i have an opel astra twintop 1.6 2009. oil is mixing into coolant system. there is oil in expantion tank. almost all the oil goes into expantion tank. Can you show me the way how to solve it? we changed oil cooler but problem still exist. Same thing happened again. Now water is not circulating too. may be oil blocked circulation way of water? last thing we tried we blocked water passing way inside oil cooler. so that no water enters into oil cooler. again i saw oil inside expantion tank. i want to be sure if it is new or old.

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    You likely have a blown head gasket. Have you overheated the engine? What are the results of a compression test? Oil and coolant passages in the engine are completely isolated. For them to mix, you must have a blown head gasket or a cracked block. – 3Dave Jan 3 at 17:58
  • probably it is overheated. i didnt make compression test. broken head gasket cracked block and oil cooler damages can cause them to mix. problem seems it is not in oil cooler. should i change gasket? – Mehmet Gökşin Jan 3 at 19:47
  • It will not be the oil cooler. See @SalvadorMartinez’s answer. Inspect your oil for coolant - you need to drain it all anyway, and it will tell you a lot. If the gasket is blown, you’ll need to replace it, but also check the head for flatness. This is not an easy repair. If the engine block is cracked, you will need a new engine. – 3Dave Jan 3 at 21:51
  • Depending on the location and severity of the leak, you might be able to fix it with block sealant. But, I have never had good luck with those products. Still, cheaper to try that first. Good luck. – 3Dave Jan 3 at 21:59

The only place where oil and coolant can mix is in the engine itself. So as Dave said, either you have a bad head gasket or a cracked engine head. Check the oil to see if there's coolant in there. You can tell because the oil will be a coffee brown milky color.


i found the problem and it is solved. problem was not head gasket. it was oil pump gasket. oilpump gasket is separating oil and water from each other. previously oil and water mix happened in the past. previously it was oil collant. because in oil collant oil pass inside it and from other side water pass. oil collant had 4 holes. 2 enterance 2 exit. from 1. enterance water comes in from 2. enterance oil goes in. 1. exit is water 2. one is for oil. but problem was not oil collant. it was oil pump gasket.

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