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Where do heads usually crack

lonestar

Explorer Addict
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August 29, 2001
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City, State
lou,ky
Year, Model & Trim Level
91 XLT, 02 XLS
After noticing my antifeeze dissappear, getting an oil anaylsis with indications of antifreeze in the oil and learning that that early 4.0's had head cracking problems I decided to just change the heads with heavier aftermarket heads.

Now that I have tore it down the heads appear to be ok, no visible cracks as I was inticipating. Where should I look, or do they usually crack internally?

Also, most of the water ports in the head gaskets seemed to be clogged. The new head gaskets only have a small, maybe 1/4 hole, opening for the water ways. Should these openings be larger or triangular to match the openings on the block?

Side note, I also noticed the new lower intake gaskets to be different. Old gasket was a 1 peice metal/rubber gasket that was bent to fit betweenm the heads. The new gasket is a 4 peice system, intake-head opening areas have a heavier almost head like gasket, and the intake-block areas use simple cork which I will coat with high temp Black RTV.
 
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Alec

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Houston, Texas
Year, Model & Trim Level
2008 JK
Most head cracks are not visible to the naked eye. They should be dye penetrant tested to bring out any cracks.

They can crack pretty much anywhere: around bolt holes, between bolt holes, between oil galleries and water jackets, around the combustion chamber, between ports, etc.
 
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stubborn1

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WISCONSIN
Year, Model & Trim Level
'98 4wd XL
When my heads cracked, they cracked right between the intake and exhaust valves where the material was the thinnest. The crack was on the rear-most cylinder on each side of the engine(sorry, don't remember cylinder #s).
 
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james t

Elite Explorer
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Texarkana AR/TX
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94 SAS sport
The last time my head cracked it was right above the left eyebrow. I must say i deserved it.









































:D
 
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