Mk6 1.6 TDI coolant/oil temperature increase

[Progessive]

Hi all,

Have searched the forums for any other similar issues and couldn't see anything so thought I'd post and see if anyone can offer any advice:

• Car: 2010 MK6 1.6 TDi Bluemotion
• Mileage: 200,000
• Last service: 10,000 miles ago (due fresh oil and filter)
• Last coolant flush: July 21' - G12 used, no additives ever added
• Coolant level: holding
• Engine oil level: holding
• Heaters: Working OK
• Daily commute: 50 miles each way - motorway

Issue:

• Since having the car I've never known the coolant gauge to go above 90. Until recently. When the engine was working relatively hard the other day, driving uphill, the gauge increased to around 100 degC before dropping back down to 90 degC on the flat. This was doing 75 mph.
• Now I've been checking the oil temp when driving and notice it's quite a bit higher than normal. Average temp is about 108 and it has been as high as 118 when giving car some gas going uphill.
• Seems to me there is something amiss, but not sure what it could be.

Can anyone advise any diagnostic tests I could carry out?

Is it worth replacing thermostat?

Could it be head gasket?

Local indie garage (VW specialist) can get me in for diagnostics in a months time but I've got quite a lot of driving in between so keen to get it sorted. Thanks in advance.

[Marchanic]

Local indie garage (VW specialist) can get me in for diagnostics in a months time but I've got quite a lot of driving in between so keen to get it sorted. Thanks in advance.

Hi, what was the result of the diagnostics?

[Progessive]

Apologies for the delay responding.

So the problem was down to the heater matrix. Despite a number of garages questioning this I found a post elsewhere online of someone having a similar issue, replacing the heater matrix solving their problem. The same happened for me. Replaced the matrix and the gauge hasn't moved off 90. Engine oil temperature however does continue to run hot. I actually changed the thermostat as well, this made absolutely zero difference.

[Crasher]

Heater matrix? That should (in theory) not have any influence, especially in summer as it isn't removing heat but yours was in the winter so it sort of makes sense... ish.