it sit after a Hwy run, gets up to temp, then cools off when I get rolling again like after a stop light. seems like a classic case. will just replace the sensor anyway. Is there another valve somewhere in the system that opens up the Aux. Rads when needed, or is it all or nothing ? Thanks, C300