Subtle 0331 Crack?

01 XJ
160k miles

Only symptom: coolant loss
Oil pressure normal, no milkshake.
No white smoke from exhaust

Had Blackstone labs run an oil analysis, here’s what they said:

You were looking for coolant, and you found it. Potassium and sodium show a pretty big leak. Silicon might also be from coolant, but it could be from abrasive dirt or maybe sealer/lube if any was used recently. Contamination (coolant alone or coolant + dirt) is causing the engine to wear quite heavily. Aluminum shows wear from pistons, iron comes from steel parts like rotating shafts and cylinder liners, and copper/lead/tin together come from bearings.

Potassium 1058 PPM vs average of 4
Sodium 1181 vs avg of 47

Today I pulled the valve cover. What I found wasn’t nearly as obvious as what I’ve seen out there for cracks, but there’s a faint brownish gold color running down from the exhaust valve on cylinder 4 toward the pushrod. I’ll upload the photos in the next post.

I also pulled the spark plug for #4. Significant rust on the washer and seat compared to 2 and 3, which I pulled to compare.

Thoughts? Am I looking for something that isn’t there? Based on the oil analysis is it time for a new motor? Or should I slap on a new head and send it?

The rust on the outside of the plug is unrelated. Running temperature will keep most of the coolant evaporated, all thats left is the additives. And it isn't as big as a leak as an old 3.1 chevy intake. If you replace the head before the oil pressure bottoms out the short block may survive, but with that oil analysis I would agree that the head is cracked.

And THAT is why folks with 0331 heads should do oil analysis. Catch it early before the big damage happens.

I should mention that Valvoline oil has sodium in it which confuses the analysis whether there is coolant in the oil or not. Coolant has sodium in it.

2X_01_Jeeps said:

I should mention that Valvoline oil has sodium in it which confuses the analysis whether there is coolant in the oil or not. Coolant has sodium in it.

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Wasn’t running valvoline.

2X_01_Jeeps said:

And THAT is why folks with 0331 heads should do oil analysis. Catch it early before the big damage happens.

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So you’re in the slap on a head and send it camp?

My 2000 did exactly the same thing. I bought a new CCH head to replace it. I did not ever find anything cracked but it seemed to have a small warp which was leaking minute amounts of water directly into the cylinders so there was no evidence in the oil.

IslanderOffRoad said:

So you’re in the slap on a head and send it camp?

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I would do a compression test at the minimum before making that decision.