Hello Ranger community!
Quick background, I have a 2004 with 3.0. 230,000 miles. I replaced both heads about 5000 miles ago, dreaded soft metal head issue. No issues after replacement. Today the truck temp went all the way up to max heat. I stopped the truck, checked for leaks at hoses, no hissing or leaks anywhere. I let it cool down, radiator was empty, I added water and drove the truck home, it started a little rough but smoothed out right away.
10 minute drive to my house, temp started going up, but got it home before it hit the red.
Checked the dipstick, oil is like chocolate milk. I know what this probably means, blown head gasket. I did a compression check, all cylinders check out, no loss on any cylinder. I did the radiator bubble test, all plugs removed, put a plug in one cylinder at a time and cranked the engine watching for bubbling water in the radiator. All 6 cylinders tested, no bubbling. All spark plugs are dry, and look good. Truck is not smoking.
Decided to drain the oil, found all of the coolant! Pure coolant poured out of the drain, still green, before the oil drained.
I have been a DIY car guy for 35 plus years, have never seen this before. What am I missing?

 

Well the 3.0l engine has 2 coolant passage thru the timing chain cover and the internal gasket is a known coolant leak point

Here is picture of the 3.0l with timing chain cover off: https://i.ytimg.com/vi/bRVz90PlZT4/maxresdefault.jpg

You can see the 2 coolant ports and if either leaks inside it goes right down to oil pan

So thats where I would start
After you get the cover off it should be easy to spot where gasket failed
If not I would put water in each side of the block, with oil pan bolt out
See if water comes out..................cracked block

Lower intake has a coolant crossover from head to head.............if it leaked then coolant goes into Cam Valley and right down to oil pan
BUT..........lower intake would only leak into oil pan when radiator was full, level high enough to reach lower intake level

Timing cover leak would start to leak into oil pan when rad was just over 1/2 full, water pump level
So you might be able to test that way

 

Hoping RonD is right BUT,

That's what a jeep 3.7l did to me once. Overheated in traffic and the HG went. Only coolant into the oil. Otherwise all was fine. When I dissected I could see where the coolant passage and oil passage "merged". I had no issues with the combustion chambers or pistons.

 

+1
Rare occurrence but certainly can happen

 

Thanks RonD,
Did some Google searching and do see that the timing cover is a leak point, now trying to decide if I should go after the lower intake first, only because I worked on that when I replaced the heads, hopefully I will be able to see if there is a failure. If not then it will time to tackle the timing cover. Thanks for the advice. I will report back once I figure it out.

 

Sounds good

Use cheap oil(30w) and a cheap oil filter on restart, run it for 10 -15 minutes, warmed up, then drain oil and change to good oil and filter
And I would change oil again after a month or two

Coolant has a boiling point of 230deg or so without pressure, so coolant in the oil is a problem because it can turn to steam when bearings get HOT, which is why we use oil to lube and cool engines
Coolant in the oil, in the amount you described, should be diluted a bit more before longer term driving, so the start and run then stop and drain

 

Okay, I decided to go after the intake manifold and see if the intake gaskets had a failure. Both intake gaskets are torn at the coolant passages, but I cannot confirm if this happened when I pulled the manifold out.
Also, it looks to me that if there was a failure at the coolant passages, coolant would have to be leaking outside of the engine, not in the cam valley as the location of the coolant passages are outside of the cam valley. See attached picture, the coolant passages are at the ends of the heads.There was no leaking of coolant outside the motor when the motor overheated. Does anyone agree with my thought?
Now I guess I have to check the timing cover?

 

It depends on where the gasket fails, it can certainly make it to the valley, don't see that in the picture though

Cooling system has 14psi pressure when engine is warmed up, valley is usually -1psi from PCV Valve so nothing to stop a leak from going that way

 

The saga continues, I pulled the water pump first, no problems with the pump, actually in very good condition. So I decided to pull the timing chain cover. I do not see any obvious gasket failure around the coolant inlets.
There is some bad pitting on the timing chain cover in a few places see pictures, I tried to see if any coolant might be leaking thru these pitted areas, it does not appear that there is, but there are some bumps on the other side of the timing cover in the same spots were the pitting is. Pictures of both sides of the timing chain below. This is driving me crazy, not finding an obvious failure.
So, do I clean everything up, get new gaskets put it all together and see if problem is resolved, or do I replace the timing chain cover?
Thoughts anyone?
By the way, coolant is still in the block passages, I think the block is okay.
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Must be head gasket, you replaced the heads were they new heads or rebuilt...... rebuilt bet they are cracked.... if the engine got hot the heads could have some gasket failure between the water and oil passages, best pull and check..

 

Thanks uksparky,
After eliminating the intake gaskets, and now the timing cover, I guess I am going to go back to the heads. I replaced the heads with rebuilds, I had no issues for 3000 miles, so did not think this could be it. Never any overheating issues. I did compression checks and the radiator checks, both came back normal, what is the best way to find if the head gasket has a failure between oil and coolant passages, other than pulling the heads? Is there a way to determine?

 

The pitting looks kinda deep in the pictures, would not hurt to replace that cover now instead of later. As far as the heads i had about 25k on my rebuild heads, done by the PO... took them to my local machine shop, they did the magna flux and they were cracked, and had the valve seat problem, the machine shop owner said dont use rebuilt heads they are junk and will have cracks before you install them. As far as i know there is no way to determine the oil water passages until you pull the heads, check the gaskets and get the heads to the machine shop for inspection. My problem was the other way around to yours i had oil in the coolant...block failure... i got brand new heads from here.. https://adv-cylinder-heads.business.site/.... you could get away with just head gaskets, but going that far into it ...get the heads checked out

 

That is where I purchased my heads. I will pull the heads next weekend, hopefully will finally find an obvious failure. Update to follow at some point, might be time to buy another car for daily driving and keep the truck as the pain in the *** project!

 

Did new heads and gaskets on my son's 97....coolant ran directly into the oil pan when he got it done...turns out the fan impeller cut a hole thru the timing cover

 

Oh my