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Matt, Engineer
Category: UK Ford
Satisfied Customers: 21362
Experience:  BEng hons Mech engineering, in auto industry 23 years
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It had a oil cooler fault 2 years ago got oil in water

Customer Question

It had a oil cooler fault 2 years ago got oil in water changed cooler flushed sytem many time now using coolant at times thermostat drops to 0 and the comes back to normal no obvious leak but it has lost all header tank contents not my car a friends any help very appreciated
JA: What part of the car is the leak coming from? And are you sure it's water?
Customer: no sign of leak
JA: What is the model/year of your Ford?
Customer: 57 plate focus
JA: Are you fixing your Focus yourself? What have you tried so far?
Customer: its not my car im 112 miles from car changed cooler and header tank its been to garage and had pressure test
JA: Anything else you want the mechanic to know before I connect you?
Customer: not that i can think of on this issue
Submitted: 8 months ago.
Category: UK Ford
Expert:  Matt replied 8 months ago.


If you have a tiny pinhole leak in a radiator then these often don't leak water but will lose water as steam ( steam molecules being small enough to pass through the hole where liquid cannot) take a look on the rad for any signs of localised corrosion and for areas that look like they've been 'steam cleaned'.

If all of this is OK it may be worth replacing the header tank cap as again you can lose coolant as steam if this is blowing off too early ( the cap should hold pressure of around 1Bar)

The other thing to try is a head gasket / block test kit as these take a coolant sample and analyse it for any signs of combustion gas - if present this would indicate the head gasket is on its way out