Mayonaise under oil cap

[Hannes]

Hello guys,

Since last week I am the new owner of a 2005 AXX GTI. I have unfortunatly noticed some issues. Yesterday I was driving and suddenly the car started beeping and saying ‘STOP’ togheter with a red oil warning light. So I’ll be checking the oil pick-up line this week. Now the other issue; the coolant fluctuates between 50 & 90 degrees so probably a bad thermostat. But now I checked the oil cap and have noticed white gunk (mayo) on the underside of the cap. As far as i know the car was used for longer trips (30km+) so I’m a bit worried. Is it possible the mayo is caused by the coolant not getting up to temp? I have no idea how long the thermostat has been broken for.. 🤔
Hoping for some answers
Friendly greetings
Hannes

[Ripstop]

First don't drive any real distance unless you have checked the sump and oil strainer and topped up the oil. The thermostat is a common issue and plagued most of us at some point and they just start to go "off" Start by changing the main thermostat which is labour intensive but doable. The second more important issue sounds like oil pickup or low oil. Drop the sump and change the pickup strainer as that's also known to block up. Highish miler cars need a reputable VW approved oil like Quantum Platinum or Millers and a strainer clean or better still a replacement.

The mayo in the cap could just be that it needs longer runs but check the oil strainer first. I wouldn't worry about the mayo unless you are seeing drops in coolant levels at the same time. A longer run of 100 miles should clear that 

[pudding]

Mayo is just condensation.  ALL cars do it.  Hot crank case air and oil vapours rise to the coldest part of the engine and emulsify. 

It happens on mine and I do 60 miles a day.  The summer months will get rid of it as engine warm up is a lot faster.

Head gasket failure is extremely rare on engines with MLS head gaskets, which have been standard fitment for nearly 20 years now.  So don't worry about that either.

Do worry about the oil pickup though.  Get it done asap!  And do the thermostat.  Your engine is running too cold, exacerbating the problem..