Head bolts final torquing. The final 1/4 turn.

[Nevadan]

It's been over 2000 miles since I replaced a head gasket and I still haven't tightened the bolts the final 1/4 turn. Is it wise to do it now?

On another post which I can' find now someone had a suggestion for the final tightening: loosen each bolt individually and then re-torque per the book. Or maybe it was: re-torque until you feel the bolt give. I'm not sure about that last statement and I don't want to snap off the bolt. Any suggestions? How do you feel the bolt "give"? And what stretches? The entire bolt?

[Nevadan]

I found the post from Quantum-man....

I need an explanation on "when the plastic position is reached". I can't find Fats' or Quanutm's original post.

Quote: 1000 miles is too long. Bentley transcribed 1000km to 1000miles when plagerising
I believe in about 500 miles revisiting the head. Unlike the 'new' poilicy of not undoing bolts first.., I still use the contrary method.

This, for me shows up those bolts that have worked surprisingly loose, be it from actual bolt loosening or probably variation in the gasket spread. It will also prevent those nasty bolt creaks. I loosen, then retighten each bolt individually. As per Fats, which I believe is as per me; I peer down onto a torque gauge, and I personally stop when plastic position reached. End Quote.

[Nevadan]

Adding a few more quotes from related posts for my own reference:

Quantum TD:
Jack used to claim that you didn't need to do the 1000 mile retorque unless it was seeping. Something about the new head gaskets or something.

I just get leery on that last round. It seems like everytime I try to do it, I can feel the bolts give out and stretch.

Coke:
Yeah, I went and dug up his instructions he wrote for the procedure and he left the 1000 mile retorque out. Brings up an interesting question. Do I do it or not?

Quantum-man:

For the angular series, I use my Snapon torque gauge, and I do it in two steps.
However I only angle torque until I reach the stretch point, where the gauge fails to rise, ie about 45 degrees..
This halting of the gauge tells me that no further pressure is being applied, further torquing, does nothing for clamping, or the bolt.
This maybe between 105 to 120 lbft.
On the second run through, [equivalent to the second lot of 90 degree torquing], I do the same thing and gain a further 45 degrees or less

After 350 to 500 miles , I undo each one individually, and retorque to elastic point, which IIRC may be down to 95 to 100lbft [or was that the one after the trip?.]
Marking the ends of the bolts first with a punch to record their history can help, if you intend to reuse, (which I do) .
Somewhere, there is a graph that claims that a bolt stretched within it's elastic range, rested, then stretched again, actually gets stronger than it would otherwise be, if stretched all in one go,... I suppose it's a kind of work hardening

Quantum-man:
I believe that just about everyone has torqued up a head, and come across one or two bolts that stuck and then suddenly yielded and gave the torquer a real fright.
By backing off the bolts, not only do I avoid this fearsome snatch, and get a nice gradual increase on my gauge, but on the second round of 'sbstitute' 90 degree torquing, I get to find which of the bolts undo really easily, and find the areas of the gasket that have given way more than others.
My thoughts on studs, is that they a a good thing, but especially with the fine threaded type there is a danger of over plasticising the gasket

Incidentally, I do the second part after I have idled the engine for a couple of minutes to get everything hot.

Re the possible 'waste of stretch', I don't think that that is the case, as the first part of the yield of the bolt is actually elastic... Even a plasticine bolt has some small elastic range before reaching the plastic

RE the sketchy part, are you referring to the bolt reuse, or the strengthening of the bolt?
I'll try and find the reference. Meanwhile, with a little lateral thinking, and thinking of work hardening, take the specialised steel used in crushing jaws on demolition machinery, that work hardens, or, maybe a better analagy would be in the work hardening of copper sheet when planishing to make a bowl, and that stuff definitely starts off as plastic.

[bbob203]

all I can say is whenever I have to do a head gasket I'm getting studs. these stretch bolts would rack my nerves far to much.

[zman]

all I can say is whenever I have to do a head gasket I'm getting studs. these stretch bolts would rack my nerves far to much.

Me too. I did a micrometer measurement last time and it was so very close to bottoming out the new bolts It had me worried how much room I had. So far so good...But next time it will be the studs.

[Fatmobile]

Lots of people use stock headbolts so I'm glad you got all this info into one easily searchable post.
I really like using a torque wrench so I can see along with feeling the bolt as it turns
and am glad Quantum man told us about it.

Studs probably work better but that's beyond the scope of this topic.

