Engine Cooling Circuit Logic?

A6 All/ S6 All
#1

I think someone here may be able to explain what I am observing. Sorta cold right now, 20s and 30s DegF. Upon cold start, I notice the coolant gauge creep from COLD to 1/4 in a “short” duration ~3 min of driving and stays there for “some time”. Warm/Hot air comes from the HVAC

Then after a “noticeably longer duration” the needle moves from 1/4 --> 1/2 (middle). At this point OBD shows ~91DegC

Is this normal or part of the “diverting” cooling circuit these 5.2’s have? Pump and t-stat was replaced 58k ago so possibly stuck? I would assume a cel if the tstat was stuck

I have just always noticed on most cars a linear coolant gauge warm up not a “2-step”

#2

Mine does not operate that way.

#3

Its hard to say. Lots of things come into play. like do you park outside or in a climate controlled garage. Generally the temp on the dash isn’t super accurate there is quite a swing for what range you can see it in. So most likely what your seeing is just whatever the set trigger point is in your ECU to send a signal of movement to the dash.

#4

I am starting to consider the same. Car is garage kept 40DegF, outside is 10-20 in the morning. Possibly my imagination as I’m used to the 4.2 heating a bit quicker. I’ll quickly log it from a cold start in the next few days and have a looksie.

In other/older audis, the CTS is DPDT and provides temp to both the ECU and Cluster separately. Are you saying on the 5.2 the CTS sends temps to the ECU and then the ECU sends the data to the cluster?

I have in the past seen discrepancies between cluster CTS temp and ECU CTS temp resulting from a bad CTS

#5

Mine moves in a similar way, not notchy but normally takes 5 mins to get onto the gauge. And when it does it sis at the 1/4 area then about another 5 mins passes before moving up to the just a hair over 90. Thermostat changed 2 weeks ago.

I live in 15/20C climate

Neil

#6

I am starting to think there is a problem with my thermostat, like yours it heats up to 1/4th after 5 minutes and then a decade to get to half. I get warm air after waiting “too long” imo, my 3500 ram starts pumping heat after 5 minutes no matter the exterior climate, and is pegged in the middle far before my 12 minute drive to work. S6 is struggling to get to half by the time I get to work. “struggling!!”

I am not familiar with these solenoid driven thermostats at all, but if there was a fault in my thermostat, I would assume a code?

Will assume the “new” engine did not come with a water pump or thermostat unless that is part of the long block. I do see they replaced the electric water pump but no mention of the waterpump or thermostat.

So question: From the bottom, how hard is it to replace the thermostat on this car? From the TES and diagrams it appears it is easily done… I want to get this done now before summer as well a coolant flush.

I am not touching that waterpump until it fails! Ill do the engine drop / downpipe stuff at that time… hopefully years from now

#7

[quote=“laketahoequattro,post:6,topic:10322”]
The thermostat is easily removed from underneath. You will need an E8 socket to remove the five screws attaching it to the waterpump housing.

#8

The thermo isn’t too hard to mess with but you would do a lot better to just either put the car into service or even just pull the front core if you haven’t already. The part your talking about is just the housing that has the ele connection to it. As mentioned that can be removed. That might be your best bet as its usually just the unit or the thermo itself.

#9

10-4, thanks guys. Im sure I can handle it.

I have changed the thermostat in a belt 4.2 and a 2.7 by walking the belt off the cam sprocket just enough to wiggle the t-stat out. Total pita lol

#10

Yes PITA… been there… IMHO just pull the front end off its like a total of 45 more min to save all kinds of grief

#11

Haha I was considering doing so.

Honestly “afraid of what I may find” once I pull the front off, as “you dont have any cavities until you go to the dentist”

I used to be able to pull the front of my c5 ar in 15 minutes as I would be doing it monthly lol, hopefully I can get down to that time frame on this c6

#12

honestly the C6 bumper isn’t too bad. this video tutorial shows just how easy it is - https://www.youtube.com/watch?v=ofhFw4BSBlY

getting to the bumper nuts/bolts is more annoying than actually pulling the bumper. just make sure to support your bumper when pulling it off, since there are electrical connectors for the DRLs and headlight washer units, as well as the headlight washer fluid line (i broke mine…oops. capped it off since i don’t like it anyway)