kayakermike

My cylinder head has 7 to 8 cracks it was x-rayed could the engine block be to?
i have put 2 head gaskets in and had the cylinder head machined once before i did not put new head bolts in is their any way to check if the engine block is cracked
Its a 98 cherokee with a 4.0 with 201,000 miles

perez1989

Heads crack because of overheating. Since they are made with aluminum or cast iron that is why they crack. The engine is metal and will not crack like a head does.

5-90

Um, cast iron and aluminum are both metals. The crank is cast iron as well - I believe it's still nodular (while the block and head are grey.)

However, the assessment that heads crack due to overheating is generally correct. You can remove the block to have it X-rayed or Magnafluxed, or you can get a dye check kit and check it yourself (Magnaflux offers a DIY dye kit for about $25, last time I looked.)

You really only need to check the deck (upper surface of the block, one side of the cylinder head gasket sealing surfaces) and the bores (round holes where the pistons are.)

However, a cracked head is not an automatic indicator of a cracked block.

Why did you pull your head in the first place? That may be instructive... Since you've got a 1998, that's the 0630 head - which isn't normally prone to cracking (a replacement can be sourced from 1996-1999XJ or 1996-1998 WJ/TJ, as a direct swap. The casting number can be found on the driver's side of the head, outside of the valve cover, above and between the #3 and #4 exhaust ports.)