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Old 12-09-2007, 02:27 PM
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Re-torquing Head Bolts

I received some great advice from the fine folks on this forum, so here is another question:

Is it absolutely necessary to have an engine at operating temperature to re-torque the head bolts?

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Old 12-09-2007, 03:29 PM
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I believe the necessity is for the engine to have undergone a heat cycle so that the head gasket has heated up and minutely thinned out. After this you can re-torque.

I don't believe this is necessary if you're engine uses the cylinder head stretch bolts such as the m103/m104 engines. I do remember my uncle re-torquing his m110 though...
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Old 12-10-2007, 01:38 AM
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I don't know if my 110 engine uses stretch bolts or not. My other concern is that I keep reading that if the head or block is aluminum, retorquing should be done with the engine at "room temperature."
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Old 12-10-2007, 03:12 AM
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That just means you run the engine, take the car for a good drive for an hour so such that everything has been fully warmed up. You can re-torque the next day. The important thing is that the engine has been warm so the gasket will have minutely shrunk and remain thinner, thus you can re-torque. You can ask Mercedes if it they are stretch bolts or not, they should know! If not I'm sure someone on here knows!!!
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Old 12-10-2007, 08:03 AM
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On the M110 engine, "stretch" bolts became standard around 1980.

The easiest way to determine is the type of socket required.

IF the bolt uses an allen socket(6 pointed), the bolts are standard type.

IF they are a "spline" type then they are STRETCH bolts.
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Old 12-10-2007, 11:26 AM
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Thank you both for clearing up this matter. Yes, the headbolts are allen socket(6 pointed) - 1977 model. So it looks like I'll use the car as us usual and the following day, it will be ready for retorquing - assuming it's not freezing over night (unheated garage).

Last edited by 280EZRider; 12-10-2007 at 11:54 AM.
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Old 12-10-2007, 12:19 PM
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Quote:
Originally Posted by 280EZRider View Post
Thank you both for clearing up this matter. Yes, the headbolts are allen socket(6 pointed) - 1977 model. So it looks like I'll use the car as us usual and the following day, it will be ready for retorquing - assuming it's not freezing over night (unheated garage).

You want the engine just warm for retorque.
The trick is to lossen each bolt and then retorque it before going on to the next sequenced one. And make sure you have the radiator cap OFF when doing them.
I alway go back after the car is cold and recheck each one, but you do not have to. If the car being done has valve lash adjustments, then you want to do them after the head retorque procedure.
Also look close around the timing chain area..some heads have a couple of bolts that are hard to see/easily missed in that area..................
The required allen drive should be 10MM........
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Old 12-10-2007, 01:51 PM
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I suspected as much with the losening of the headbolts, albeit just slightly, right?

The radiator cap off - great idea. I would have missed this one. Thanks!
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Old 12-10-2007, 01:58 PM
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Quote:
Originally Posted by 280EZRider View Post
I suspected as much with the losening of the headbolts, albeit just slightly, right?

The radiator cap off - great idea. I would have missed this one. Thanks!

Yes ...the concept is you have to start with a headbolt that has been cracked loose , or else your retorque reading means nothing..if often takes much more to crack loose the old bolt free than the retorque requrements, so you have to start off with a free turning bolt or you are wasting your time.
Do ONE at a time.... crack loose/retorque/move to next one in the pattern
[ you know that, but I mention it for other readers]
When I do the cold check, I just verify torque with no other adjustments..a clicker torque wrench works well here.


Last edited by Arthur Dalton; 12-10-2007 at 02:11 PM.
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