Motor Oil in the radiator

Our Honda Accord had motor oil in the radiator overfill. Our mechanic thought it needed a new head gasket; it was repaired about three weeks ago. The problem is still the same. The dip stick is down on oil about 2 quarts and is clear. the overflow is mixed with oil. I would welcome any suggestions and thanks.

There are several possibilities but any chance that is transmission fluid in the radiator and the engine is just burning oil?

An engine should never be allowed to get 2 quarts down as that just exacerbates any oil consumption problems.

Year, miles, any past overheating episodes, mechanic check block and cylinder head surfaces for flatness, etc?

By chance does this Accord have an oil cooler? My research of 2004 and 2008 does not indicate a cooler. Ask your mechanic?

To help us out specify the year, the engine configuration, and size i.e. example 2003 Inline 4, 2.3 liter.

What year is your Accord? Older models have an engine oil cooler mounted between the oil filter and engine block. If this part has ruptured you will have engine oil mixing with coolant.


When the head gasket was replaced, did the shop measure the head for warpage?

If so, did they have the head machined?

I hate to be the bearer of bad news but, some Honda engines had problems with the castings becoming porous. If this is the case the fix is to replace the short block. Having the year of the car would help.


Speaking of those porous Honda blocks, I know to what you’re referring

It was the smaller aluminum engine, used in the Civic. The daughter of an acquaintance brought a 2006 Civic to me, complaining about overheating and losing coolant. I found the block to be cracked. I learned about the warranty extension on the Honda website, it applied to her vehicle, so I sent her to the dealer. They installed a new block with fitted pistons, free of charge.

I don’t believe the larger engine in the Accord had this problem, but I may be mistaken

Ask the shop to drain all the oil out of the crankcase, put it in a clear container, and see if there is water in it. Any water will layer at the bottom and the oil will often have a milky appearance indicating there is an oil/water emulsion.

Then do the same with your automatic transmission fluid. Do you see any signs of water in that?

I expect there is no water in the crankcase oil, but there may be indications of water in the transmission fluid. And the oil you are seeing is from the transmission oil cooler which pumps transmission fluid in tubes through the bottom of the radiator. Those tubes inside the radiator can spring a leak, and the transmission fluid will go into the coolant. On certain make/model/years of cars this is a known problem, and sometimes the manufacturer will help out. Whether this is the case for you car, you’ll have to do some research.