How to Check Oil Cooler Defects . Toyota L Engine Guide

How to Check Oil Cooler Defects

Have you noticed your radiator tank water has been contaminated with oil?

There is no other possible oil passage that could give you the laborious repair of your engine and give you expensive buy of parts.

It is the least impression that the head gasket is the reason for this.  Rarely, that the engine oil will go the radiator coolant or the water will be mixed with the engine oil through the head gasket.

I say this because that was my impression when I encountered the problem.  I called for the technician and had the head gasket replaced because of the oil being mixed with the water in the radiator but it did not solve the problem.

I even asked them to replace the gasket of oil cooler to be sure that there will be no let up for oil and water mixing together whether it be in the radiator tank or in the engine.

How to Check Oil Cooler Defects-oil cooler

After the mechanic had assembled the parts and it was already an evening there was no sufficient light.  He instructed me to wait until the next day to fill the engine with new oil.

So early in the morning, I was very happy to prepare my car for a new start. Because in the evening we had not change the oil yet the oil pan drain valve was not yet returned. The first thing I did was to fill the radiator tank with water. To my surprise when the radiator tank was full I heard something dripping under.  It was water coming out of the oil pan. 

Could you imagine that you are filling the radiator tank with water and it goes down straight to the oil pan? I tried to figure out in my mind how had it happened for we have just replaced the necessary gaskets.

I have spent more than two thousand pesos for head gasket and oil cooler gasket replacement including service fee and the problem was still there. I tried contacting the mechanic but answer.  I was too irritated.

I decided to consult another mechanic to hear what’s all the problem.  He told me that the oil cooler must be checked.  I don’t know what he was referring but I removed the oil cooler from the engine and that’s a hard work for me but I had to do it.

I bought the oil cooler for him and this is what he did which I was so convinced that he has the wisdom that other mechanics didn’t. When it was proven that the oil cooler has defects I decided to replace it. 


Checking oil cooler defect through the use of water and air pressure.

Posted by Jimmy A. Dolo on Thursday, June 8, 2017


As you can see the water bubbles in between the air pressure and the thumb that shows that there is a hole in the oil cooler. 


Try checking the oil cooler to ascertain that it has no defects before doing anything else on the engine.  This will prevent unnecessary repairs on parts that should not be given attention to.

What if your oil cooler has no defects?
How to Check Oil Cooler Defects-oil cooler

Oil Cooler: Its Function
This oil cooler is where the water and oil meet but not mixed because they are separated by seals in between the above-disassembled parts (the image). 

The oil cooler serves as the cooling system between the water and the oil. Because on the one side of the oil cooler is water and the other side is oil, the water cools the hot oil before it circulates again and again in the engine.

It is logical that when there is no problem on the oil cooler it must be the oil cooler gasket. When the seal is perforated it’s either water being mixed with the oil in the engine or the oil mixed with water in the radiator tank.

If you see indications that your coolant is being diluted with oil this is the only way where it could pass.  If your car is a newer model maybe it’s just a replacement of seal is needed but when your car is a vintage one there could be perforations on the metal and should be replaced.


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