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Head Bolt on Jeep 4.0 Inline 6

When I took the head off the block I discovered the threaded bolt hole closest to the water pump on the drivers side of the block was not closed at the bottom. All other bolt holes are essentially threaded wells escept this one. I believe the bolt hole has broken or rusted through. I don’t think it will cause a problem but have concerns. Has anyone ever experienced this? Do I need to use some type of weld to close the threaded hole back up? The condition of the headbolt in that thread was no worse than any other bolt but did have rust on it.

The reaon for pulling the motor apart in the first place was lack of compression in #1 cylinder (closest to the headbolt in question). It appears as though a ring is bad; I don’t think the lack of compression is related to this.

What is below the bolt hole? If the bolt hole goes into the coolant portion of the block, I would coat the bolt threads with RTV sealant and call it a day. If it goes to the outside of the engine, don’t worry about it.

May I assume you are describing the manifold bolt/hole? If so, yes it is open to the water jacket. When reassembling use a high temperature thread sealant on the bolt.

Some bolt holes in intake manifolds and cylinder heads will thread into the water jacket so that is likely normal.

Thanks! Great advice.

Yes, the bolt hole opens into the cooling jacket near #1 cylinder. Good advice.

You’re quite welcome.