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Re: Retorqued my headbolts (long) Posted by SWEDECAR [Email]  (#112)  [Profile/Gallery]
(more from SWEDECAR) on Sun, 11 Oct 2009 21:47:33
In Reply to: Re: Retorqued my headbolts (long), ryan  [Profile/Gallery]
, Sun, 11 Oct 2009 17:48:45
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Sorry, I'm only a mechanic, not a scientist or engineer. I have no clue if you can substitute a drop of oil for 45° of torque to yield on a stretch bolt.
I would in your case go in and loosen one bolt at the time and torque to the high number (60 Nm) until all of them are done and then pull 90°.
Here is a link to my very first post and when I asked about these new style bolts (grey ones).
Back then I didn't know what the heck was going on but have since then learned.
Up until then I had always reused the old bolts when doing head gaskets except if I felt that one bolt was soft and in those cases just grabbed another used bolt to install.
This particular job I decided to go with a whole new set of bolts and my problems began.
I put a dab of oil on them as I had always done, torqued down to 60 Nm as always but when doing the 80 Nm torque, I could feel how several bolts "gave up" and my wrench never clicked. I continued a little bit further to see if the bolts would reach the 80 range but luckily, finally gave up and pulled them out discovering the waistline on the bolt.
To the story goes that back then it was not as much internet help and we mechanics didn't really have a good network going between us but I quickly realized the value of it after finding Saabnet.
I called the local dealer and asked them if the torque specs had changed with these newer looking bolts but they said no even though the specs indeed had changed (lowered to 40, 60).
I finally got help from Tom Townsend that found a memo saying that the torque specs had changed with the new bolts.
And then years later, we start to see the aftermath of all this with the loose #10 bolt on the late 900 early 9-3 engines with premature head gasket failures and oil leaks from the rear on later 9-3 and 9-5 engines even though that has not entirely gone away after 2001 with the latest bolts installed.
So, a dab of oil on those weak bolts was enough to lower the friction and using the higher older torque spec brought them over the edge to give up. That's how close the tolerances were on them.
After removing hundreds of these grey bolts, the old good bolts and also quite a few of the newer bronze colored ones after 2001, I can tell a huge difference in the force it takes to crack them loose (or lack thereof).
The original ones and the newest ones you have to give quite a bit of force before them come loose. All the ones from 97-2001 you just look at the wrench and they unscrew all by them self.
Anders
, Sat, 10 Oct 2009 14:15:13, Sun, 11 Oct 2009 09:08:25, Sun, 11 Oct 2009 17:37:49, Sun, 11 Oct 2009 17:48:45, Sun, 11 Oct 2009 21:47:33 <-- Viewing This Message, Mon, 12 Oct 2009 18:09:04, Sun, 11 Oct 2009 17:04:30
, Sun, 11 Oct 2009 16:07:20, Sun, 11 Oct 2009 17:15:58, Sat, 10 Oct 2009 16:40:51, Sat, 10 Oct 2009 17:54:14, Sat, 10 Oct 2009 18:18:46, Sun, 11 Oct 2009 08:40:28
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