Trilobular background of the bolt issues - Saab 9-5 Bulletin Board - Saabnet.com
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Trilobular background of the bolt issues
1 Saabers Like This Post!
Posted by Name Left Blank (more from Name Left Blank) on Wed, 11 Nov 2020 23:35:25
In Reply to: Re: I agree with Boris, Dave The Ice Age Knave [Profile/Gallery]
, Wed, 11 Nov 2020 15:35:00
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The problems with sway-bar mounting bolts come from the design. Saab from some model year, (somewhere after 2000, probably from 2002 for 9-5) used a novelty - self locking/tapping screws (they are called trilobular). They can roll a thread and lock themselves very effectively. Unfortunately this screw profile (shaped like rounded triangle) has one disadvantage - it's not watertight. Water can get into full length of the thread. Second problem in this joint is a gap just under screw head (bad metal mounting design) what enables water to flow under screw head and then into the thread. Usually soaking this kind of screw for several hours in rust solving agent helps and the joint could be loosened using back and forth technique. Do not use any impact tools here - it will just chop off the screw head. Just back & forth, back & forth, back...
I advice to throw away those magic "tri" screws and use standard metric ones with blue Loctite after tapping the nuts in the subframe. Remember to degrease the threads before applying threadlock (Loctite advises their Loctite 7063).
The same bolt type is used to fix McPherson to the body. That's why many people are surprised when they get new strut mount without tapped threads.
posted by 80.50.141...
Posts in this Thread:
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- Sway Bar Bushings DIY?, Itsasaab , Sun, 8 Nov 2020 12:58:09
- Re: Sway Bar Bushings DIY?, Boris Bubbanov, Tue, 10 Nov 2020 20:05:43
- Re: Sway Bar Bushings DIY?, bobc , Sun, 8 Nov 2020 13:14:02
- Bolt #18, Paul from Palmyra, PA, Sun, 8 Nov 2020 13:40:27
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