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A3 1.6 petrol smokes after thermostat change

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i am new to the forum and would appreciate some advice on my 2004 a3 1.6 petrol car

I have had low temperature gauge readings for a while now and thought i would change the thermostat to see if that would resolve it.

replaced thermostat ok and temperature now goes up to 90 (halfway) when up to temp and stays there, thought that sorted it but now the car runs weird it sometimes fluctuates on tickover between 800 and 1200 up and down and when i get stuck in traffic and then set off it blows whitish smoke out which has a sort of carbon smell. I am not loosing water and I dont think it is steam from the exhaust. before i replaced the thermostat i had none of these issues apart from low temp gauge reading and maybe poor mpg.  the engine management light is not illuminated

hope you can help

many thanks in advance


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Hello Dave,

Welcome to the forum. I have recently renewed the thermostat on our 2006 1.6 due to the car failing to consistently reach 90 - although it would sometimes get there. Touching wood, I have not experienced any issues similar to what you have experienced. 

Couple of questions:- How long had you been experiencing low coolant temperatures, and how low was the then-normal running temp? How many miles has the car now done since you renewed the thermostat? 

It is possible that the car is now ‘learning’ it’s newly corrected running temperatures, and if it were mine, I would be treating it to some Redex additive and giving it a good ‘Italian tune’, and see if that improves the general running. 

If not, then you would need to start to look at other possibilities. You have the bonus of no coolant loss and no engine management light on, so some positives there.

Perhaps you could let us know how you get on.

Kind regards,



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Hi Gareth

thanks for the reply

it was my sons car and he ran it for over a year with low temp readings it sometimes got to 90 similar to yours but mainly around the quarter mark.

i have the car now and thought i would change the thermostat yesterday it now reaches operating temp but with those issues i described .I have only done about 30 miles so far so i will try some redex and give it a blast.

i took plug 1 and 4 out to have a look at them and they were sooty not a nice brown colour (didnt take 2 and 3 out yet as they are a pain to get to)

many thanks dave

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