Today's Game: Find that coolant pump "c"? (Another b9 coolant story)
 

Hello,

Similar to many with the b9's starting to get enough miles on them for issues to begin popping up.

My 2018 S5 Sportback Prestige has been through hell this last year, from a nowhere "coolant temp high" light while on the highway doing 90mph... Spiraled quickly to a water pump replacement, then they found that everything overheated THAT QUICK and shredded the turbo- which in turn threw scrap metal into the cat and took it out at the same time.

Normally, I feel as if most folks would have got rid of the vehicle ASAP @ 78k miles. However, I just paid the damn thing off, and it is the first vehicle I have ever done so with- so I wanted the idea of no payments for a while... Bad move.

So, 3 months later, and after all the work was done here at my local Audi tuner shop in Austin, I thought the ordeal was over, and I could enjoy life again thousands of dollars shorter... Until yesterday when I got that terrifyingly familiar dash pop up "Coolant temp too high".

Did a scan with VCDS and found intermittent code for:
"Coolant Pump C- Stuck"

I have searched the internet far and wide and cannot find where in the hell this "C" pump is and I'm hoping someone here can lend some guidance (other than scrap that ride, lol!)

I'm thinking it's the only other coolant pump in the engine compartment - the auxiliary coolant pump:

https://parts.audiusa.com/a/Audi__/4...P/1343130.html

Complete DTC info would be more interesting to start from.

There's the main coolant pump, which is managed by the N649 (misprinted as N694 in some places) switch valve.
There's the V51 afterrun coolant pump, which circulates coolant through the turbo after engine off. 12v, ground, and control lines.
There's the V50 stop/start coolant pump, which circulates coolant through the heater core when engine stopped. 12v, ground, and control lines.
The V55 coolant pump is not relevant to US models as we do not get PR 9M9 auxiliary coolant heater option.

The V50 and V51 are specifically documented to have self-diagnosis and feed that back over the PWM control line.
Both are mounted to the back of the chain cover at the back of the bank 1 cylinder head. SSP 655, page 45.
(that SSP seems prone to typos, such as swapping the V50/V51 descriptions on that page, and the "N694" error on the diagram)

Which is "pump C"? Unplug one, see if you get a new DTC saying pump C or pump B or something. Plug that back and unplug the other. See what you get now.

Check out SSP 655 (B9 S4/S5 engine), page 40-48, which goes into coolant details:

www.audiworld.com/forums/attachments/Faudi-a5-s5-rs5-coupe-cabrio-b9-220/97364d1609395727-catch-can-b9-a5-audi-ea839-series-ssp655.pdf

Thank you for that great information,, I am going to give that a try right now and will post another update. I will also note that after the vehicle had that dash popup and I pulled over to get out and open the hood,, the driver side coolant hoses coming out of the upper radiator hose were completely cool, while the passenger side lower hoses were extremely hot, as well as the 2 heater hoses that go into the dash which were even hotter.

Meanwhile, here is the complete DTC:

OBDeleven data log

Date: 2023-05-30 11:50

VIN: WAUC4CF56JA041392
Car: Audi S5
Year: 2018
Body type: Sportback
Engine: CWGD
Mileage: 130600 KM

---------------------------------------------------------------
01 Engine

System description: V6 3.0l TFSI
Software number: 8W0907559H
Software version: 0009
Hardware number: 06M907309D
Hardware version: H22
ODX name: EV_ECM30TFS0118W0907559H
ODX version: 001010
Long coding: 1A2A00322326010E34280000000000000000000000000000

Trouble codes:
P26F800 - Coolant Pump "C" Stuck
Intermittent
Date: 2023-05-29 14:47:45
Mileage: 130582 km
Priority: 2
Malfunction frequency counter: 1
Unlearning counter: 255
Engine speed: 1672.50 1/min
Normed load value: 20.8 %
Vehicle speed: 105 km/h
Coolant temperature: 100 °C
Intake air temperature: 36 °C
Ambient air pressure: 980 mbar
Voltage terminal 30: 12.020 V
Dynamic environmental data: 20962712910EC015CD0CEB129A0E8F13A00D6614F80BEB
P13EF00 - Coolant temperature sensor for engine block Temperature too high
Intermittent
Date: 2023-05-28 22:15:29
Mileage: 130570 km
Priority: 2
Malfunction frequency counter: 7
Unlearning counter: 255
Engine speed: 572.00 1/min
Normed load value: 4.7 %
Vehicle speed: 0 km/h
Coolant temperature: 109 °C
Intake air temperature: 44 °C
Ambient air pressure: 980 mbar
Voltage terminal 30: 13.060 V
Dynamic environmental data: 209628107A0311BD0EAC3EFC05121603841514041770000000 01101001E4
P017C00 - Cylinder Head Temperature Sensor Circuit Low
Intermittent
Date: 2023-05-29 16:10:46
Mileage: 130594 km
Priority: 2
Malfunction frequency counter: 1
Unlearning counter: 255
Engine speed: 653.50 1/min
Normed load value: 6.3 %
Vehicle speed: 5 km/h
Coolant temperature: 145 °C
Intake air temperature: 39 °C
Ambient air pressure: 980 mbar
Voltage terminal 30: 13.000 V
Dynamic environmental data: 209628107A0311BD0F233EFC06121604C21514041770000000 0A1010028A
P042000 - Catalyst System,Bank1 Efficiency Below Threshold
static
Date: 2023-05-29 16:01:04
Mileage: 130587 km
Priority: 2
Malfunction frequency counter: 1
Unlearning counter: 255
Engine speed: 1897.50 1/min
Normed load value: 17.6 %
Vehicle speed: 94 km/h
Coolant temperature: 97 °C
Intake air temperature: 45 °C
Ambient air pressure: 980 mbar
Voltage terminal 30: 13.060 V
Dynamic environmental data: 209628127226171538FFFF153400001538FFFF15340000

