Hi, I recently purchased a 72 spider as a first time project and looking for opinions on oil in the coolant on our cars. There is no coolant in the oil. I'm hoping this points to a blown head gasket and not necessarily a cracked block or head.

Background
The car sat for the last few years before the shop I bought it from got it up and running for me.
I first noticed some dark oil spots in the coolant so I decided to do a flush over the weekend with Prestone Flush + Cleaner hoping it was just residual. After the first flush the coolant is now all milky and I'm still hoping this is just from residual oil mixing in. I plan on doing a couple more flushes.

I haven't driven the car around but idling in the driveway for 20 minutes it doesn't overheat and there is no white smoke coming out of the exhaust. I also bought a leak test kit and the blue fluid never turned yellow, though I could have been messing up the test.

I guess my questions are:
1) Would a blown head gasket cause oil in the coolant but not coolant in the oil. There are varying opinions of this online.
2) If after a few flushes the coolant remains contaminated what should my next steps be. I was thinking of taking the head off to at least replace the gasket and maybe sending the head to a machine shop to have it checked for leaks.
3) If I don't see a crack in the engine block and the head isn't cracked does the engine still need to be pulled and checked somehow for a crack or would it be fine since head isn't cracked.

Thanks a lot for the help.
- Tony

Yes there have been instances where oil gets into the coolant and not into the oil.

When you pull the head you will better know when you inspect the head gasket as there will be signs where the coolant and oil are getting mixed which I am leaning towards where the oil gallery comes up to the camshaft journals since this would usually happen where there is oil pressure and not where the oil drains back into the block. Oil pressure can be upwards of 50 psi while coolant pressure is much lower making it so the oil pressure would overcome coolant pressure. It also possible that the leak is so small that when the coolant cools it is sucking small amounts of oil through a small leak in the gasket.

Are there any obvious signs of it overheating in the past? If it overheated in the past the head may be warped and need to be honed.

Thanks diesel. What would be some signs of overheating in the past?
I’ve run a couple flushes and both came out gray where as before the coolant was mostly green with just oil spots floating around in it. Hoping this means it’s breaking down all the oil that was in there.
Theres a burp kit installed in the heater hose, was thinking of running a hose thru it with the block drain plug out to flush out what’s sitting in the block. Anyone with thoughts on that? Not sure if that’s a good way to go.

It sounds like you're doing all the right things, and DieselSpider has good advice. I wouldn't assume the worst (cracked block or head) until you come across the proof. A leaking cylinder head gasket is more likely, and that's a relatively easy thing to fix. As for signs that an engine has overheated in the past? I'm not aware of any things that can be checked without taking the engine apart.

I'd definitely keep flushing the cooling system, removing hoses and opening drain valves as necessary and running a garden hose into the various openings (on a cold engine of course), until it looks like you've really flushed everything out. Also check the tightening torque on the cylinder head bolts. I "crack" each one in turn ever so slightly loose, then slowly retorque to the spec. Put it all back together, fill with coolant/water, and run for a while and see what you get. If you still have milky coolant or oil droplets in the coolant, there's more work to do.

-Bryan

The aluminum can turn white and duller when it overheats and sometimes rubber hoses will look a bit cooked where they are clamped to the engine. There may also be a bit of staining where the expansion tank drains along with signs of damage from steam going through the vent line.

Another sign to look for regarding overheating: spark plug color. Normally, the spark plug porcelain insulator is tan to light brown and maybe greyish, but a spark plug that looks glazed, pure white, or (heaven forbid) with melted electrodes is definitely a sign that the combustion chambers were way too hot, although this might not necessarily mean that the rest of the engine had overheated. However, if you have run the engine for a significant time since a possible overheating event in the past, the spark plug color may not tell you much.

In general, spark plugs tell a lot about the condition of an engine and how it's operating, and it's worth studying pictures you can find online for symptoms that you might have.

-Bryan