NottsDam

SOLVED!! Was the thermostat in the end, which some reffer to as coolant actuator. Latter is probably more accurate since it's an electronic motor driven device which performs the same function as a thermostat. It looks as though the thermostat housing had failed, and not at the classic location of where the unit attaches to the block either, but somewhere right in the middle. The garage has let me keep the defective part so i'll be ken to investigate the cause more closely. Not just ouf of curiosity but also to provide feedback to audi themselves. A £300 pound part, in my view should not fail on a 6 year old car. Especially when any typical thermostat would cost less than £40 and probably be easily fitted by the owner and certainly not a multiple hour job for garage like this was. I also believe that it's this leak which must have cause some kind of oxidation of the coolant which then also cause a secondary water pump motor to go - which shut off the stop/start function, and the level sensor in the coolant reservoir. All in all a very expensive, time consuming and frustrating few months. I'll post some pictures up soon of the faulty part. Be interesting to see what anyone else thinks

Hi Chris, Brief update. I'd bought a replacement thermostat but still wasn't 100% sure where it goes. The pictures on the sites that sell them show an arrow pointing to the collant actuator / water pump housing. I'd asked the supplier via email where its located on the car and they replied saying they weren't allowed to tell me - wtf? Out of curiosity i'd asked a local garage how much to replace the thermostat and they wanted £750 with no guarantee it would fix the issue. I was all set to remove the entire water pump and coolant actuator but in the end i thought i should probably get a second opinion. So yesterday i took it to another 'Audi specialist', in Nottingham. They called me back to say its the coolant reservoir. I was surprised and asked could that really cause the temp to read funny, they believed it could. £70 replace and fit + £50 diagnostic I thought my luck was in. But at the back of my mind i remembered that you had also tried this approach so i wasn't overly excited. Just picked the car up, drove about 2 miles, called into a shop and when i jumped back in the engine management light back on. Car didn't reach temp driving home and scan reveals the P2556 coolant low level fault is still there. They've asked me to take it back in tomorrow. I can only assume that they didn't actually do any kind of diagnostic into the cause but simply plugged into scanner and believed what it was telling them - so much for being a 'specialist'!

Thanks Chris, I spoke to the so called Audi specialist today who was frankly useless. As soon as i mentioned that the fan was running on full whack he assumed that this was causing the temp issue and started waffling about the fan control module -frankly he seemed as baffled by it as me. I did some more investigation tonight though. I plugged in my scanner after a 7 mile drive, same faults as usual. I then started the car but just ran the engine without moving and the dash temp climbed to 90 deg, the live data on the scanner (ECT temp) only climbed to 74. Fan didn't come on whilst i did this. I tunred engine off to see what would happen. Sat watching both readings for nearly half hour and barely any change in either. ECT dropped to about 71deg. I then started the car for about 5 seconds and the ECT dropped by 7 deg within seconds but dash temp barely moved. Waited again for another 10 minutes and repeated. this time ECT dropped to about 65 and dash temp to about the same? I'm really trying to figure out if it's a thermostat issue or an electrical issue? Can't find anything online at all ref this and this site hasn't been much help either as it feels like there's only me and you on it! Still trying to figure out where the thermostat is, seems there's 2, one regular type and another one which is really slender, think it's part of the water pump? So i'm now faced with either getting an auto electrician out of having a go at the thermo but don't know which one to replace. think the reason i can't find anything for this particular model is as you say - 5 year old audi's aren't expected to have such issues....... really tainted my view of Audi!

Hi Chris, Yes i do have a scanner but it's only a £70 jobby. I changed the coolant temp on the rad hose last weekend but still got a dodgy temp gauge on dash. I scanned just before i changed and i've still got the P2556 + had the P0116 <which relates to temp gauge issue, come back. I've cleared these fault codes several times yet the P2556 comes straight back as a pending fault and then within a few starts and stops of the ignition it lights up the MIL again. The scanner can display live data and the ECT degC was reading 70ish while the dash went up to 90 while sat on the driveway. As soon as i drove it though the dash temp dropped to 70 and the scanner to 65 so defo something weird going off on that front. I also cleaned the contacts again for the coolant bottle Re: the 2556 code but as you say its probably nothing to do with that at all. Reading around on the net the only two remaining options seem to be a thermostat Re: the dodgy temp gauge although i still can't get my head around that one or some kind of electrical fault / bad earth. I'm not really any good with electrics although i do have a multi meter. I was able to check the resistance change on the old temp gauge by running under hot and cold water. I did get a change in resistance so seemed that might have been working fine. Spent about £50 on new sensors so far so not too bad really. No mines White but is a 63 plate so not the same car. Interesting though that it's exactly the same fault and same model and there are a host of other people on various forums and different models of Audi that report them same issue - I've just not yet found a single person who found a fix as of yet. I've had the car 5 years and bought from an independent garage in Peterborough so no chance of getting much assistance off Audi. So this weekend I'm hoping to take it to an Audi specialist garage for a proper VAG scan (Not dealership as they've already charged me £160 for a scan while it was in for a service) although to be fair the temp gauge issue wasn't happening then (i don't think - conspiracy theorists eat your heart out) and the fault code i had has since gone after i changed a coolant actuator - something they'd highlighted. they wanted £700 to do that and it cost me £30 :) I'll see what this garage recons and take it from there. Hoping they also help me figure out where the thermostat is and i may change that myself. Looking at the parts on web it looks like it could be accessible from the side of the block but i'm not 100% on that yet. There seems to be about 4 different versions that come up even when i use my reg to identify the car? I'm a bit of a stubborn git when it comes to problems like this so i'm still determined to get to the cause - i just can't afford to fork out a small fortune as i'm currently saving like mad for a new kitchen which I've already had to put back 3 months - living in building site is no fun! I'll keep you posted..... PS: If anyone is reading this in the Nottingham area and has a proper scanner or is a dab hand at auto electrics please get in touch - i'll sort you some beer / cash...

Thanks Chris, I've tried a few things myself already. Going to change the fan sensor tomorrow since it's pretty cheap and easy to get to. Have already changed the temp sensor in the block and disconnected and cleaned the contacts for the coolant bottle. Also did a full coolant flush and change the other week. Suppose next step might be a thermostat change but not sure how easy / difficult that is on this engine. I watched a vid on youtube of a guy doing an S5 and it looked a right pain. I don't trust the code i'm getting either so might have it properly scanned. Typical as i was just about to sell the car too! If i do ever suss it out i'll let you know what it was. All the best Damion

Hi Chris, I’ve exactly the same car and exactly same issue. Did you sort it in the end? If so what was the cause?