Sophrony

Hello, I recently purchased a 2000 Cherokee (RHD) for work.


After the purchase, I replaced the valve cap gasket and flushed the coolant/radiator system. Although the coolant had a brownish, rusty look about it (but not particularly oily), the oil looked good without any sign of creaminess.


On route, after 3 or 4 hours of driving with the engine running well, the temperature spiked at a stop. I checked the engine and only found the coolant to be low, about halfway between low and full. I added more coolant. I thought that perhaps I had left some air in the system after flushing it and that this would probably solve it. I let it cool down, before taking it back on the route. The same issue occurred again - at a stop the temperature spiked. I called the supervisor to be pulled out, thinking that the water pump may have been broken. Seeing that the temp only spiked at stops, I figured I could make it back home. I didn't make it, because the temp spiked again while going 55. I pulled off at the nearest location and saw steam coming from under the hood. The coolant tank was up to the cap with brown liquid and floaty oily stuff. Steam was coming up from the middle right of the engine, in the middle where the air intake and outtake meets the head. Two puddles were under the car, one was oil and the other was coolant, but they were distinct puddles. Oil had gone up and out through the dipstick, which showed the oil was creamy. I had it towed and now suspecting the head gasket and maybe also the head might need to be replaced, I've taken it apart.


Removing the valve cap showed mixing, with creamy stuff in the oil. The air filter had oil/coolant slime all over it.


Looking at the head,

• The head gasket looks new.
  
• There was no visible crack or coolant streak on the head.
  
• There are no observable fractures or cracks under 7X magnification.
  
• I could not find any evidence of minor warping using a metal straight edge and a 0.0025 gauge.
  

The head is a 0331, but no evidence of cracking between 3 and 4.


I know the previous owner rebuilt the block about 4 years ago. I've looked at the block for warping and cracks too, but didn't find any.


I am hesitant to put it back together, since I have no idea where the failure occurred. Any suggestions for what might have gone wrong?