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After rebuilding my L67 SII, and running it probably 30 minutes total I've been going over various leaks. The major one of concern is a head stud leaks coolant, located at the firewall bank outside of head, closest to the passenger side. It leaks very little, but its a leak that I don't want. I used ARP lube in the assembly, which I thought was going to seal it, but apparently not, others have reported that it doesn't as well, which in hind sight, I should have done my research.
Two things, how do I go about fixing this? I know I need to add an RTV like sealant but is it possible to remove the 1 culprit, add the sealant and then torque the 1 stud. Or does the SC and LIM need to come off to loosen all studs and then re-torque all?
Also do any of the studs that are seated in the head run through a coolant passage? Or does anyone know exactly which ones do? If I recall correctly when assembling, the studs inside the heads looked to all pass all the way through to above the crank, which would indicate they wouldn't hit a coolant passage.

I used PTFE paste on all threads going into the block and the provided ARP assembly lube for the nut threads. No leaks.

The only easy way to figure out which head stud/bolt locations hit coolant passages is blowing light compressed air into the holes and checking for coolant side pressure.

You can remove just the 1 stud, add the sealant and re-torque, without removing the head, provided you have enough physical room in the engine bay to get it out. The rest of the bolts will hold the gasket solid till you get it in and re-torqued. Guys do it all the time on other engines, especially newer diesels that have good head gaskets and just need the fastener upgrade.

95naSTA wrote:I used PTFE paste on all threads going into the block

Yes - The stuff I used is resistant to water, coolant, oils, even jet fuel.

00Beast wrote:You can remove just the 1 stud, add the sealant and re-torque, without removing the head

Yes!

IIRC, every stud runs into the coolant passage: each bank is essentially a water jacket and 3 cylinders. Sometimes, you get casting flash inside between the cylinders or at the base of the threaded holes for the studs that is not removed during manufacturing that can seal the bottom of the hole. When I tore my l67 open, I seem to remember water coming out of all 8 outer bolts on the heads. The inner 8 did not, due to the angle it was on the stand compared to the level of water still in the block. (Then again, I pulled apart the same 3400 three times later that year, so maybe I'm confused between the two)