I have a 390 in my '68 Cougar with about 30,000 miles since I rebuilt it 14 years ago. Its been sitting for the last few. I've had an on going problem with the coolant turning to chocolate malt since early on. I've torn it down 3 times over the years trying to figure it out, but the problem is still present. My machinist had heard of a few instances of the oil passage in the block that feeds the rockers cracking and pumping oil into the water jacket so we sleeved both sides last time it was apart, but it didn't help. Obviously there is an issue where pressurized oil passes near a water jacket but I would also expect water to get in the oil when the engine is shut down and the coolant is still pressurized before it cools down. However, the oil has never has never been contaminated. Where could it be comming from? Has anyone heard of a problem like this before? How about a crack in the head bolt hole where oil is fed to the rockers? Any advice on where to look would be appreciated. Thanks.

 

Most likely is intake manifold gaskets. Even tearing it down mulitple times won't help if the geometry is wrong. You have to measure intake maifold angels and compare them to intake port angles, etc to make sure you have a good fit. Especialy true with aftermarket aluminum manifolds, heads and/or blocks which have been re-surfaced, etc.

Also, use the best head gasket you can get,.....Fel-Pro 1020. Fel-Pro also makes a cheapie head gasket....got one by mistake once.....lasted about 500 miles and then antifreeze in the oil. Had to have the crank re-ground.

Now, did it always do this since you rebuilt it 14 years ago? If so, you may have a cracked block and your rebuild was OK, just a major part (block) wasn't. If it was fine for a long time after the rebuild, suspect a gasket or a warped gasket surface from over-heating. Did it ever overheat?

 

It didn't happen after the initial build, just after the first teardown which didn't include the rotating assembly. Cooling has never been an issue.

As far as intake gaskets go its never had oil in the coolant, just the other way around. Since there's no pressurized oil passing through the manifold I don't see that causing the problem. I would assume it would have to occur where a pressurized oil galley passes through a water jacket. Are there any places besides the feeds that run through the block and heads to the rocker shafts? I wish I had a bare block to look at.

 

When I used the "cheapie" Fel-Pros, I had coolant in the oil. There are a number of very small (maybe 1/4") coolant passages on the top of the block about 1/2" away from the cylinder rings on the head gasket.

I always put gasket shellac (stuff like molasses) around the intake manifold gasket water passages. Fel-Pro pinto-seal only appears to me to be good for one side of the gasket, but I coat both sides around the water passsage openings.

Again, I stress that the last part to go on is the intake manifold, and if the heads and block angles are the least bit out, the manifold may not seat properly in places, particualrly underneath where you can't see it. This can also cause smoke out the exhaust from oil....got any smoke? Especially true for both water and oil if the manifold is out in geometry.

 

I do understand what you're getting at but I'm having the opposite problem. I have oil in the coolant. It's in the radiator, the overflow and has even softened the hoses enough to cause premature failure. I suppose the water pump bushing should last a while though.

 

Oh...I'm sorry...I misunderstood. Moast likely place is head gaskets assuming block is not cracked somewhere.

EDIT: Get a rad pressure tester. If oil is leaking into coolant, coolant can leak into oil. Take sparkplugs out and see if a cylinder is filling up with coolant when you do the test.

 

I'd look at those oil passages in the block again. If they were'nt sleaved properly (ie deep enough) you could still get oil in the coolant. Don't ask me how I found out. LOL. A lot of guys here have never heard of this problem , but it is real.

 

Sounds like a sore subject but I'm guessing you actually experienced it? Were you able to salvage the block? I'm hoping to give this one a clean bill of health so I can decam it and use the shortblock in my pickup with a pair of aluminum heads.

 

Yep, Had it happena few times. The last one I didn't go deep enough, it took a bit of work to get the sleeve out ( I used a 302 pushrod w/red Loctite) then drilled a little deeper and re-did it. So far so good. You just have to watch you dont go to deep and hit the cam bearing. Do a search over on FordFE.com and there are some pics of blueprints with instructions from FORD.

 

If you have an automatic trans, it could be tanny fluid and not motor oil in your coolant.

 

I appreciate the info and I'm sorry to bring back bad memories. Have you ever heard the heads cracking and causing it?

BTW the car has a top loader in it.