Oil in coolant.

[1967FEGT]

Over the last few months I wound up with about 8 ounces of oil in the cooling system. It was a new build and the block passed mag and pressure test.
Is the problem always related to the oil feed passage for the rockers or are there issues sometimes at the head bolt next to the passage?
The previous owner of the block said there has never had been an issue with two previous builds on the block. 
With the variety of builders here after reading the forum for some  time there is quite a bit of experience here.

[My427stang]

I have only seen it as a head feed problem for the rocker passage, however, I suppose it could cross channel with a leaky head gasket too

Edited due to pre-coffee nonsense

[cjshaker]

Typically the problem stems from the passage in the block, in the 'tube' that passes oil up to the head, inside the water jacket area. The 'tubes' can rust out or split if they get thin. It also can not be checked by magging it because you can't get to that area. A pressure test will only catch it if pressure is held and monitored to see if it drops, or the tubes are very carefully inspected during the test. A low pressure test may not even show an issue; sometimes it takes a higher pressure than might be used for your standard "pressure test", or heat, to make the issue pop up. 50+ lbs of oil pressure can easily overcome a crack that won't show up under a 5 lb pressure test.

[SMA390]

I have had several blocks that were pressure tested etc and everything was fine. When they chased the threads in the water pump bolt holes they went too deep and put a small crack in the casting inside the valley area. It was just enough coolant to see a small puff of white smoke when I dropped the hammer on the highway. I am by far no expert but this seems to be the most likely spot. I always use a Loctite thread sealant and double check bolt length now.

There might be the smallest leak in the intake gasket as well. I have seen that also
Great place to ask questions here You will get a fix..this forum is the brain trust for Fe motors

[cjshaker]

I have had several blocks that were pressure tested etc and everything was fine. When they chased the threads in the water pump bolt holes they went too deep and put a small crack in the casting inside the valley area. It was just enough coolant to see a small puff of white smoke when I dropped the hammer on the highway. I am by far no expert but this seems to be the most likely spot. I always use a Loctite thread sealant and double check bolt length now.

There might be the smallest leak in the intake gasket as well. I have seen that also
Great place to ask questions here You will get a fix..this forum is the brain trust for Fe motors

That would put water in the oil, but not oil in the water. For oil to get in the water, it has to be a place where oil pressure will overcome the pressure of the cooling system. There are only a couple areas where that typically happens.

[Royce]

In my experience a unique problem with an FE.. I had it happened to me 2 times.  Both were caused by a failure in the oil passage from block to the head.. Crack develops and pressurized oil is pushed into the cooling system.. hell of a mess to clean up.. Old mechanic's trick I am told was to find a hollow pushrod close in dia to the oil passage and insert it with some sealer. Shade tree for sure but if it prevents pulling an engine...

[chilly460]

Just adding to the evidence, same issue happened with the reverse 105 block I run.  I believe my machinist used an old SBC pushrod and sleeved the passages, haven't had a problem since. 

[SMA390]

That would put water in the oil, but not oil in the water. For oil to get in the water, it has to be a place where oil pressure will overcome the pressure of the cooling system. There are only a couple areas where that typically happens.

Thanks for pointing that out..I have always seen it the other way around with coolant in the oil. Good to know about this, never would have thought of those oil passages failing

[C6AE]

Not uncommon, For many years it was standard rebuilder procedure to sleeve this passage. I have done it three times,mall after the problem was discovered, once in situ, the others on the bench.
I used aftermarket small block chevy pushrod tubing 5/16" OD.  I drilled with a long drill bit 1/64 under then reamed with a long reamer 1/2 thousandth under the pushrod od. drove the pushrod into the hole and sealed it with  "wicking" locktite which is thinner than water.  All worked perfectly. What a mess to clean the system. The oil ruins the hoses, and the radiator has to go in the tank.
AERA had a service bulletin on this 30 years ago. You can find copies online. (I posted them to the old forum years ago)

https://www.ford-trucks.com/forums/1215888-75-ford-f250-390-oil-in-coolant.html#post16743222

[RJP]

Before you tear into the engine pull the head bolt on each bank where the oil passes to the rockers. Carefully lift it out of the head and look for traces of coolant in and around the base of the bolt shank and threads. If there is coolant it is likely there is a small crack in the block deck between the oil passage and the head bolt hole. The quick fix that has worked for me is to clean out the bolt hole and threads with anything that breaks down oil like spray carb cleaner, Brake-kleen, lacquer thinner etc. then blow out with compressed air. If you still get coolant, oil or debris repeat until it is spotless and that includes the head bolt as well. When you are done cleaning everything coat the headbolt threads with liquid teflon thread sealer all the way to the top of the threads. Reinstall the head bolt, torque to specs and let it sit for 24 hours, that gives enough time for the sealant to wick into the crack and set up. This worked for me on a D4 390 truck block that I did 25+ years ago and is still sealing today. This will not cure the more common problem of a cracked oil passage that usually occurs at the base of the block just above the cam bearing but may save you the effort of pulling and tearing down your engine. For that repair search AERA or FoMoCo technical service bulletins for the approved repair recommended by AERA/Ford   

[fryedaddy]

or you could have blown a head gasket .i blew one on one side and it steamed out the tail pipe and mixed in the radiator too.but i did not have any coolant in the oil,just oil in the coolant.

[turbohunter]

Orrrrrr, if it’s not that bad you could live with it. Hey you don’t have to buy coolant .
The first FE I did (a 105 mirror hmmmmm) has had that leak for years. I have grey coolant now. I put a little Pine Sol in every now and then just to keep everything loose and flowing. I vacuum the top of the radiator out at oil changes just cause oil rises to the top. It’s become regular maintenance. Your heater hoses weep a bit. It started heavier than it is now.
I’ve been so busy on other projects I haven’t gotten around to fixing it.
Do I recommend it? No. But can you live with it? Yes. Am I going to take care of it eventually? Yes.
But in the meantime the truck runs great. Have had it out in Death Valley many times and no problems.

[runthatjunk]

I did the roll pin cause it was easy and more for preventative measure.  Think the sheen I always had in radiator was more due to original head gaskets

[1967FEGT]

The oil is black in the coolant and doesn't ever seem to mix like I noted when I had a cylinder wall crack which caused the dreaded milkshake.  I saw the  tube repair. I was hoping that there was another common possibility. Thank you all for the imput. I will go ahead with the removal of the bolt next to the gallery, clean out and PTFE sealer.  Is there any need to worry about head gasket issues with the removal of one bolt? I used the Felpro 1020 as recommended by the forum with the Edelbrock heads.
Thank you for the responses. If this doesn't work I'll have to pull it again and tear it down for the tube inserts.

[RJP]

The oil is black in the coolant and doesn't ever seem to mix like I noted when I had a cylinder wall crack which caused the dreaded milkshake.  I saw the  tube repair. I was hoping that there was another common possibility. Thank you all for the imput. I will go ahead with the removal of the bolt next to the gallery, clean out and PTFE sealer. Is there any need to worry about head gasket issues with the removal of one bolt? I used the Felpro 1020 as recommended by the forum with the Edelbrock heads.
Thank you for the responses. If this doesn't work I'll have to pull it again and tear it down for the tube inserts.

I've never had any problems with head gaskets by removing just one bolt.