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I recently bought an Audi A3 2.0 TDI and after a couple of days I realised that it has a coolant leak.

I can see where the coolant is leaking too. It looks like its coming from the coolant bottle like a little crack because the water is on the undertray underneath the coolant bottle. However sometimes the car blows white smoke not a lot but it blew a lot one time when I put pure water in the coolant bottle to get me home.

The oil looks a bit gunky and mucky but it's on 168k and hasn't been serviced for a while. The engine sounds sweet.

Will it most likely be a crack in the coolant bottle?

  • where is the smoke coming from? the exhaust? do you have some kind of warranty? – Ben Nov 22 '17 at 2:33
  • Yes the exhaust and no it was a private seller – Ryan Nov 22 '17 at 7:01
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That engine has been severely neglected. Cracked coolant reservoirs and white smoke indicates your A3 may have a blown head gasket.The oil is old too. The crack in the coolant bottle means gas pressures from the engine has escaped into your coolant system and it was so great it cracked the coolant reservoir tank.

If you want to keep the car and save it that's up to you but be aware that repairs to a blown headgasket may be relatively expensive. Ask a mechanic to perform a compression test and a leakdown test on the motor. If the compression numbers are healthy, then the motor can be saved. A leakdown test will verify if your head gasket is blown and will tell you where the leak is coming from. Also if you do have to replace the gasket, ask the shop to check if your cylinder head is warped. If it is you will have to send it to a machine shop.

Now, this all could be not too bad perhaps there is no gasket leak. Perhaps the crack on the fluid reservoir tank is superficial and you need only a new reservoir. And perhaps the white smoke is from bad injectors or glow plugs. There's really no way to tell unless the shop does a compression/leakdown/coolant combustion gas leak test.

But with white smoke, a cracked reservoir, and murky/gunky oil (this means water has mixed with the oil). These are all indicators that it is very likely a blown head gasket.

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    Another possible way for coolant to get in the exhaust on a modern diesel is a leaking EGR cooler. Could be this if there is no water in the oil and it's just dirty – Dave Smith Nov 23 '17 at 15:16
  • What you say about the failure mode is plausible, but I've had a coolant reservoir crack without any issues with the head gasket or cooling system. It's amazing what age and heat does to plastic. – Zaid Feb 21 '18 at 15:32
  • there's also a simpler test to detect hydrocarbons in the coolant. The oil may not be "old". It probably has coolant in it. – John Lord Nov 27 '18 at 22:26

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