Issue: 59ab with coolant in oil pan

[37Ford]

1948 59ab flathead engine. Engine rebuilt 12 years ago, has run fine all this time, about 25,000 miles on engine. Was time for spring oil change. Normal coolant level. Checked oil and it was at normal height and oil was black on dip stick. Started engine and let it warm up, it ran fine. Loosened the drain plug and noticed clean antifreeze dripping. Drained out about 3 ounces of antifreeze, all clear, then the old oil started draining. Normal dark black used oil, no milky color in oil. Use 50/50 antifreeze mixture. 2 loose head bolts on one side (studs 10,12 middle passenger side) 2lbs loose. Original Edmunds aluminum heads, Felpro head gasket. Oil last changed 12 months ago driven about 1,000 miles last year. Plugs look good.
Car garaged, No freezing temperatures.

Thoughts ?

[Don T]

Are you sure it was antifreeze that dripped out; could it have been just water?

[37Ford]

It is definitely anti-freeze

[38 coupe]

Several possibilities, most not dire.


1. weeping head gasket due to loose fasteners that is fixed once the head is tightened down


2. weeping head gasket that is dead since the engine was run with a loose head (you would probably know it if this was the problem, bubbles in the radiator, etc.)


3. weeping water pump, the 37-48 factory pumps have an oil passage in the pumps to lubricate the bushings, do you have rebuilt factory pumps?


4. corroded or cracked head (unlikely in my opinion since you haven't overheated or abused the engine and you use antifreeze that is supposed to prevent corrosion)

5. cracked block (very unlikely in my opinion since you haven't overheated the engine, assuming there are no old crack repairs to start weeping).


Others here will likely have more ideas.

[Flathead Fever]

Tighten the heads and keep an eye on the oil, that might fix it. If its getting into the cylinders after sitting it would put out a cloud of white smoke when it was first started until the coolant burns off. Whichever cylinder it is would have a shiny spark plug. When it sits the coolant can also run through the ring gaps and into the oil pan

At work we would pull all the plugs and then put a Stant radiator pressure tester on the radiator and pump it up to about 15 lbs. and let it set for hours. Then we would crank it and see if coolant shot out one of the plug holes. Your flathead radiator will only take 4 lbs of pressure, any more than that could separate the narrow solder joints on the tanks.

I have never tried this on a flathead but I used a similar tool for finding leaks in evap systems by pressurizing the gas tank with just a couple pounds of air. Buy a rubber ABS pipe cap and clamp it over the lower inlet on the water pump sealing it off. Then take a piece of hose with a freeze plug clamped into one end. Drill the freeze plug for a tire valve stem and install it. Now you can clamp the hose over the head outlet and pressurize the system and check for leaks. That way you could put enough pressure in there to make it leak without damaging the radiator. Leave the oil drained out so you can watch for coolant dripping out of the pan. Leave the spark plugs out so you can crank the engine and see if it spits out coolant. Doing this you might be able to see which bank of cylinders is leaking and if it's going into a cylinder or coming from the water pump or a crack. You want to try and find the leak before you tear stuff apart because you have no way of testing it.

This is tool I use for leak testing. I recently sand blasted the inside of a '32 gas tank on the. It now looks beautiful in there with a bore scope, except it opened up a rust hole in the side that needed to be tig welded. Weird, if anything I would have thought it would have been in the bottom of the tank. To verify there were no more leaks I clamped this phone company nitrogen pressuring fitting to the filler neck. Pressurized it just a little and sprayed the tank with soapy water. I worked at the phone company and these pressurizing rubber nipples were used to force nitrogen into the copper phone cables to keep the moisture out. If you remember seeing what looked like welding tanks chained to telephone poles that is what they were doing. You can make the same thing with a piece of radiator hose, a freeze plug and a valve stem. The fuel sender hole is plugged with a rubber freeze plug and screws with o-rings under them. I don't want to find out there is some tiny leak in the welded seam or under reinforcemnt brackets after I paint the tank.

[Brian]

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Do your USA 59A blocks have the freeze plugs in the pan rails? If so, one of them could be leaking....

[38 coupe]

Originally Posted by Brian

Do your USA 59A blocks have the freeze plugs in the pan rails? If so, one of them could be leaking....

Oil pan rail plugs are a 1940 and older engine thing. I got schooled on Ford's terminology a while back and learned to call them "core plugs". It does bring up the question, is it a 59 block? I have heard some people refer to any 24 stud center water outlet motor a 59 motor.

[Flathead Fever]

There are no sand core casting plugs on the pan rails of a 59A block.

That did happen to a friend last year. He had coolant in the oil, and it was one of those plugs leaking into the pan. Those engines will have two distinctive bulges on each side of the block above the pan where those passages are.