MK5 Golf GTI
All Things Mk5 => How to Guides / Troubleshooting => Topic started by: chris s on August 16, 2014, 07:49:29 am
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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
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Definitely go with the Coolant Temp Sensor :happy2:
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Cheers mate, is it likely to be the sensor under my itg intake, to the left of the battery?
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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
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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.
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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?
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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
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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
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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 :laugh:
Best going with the main stat then you know it's sorted and eliminated from the diagnostic process!
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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?
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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
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This is thermostat 100%. As said it's a mechanical part that won't show up with a fault code.
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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
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adas
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srwer
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stwrt
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Thanks Dan you live and learn eh.... Interesting thoughts from rich wig??
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My thermostat failed when I bought my ed30. No fault codes, just temp gauge dropping when coasting.
Part was around £30 from VW. . . Fitting yourself is not fun at all - basically the whole front of the engine has to come off. I gave up and got Awesome GTI to do mine. The tech said he hopes to never do another one of those
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Exactly what I found out... Quoted £224 all in by the loa all vw dealer so worth it for the amour of work needed
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A quick update to this issue... As I eventually worked out the problem I had was down to a knackered main thermostat. Cost me £224 all in so not cheap but the gauge is upto 90 after 5mins and is rock solid! Not noticed any better mpg and I drive like a granny on my commute so can't comment on performance but expect both to be better
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Definitely have the same problem. I really don't like paying vw to fix my car but judging by people's reaction to this work I might have to.
Did you just bring it into vw and they determined it was the main thermostat or is this a trial and error approach and you fix one part after another until you fix it?
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Pleased you got it fixed :pomppomp: even at that cost :surprised: will be beneficial especially as winter approaches...
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I wasted my money by changing the coolant sensor first, but if your symptoms are like mine I'd advise going to vw and ask them to change it. I'd prefer to use a good Indy garage too but vw is next to my work now. They did say they had to diagnose themselves but surprisingly they agreed me.
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I'll take a look myself tomorrow and if it all looks too much I might just book it in.
My next question if I anyone can answer. Is this sensor not just to show when you get to the ideal operating tempwrature or does it actually cause your engine to operate differently.
For example I'm driving 6 hours but the temp still shows about 80degrees. Will my engine now pump more fuel in to get it up to operating temp?
Does it actually have any detrimental affects?
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I'm no expert but I would have thought it would be like running with a choke out?!? Ie possibly over fuelling and I think the ecu holds performance back a litt but could be totally wrong
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I'm no expert but I would have thought it would be like running with a choke out?!? Ie possibly over fuelling and I think the ecu holds performance back a litt but could be totally wrong
I think your right. Mine was definitely holding back when the stat was busted
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So I spoke to VW about it and they said it's 3 hours work so total cost is just shy of €400!!!!!
From the thread I've gathered that I won't (which I don't) get an error code but I can have VW live read with VCDS to see if the main thermostat if relaying info.
I've booked in for laser alignment with VW on Friday so they said they can scan it then and find out if it is at fault.
In terms of the work, I've changed brakes, suspension, dv and all service items on my car. Should I tackle the main thermostat myself or is it too much of a heartbreak and am I better off getting VW to do it?
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That's very high, I had mine done at VW Benfield in Newcastle for £224, and beeline it is about 3hrs work, and not easy work, so depending on how competent you are with some spanners I'd get the garage to do, but it's your call. Maybe suggest they contact the place I had it done for a price match?
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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
Sorry to resurrect this, but which blocks show the water temp sensor readings?
Am going through the same process and I have the error code P1285 (engine coolant sensor 2 circuit high, lower limit not reached) with fans running constantly.
I’m hoping this is just an over cooling issue with fans running maximally all the time, but would really appreciate guidance of which blocks to check for sensor data.
Thanks
Ollie
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What scan tool do you have? You can't miss coolant temp with VCDS under advanced measuring blocks, it's one of the first ones in the list.
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OBDeleven
So I normally go to live data and the select a “block” to see live data (like when I check the chain on our Tiguan TSI)
Don’t want to rush in to main thermostat if it turns out being a sensor. Interestingly fans come on within 10 seconds of car being turned on, and the needle sits just below 90. However OBDeleven shows coolant temps of around 70 degrees max
Thanks
Ollie
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If it never gets above 70, your main thermostat is indeed goosed. The sensor could also do with replacing as they've revised it a few times over the years. Although the sensor costs almost as much, if not more than the thermostat.....but whilst it's in bits and all that!
If the fans come on after start-up, check you haven't got climate control on 'Auto'. Switch it to 'Eco' and they should turn off.
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Thanks for your reply.
So does not display the normal signs of thermostat failure (I’ve had 3 that did in the past).
I have a temp sensor fault code and the fans run all the time.
When the car is driving the temp will reach 90 degrees on dial (less on OBDeleven block readout) but when stationary and in the cold (with fans running) drops temp (I imagine the fans running maximally cools its).
Aircon on or off doesn’t matter.
Was hoping to rule out which sensor I needed to replace (rather than throw both at it, hence the conversation about which “block” show the temp sensor read out so I could work out which one).
I will just unplug one at a time and see which one I can unplug without gaining another fault code and work it out that way
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Was hoping to rule out which sensor I needed to replace (rather than throw both at it, hence the conversation about which “block” show the temp sensor read out so I could work out which one).
I will just unplug one at a time and see which one I can unplug without gaining another fault code and work it out that way
They both use the same grey sensor.
The one above the gearbox is very easy to swap out.
Logic would suggest it should be 50/50 between the 2, but by the law of sod it will be the one in the main thermostat, that is an awkward stinker of a job - if it's that one and you have any doubts at all about the main thermostat, replace that as well, make sure you get a new O-ring seal and clip for the sensor too.
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Was hoping to rule out which sensor I needed to replace (rather than throw both at it, hence the conversation about which “block” show the temp sensor read out so I could work out which one).
I will just unplug one at a time and see which one I can unplug without gaining another fault code and work it out that way
They both use the same grey sensor.
The one above the gearbox is very easy to swap out.
Logic would suggest it should be 50/50 between the 2, but by the law of sod it will be the one in the main thermostat, that is an awkward stinker of a job - if it's that one and you have any doubts at all about the main thermostat, replace that as well, make sure you get a new O-ring seal and clip for the sensor too.
Thanks for the info.
When I scan it comes up with sensor 2?
Do you know where I could find a diagram which would indicate which one of the 2 is sensor 2 please?
Thanks
Ollie
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Afraid I don't know the numbering.
I would suggest elimination - disconnect the easy to reach one above the box and scan again to see if it can still see the faulty one - if you can see it, that would suggest its the one in the main thermostat.