Engine speed: 1672.50 1/min
Voltage terminal 30: 12.020 V
That's a major issue. Voltage should never be in the 12s with a running engine.

Engine speed: 572.00 1/min
Vehicle speed: 0 km/h
I wonder if these are tripping on engine off.

Engine speed: 653.50 1/min
Vehicle speed: 5 km/h
Does that engine actually idle at 650?

Coolant temperature: 145 °C
It's clearly reading at end of range. Either the sensor is toast, or there's a wiring issue. You need to log the four coolant temp sensor values from start to warm up to drive around to off and see if they seem logical the entire way. You might have a flaky electrical connection, or a flaky sensor.

CWGD has four coolant temp sensors:
G62 - this is on the bank 2 cylinder head hot side after receiving the turbo coolant output
G82 - this is on the feed from the block into the F265 managed thermostat; ECM probably uses this to decide if the F265 needs to send the flow direct to the main pump or to the radiator core; the G82 target is no more than 105°C at partial load to 90°C at higher loads
G83 - this is on the radiator outlet leading back to the main pump; G82-G83 gives a pretty decent temp drop assessment of the radiator effectiveness
G694 - this is on the bank 1 cylinder head hot side leading back into the block

Your P13EF is probably about the G82, where the freeze frame value is 109°C.
The P017C is probably about the G62.

The V51 is in the coolant flow path to the turbo.
The V50 is in the coolant flow path to the heater core.
So I guess you could determine which is which by following the coolant tubes from them. While they are normally used at engine stop, and engine off for the V51, it seems the V51 is additionally used under normal conditions to assist the main pump.

It could be if the V51 is not invoking as expected, the coolant temp might rise above expected?

So you got more than just a pump you need to review.

Per your recommendation (thank you), I was able to isolate this mystery “pump C” by removing the connectors to each pump one by one until a dash light or error in the VCDS scan arose, which it did in the form of dash engine light, to aux coolant pump v50 that goes to the heater core.

Ordered the new one and it should be here Friday to install. Hopefully smooth sailing from here. I’ve just thrown salt over my shoulder and started holding my breath though.
https://cimg6.ibsrv.net/gimg/www.aud...7ca2eae3d.jpeg

So I successfully replaced pump v50 which did clear the "coolant pump C- stuck" code with part# 06h121601M from
for $45.

Only issue now is getting air our of the cooling system. I cannot seem to get it all out and could use some help there.

I used a vac and fill system after draining all of the coolant (removed lower radiator hose and transmission hose behind the oil cooler), then used a funnel with heater on high and fan on low to try and get the rest of the air out and finish topping off. While the funnel device with coolant sat in the expansion reservoir, I by hand squeezed the coolant lines for air out while cycling the "heater support pump" in VCDS no less than 8 runs.

Am I missing some trick to getting this dang air out?

bump

You opened the bleed port by backing off the right side heat exchanger coolant hose? The two hoses that connect right below where the two strut tower braces connect in the middle. The right side one, you back it off to expose the bleed hole. Once you have coolant coming out, then you close it back up. Then you either manually run the engine as documented or use the bleed routine in the ECM (I'm guessing it's a basic setting? Something about 0119 coolant circuit vent routing). Set AC off, climate temp to Hi, fan speed 0. Manual engine run is 3 minutes at 2500 rpm, idle until coolant fan starts, 2 minutes at 2500 rpm. That's all the workshop manual says. But it's three pages on just filling and bleeding. Cardiagn.com if you just want a quick look at it. Better to get your own local copies; erwin.audiusa.com, pay for a day, get all the PDFs for your VIN. And a big FU to whoever at Audi thought these "servicing" manuals were a good idea. The coolant drain/fill/bleed is in the "not" servicing manual for the EA839 3.0T CWGD.

