Head Bolt with Carbon in Threads

[Dibbons]

I was concerned when one head bolt I removed from a '92 Jeep Cherokee had half the threads that feed into the cylinder block filled with what looked like black carbon. The bolt was also more stubborn than the other bolts to break free. An online search found some believe it is oil on the threads that over time and after many heat cycles has "coked". I am hoping that's all it is. I removed the cylinder head suspecting a blown head gasket because of recurrent overheating, but the head and gasket look fine.

 

[pnora]

Nothing to worry about. That motor is not known for head gasket failures.

 

[Dibbons]

That motor is not known for head gasket failures.

Thanks, I didn't know that. I do find many similar owners like me finding overheating problems though.

 

[pnora]

Thanks, I didn't know that. I do find many similar owners like me finding overheating problems though.

There are two fans and one is commonly overlooked.

 

[QuickBpBp]

Never had an overheating issue with our 99 Jeep Grand Cherokee but I had 2 4.0 Jeep engines grenade. Both engines were piston skirts that failed. One blew the piston skirt apart along with the piston and sent the #1 rod through the cylinder wall and into the water pump housing area. Then the Junk yard engine I put in broke the skirt about 15,000 miles later it knocked but still ran when I sold it...

 

[dvw]

I have seen 4.0 heads crack. Take a good look or have it crack checked. Lets see a picture of the head gasket.
Doug

 

[junior340]

My `98 Cherokee use to over heat, it was the tiny radiator they come with. I put a Mishimoto in there and all fixed. But there are many other parts to check before putting a expensive radiator in there. Early ones have air pocket issues from the side radiator tank also.

Agree with above other issue to look at also.

 

[Dibbons]

Lets see a picture of the head gasket.

The head gasket was left with the machine shop for inspection and was disposed of afterward. Actually, the gasket looked almost new to me and my compression check before dis-assembly was 130-150 PSI.

 

[dvw]

The gasket doesn't have to breach into the cylinder. It can fail between a coolant passage and the head bolt. My Cummins failed in that manor. The bolt looked similar.
Doug

 

[Dibbons]

The gasket doesn't have to breach into the cylinder. It can fail between a coolant passage and the head bolt.

Agreed, the old gasket looked fine every which way to me, but I am still hoping this new gasket fixes the problem.

 

[bm02tj]

there is also two pumps for opposite rotation make sure you have the correct one
The wrong one still pumps water but not enough

 

[dvw]

Now that I think back on it. I repaired a overheating 4.0 years ago. The water pump impeller was spinning loose on the shaft.
Doug

 

[Dibbons]

The water pump impeller was spinning loose on the shaft.

I discounted that as being an impossible scenario, now I'm going to look into it. Thank you.