# Oil in coolant, but not an engine block leak?



## Look for it (Oct 12, 2014)

I'm working on a 93 Maxima for a friend, and wanted to ask a question. I found oil in the coolant and thought it would a head gasket leak, but after using a Combustion Leak Tester, like this (Sears.com). I found no combustion gas in the coolant reservoir, my question is now does that rule out a head gasket leak? And if it does what else could be the problem? 

As a side not I looked as the transmission fluid and it was the cleanest I have ever seen, plus it really looks like engine oil in the coolant. So I don't think it is the tranny cooler in the radiator.

Thanks for the help.


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## rogoman (Dec 16, 2004)

There are three oil passages in each bank of the block that feed the cams. A break in the head gasket between an oil passage and a coolant passage is possible without affecting the sealing of the cylinders. As a side-note, you might want to perform a leakdown test on all cylinders which might show up a possible gasket breach.


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## smj999smj (Jan 1, 2006)

rogoman said:


> There are three oil passages in each bank of the block that feed the cams. A break in the head gasket between an oil passage and a coolant passage is possible without affecting the sealing of the cylinders. As a side-note, you might want to perform a leakdown test on all cylinders which might show up a possible gasket breach.


The problem with that is that a leakdown test still wouldn't show a head gasket leak between an oil passage and a coolant passage; it would just re-confirm that the head gasket is not failed at the cylinder bore's seal with the head gasket. Assuming no one put oil into the coolant system and we ruled out a failed radiator cooler for the trans fluid, the only way to tell would be to remove the cylinder heads to inspect the gaskets. If no damage is found on the gaskets and have the heads checked for cracks doesn't turn up anything, the decision would have to be made whether to install new head gaskets, put it together and cross your fingers, or, remove/teardown the block and have it tested (assuming no cracks were seen with the heads off). Of course, at that point, you mind as well rebuild it.


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