Coolant temp

[chris s]

Hi guys, I think I know the issue but wanted to see if anyone else has seen this issue and fixed it? The temp gauge on my dash no longer consistently shows 90 deg, it warms up in the usual timescales but on my new commute to work (20miles on the a1) the temp usually shows between 80-85deg, but rises to 90 when in traffic.  I've done some research and it looks like it's the coolant sensor or thermostat.  I hope it's the former but not 100% sure.  Has anyone else seen this issue and fixed it? I'm keen to fix it once rather than try a few options and waste cash. Thanks in advance

[phillips]

Definitely go with the Coolant Temp Sensor  

[chris s]

Cheers mate, is it likely to be the sensor under my itg intake, to the left of the battery?

[lukemk5gti]

I've actuly noticed the exact same in the past month. I drove 100 miles at 120km/hr and when I got home I was still around 80 degrees!

The following day as you said in traffic it rises to 90 so I thought all was ok!

Let me know how you get on with the repair. Going to tackle this and dv next week as I just got boost leak error code

[phillips]

Cheers mate, is it likely to be the sensor under my itg intake, to the left of the battery?

That's the one buddy just make sure you get the correct one. See below description:

The coolant temp sensor is on a plastic housing underneath the fuel pump on the right side of the head.  Its also a grey sensor.  You will need to remove the airbox to get to it.  Make sure you remove the coolant cap to release the pressure, then replace the cap before removing the sensor.  This stops you losing too much coolant.

[chris s]

Well, finally got around to changing the Coolant Temp Sensor [OEM from VW] yesterday and I was watching the temp gauge like a hawk during my 30min drive into the office this morning.  The main difference I noticed was that that it took much longer to warm up and actually only got to 90 degrees when stuck in traffic in after about 20miles.  For the majority of the drive it hovered between 75 and 85 degrees.  From having read as much as Google will provide it does look like its the Thermostat at fault and not the sensor.  Bit a pain as the sensor, O-Ring and Coolant set me back about £55.

Does anyone have any experience of changing the Thermostat, I believe its not a job for the faint hearted so would prefer to get a garage to do the job... and I was wondering how much it costs?

[v4rley]

I had coolant tempature issues, have you checked / know about the inline thermostats? I change these first but made little difference so changed the main one, think it was roughly £35 for the part from vw.

I managed to change myself, it's just a bit fiddly and time consuming. I just took my time and wasn't to bad. Fixed my problem and always feel great at the end of a successful DIY! There are a few thread about on here with great in-depth info 

[chris s]

Cheers - I'm more than happy to try DIY, but it's the thought of taking my car our of action, and with a young family and having a 40m commute I'd be knackered if I messed it up.

I've read about the inline stats as well and could try them, but it seems they are not the problem if the temp fluctuates, they are usually the cause of a slow rising temperature

[v4rley]

Yeah that's the only issue with DIY'ing. I'm fortunate that I got a spare car and worst case 1/2mile from vw dealship 

Best going with the main stat then you know it's sorted and eliminated from the diagnostic process!

[chris s]

Well after my disappointment with the temp sensor I've scanned my car this evening and no faults came up, so does this mean I can discount the main thermostat as being faulty?

[v4rley]

Did you scan before changing sensor? Don't believe the thermostat would show a fault code as it not electronic so wouldn't be able to "talk" to the car to throw a fault code.

Some helpulf threads I used when I have the issues
http://www.mk5golfgti.co.uk/forum/index.php/topic,78220.0.html

[swedishfireball]

This is thermostat 100%. As said it's a mechanical part that won't show up with a fault code.

[Dan_FR]

Thermostat as said above. You could have verified the sensor was working correctly with VCDS before rushing out to buy new.

Don't rely on fault codes for errors, live data reading of measuring blocks is far far more useful

[rich83]

adas

[rich83]

srwer