I have several boxes of 12mm headbolts that will need to get put to work
and they are holding well on all the engines I've used them on.

zman: are you saying the stock bolts reach all the way to the bottom of the holes,.. and maybe a little too far for comfort?
I haven't really checked that, I know the 12mm stretch bolts are longer than the 11mm,
just assumed they weren't close to being too long..

[Nevadan]

A quote from "demon" with "quantum-man's" replies, very interesting as it relates to my original question about torqueing the final 1/4 turn:

demon:
So i pulled the head offf today. Head looks great, no cracks, all cylinders look to be burning evenly and the same. The cylinders look good too, including cylinder 4. All look the same, no scratches, no cracks, carbon is evenly distributed and looks the same on all pistons.

When I removed the head bolts, I loosened them in reverse scequence of torquing them. Number 10 bolt, at the rear of cylinder #1 was completely loose, no torque at all, and was just sitting there. I unscrewed it with my fingers! I was amazed at how little torque was on all the others too. Felt like an equivilant of about 30 ft. lbs!!!

quantum-man:
That is always disconcerting, and why I always undo bolts before doing final angled torque into plastic range of bolt. This gives them equal clamping. It's surprising how little tightness bolts need to stay water tight. Not done any research on it, but perhaps 30lb to undo is say 50lb to do up. Maybe I wrote it down somewhere when doing a head.

demon:
I originally torqued the head bolts in the correct (Bentley) procedure, while on the engine stand. Then finished the final torqueing while in the car. Ran the car for approx 1400 miles with no problems. Then I did the last & final torque procedure with the engine hot. This is when all the problems started.

All the threads look good in the block and on the bolts.

quantum-man:
I thought I read somewhere, a stand that held engine from one end should not be used when applying the head because the block bends!

demon:
My Theory:
I'm wondering if while torquing while hot, then have everything contract while cold, then heating up again repeatedly started loosening the bolts up. I think that would explain the coolant working its way past the head gasket and into the oil passages. Once my pan filled with the oil plus approx 1/2 gallon of missing coolant it created to much pressure inside the block and had had to come out somewhere. Following the path of least resistance, it went past the rings and oil passages of cylinder 4 to reach the valve cover breather right above it.

Make any sense?

quantum-man:
I think piston pressure will either push water out of filler cap, or across to the oil supply near #4 cylinder or into one of the oil drains/vents. Any water pushed by any cylinder into the oil will steam out of the vent, so I think #4 cylinder being under the vent is mere happenstance

demon:
Question #2
It is a 12mm Mechanical engine 1.6 TD

Why does the Erling head gasket not have 3 of the small coolant holes drilled thru it, when the block and head both have those holes? I called a vw shop about it and they said it was designed that way. Sounds fishy....why would vw put the holes there, if you don't need them. The holes I'm referring to is, one on either side of the front main oil drain passage, and one at the front of cylinder 1.

quantum-man:
The missing holes are purposeful to direct the coolant into certain directions around the headThanks guys!

[Nevadan]

When these engines were new, right off the assembly line, did the owner bring the vehicle in to the dealer to have them re-torqued?

I'm having trouble making a decision to do the final 1/4 turn since I've driven the car over 2,000 miles since replacing the head gasket.

[Nevadan]

Quote from Mark (The Miser) UK on the TDI-IDI site:

This is what I have personally experienced. This is for M12 stretch bolts

I use a Snap-On dial gauge torque wrench. IIRC it's 2% or better.

Initial angular torquing peaks at approximately 115 to 125lbft.

The final torquing only reaches 95 to 105lbft...
I have done this warm. I believe this is optional but I like the idea that the gasket is slightly more pliable when warm, and likely to fill any divots. I might be wrong on that, but it's just how I do it because I have justified it to myself. .

A little more on 'my' procedure. I could be wrong, so it's just for reading, but I've not failed yet...

With the 90 degree torques, I actually only torque until value levels off. This may result in only 45 deg.
I split the 180 deg turn in two, for a 'more even' clamping [or so I tell myself]

To avoid that nasty bind and cracking sound that I'm sure we've all experienced as we torque some of the head bolts up, I still use the old method of slackening each bolt in turn [release water cap if done with any real warmth remaining]

The final torque gives a nice smooth rise to the afore mentioned figures. Slackening actually reveals just how slack some of the bolts have become, yet [hopefully] not allowed any leaks.

