white smoke advice

[zeroasylum]

Long story but all info is needed.
Purchased a vw mk4 1.6l Golf with just over 160000km on clock AVU engine code recently. It had a few issues including a nonworking temperature gauge and also needed a good service.
My wife drove the car for a few weeks’ mainly short trips while I was waiting for the parts. It ran well no issues and accelerated well. It was not burning or dripping oil and coolant levels remained constant. It was not overheating but the fans did come on sometimes when there were not supposed to so assumed this was related to the temp issues which on further investigation I realised was a thermostat that was broken so ordered a new unit part number 06A121114. Due to the temp issues and short trips and engine not getting to temp fully with fans on a lot I did get some condensation under the oil cap and a small amount of milky residue.

So last weekend I drained the coolant. I changed the stat and the green top 3 pin sensor and the bottom 2 pin grey ( thought I migh as well with the coolant out). All part numbers correct like the ones that were in there.

The coolant came out clean but rather than reuse it as I did not know the last time it was changed I refilled it with just distilled water to flush it out. I brought it up to temp. Gauge moved again and fans stayed off and were not on all the time like before. Checked for leaks and all was good. I left it a few hours to cool then drained it again and filled it with penrite approved VW coolant. I brought it back up to temp all good and in working order.

As the engine was warm I left it cool a little bit and decided to do an oil and filter change. Drained the oil and changed the filter with genuine vw unit. Oil was dirty (clearly not done for a while) but moisture free and no bad residue in it.

I refilled it with Nulon 5w 40 Long life engine oil fully synthetic. I measured it in a large measuring jug so as not to over fill. I Put about 4.3L in. Checked level all was good.It all started and ran good in the garage no warning lights etc. I left it overnight. I then checked it in the morning and the level need slight top up to get mid-way to hatching area on stick. Car was on level ground.

So the problem.

I took car out. And it ran well. Heater was now works and temperature guage moves to around mid-way and stays there (weirdly fans did not come on but it was a cold day). Once up to temp I noticed white smoke on take-off or heavy acceleration (was not there till about 10km into the drive). It was fine when moving. Stopped after about 18km. Left it a few hours while in shops then drove home. The exact same thing happened once up to temp. Fearing coolant getting into the engine and a head gasket failure I checked the coolant and oil levels but all remain constant.

Someone mentioned that as it may not have been running at proper temp for a while and with new oil it is simply burning off gunk and carbon deposits. I was thinking a blocked PCV valve but I am not sure.

What do people think? Advice needed.

Thanks

Zeroasylum