"Stretched" head bolt length

[ToddA1]

So I made a boo boo and neglected to oil the 12mm head bolts, prior to installation. Bolts were cracking and popping, but I marched forward with the installation.

After a test drive around the block, sure enough, the head gasket was leaking. I have a new set of bolts on the way, and I was planning on swapping and going through the torque process, one at a time. 

My thought was the bolts may not have stretched, if the initial torque specs were never met.

Has anyone ever measured the length of used head bolts vs. the 115mm that new bolts measure?

-Todd

[RunninWild]

When they say stretch bolts they mean more the bolts are stretched in a way that they have spring tension holding them at maximum clamping force. When loosened They should return to practically the same size They were originally. Think of a spring. They shouldnt actually deform and elongate unless overtorqued and stretched too far. Over torqueing them causing them to physical stretch beyond their integrity and creates less clamping force. Basically you're tightening the bolts to the point that they are at their peak holding strength. The reason they arnt reuseable is the integrity of the metal has been compromised once they have been "stretched". Its like bending metal back and forth a bunch of times until it snaps.

[ToddA1]

Hmmmm....  I understand the metal has memory, but I was under the impression they actually elongated and stayed elongated. 

Thanks for the reply.

-Todd

[air-cooled or diesel]

anti-seize will do, i like the copper stuff, although if you torqued correctly not oiling shouldnt cause hg to leak. bolts 'cracking&popping' is normal during 180dg & 90dg turns. ?clean threads in block? i use qtips& brakecleen.

[745 turbogreasel]

They permanently elongate.
Lay the threads of a new one up  next to the threads of an old one, the only part matching will be that which was protected by  the threads in the block.
They are called  'torque to yield' fasteners because you  tighten them beyond the  elastic range.
You can measure the  difference in length as well.

Clean the threads, you can file a head bolt into a tap if you don't have one the right size.

Installing head bolts dry is one of the stranger assembly choices I've seen.  if you initial torgue is off,  all the subsequent angles are too, although they will usually  still be within range.

Lastly,  if you get the really cheap head  bolts, they don't always work.  We had a  bag of 50 at about $1.40 each, and  25% of them broke off.

I install head gaskets dry and have good luck that way.  if yours is already leaking, I'd be concerned about   contamination from that  compromising the seal, and i'd probably  lift the head enough to dry it and  slip a new gasket in there.  that would also  let you inspect where the  failure occurred.

[ToddA1]

It's a MLS gasket, not fiber. I don't recall seeing any silicone sealing rings on it, so I figure I have nothing to lose, other than the cost of the head bolts.   The gasket cost me $55 + shipping, so I figure it's worth a shot.  I paid $20 plus shipping for the German bolts.

If the used bolts measure the same as the new bolts, maybe I'll reuse them and see what happens.

I've read others had luck with the "one at a time method", where it cured their leaks.

-Todd

[RabbitJockey]

i wouldn't do that again with out sticking a new gasket in.  if it werent leaking already itd be a different story. but i have messed up the foil around the cylinders before and had to redo a headgasket,  just depends how much your time is worth to you haha.

[RunninWild]

I reused a mls gasket and got it to seal. That being said it sealed the first time and I drilled out the rivers cleaned it very well and applied copper gasket spray on each surface. I also used arp studs. Like rabbit said, if you have more time then money it won't hurt to try.

[ToddA1]

I doubt I put 500 miles per year on the truck.  It was perfectly fine with the 1.6.  I have no clue why I put a AAZ in it. Not sure if I'll complete the installation of the turbo or TD IP.

I'm gonna try this weekend. If it sits a week or month longer, no worries. I only want to get it running so I can have another running vehicle.

-Todd

[ToddA1]

I finally got to swapping the bolts, today. Oddly enough, the new bolts were a smidge shorter than the used bolts. Both sets were the same Viictor Reinz brand and both sets were made in Germany.

I nested the threads together on a new vs. used bolt, and although tight, the fit wasn't prefect. I decided to use new bolts.

About an hour later, I start it up and hear a hissing after shutdown.  The head gasket still leaks. Guess I'm ordering a new MLS head gasket.... maybe I'll spray it down with some copper spray for cheap insurance.

-Todd

[theman53]

mls is harder to seal than a fiber gasket.

did you check to see if both surfaces are flat?

[ToddA1]

No, I didn't. This was a running engine, that the PO started breaking down for no apparent reason, after the intermediate shaft froze for a couple seconds in his garage.  Engine was immediately shut down when he heard the belt squealing. 

His plan was to rebuild it, just to rebuild it.  He ended up installing a gas engine that he understood, more. It didn't overheat or anything, so I had no reason to think something was warped.

It turned out being the oil pump.  I pulled the main caps and the bearings looked perfect.

I've also heard what you stated about the MLS gaskets.  Thought the spray would help. 

I also see that Bentley recommends  another 90° angle, after running the engine to operating temp IF running a fiber gasket.  At this point, I have nothing to lose, so I was considering adding a 45° angle.

Any idea where to get a 1 hole fiber gasket for a AAZ?

-Todd

[ToddA1]

I was able to get the extra 45° on the bolts, installed the valve cover, plugged the block vent and started it up.  Let it run for a minute, shut it down and didn't hear any hissing... it worked! 

Started it back up, sprayed some degreaser on the engine, and started cleaning up.  About 5 minutes later, I heard the idle jump, maybe 500rpm.  Shut it down and I heard hissing... I guess it didn't work.

Called GAP and ordered another MLS HG. I was told fiber was never available for AAZ and I wasn't going to argue. At least the HG was $20 cheaper than I thought.

-Todd

[RunninWild]

If you want to run a fiber gasket just use a 1.6td one.

[theman53]

fiber wasn't available for aaz, I must have missed aaz in your post. Check both block and head for flatness before throwing the new gasket on.