Drained $280 into a rebuilt head only to find the block was the problem

I put a fresh rebuilt head on a 5.9 Cummins last March, torqued everything perfect, fired it up and still had coolant pushing into cylinder 2. The machine shop that pressure tested the head never checked the block deck for flatness, cost me 2 weekends and $280 for gaskets and studs. How many of you check the block surface before swapping heads, or do you trust the shop when they say the head's good?

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bailey.jennifer15d ago

Checking the block deck should be step one honestly, not something you skip because the head got a clean bill from the shop. A pressure test only tells you the head holds coolant, it says nothing about whether the deck is flat or the fire rings will seal against it. Pull a straight edge and feeler gauge across that surface before you bolt anything down, it takes ten minutes and saves you exactly what you just went through.

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