Cracked Head

[optmaxx]

So my 7120 head has a crack on the top, near a valve stem that seeps coolant into the oil, and I realized that I may have head issues when I checked the oil and it was milky and kind of thick, and it looked like milkshake when I drained the oil.

I did an oil change before this happened and the oil looked normal, maybe some tiny bubbles but my oil catch pan was dirty, and the color and texture of the oil looked normal, and nothing strange in the crankcase. So I believe that this issue started to develop over time, plus I bought the head rebuilt on ebay that may not have been in very good shape.

So I'm going to have to change the head, but I'm kid of worried about the goop that built up on the inside of my valve cover, cause it looks nasty and I know I'm going to have to clean that up as well as the oil pan probably. Oil flowed good after I changed the oil again, but it started to pump up the rockers slower once more water started to mix with the oil, probably causing it to get thicker.

Should I change the lifters and oil pump once I get a replacement head? Or would cleaning out the pan, and then running clean oil and then changing quickly a few times be enough to clean out the motor? I didn't hear any concerning noises, and the rocker arms and push rods moved fine with no issues...I just hope I didn't do any internal damage.

About the head...do you guys think the crack can be JB welded just so that I can try and flush out the motor as I wait for a replacement head? There's no smoke from the exhaust, no over heating and no performance issues as far as I can tell.

I had no overheating issues, and the crack symptoms first started to show when I saw a milky build up under the oil cap, so I took it to my mechanic and he said that it was just condensation after looking at the oil on the dip stick and crankcase and saw that it looked normal, but my gut was correct.

So how bad do you guys think I'm screwed? Lol, I mean I guess I won't know till I look inside, but nothing sounds bad.

[optmaxx]

Here are some pics of the crack.

[optmaxx]

Luckily I have another 7120 head that I have in the garage that I used to have on my 4.2 that never failed and would pass smog with. I didn't use it on this build because the water jackets were welded shut, so I thought it'd be better to use an unaltered head, but I realized that those water jackets are sealed by the gasket anyways so I'm planning on getting that one rebuilt.

[amcinstaller]

Biggest problem with the forbidden milkshake is that the coolant eats all the bearing material. Past that, if you're capable and have a auto wrecker or pick n pull near to you, I'd get another head

[optmaxx]

I don't see any metal flakes in the oil. I plan to get the 4.0 head that I have laying around in the garage checked for cracks and flatness, and I doubt it has any cracks cause it came off of a running engine, but we'll see.

[optmaxx]

Stroker is back together with the spare 1992 4.0 head that I had in the garage that had no cracks, so I had it rebuilt withe new seats, guides and a 3 angle valve job. I must have been losing compression cause this Jeep feels a lot different now, it's much more tourqey than before, and it's much more fun to drive cause it really pulls, and no more coolant in the oil.

There was some valve train noise once I put on the head, but I traced it back to the rockers and changed all of them for new ones, and the noise went away, but I also put in that Rislone engine treatment and a zinc additive to help the lifters clean themselves out, but I think changing the rockers helped a lot, and I think it all has to do with my old rockers having a round hole where the pivots goes through vs a rectangle one that the new ones had, but I'll save that for another post. Mainly, I just think that the old ones had uneven wear due to them being poorly made.

I also changed the water pump with an AC Delco unit from Amazon which turned out to be total junk because it made my Jeep run hotter at 210 and sometimes a bit higher, but never in the danger zone, and it made a rubbing noise that I had a hard time tracing until I took it off cause it finally failed...it's a good thing I was just letting it idle when I noticed the temps going up and shutting it off. Bought a new water pump from Autozone, and my temps now go to 195 with a Duralast Gold stat, that a good combo IMO.

Things I plan to do next is an oil change soon, and change out the rod and crank bearings just for the heck of it.

[optmaxx]

The head that failed was from ebay. I always suspected that it had a crack, and the company even offered to exchange it if I could prove it was a crack, but unfortunately the machinist I took it to couldn't get the magniflux to catch on that suspected crack. The company has since closed up, and either moved and changed names I suspect.

The head I put on was pretty reliable, and I should have started with that one, but oh well.

[optmaxx]

I would like to add that the horse shoe intake is totally worth it.