Browse over 9,000 car reviews

Why is the coolant in my 2007 Holden Astra a milky colour?

Why is the coolant in my 2007 Holden Astra a milky colour? The engine oil is clean as a whistle.

The first response of most mechanics on this would be that you have a head gasket leak in the engine. Coolant in the oil and/or oil in the coolant are classic symptoms of this. It happens because the faulty head gasket allows the two fluids to mix but, depending on exactly where the gasket fails, you don’t necessary get both symptoms. A workshop can pressure test the engine’s cooling system and perform what’s called a TK test to show up any contaminants in the coolant that have found their way there via a blown head gasket.

But before you go tearing into the engine, check the service records to find out how old the coolant is. Coolant will discolour over time and kilometres and what you’re seeing as a `milky colour’ might simply be old coolant that has gone cloudy and needs changing.

Disclaimer: You acknowledge and agree that all answers are provided as a general guide only and should not be relied upon as bespoke advice. Carsguide is not liable for the accuracy of any information provided in the answers.

Comments

Have a new question for the CarsGuide team?
More than 9,000 questions asked and answered.
Complete guide to Holden Astra 2007
Complete guide to Holden Astra 2007 CarsGuide Logo
Reviews, price, specs and more