Hi i recently did my first set of head gaskets and i took up a set of heads to a shop to have 4 manifold bolts removed and/or retapped. Some broke flush and a couple higher up. Since reinstalling weve put about 400 miles on it and the fluid levels have held very well but im seeing a wet spot starting to form on the drivers side manifold bolt 3/4 of the way back. The only thing i could think is it was retapped too wide or on an angle but being ive never performed that myself i wasnt too sure. The reinstallation of the manifold bolts seemed perfectly normal. I dont see any carbon forming anywhere on the heads around the manifolds like there is a leak and its very quiet. Also i used all new gaskets and seals from mahle. I thought maybe the valve cover was leaking down onto it but that checked out fine. Its a wet cirlce surrounding the bolt. Being a greenhorn id appreciate any input. Thanks. Late model 99 4.8l 862 heads

 

Pull the bolt and see if any fluid drips out - see if you can identify it. It’s possible the head passed crack inspection at the machine shop but once it started thermal cycling, the repair on that thread boss was too close to a cooling passage to remain sealed.

If any fluid does drip/run out, you could try using thread sealant (liquid thread sealant or RTV) to stop the leak. If that doesn’t work, call the machine shop and ask if they want you to bring it in for inspection, or if they have any other suggestions.

 

Will do and update. Thank you