1939 ford flathead engine issues

[39-Ford-Tudor]

• Ford Flathead V8

Hello all here on the forum. I am hoping to get some advise. My 1939 ford with the 221 ci. V8 runs pretty good. The issue I am having is when we drive the car at highway speed I am getting engine oil mixed in with my radiator coolant, but no coolant in crankcase. Just driving car at city street speeds this does not happen. I can not seam to find much in the net about this. I can find lots about coolant getting in the crankcase not not my problem. Please help.

 

 

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[Spinneyhill]

2 hours ago, 39-Ford-Tudor said:

no coolant in crankcase

....yet!

 

I wonder if there is a crack somewhere. Perhaps oil gets into the coolant because there is a high enough pressure at high speed but not enough at lower speeds. The coolant is not under pressure, of course.

 

It doesn't sound like a head gasket, but have you done a compression test? Also, when it is running, are there any bubbles in the coolant in the radiator?

[lump]

Get one of those hand held units which tests the coolant for the presence of carbon. IF you have a leak from the combustion chamber into the coolant, it will change color with this tester. EXCELLENT diagnostic tool. 

[studeboy]

I would say you have a cracked block. The pressure of the oil pump pushes the oil into the coolant. This is a common problem on Continental F140 engines. An internal crack usually after over heating leads to frothy oil in the coolant.

Edited March 5, 2019 by studeboy
punctuation (see edit history)

[Bloo]

Let's not say cracked block yet. Thats expensive. Cracked blocks were a death knell for any car back in the day. Repairs were possible but any such history dramatically reduced the value of the car, because the problems had a good chance of coming back. It didn't help (at least in the USA) that many states titled the car to the engine block number.

 

It is time for some detective work. It is not always possible to figure stuff like this out without tearing the engine completely down, but sometimes it is! Let's figure out what is actually happening.

 

First of all, you say oil gets into the coolant only at highway speed? How can you tell? When I have had cars with oil in the coolant, it makes a nasty brown foamy muck that is almost impossible to remove. How do you get clean in-between tries? Are you flushing it every time? Does that even work? How can you tell it is OK at low speeds?

 

Since it seems to matter what speed you drive, the first thing I would do is hook up an oil pressure gauge. A real one, mechanical, with markings you can trust. I would then tape it to the windshield and drive the car. Most cars have very low oil pressure at idle, but underway it is about the same at any speed. There is typically a blow-off valve in the oil pump, and once it is turning fast enough, the excess oil pressure is just blown off. This is why most cars have the same oil pressure from fast idle all the way to high speed. There are exceptions, and I don't know it if that applies to a 39 Ford, but... I would sure want to know if the oil pressure is lower driving around town than it is on the highway. The gauge will tell you that.

 

The next thing to do would be to find a cutaway drawing of the engine that shows the oil galley routing. These exist for many old engines, and almost certainly for the flathead Ford. Follow the oil galleys. Where do they touch the water jacket? Can you see any of them, whether they touch the water jacket or not? A crack might extend beyond the area causing the problem. Do whatever you can to see the outside of the oil galleys. Are any visible under a valley cover? Could the areas be seen that touch water if you have a head off?

 

[Bloo]

Ok, heres a Ford flathead oiling system, but newer. Does your shop manual show 1939? If I am not mistaken, 1939 would be the old "21 stud" flathead and could be a little different :

 

So, it looks like the oil comes up out of the pump, goes straight up the back to an oil galley that runs down the center of the engine, and dead-ends behind the timing gear. It looks like oil flows down from that galley to the camshaft, around it, and on down to the crankshaft. For the most part it doesn't seem to be near water jackets.

 

We sort of need to know where the water is. In most engines if this age, water is around the top part of the cylinders, or sometimes the whole cylinder. Since the valves are in the block, there has to be water under the valve seats as well.

 

Here is that oil galley running front to back, and dead-ending behind the timing gear. Again, I believe this is a later flathead Ford:

 

 

Nothing apears to touch water here. Below that galley is the camshaft (and below that, the crank), which it oils. There is no water around a camshaft. The area you are looking at around the valley is just open. This is a crankcase vapor and oil drainback area. Those small holes by the lifters are for oil excess oil (not under pressure) to drain back to the oil pan.

 

There is most likely no water anywhere close to that galley. It would just complicate things. There is no need to exchange water between sides. The flathead Ford has 2 water pumps. You could easily think of it as two completely separate cooling systems (except the radiator).

 

Here is a diagram of part of the oil system on a military vehicle that has had the flathead engine modified for a full-flow oil filter. The view is from the rear of the engine. You can see the oil galley coming up (from the oil pump)on the left side, (Ignore the filter stuff), take a right turn (it's plugged with a grub screw in the picture, but would normally be open), and head over to the middle to feed the main oil galley down the center of the engine.

 

 

And here it is in real life, again with the military modification you don't have. I would look all around this boss for signs of trouble. That bulging area just below the head is the water jacket. Really, it doesn't look like it gets that close to it.

 

I am betting against a crack leaking pressurized oil into the water jacket at this point.

 

 

Edited March 5, 2019 by Bloo (see edit history)

[Bloo]

Well..... looking further.....

 

The answer may be a lot simpler. Apparently pre-1948 flatheads, as originally built, used oil from the engine fed from the front of that main galley down to lubricate the water pumps.

 

You may need to overhaul one or both of your water pumps.

 

Here is a current thread about water pump rebuilders:

 

Edited March 5, 2019 by Bloo (see edit history)

[automaschinewerks]

how new or old is your engine? or mileage?  if the pistion rings passed some oil, it would be worse at high speeds because of the splash and spray from the crank journals, the compression gets higher at high speeds, and oil gets past a slightly rotten or seeping head gasket to the water jacket.  the gasket may not be seeping enough to let water in the other way because there is no coolant pressure.  when you say engine oil mixed with coolant do you mean a film on top of the water level, or a half inch of oil when you look down the cap?

terry

[John_Mereness]

My first thought is a waterpump issue.  Thereafter, I have had headgaskets issues create what looks like oil in the antifreeze and it is just exhaust muck.  

[Tom_S]

I had a Farmall tractor with a flat head engine that put oil in the water but no water in oil.  Turned out to be a slightly warped head allowing oil to pass thru the head gasket from pressure but not enough water pressure to push water thru head gasket and into engine.  Since he states the oil is only noticed after high speeds, it may be the increased temperature and rpms causing the oil thru the head gasket.  Since my radiator base was bolted to the front axle housing with many 1/4 inch rusted bolts I decided not to remove the radiator and taking a chance of broken bolts.. Instead I filled  the radiator and engine water jacket with kerosene, ran to high temperature and drained.  Did this several times going from black to clear color.  Then flushed with a degreaser several times and finally with water.  Never had another coolant problem.