Oil in the coolant

Doug Owner/Technician California Posted   Latest  
Updated
Driveability
1969 Ford F-100 3.9L (A) 3-spd (C6)

The vehicle does not overheat but has about 20% oil in the coolant. Was wondering if anybody had any ideas where this might come from if not a blown head gasket? Thank you, Doug

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Glenn Owner/Technician
Texas
Glenn
 

Hi Doug, About the only place on this old rascal would be the head or a cracked oil journal. My guess is someone out a cheap head gasket on this in the past. Worst case is that it has been severely overheated and cracked the head. Make sure it is actually engine oil. Burnt tranny fluid can fool you. A blown radiator tranny cooler is another possibility.

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Timothy Instructor
Alberta
Timothy
 

Hi Doug, Wow, that question brings back memories. I agree with with Glen on the transmission cooler that is built into the radiator. I have seen these leak into the coolant. Check the transmission fluid level.

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Rusty Owner/Technician
Massachusetts
Rusty
 

I don’t recall whether or not that engine has a rocker shaft. If it does, a HG leak is a possibility around the pressurized oil passage pocket. If it has individual rockers, I don’t think a HG or cracked head is likely as there isn’t any pressurized oil in the head. In my experience, a leaking transmission cooler generates pinkish “cream” in the coolant. I’m sure someone will know which fluid…

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Justin Technician
California
Justin
 

Possibly timing cover if it has oil filter housing built into it

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Rusty Owner/Technician
Massachusetts
Rusty
 

I think this is a 240CID straight six with an oil filter that screws to the side of the block. Timing cover just surrounds the chain.

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Glenn Owner/Technician
Texas
Glenn
 

That is correct Rusty, Also It does have an oil galley that goes to the head and the head has a rocker shaft that oils the rockers. This is a push rod motor, so the lifters are in the block. The 240 and 300 CID engine were built similar and used in Van and Truck models. These also had the transmission oil cooler built into the radiator and old burnt tranny fluid will look like oil at this…

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Doug Owner/Technician
California
Doug
 

No Guys it's a 360 in this one. And i'm sorry I see I put down the automatic transmission but it's the manual tranny. Don't remember If that showed transmission lines to the radiator or not.

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Ignacio Apprentice
Illinois
Ignacio
 

Has to be from radiator oil cooling lines inside radiator that rust away

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Gary Owner/Technician
Colorado
Gary
 

Hello, Doug. I assume that the engine you're speaking of is the old 5.9 liter, 360 cid, FE block V8. The 5.9s do have rocker shafts that oil from two cam journals, one journal for each head. I've never seen one of these blocks crack from the oil gallery through the water jacket, but it's a possibility on something this old. The oil gallery in the head is drilled through pretty solid cast iron…

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Glenn Owner/Technician
Texas
Glenn
 

Ah!, The auto fill got you? Wow Doug, this whole scenario changed. The manual tranny in these has no cooler lines. Is the shifter on the column and it has a clutch pedal? ("3 on the tree") If it is a 360 CID, that was the big "FE" block with half the intake mount areas going under the valve covers (Big intake). You will need a hoist to get that intake off and back in place, they are very…

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Doug Owner/Technician
California
Doug
 

Yah that's what I was thinking also. Thanks gentlemen!

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Donavan Mechanic
Saint Lucia
Donavan
 

Does this engine have an oil cooler? Water type​.​if it is bad the engine oil pressure is higher than the cooling system pressure so oil enters the cooling system​.​another thing to check is if there are any freeze plugs in the cylinder heads which get porous due to bad coolant treatment and leaks coolant into the engine oil​.​need to pressurize the cooling…

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Richard Owner/Technician
Maine
Richard
   

This is not an unusual Ford FE issue. Edit to add: You could pull your valve covers and remove your rocker arms, get a coolant pressure tester and pressurize your cooling system. If the oil passage(s) are cracked or leaking water should start coming out of the rocker arm oiling hole in the head. This will also determine which side is defective..

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Doug Owner/Technician
California
Doug
 

Looking at the pictures, if the crack is at the bottom of the shaft wouldn't the coolant just go down to the valle not up to the top of the head, rocker area? Possibly but probably not I would think.

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Glenn Owner/Technician
Texas
Glenn
 

Hi Doug, Remember oil pressure is always higher when running than the coolant would be.

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Doug Owner/Technician
California
Doug
 

Right, but I'm talking about pressurizing the coolant system and finding where the water is coming through when not running.

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Glenn Owner/Technician
Texas
Glenn
 

Hi Doug, I would try that after the engine has been heated up (heat will expand the crack) and it may take a while with the rocker shafts removed for water under pressure to make its way up the oil journal where it can be seen. Another method that may work is to make a hose and fittings that will adapt to the oil sender unit, then apply shop air regulated around 60 psig. Watch for bubbles in…

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Doug Owner/Technician
California
Doug Update
 

Waiting on the customer to see what he wants to do. Currently he's still driving it.

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