RE-torqe new head gasket?
#1
RE-torqe new head gasket?
Just replaced the head gasket on a 92 4 runner 22re. This may be a dumb question, but I have to ask. In the manual I could'nt find any info on if the head bolts need to be re-torqed after so many miles. The reason I ask is I had work done on my nissan and the head needed to be re-torqed after 1200 miles. Anyone know anything about this, is this just crazy talk? I could'nt find any posts regarding my question, or maybe this is just something that everyone should allready know, thanks.
#3
Contributing Member
EB does recommend it too, or he has in the past.
>>>*Other than simple overheat, the #1 cause of head gasket failure is clamping force variations.
Usually when I mention this, the answer is "I torqued it properly!"
*Yes, very likely, but torque, which is a twisting force, means almost nothing when we are talking about clamping force.
Dirt or machinery debris in the bolt holes will throw the clamping force off as much as 50% and more, even though the torque wrench reads perfectly normal.
The same happens when installing new bolts. The very best bolts made will show a rough mating surface at the threads when inspected under a microscope.
When installing new or used fastners, first be sure the bolt will spin in and out ALL THE WAY freely with simple finger pressure. Be sure they are lightly oiled, not too much which can hydraulic lock at the bottom of any blind holes and spoil your day.
Use this simple breakin procedure for any new bolts: Tighten all of them to 50%, back off 1/4 turn, then to 75%, back off 1/4 turn. Then take them to 100%, back off 1/4 turn and repeat. Do a retorque after full warmup.
*This procedure simply assures that the imperfections of the threads seat to the bolt hole threads.
Yes, time consuming, but much faster and less costly than another set of gaskets, the actual clamping force will increase vastly, even though the torque load is exactly the same.
The alternative is you may be additional twisting at the top of the bolt after the threads have come to a stop from excess friction.
If any single one does that, head gasket failure prematurely is gauranteed, plus it weakens the bolt....*EB
Usually when I mention this, the answer is "I torqued it properly!"
*Yes, very likely, but torque, which is a twisting force, means almost nothing when we are talking about clamping force.
Dirt or machinery debris in the bolt holes will throw the clamping force off as much as 50% and more, even though the torque wrench reads perfectly normal.
The same happens when installing new bolts. The very best bolts made will show a rough mating surface at the threads when inspected under a microscope.
When installing new or used fastners, first be sure the bolt will spin in and out ALL THE WAY freely with simple finger pressure. Be sure they are lightly oiled, not too much which can hydraulic lock at the bottom of any blind holes and spoil your day.
Use this simple breakin procedure for any new bolts: Tighten all of them to 50%, back off 1/4 turn, then to 75%, back off 1/4 turn. Then take them to 100%, back off 1/4 turn and repeat. Do a retorque after full warmup.
*This procedure simply assures that the imperfections of the threads seat to the bolt hole threads.
Yes, time consuming, but much faster and less costly than another set of gaskets, the actual clamping force will increase vastly, even though the torque load is exactly the same.
The alternative is you may be additional twisting at the top of the bolt after the threads have come to a stop from excess friction.
If any single one does that, head gasket failure prematurely is gauranteed, plus it weakens the bolt....*EB
#5
Thanks for the info, did the full warm up re-torqe, only a few moved at all, and only a little. I'll check them again after a few hundred miles to be safe, thanks for the help.
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