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TDI 101 Got a simple/basic TDI question? Are you a newbie (new to the forums). Feel free to post your question here.

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Old February 28th, 2018, 06:37   #16
AndyBees
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I'm not sure when VW began using the CTS to trigger the Fan Control Module to turn on the fans, but I do know the 2008 EOS Gasser has that setup. Also, the FCM is built into the large fan motor.
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Old February 28th, 2018, 10:32   #17
halfbytecode
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• It seems the radiator fan would turn on when the CTS reports a temperature of 97. Whether it reports it correctly or not, seems like another story.

• I was reading about updating the ECU software using ODIS, and it seems it can be done to versions older than the latest. I just need the .bin to supply to ODIS. There is apparently a flag in ODIS, that disables the software version check. However, before proceeding I have to ascertain the software version installed on my car's ECU, and determine the ECU part number, followed by getting ahold of the software 9972 for it.

• I should have access to an OBD2 scanner in a few days, and I will try to check the coolant temperature at cold starts, the time it takes for the temperature to rise, etc. Should I do that first while the car is idling, followed by going to a long drive after that, or both separately on two different days right at cold starts?

Last edited by halfbytecode; February 28th, 2018 at 21:06.
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Old February 28th, 2018, 11:33   #18
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If you have a faulty sensor (or wiring!), you will notice it right away. Usually these sensors crack internally. Maximum value for this sensor is set to 140 *C I think, minimum is -40 *C. Both will trigger fan to come on at highest speed as the car doesn't know the real temperature (safety feature).
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Old February 28th, 2018, 13:18   #19
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Thanks. By the way, I was taking a look at the service manual, and there seem to be two coolant temperature sensors!

One is labelled -G62- which is what we have been referring to, so far. Apart from that there is another CTS labelled -G83- which is called the radiator outlet CTS.

I looked up the part number for G83, and it is the exact same part as G62, just installed as a secondary unit.

Does this change the way the issue should be diagnosed?

Last edited by halfbytecode; February 28th, 2018 at 21:07.
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Old February 28th, 2018, 21:20   #20
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While reading through the service manual, I came across a rather interesting piece of information:

Checking 4/2-way valve
with thermostat ⇒ Vehicle
diagnostic, testing
and information system
VAS 5051 „Function
and component selection“.

I am going to have the thermostat checked this way.
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Old March 1st, 2018, 00:59   #21
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Yeah, there are two sensors. The G83 (which is located next to alternator) is not very important and its value often can be substituded. But you want your G62 working properly.
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Old March 5th, 2018, 09:15   #22
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I got access to an OBD2 scan tool. I scanned the car for errors, and, as expected, there were none. I will check the coolant temperature shortly, using this tool.

My car does not seem to have am engine oil temperature sensor. There is no data available for engine oil temperature.

I was able to know the ECU software version, and also the exact ECU part number. The software version is 9971. I will try to have it updated to 9972 using ODIS.
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Old March 6th, 2018, 01:08   #23
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That's great. 9971 is very good software. 9972 is improvement of course but luckily you don't have those buggy ones versioned <8000
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Old March 6th, 2018, 07:44   #24
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Quote:
Originally Posted by Henrick View Post
That's great. 9971 is very good software. 9972 is improvement of course but luckily you don't have those buggy ones versioned <8000
Yes, I was quite certain that I had good software, as the moment it was installed, all earlier cold start issues due to the earlier software vanished. This was way back in early 2011.

The car had no cold start issues for years following that.

Anyway, I checked the coolant temperature today using the OBD tool, while driving the car in the city.
  • Right upon ignition, the coolant temperature was 22C, as per the data from OBD tool. The outside temperature indicated on the MFD was 23.5C.
  • The coolant temperature gradually increased to about 60C in about 10 minutes.
  • From there on, it took a lot of time for the coolant temperature to increase, especially after about 70C. It finally reached 90C in about 35 minutes.
  • The coolant temperature began dropping slightly after reaching about 90C, by nearly a degree or so. It kept fluctuating around 90C.

As per the service manual, the thermostat starts to open at 92C. [Fully open at 107C, just to throw that in]

Does this help?

I will try the same with the car idling, as well as by going on a long drive.

Last edited by halfbytecode; March 6th, 2018 at 08:01.
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Old March 6th, 2018, 10:35   #25
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is the thermostat stuck open?
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Old March 7th, 2018, 01:39   #26
Henrick
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To me it looks like your thermostat is working properly. It might have 1 degree "loss" due to normal wear/age on it.

Idling is not a good measure to check anything in these engines. I have noticed that the coolant temperature gets higher with engine under load and idle RPMs, e.g. when parking in a lot back and forth
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Old March 7th, 2018, 05:15   #27
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Quote:
Originally Posted by Henrick View Post
To me it looks like your thermostat is working properly. It might have 1 degree "loss" due to normal wear/age on it.

Idling is not a good measure to check anything in these engines. I have noticed that the coolant temperature gets higher with engine under load and idle RPMs, e.g. when parking in a lot back and forth
I forgot to mention the service manual has approximate temperatures listed for the thermostat opening and fully open states.

What can be the issue for me, if the thermostat and the CTS seem alright? Is it possible there is significant sludge formation in the engine, engine components starting to wear over time, or something else?

Cleaning the fuel injectors using diesel purge helped somewhat.
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Old March 7th, 2018, 13:41   #28
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Since I have no clever ideas, I won't comment anything on this.
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Old March 8th, 2018, 06:16   #29
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Is the car with DSG? There is a separate thermostat for the DSG which may be faulty.
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Old March 9th, 2018, 02:45   #30
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Quote:
Originally Posted by Henrick View Post
Is the car with DSG? There is a separate thermostat for the DSG which may be faulty.
It has a 5-speed manual transmission. I was thinking about the time it takes for the coolant to reach 90C, which is over 30 minutes. Does that seem normal?
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