M12 or T-55 for head bolts?

[Ruby Doom]

So I must have lost my M12 bit in the mists of time, which is odd, as I still have the 27mm deep socket for removing injectors.

So I picked up a set of star bits, M6,8,10,12 and as today got above freezing, I started pulling the engine apart. When I got the valve cover off, and went to do the head bolts, I was surprised to find the M12 didn't fit right. After a lot of struggling, and mild persuasion (couldn't find my mallet so had to be careful) I got the first bolt out, none of the others seemed to want to co-operate. So I took the bolt with me back to the auto store, we futzed around and found a T-55 was the best fit for it BUT I was nervous that it was too wide a socket and wouldn't fit behind the bearing caps, so I got another of the same set, and the M12 in that fit better, though not as nicely as the T-55.

So what does the modern VW diesel enthusiast use to remove his head bolts nowadays? Should I just get myself a T-55 in a narrower socket as well, and have a choice?

[libbydiesel]

The 1.5 and very early 1.6 engines with 11mm threads on the head bolts are allens.  Anything newer than '82ish is indeed m12, but that refers to the diameter of the threads, not the tool used for loosening or tightening.  The socket heads are NOT allen and are NOT Torx.  Using either will very likely result in loss of money $$ and anguish.  They are triple-square, also known as XYN.  I believe the size is 12mm but I'm not at my toolbox and don't feel like looking it up.  They come in sets for cheap available at most FLAPS.

You should NOT remove the head bolts one at a time.  You need to loosen them progressively in the reverse order of the head bolt tightening sequence listed in the Bentley or you will warp the head.  I use 1/4 turns through the sequence.

EDIT:  I see you added the pic while I was typing.  Yes, those, unless you have one of the earlier 11mm (threads) engines in which case they are allen heads.   

[Ruby Doom]

What's a FLAPS?

And yes on the headbolt, I agree, but this was the only one I could move.

[libbydiesel]

Errr, you added the pic while I was typing. 

Friendly Local Auto Parts Store

If there was only one you could move, you should have stopped at 1/4 turn until you got the rest of them loosened in sequence to the same 1/4 turn.

[Ruby Doom]

Well they were fairly friendly, they let me change it without having a receipt. Maybe the fact my accent gets a lot thicker when I'm grumpy, and I had just driven 30 miles to my local store

Sorry about the pic, realized it would help clarify, but took me a while to find it.

So M12 is the thread size? So how do they define the head of the bolt, back home (25+ years ago) I just got an M12 star bit and it worked.

I was trying to figure out the relationship between the 12 and the 55, but even multiplying by PI didn't seem to help.

And yes, I realize I have modified a subject again, sorry.

[fatmobile]

What year is your car?
 Does it have allen heads?