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Author Topic: mk5 gti thermostat  (Read 3901 times)

Offline col012

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mk5 gti thermostat
« on: September 28, 2017, 09:16:36 am »
my mk5 gti runs at 90 degrees fine round town but as soon as i get on the motorway (70-80mph) it soon drops in temperature to 45degrees!! Would this be a sign of a bad thermostat? Its in today anyway (28/09/2017) hopefully it sorts the problem!
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Offline slix

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Re: mk5 gti thermostat
« Reply #1 on: September 28, 2017, 01:35:13 pm »
Yeah defo thermostat. If you have a manual you have 2, a dsg has 3. The main thermostat is usually the culprit though.
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Offline Prewy

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Re: mk5 gti thermostat
« Reply #2 on: September 28, 2017, 05:33:18 pm »
Sorry to jump on the thread but I had similar experience on a recent drive to Devon 130 miles, temp fine in traffic town etc but 45 on A road constant 60mph. What will ultimately happen if not fixed soon just out of interest?
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Offline slix

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Re: mk5 gti thermostat
« Reply #3 on: September 28, 2017, 08:37:50 pm »
Quote from: Prewy on September 28, 2017, 05:33:18 pm
Sorry to jump on the thread but I had similar experience on a recent drive to Devon 130 miles, temp fine in traffic town etc but 45 on A road constant 60mph. What will ultimately happen if not fixed soon just out of interest?

Nothing. I've been putting mine off getting done for 6 months now as waiting for cam belt to do it as will have to drain coolant anyway. Will maybe use a tad more fuel that's all.
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Offline lukemk5gti

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Re: mk5 gti thermostat
« Reply #4 on: September 29, 2017, 08:04:55 am »
Technically it can limit power also as your ECU won't give full bhp until your engine reaches a safe operating temp. I've never tested this but it was mentioned before on here and I suppose I can see why that would be the case.

This thread has come up a million times. Here is the definitive answer.

Manual has one main thermostat and one inline. Some DSG have a second inline

Main thermostat failure - The car never reaches 90deg unless sitting in traffic. It then drops again when you hit the motorway. This is a hard job and not an easy diy. Expect maybe £200

Inline thermostat failure - The car takes abot 20 miles or 20 mins to reach 90. Even in the depths of winter it should be around 5mins or 5miles. The inline thermostat is very easy to do but you need a special "pliers" to undo the circlip. Still a 30min job and it doesn't require a full coolant drain down. Just top it up after.

DSG Second Inline - This isn't on all DSG's. Only some years have it. I don't know enough about this anyway but I think it's the same thermostat as the inline.
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Offline OEM+ DUB

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Re: mk5 gti thermostat
« Reply #5 on: September 29, 2017, 01:34:21 pm »
Yep, if your DSG has two inline thermostats then they are the same part. :happy2:
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Offline col012

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Re: mk5 gti thermostat
« Reply #6 on: October 04, 2017, 12:32:18 pm »
Had my main stat done - £280 @ a VAG specialist reaches 90 in no time
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Stobo91

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Re: mk5 gti thermostat
« Reply #7 on: October 06, 2017, 07:39:58 am »
I’m having exact same, garage quoted £100 labour to fit it next Thursday


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Offline JoshJaggard

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Re: mk5 gti thermostat
« Reply #8 on: October 09, 2017, 03:35:00 pm »
I had the same problems, mine was the stat as well
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