Remember slackening a bolt that has not been set for years, will never repeat the torquing up values so you will only see about half the values. [or less occasionally ]

By not using up all of the angular torquing on the first use, I personally reuse the bolts once more. I don't advocate doing that, but by having the angular stretch in reserve, can also be useful for shutting off that slight gasket leak that may develop early on.

[Nevadan]

Link to a good discussion about this:

http://www.vwdiesel.net/forum/index.php?topic=29728.45

[StevenPH]

Could someone describe in more detail the loosening procedure suggested here prior to the final retorquing? Do I loosen the bolt just enough to break the initial bond and then retighten to where the torque levels off (105-120lbs)? Or are you completely loosening the bolt and following the entire procedure again?

I'm at about 450 miles after head gasket install. No seeping so far.

On a related note - any suggestions for a sealant to use on my valve cover gasket? Im looking for something to use in the tight corners near the cam shaft seal where I keep getting leaks... I had RTV blue but the guy at Napa said its not the best as it hardens.

[Quantum-man]

Could someone describe in more detail the loosening procedure suggested here prior to the final retorquing? Do I loosen the bolt just enough to break the initial bond and then retighten to where the torque levels off (105-120lbs)? Or are you completely loosening the bolt and following the entire procedure again?

I'm at about 450 miles after head gasket install. No seeping so far.

On a related note - any suggestions for a sealant to use on my valve cover gasket? Im looking for something to use in the tight corners near the cam shaft seal where I keep getting leaks... I had RTV blue but the guy at Napa said its not the best as it hardens.

Hi,
The way I do the final torque, is to loosen each bolt, in the normal tightening sequence, and then retighten it BEFORE moving onto the next one.

I like to do it warm, but cold is probably fine. Doing it warm I always release water filler cap, incase of any residual pressure [again probably not neccessary, but I liketo remove any chance of creating a leak where there was none ]

This quote below should read 'sat' and not set,... but thinking about it set would probably do as it was a clumsy attempt to distinguish the occasional bolt that has all-but fused to the block over a period of time, and so gives a high torque reading when undoing.

"Remember slackening a bolt that has not been set for years, will never repeat the torquing up values so you will only see about half the values. [or less occasionally ]"


[ I always use the torque wrench to observe undoing values] On the final retorque some bolts may have as little as 30lbft, but still seems to have escaped a leak. Generally the bolts will be from about 1/2 to 2/3 what you put in them to torque up but this is not wrong, but merely the physics of screws and gasket easing combined. Angle torque to yield and then stop.

Get a Corrado all-in-one rubber gasket for the valve cover, making sure the cover is flat. Should not need more than a screwdriver type with socket to torque up, and stop leaks.

[StevenPH]

Thanks for writing -

Could you describe the angle torque method you use after loosening? I've read so many different accounts and methods I'm worried I'm going to use the wrong one at the wrong time.

Does the corrado gasket fit over the shouldered bolts? I tried a beck/arnley rubber gasket that didn't fit over the shoulders. If so - Can the shoulders be removed? Are they fixed to the bolt and could just be twisted out with them?

So far everything else is running perfectly - I advanced the timing yesterday a bit more and it's made a world of difference - more power, less smoke, smooth idle when cold. Valve cover leak has stopped and my dipstick doesn't get pushed up anymore! I was worrying I still had blowby even after the new rings...

Thanks for all the invaluable help on this project.

[Fatmobile]

You need different studs.
I prefer allen head set screws.

[Quantum-man]

As 'Fat's says shoulderless studs required.
Don't do as I did which was to use an old hand rotated grind wheel and allow the 10 'shouldered' bolts to spin between finger and thumb. Cheap to buy, and gives you both options.

Re retorquing; all done to the point of no gain in torque value whilst staring down at the dial gauge. Further turning only serves to weaken bolt.

WRT bottoming out of the bolts; my method keeps elongation of bolt to a minimum. Something I think I have stumbled upon with the development of these engines, ie 1.5, 1.611mmbolt, 1.6 mech 12mm, 1.6hydro, 1.6 SB/RA intercooled, is the gradual increase in bolt clearance after final 'official' torques.

Although I have examples of the last three engine types, they are all functioning engines, and so I cannot measure the block/ head depths.
I did have the info somewhere, but seem to have mislaid it.
Either the late mech or the early hydro had 14 turns of screw thread and 12 turns for final final torque.

Perhaps those with spare engines lying around can experiment and collate the results.