My TTY Head Bolts; their care, and Re-care!

[Mark(The Miser)UK]

As part of my on going experiment with this daily  driver; last week I replaced my head bolts. I thought they dated back to my head skim back in August 2008. However it would appear they date back prior to my purchase in April 2005, and probably about 2002/3 when the gasket was previously changed.

The significance of this is that they have been reused. Some would say that that is risky. I would surmise that the PO changed to the brand new aftermarket head, at the same time so didn't need to retorque to stop leak issues
 
When I had the warped head  in 2008, I decided to reuse the bolts once more. This time on the start of the learning curve, I substituted 45 deg turns for the usual 90 deg. When I had the starting problems in Sept 2010, I stripped the engine and did my 'hone' and rering. IIRC VAG wanted over £100 for a set of bolts 

I measured the bolts, and decided that they hadn't stretched much. From this point in time on, I limited my head retorquing to getting as close to the start of plastic, as my torque wrench would allow, and no further.

Not to bore you all with the details, last weeks change meant that I had reused the bolts SIX times.

As I took the old bolts out I recorded their overall length, and torquing position.  Position not important on the old bolts as I had moved them around previously, spoiling the data for the couple of rear bolts, that I needed to give extra torquing  to stop a leak, which worked for a short while, but was due to a corroded gasket; so flogging a dead horse in the long run.

If you see the tabulated data below; the new bolts will have a specific history:
[I do this with injectors and heat shields too, keeping them to their specific 'homes' ]


Bolt    Old          New
Pos‘n   (mm)       (mm)   
1:      127.45;     126.85
2:      127.35;     127.12
3:      127.24;     127.06
4:      127.25;     126.75
5:      127.61;     126.86
6:      127.04;     126.90
7:      127.65;     126.85
8:      127.52;     127.08
9:      127.30;     127.10
10:    127.29;     127.04

Avg:  127.37       126.99

In the future, I will only reach the plastic stage on a new gasket. No more angular torquing, on the subsequent reuse of head gaskets: [ones where head removed for other reasons than gasket leaks that is ]

My new torquing procedure:
5 lbft-25-50-75- 85 to 95 lbft
 Below is supposed to be a cylinder head and my version of torquing sequence
---9, 3, 1, 6, 8  ||
---7, 5, 2, 4,10 ||

[bbob203]

Go put this up on tdiclub people will go nuts 

[vanbcguy]

HA. Would they ever!!

And to think, there's still yet another diesel forum we refer to as the "hillbilly" forum.... ;-)

[Gizmoman]

Mark, I dig your perspective. The way you talk about pulling heads, rebuilding motors, weird injectors and so on, you make it all sound like just part of changing the oil. I can appreciate that you seem quite "in tune" with your engines - practically down to the molecular level

As for me, I'll stick to the Bentley for the most part and re-use bolts for bracketry and such. Still an interesting perspective though. The thought of having to pull a head after all the work I've put into it makes me queasy.

[bajacalal]

How do you measure the bolts? I thought the stretch was not just lateral but radial, like a "twist."

[745 turbogreasel]

Mark,
Were your bolts OE, good aftermarket, bad aftermarket, or unknown?

I had some bad aftermarket ones that came in a bag of 50  where probably 2-3 per head  broke before the final angle tighten.  They did seem to hold OK once you got a full set in at least.

[Mark(The Miser)UK]

 

Mark,
Were your bolts OE, good aftermarket, bad aftermarket, or unknown?

I had some bad aftermarket ones that came in a bag of 50  where probably 2-3 per head  broke before the final angle tighten.  They did seem to hold OK once you got a full set in at least.

The 'long life' bolts have "BUS 10.9 Germany" written on them.
The ones I just put in are Elring. I think they had "Elring 10.9" written on them.

The used ones that came with my 'new' German head, have "?XA 1000, Germany" on them. Googling seems useless
I picked one of the ?xA's up  at random, and cleaned it up to read it. I've just measured it and it reads 128.1mm!

Bajacalal;
I expect that there is some rotational twist, but re the shrinking of the radius, unless point failure about to occur, I should think the stretch is distributed along the entire exposed threaded portion of the bolt and so for the 0.25 to 0.5mm stretch I've experienced, it would show up as root(6)ish/60 * 0.25, or not very much.
Looking again, the unthreaded part is smaller than thread peaks hence washer is captivated, so that will elongate too...

[smutts]

A right bag of worms these things are. The 10.9 is a standard type and quality of steel. So anything that fits, and is stamped with 10.9, should act exactly the same as the factory ones. Trouble is "yes we can make those" means that somebody has some metric bolts and a 0,1,"." & 9 in a letter punch set somewhere in the far east.

Quality is more than having the right paperwork.

But, if there is a fastenings stockholder near you who will let you have a rummidge, you might get a set of equally good bolts for pennies.