Mayonnaise on Coolant - Oil Cooler ?

[Lacostas]

Hello Folks! Long time no see

Problem has already been discussed here quite some times, strong presence of mayonnaise inside the coolant . Ill start with removing the oil cooler and checking for internal mixing, since there is no external leaking (seems that rubber seals are "fine").

The question is - can this be done without draining the coolant ? Eventually ill drain it - and change oil too - but can i just remove and test the cooler prior to the drain ?

Regards