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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21631
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Audi A5 2.7 diesel, 101k miles, intermittant coolant leak,

Customer Question

Audi A5 2.7 diesel, 101k miles, intermittant coolant leak, with no evidence of a drip !!!
Any advice ???
Submitted: 2 years ago.
Category: Car
Expert:  Matt replied 2 years ago.
Hello

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

http://www.uktools.com/block-tester-p-12508.html
Customer: replied 2 years ago.

will check the radiator in the morning. thankyou

Expert:  Matt replied 2 years ago.
no problem Russell