Hi FOC,

For the past18 months or so I've noticed some odd things occurring with my 2013 MK3 1.6 TDCi (95,000 miles), they are:

·         Occasional (depending on driving amount, perhaps x2 times per month) requirement to top up coolant in the expansion tank to min/max level, not dropping much - perhaps x2/x3 tea cup full each time.

·         On warming up to running temp, the gauge rises and falls (sometimes fairly quickly) x1 or x2 times before settling at the correct gauge mid-point.

·         During extended driving (e.g. motorway runs) the temp gauge sometimes drops back to the 60 deg mark but then rises and settles back at the mid-point.

·         No noticeable coolant leaks within the engine bay although rear engine hoses/aircon heating element side difficult to check, but again no noticeable evidence of water leaks from beneath.

·         Clean oil filler cap, no white residue associated with oil/water mixing e.g. head gasket issues.

·         Never over-heated, fan kicking in when required although has smelt 'a little hot' on occasions after long drives.

·         Have replaced expansion tank & cap when filler/rad cap got stuck and had to remove it ‘in pieces’.

·         I’ve had the timing belt/water pump (90,000 miles) replaced during the period of the above observations.

 

Google searches point to thermostat, rad cap, head gasket, temp gauge and/or temp sender.

Any thoughts/solutions greatly received as this one has got me stumped.

 

Best regards,

James.

Hi James, with an engine of 95000 miles I'd suspect a very slight head gasket leak. You have already replaced the usual items, expansion tank, filler cap, water pump.

Personally on your engine I'd put some 'Radweld' or similar in the expansion tank and that should be an end of the problem.

https://www.holtsauto.com/holts/news/radweld-work/