Checking torque on head bolts

[BavMoWo]

I need to check the torque on the head bolts, as I found out the previous owner had it off at some point (and considering the quality of the rest of his work...). I get the "start at 22 ft lbs, then rotate 90 degrees, then another 90" thing, but does anyone know what the torque will be at that point so I can check? I did a check tonight and narrowed it down to all of them currently at 52 ft lbs (they all just slightly turned as the wrench broke over, so that's my reasoning), which seems really low for a head bolt. But then again, this are stretch bolts, right? And I don't have much experience with head work yet.

Any tips? I'm trying desperately to avoid taking the head off, since nothing is running poorly. Just trying to sort out a couple of things.

[Jeffnhiscars]

Those are torque to yield head bolts and are one time use so you should not be retorquing them. Since there is a process to swap out the original bolts without removing the head by changing them one by one in the proper sequence, that may be an option. On the other hand, if you have compression or leak issues swapping bolts is probably a waste of time.

[mmark.]

Leave them alone

To retorque you have to loosen them and this could ruin the heat/ chemical seal of the headgasket.
The bolts will need to be replaced as above, and the headgasket.


m

[BavMoWo]

Well, I'm not looking to retorque them, just make sure that they are torqued correctly. But yeah, I suppose I may need to just replace the bolts instead. Unfortunately I'm quickly running out of time to work on the car and I still have to do a complete rebuild on my bike in the space I have left, so I don't have time to pull the head right now. I'll see what I can do.

But to clarify anyway, if I were to reinstall the head, what would the actual torque spec be? This "22 ft lbs, 90 deg, 90 deg" thing seems very...non-technical for BMW. I would have expected 22 ft lbs, then another step at say 50, then another step at the final torque setting.

[thejlevie]

But to clarify anyway, if I were to reinstall the head, what would the actual torque spec be? This "22 ft lbs, 90 deg, 90 deg" thing seems very...non-technical for BMW. I would have expected 22 ft lbs, then another step at say 50, then another step at the final torque setting.

The first thing you would do would be to purchase new head bolts. Torque to Yield (TTY) bolts are one time use. The requisite clamping pressure is achieved by stretching the bolts beyond the elastic limit and into plastic deformation. Thus causing a permanent deformation. The load on the bolts is designed to be less than the elastic limit and thus clamping pressure remains constant. TTY bolts are always angle torqued. An initial torque and then tightened through specified angles (22ft-lb, 90deg, 90deg in this case).

When replacing head bolts the threads in the block need to be clean. Which means using a thread chasing tap, solvent, and blowgun with a long tube nozzle that can reach the bottom of the hole.

[BavMoWo]

Aah, that makes more sense. So it's not as simple as a torque measurement when using stretch bolts. Hm, I have another theory about this leak I'm trying to fix, so I'll roll with that for a bit and see if that helps. Looks like I'll need a proper amount of time to pull the head, do the gasket, and replace the bolts.

[strad]

Aah, that makes more sense. So it's not as simple as a torque measurement when using stretch bolts. Hm, I have another theory about this leak I'm trying to fix, so I'll roll with that for a bit and see if that helps. Looks like I'll need a proper amount of time to pull the head, do the gasket, and replace the bolts.

and when you do that, you will need a new timing belt. There are also several while I'm in there items to consider.

[vschlueter]

Sorry - trying to understand the #22 torque then a 90 deg ...then another 90 deg ... set up and execution - what do you man by that ?

regards

[Rudolph320i]

it means you torque the bolts to 22 ft-lbs in order, then turn them all 90 degrees in order, then turn them all another 90 degrees in order.