What should I check/replace now?

I already replaced a set of gaskets in the oil cooler. It did no help.oil cooler Z18-XER

Set of gaskets

Engine Z18-XER. Year - 2008.

Nothing else happening. No white smoke, no external oil leaking, no external coolant leaking. No unusual sound,

  • Same thing happening to me, anyone used a leak stopper? i tryied and worked for a month and now it has oil on the coolant reservoir Commented Dec 20, 2016 at 15:47
  • I posted my own answer. It shows how I fixed it. Commented Dec 21, 2016 at 5:23

2 Answers 2


The part number that solved my problem is 24405911.

It is known as Oil Pump front main gasket.

When one will replace it it will remove the timing belt, thus consider replace them together.


  • How did this solve the problem? I'm told that there's no way the problem of oil in coolant can be caused by this gasket because it only seals for oil, not for coolant. Is it possible that while replacing the timing belt, some vibration was eliminated which has reduced the rate at which oil enters the coolant or increased the pressure at which oil will enter it?
    – codeshot
    Commented Oct 27, 2019 at 15:15
  • 1
    I have now found out I was told the wrong thing, this gasket does seal both coolant and oil - the square part at the top at least is for coolant as far as I can tell.
    – codeshot
    Commented Oct 27, 2019 at 20:53
  • How was it diagnosed that this gasket was the cause of the problem in order to save money on trying other ideas? I've been told just replace the oil cooler, it's always the oil cooler but I don't think I believe it. The oil first came into the coolant head as a 3cm diameter blob of oil on top - not creamy, just mid-brown used oil. I'm wondering if that means the oil entered the coolant strictly after the water pump because I suppose the impeller there would whip it to mayonnaise instantly.
    – codeshot
    Commented Nov 1, 2019 at 18:49
  • @codeshot, there is no diagnosing procedure, you just replace rubber parts everywhere starting from cheaper ones and going to the most expensive. See the question for more details. Commented Nov 6, 2019 at 0:39

Oil in coolant most often comes from a leaking head gasket. You may want to perform a compression leak-down test to confirm.

  • In this case I would loose coolant as well, but this is not happening. Nothing else happening, actually. No white smoke, no external oil leaking, no external coolant leaking. No unusual sound, nothing like Blown Head Gasket Symptoms. Commented Jul 18, 2016 at 4:06
  • I added this info into question. Thanks for this idea. Commented Jul 18, 2016 at 4:11
  • I just saw a video of someone testing the coolant tank for combustion gasses as well.
    – codeshot
    Commented Nov 1, 2019 at 19:24
  • Some engines might break the seal between an oil line and a coolant line rather than between a combustion chamber and coolant line. In this case I'm told the compression will be unaffected.
    – codeshot
    Commented Nov 1, 2019 at 19:25

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