So I do have both ERWIN versions for the vehicle,, the first 2019 edition has the mention of the heater bleed hole when doing the actual routine. The second 2020 version leaves out any and all mention of using that heater hose bleed at all.
Strange, but ive tried both methods and still cant seem to get every bit of the air out.

Before running the bleed routing- which for my vehicle I have just one VCDS option under basic settings for "bleed cooling circuit".. So before i do that basic setting routine,, with engine off and heater high fan low, I've been running the output for "heater support pump" and "coolant pump 2" ,10 cycles each,, as soon as a cycle is done, I have been by hand squeezing every coolant line for air bubbles. Rinse. Repeat. I have no option to run main pump, just the "switching pump" which only makes the click sound.

Hell, I even lifted the front end and did the entire hokey pokey dance as just described and still have some air pockets after driving.

I did find this random hose hanging out pointed below the vehicle that looks like it has some intentional filter at the end, but cannot find in any manual wth it is.
https://cimg6.ibsrv.net/gimg/www.aud...862a0df278.jpg






https://cimg6.ibsrv.net/gimg/www.aud...0cf6872ed6.png
https://cimg2.ibsrv.net/gimg/www.aud...b7f17b855c.png

So its confusing, but ive tried both methods and still cant seem to get every bit of the air out. Before running the bleed routing- which for my vehicle I have just one VCDS option under basic settings for "bleed cooling circuit"
https://cimg0.ibsrv.net/gimg/www.aud...20c6cdd3ed.png

Yeah, cardaign.com only has typically the initial releases and never updates from there. I don't have a self copy for CWGD. Sometimes the updates are good, sometimes they are bad (recent structure and leaving out a lot of diag test procedures), and sometimes they are critical (updated torque specs for the changed crank bolt on the EA888 Gen2, e.g.). Wonder why they elected to remove the reference (assuming the employees doing the documentation edits have ever even been under the hood of an Audi vehicle).

It is interesting that the VCDS label just says "test". I wonder if this is the same as 0119 - coolant circuit vent routine in ODIS. Would be interesting to run a CAN sniffer during the VCDS action and the ODIS action and compare the actual commands forwarded to the ECM. Seems to be no quick search hits on bleeding a CWGD or DECA out there.

No search hits brought me here hoping for some luck. You’d think there would be something out on the web by now, given how long this engine has now been on the market. Not to mention the vast amount of pumps, valves and thermostats that have gone bad on it.

I have been videoing everything I’ve done so far (including the half-wit idea to drive only the front passenger wheel up onto a ramp 🫨), so if I accidentally figured out the magic method to bleed this thing correctly, I can post up the instructional.

Since there's no sight glass to see air in the coolant system, how are concluding you have air that still needs to be removed?

Oh, and that tube. I assume it's the drain/vent line for the headlamp, the way it looks. Should slip into a notch in the air guide along the radiator.

I think that there is air in the system because after bleeding, I’ll go on a test drive and as soon as I engine gets to operating temp 207c, I get the dash pop up for “coolant temperature too high” when I’m a bit aggressive with a WOT. I’ll then get some nice coolant boil over.. At that same time I have vcds open and watch the coolant temp go from normal 98C to 108-116c for a minute.


Then, as after I let off gas, it’ll make its way back down to the normal 98-ish. But I’ll still now obviously have to do a top up of coolant right afterwards, aggravatingly.

So I am guessing in its finest form, that the issue alert would be the un bled air that made its way back through the cooling circuit, but I can’t explain why it happens only when engine is hot .

Bump

So here is something strange that may help diagnose my issue I hope. In VCDS I have this output test option to run "IDE05036- Switchable Water Pump". Typically, when I run this output, I only get the "click, click" sound and nothing else ever happens.

Today however, I ran this output on a dead cold engine that sat for a day, with the electrical connector to my upper switching valve removed,, but left the vacuum lines on it alone. Now i hear an actual pump pushing coolant through the system. What is up with that?

(connector in reference)
https://cimg5.ibsrv.net/gimg/www.aud...3e370d217a.png
https://cimg6.ibsrv.net/gimg/www.aud...71f8fe8b9f.png

Well,, I vac n filled and bled the circuit overnight by running a Microsoft power automate session that ran the heater support pump and coolant pump 2 every hour while leaving the reservoir lid off. Went to test drive this morning and got the wonderful “coolant temp too high” alert… So I pull over and turn off the engine and let cool down for 20 minutes.

Started back up— with a puttering whole car shaking vibration and a new code for P0203… sprayed all the injector contacts with electronic cleaner and reconnected with no luck. Now I have a whole new damn problem and can’t find any solutions on the web past what I did cleaning connections.

Frustrated to say the least.

It appears that the factory procedure is calling for a hot/running engine to do this. This probably activates valves that normally not working for a cold engine. If this is true, then the vacuum fill probably won't work... unless you can find all the valves and pumps involved and activate them by force (applying signal or power) on a cold engine for the vac and fill to work.