Regarding those Nissan head gaskets; those were all under warranty as leaks were occurring within 5-10k miles. Warranty required gasket replacement and which was the proper method.
As to tightening the head bolts to stop the oil leak that’s just my personal opinion that was never put into practice. Subaru put out a bulletin about retorquing head bolts to stop oil seepage issues and it worked for them although granted the oil leaks on Subarus was no oil under pressure.
The oil port was located a 1/4" away from the edge of the block and the slightest looseness due to HG relaxing would cause oil under pressure to weep at a minimum or drip steadily at worst; all because the head bolt check was eliminated. There was never, ever a defect found with the blocks, heads, or gaskets. It was simply due to the above reason.
As to retightening of head bolts, SAAB also had a notice about this.
I’ve rebuilt a few engines in my early years…this included about 3 Vega engines. What I remember from the Vega engines you had re-torque the heads after your ran it for a few hours. But this was an Aluminum block with an cast-iron head. I don’t remember any other engine having this requirement.
Don’t confuse the initial installation torque specification with the required fastener tightness down the road. Just because they specified X ftlbs at installation does not mean that after several days or heat/cool cycles, that should be the torque on the fastener(s).
The installation torque required to properly compress a head gasket at installation should take into account the compressability of the gasket, elasticity of the fasteners and so on to ensure that as the assembly heats and cools, it maintains a seal. Re-torquing could actually cause problems in some cases. Unless it is specified, it’s probably best to leave it alone.
Checking torque after the initial application is nearly impossible anyway as it depends greatly on the breakaway force required to start the fastener moving again. This can either increase or decrease over time depending on circumstances (materials used, environmental conditions etc)
The engine in question for me is a Suzuki G10 3 cylinder engine. It is all aluminum for both the block and heads. The factory head bolts are NOT TTY and some people DO re-use them with VERY MIXED results. It might work ONCE but why take the risk?
I think my plan it to let it sit a couple days and then tighten again and forget about anything after that as this isn’t a concern on these engines unlike some of the engines stated above (Nissan, Subaru, Saab, etc.)
I also wondered if the torque at installation might be a different spec than the torque after a few cycles of operation. I haven’t do the timing belt on a lot of DOHC engines but I noticed one where the tensioner had a pointer mark for a NEW timing belt and a USED timing belt. Apparently the tension on a used belt is less than on a new belt as it stretches and relaxes. I don’t think I would ever consider re-using the belt on an interference engine unless it had just been put on within the past few thousand miles, especially since this job took me about half a day.
The OP was about should the owner retorque the head sometime after replacing the gasket. It was not about paying a shop to retorque a head to stop a headgasket leak. If I had a seeping headgasket on my car I would try retorquing because it would cost me next to nothing. I would not pay a shop to try it.
I don't remember any other engine having this [head bolt re-torqueing] requirement.
If my memory serves me correct, my late-70’s VW Rabbit engine was supposed or at least suggested to be re-torqued. I think it was just a one time deal, not intervals. I can’t recall whether this was a VW suggestion or a John Muir suggestion though.
@GeorgeinSanJose, yes the retorque was a one time deal. This was usually done when the valve cover was removed to inspect valve lash which was a regular procedure.
Subaru and Nissan also said it was a one time deal before stating it was no longer necessary.
The leaks occurred after the latter part of the above statement.
I’m curious as to what would happen if cwatkin was to tighten the head bolts, allow it to sit overnight, and then see how much (if any) give has developed overnight when the head bolts are rechecked the next morning.
For what it’s worth anyway, I’ve torn into some virgin engines for head gasket replacements and on several of them I’ve found head bolts comparatively finger tight. I don’t mean that literally; only that they could be broken loose with a 3/8 palm ratchet and my non-scientific estimate of torque required to break them loose was probably in the 10-20 Ft. Lb. range.
I will post the results when I get around to this procedure. I have 4 other vehicles and lots of work going on so this isn’t the number one priority at this time. I am going to remove the head and take it to a shop for blessing or a redo first, then start on the re-assembly.
I once saw an old Jeep 4.0L with like 500,000 miles on it. The entire thing was in terrible shape and the owner wasn’t going to spend any money on it. I was over at his house and noticed the head gasket was seeping and some of the bolts were LOOSE! I didn’t have a torque wrench with me but tightened them down. These were the ones that were accessible. Others were under the valve cover. Anyway, this vehicle was junked soon after so it really didn’t matter. I have to really admire that 4.0L after seeing on in that condition. Besides that, I don’t think he ever changed the oil, just added. You would fall through the floor if you weren’t careful as there was nothing but carpet between you and the road!