QuestionI have the famous 'mayonnaise' under the oil cap. I have heard this may be the head gasket (very expensive), or the relatively cheaper thermostat, which apparently is a problem.
AnswerHi Darren, the mayonnaise under the cap is indicative of moisture in the oil, however there are many symptoms of a blown head gasket;
1. Pressurised hoses after a few seconds running.
2. Tiny air bubbles in the coolant reservoir.
3. Engine overheats very quickly.
4. Heater inside car blows cold as the engine overheats.
5. Moisture present in the oil (mayonnaise).
The head gasket separates the water and oil galleries form the combustion chamber, so although any mixing (oil in the water or water in the exhaust fumes or pressure from the cylinder in the coolant system) can indicate a blown head gasket, there are usually a group of symptoms. Do not worry too much about just one. If you are showing 2 or more of these symptoms, the next step is to have a local garage perform a compression test. This will tell you if your cylinder head gasket is damaged. - Good luck and let me know how it goes - Paul
