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Stephen D
Stephen D, Mechanic
Category: Audi
Satisfied Customers: 652
Experience:  5+ years managing an import auto repair shop. Lots of experience with Audi.
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Audi a4: losing coolant..There is no visible leaks

Customer Question

My audi a4 2005 1.8 T is losing coolant during 2-5 days period. I filled it to max on Saturday and today it is below the MIN sign. There is no visible leaks. a mechanic already check it and there is no holes in hoses or visible leaks.
What is wrong with the car?
Thank you
Submitted: 5 years ago.
Category: Audi
Expert:  Stephen D replied 5 years ago.
Hello, my name is Stephen and I will try to direct you to a solution.

The cooling system on your A4 is a closed system. No coolant should ever escape and it should never require topping off. So, your loss of coolant absolutely indicates a problem.

It sounds like your mechanic just looked at the car with his eyes, rather than performing any diagnosis. Though you did not indicate it directly, I assume you are driving the car and it is not just sitting.

What happens often is a pinhole leak develops. This usually occurs where a hose attaches to a hard pipe, but it could really be anywhere. The leak only occurs when the engine is hot and pressure is in the cooling system. Therefore, the leaking coolant evaporates almost immediately in the hot environment and leaves no significant visual evidence of where the leak is.

To find the leak, the cooling system needs to be filled, then pressurized with a leak down tool; any good auto repair shop will have one. With the system pressurized and the engine cool, the technician can look for the leak. If it is not readily visible, just wait awhile and the coolant will begin to run down from somewhere. He can then follow the trail and discover the location of your leak.

Another outside possibility is that you have a failed head gasket. If this is the case, you would have coolant in the oil (it would look like chocolate milk) or coolant burning in one or more cylinders. This can be determined by having someone experienced examine the spark plugs for residue associated with burned coolant.

I wish I could just name the part that is responsible, but this will take some diagnosis in person to pinpoint. With these instructions, your mechanic (or another competent one) can find your leak. If you have additional questions, just let me know.

Please don't forget to accept may answer. I am only paid when you do so.

Best Regards,