TEMPERATURE PROBLEM

[Shasha]

Unsure what to suggest as many people face the same problem before and after me and everyone's problem is sorted. 

 

Maybe it's the other sensor which is £10 which is on top. Sorry I can't be much help as I'm useless when it comes to cars hence I came here and people helped me out. Perhaps ask people who helped me on this thread? 

[Nigel_S]

1 minute ago, Shasha said:

Unsure what to suggest as many people face the same problem before and after me and everyone's problem is sorted. 

 

Maybe it's the other sensor which is £10 which is on top. Sorry I can't be much help as I'm useless when it comes to cars hence I came here and people helped me out. Perhaps ask people who helped me on this thread? 

Thank you though. Came home an hour ago and it was ok, but it was -4c this morning. Will be frosty again tomorrow so will see what happens

[Shasha]

Hopefully it may get better by the morning etc.

[softscoop]

Did you fit a quality part when you replaced it?

[Shasha]

No just a cheap one off eBay. 

[Nigel_S]

1 hour ago, Shasha said:

No just a cheap one off eBay. 

No, was a Fabi Bilstein one off Amazon

[Shasha]

I bought mine from eBay

[Nigel_S]

Ok so this is weird.  since changing the DSG stat a couple of weeks ago, in the morning it won’t warm up (weather was -4c Wednesday +4c Thursday).

 

In the afternoon it’s been 5c both days when I have gone to the car after work and it’s been perfect on the return journey.
 

Last Friday -2c, drove 20mins and no more than 70c on the gauge. Stopped for 2 mins in lay-by, key out & locked car so hopefully systems shut down. Restarted and drove off & it went to 90c and stayed there & ok for the next 5 miles home, still -2c out?! I’ve repeated this a couple of time and works every time. 

 

anything over +5/6c out and it seem fine, when really cold it does this weird thing. Sound like a sensor feeding bad info to the engine ECU? Any ideas??

[Shasha]

Really don't know what do suggest, have you now changed both sensors? Dsg stat sensor and the normal coolant sensor? 

 

My coolant sensor wasn't faulty but initially changed that but it didn't fix the problem but then I changed the dsg stat sensor which fixed the problem. 

[Nigel_S]

do you mean the thermostats themselves, or electrical sensors? The DSG stat has been changed, and personally doubt that the main stat is duff. Water pump has been changed too with cam belt. 

Edited 28 February, 2023 by Nigel_S

[Shasha]

I got the termostats changed 

[DrCorbyLee]

28 minutes ago, Nigel_S said:

do you mean the thermostats themselves, or electrical sensors? The DSG stat has been changed, and personally doubt that the main stat is duff. Water pump has been changed too with cam belt. 

Be worth double checking you installed the new DSG 'stat with correct flow direction.  Can't 100% see how it would cause your symptoms but got to be worth a quick check.  

 

The main 'stat can cause problems.  I had all the classic symptoms of DSG 'stat over-cooling when my car was still covered by Skoda extended warranty at just over 97K.  Main stealer were pretty much ignorant of the DSG 'stat and reckoned my problem was something to do with secondary water pump.  Never quite got to the bottom of what was the primary cause of the over-cooling, certainly wasn't the secondary water pump but they billed multiple hours (fortunately covered by warranty claim) for troubleshooting the issue including testing the main 'stat on the bench (I assume using the workshop canteen kettle to heat it and watch it open and comparing water temperature with design opening and closing temperatures) which they decided was faulty and swapped out but was still over-cooling.  Spookily enough was only cured once they took my advice (thanks to Briskoda) and swapped the DSG 'stat.  So if they are to be believed (possible they were just covering their arses to get everything covered by warranty?) then both my 'stats were faulty.  So certainly worth considering swapping the main 'stat as it's a relatively low cost part and if you still have problems then, I guess it could simply be that you are getting spurious temperature readings.  If that is the case be worth using VCDS or similar to monitor the raw temperature data around the engine to get a better feel for what is going on temperature management wise

[Nigel_S]

The DSG stat is definitely the right way round, it’s odd that it happens when ambient temp is low but that a simple turn it off and back on again fixes it.

[DrCorbyLee]

On 01/03/2023 at 17:22, Nigel_S said:

The DSG stat is definitely the right way round, it’s odd that it happens when ambient temp is low but that a simple turn it off and back on again fixes it.

A thought to quickly identify if your spurious temperature readings are correct or not.  How you monitored the oil temperature at same time as you are seeing the low water temperature that then rises to normal 90C after a shutdown?  You can view digital value for oil temperature on MFD (although you may need to enable its display in the MFD settings).  With the car up to temperature (i.e. water displaying 90C), normally see oil temperatures higher than that, the difference depending on the load e.g pootling around town will be low 90s, constant 75 on motorway high 90s and possibly a little higher when under constant heavy load e.g. going up a long steady incline.  If the oil is in 90s when water is in 70s in scenario you describe then you can't trust the water temperature reading.  If it's similar to water temperature then you still have a genuine over-cooling issue.  Still doesn't explain the low temperature / shutoff fix you describe.  I wonder if the new DSG 'stat is suspect and isn't operating exactly as it should?  Unfortunately, the only way to know would be to try another one.  It looks like you can get the same Amazon supplied Febi 'stat for 11 quid on ebay (www.ebay.co.uk/itm/174960689427) so suggest that might be the simplest and cheapest next step.  

[Nigel_S]

Oil temp goes up with water but lags a bit behind so as it warms up say the water is 65c the oil will be 55c or 60c.  At 90c the oil is around the 89/90c too depending on driving.  The oil temp does not overtake the water reading so doubt its the CTS or the dash could read 65c for example but the oil could be up to 80/90c.   Also the interior heater is colder when its not warming up compared to when its at full temperature which you'd expect if the engine's not hot so it seem the gauge reads right, its just weird that turning it off and back on even for a few seconds means it then heats up as it should, and if the ambient temperature it 7c or above its ok, but when its really cold of a morning its doing the weird non-heating up thing!!?! 

 

If the thermostat was sticking open then I would not expect to see it warm up at all really when it was -2c out but it did to 65/70c and the on/off fix worked, and that wouldn't cause the thermostat to un-stick so I'd like to rule the stat out too. 

 

Its got new water pump which made no difference; system was bled before and after with no change (but didn't expect there to be to be honest).

 

Two things:

i) I read somewhere about the engine oil cooler having one of the same stats as the DSG gearbox but only read that on 1 thread and no where else so not sure if its true and certainly cannot see one anywhere.

ii) there is an electric water pump in the system; is it possible that is running when it shouldn't, or not running when it should and if that is the case what effect would it have?  I am not sure exactly what the electric pump is for......  My 5-series had one but it just circulated hot water to the interior heater so you can keep water without the engine running.