I forgot to mention that I used a 2.5 liter ultrasonic cleaner from Harbor freight. In the ultrasonic I used a bit of detergent and just a spritz of CLR so dilute it would not harm anything. I had to put the oil cooler on it's side at an angle and then after the 180 second run reversing the angle and doing the other side.

In the pan of water I used dish detergent and just a bit of CLR. not much at all. The detergent was poured down the oil passageways then the whole thing was then boiled for about 30 minutes and the cycle repeated.

The first two times in the ultrasonic the water turned brown from the fine slit (Maybe it was rust) came off the fins in the oil cooler.

The oil cooler in a 39 Super 8 is not like modern oil coolers, it has to withstand the oil pressure that averages well above 60 PSI and it is made of heaven metal when compared to the radiator which generally does not run much pressure at all in a modern car and even less if any in a '39.

It seemed that the boiling did the most to clean the internal passages.
compressed air was used to help clear out the last of the oil after boiling.

I think the dish detergent, heat, and boiling water was what did most of the cleaning.
YMMV

In working on my 1939 Super 8 that has not been driven since before 1970 I have been cleaning and servicing the engine oil system. I found that the oil cooler was completely clogged with old oil deposits. I tried brake cleaner, carb cleaner, old gasoline, and other cleaners. Nothing seemed to do the job. All the above even after soaking over night or for several days did not seem to work. Finally I put the oil cooler into a pot of water with detergent and some CLR cleaner and boiled it for a few hours. Finally I was able to get air or liquid to flow from one side to the other. So if yo are going to clean out your oil cooler I recommend boiling it in water with dish detergent (to cut the oil) several times. (I have a back up for this part and will clean it in the next couple of weeks and I will report if starting out with boiling water work as well as we think it does.)

YMMV,
Rick Mahaffey

Hello,
I am working on a 1939 Super 8. I need to have my oil pump rebuilt. Does anyone know of a reliable place to send my oil pump to have it rebuilt?

Thanks in advance,

Rick