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Self loosening bolts... AKA. someone goofed?
I decided to check the intake manifold bolts while I had the fuel injectors/fuel rails out. Interestingly enough they were all loose. Not loose enough to turn by hand, but every bolt required at least 1 full turn, if not 2, to bring it up to 18 ft.lbs.
I'm pretty sure the motor has never been overhauled in such a manor as to require the removal the intake manifolds. Did someone goof upon reinstalation, or does this just happen. Anyone ever notice if their bolts loosen up over time? A vacume leak here would cause a lean condition, right? Any other noticeable effects? ------------------ Dan Tolley 1987 911 Coupe http://www.cheaterswayside.com/911/gallery.asp?sort=0&userid=294 |
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04-09-2001, 11:11 AM
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For some reason they do just loosen up on their own, and I'm not sure why either. Excessive vibration from an older engine coupled with miniscule amounts of corrosion and thread loss seems like it would make sense. Just don't over torque em!
It's better to have to tighten them up again every year or so than god-forbid, breaking one off. ------------------ Kurt B '84 Carrera Cab. carrera_cabriolet@yahoo.com |
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04-09-2001, 11:15 AM
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Dan,
When I pulled my intake off a couple months back, I was startled by how loose a few of the nuts were. VERY little effort was required to back some off. I then recalled the faint whistling I would hear under acceleration. Thought it was the air box. Must have been the manifold. The motor ran fine, just whistled occasionally. 25 Nm/18 ftlb seems quite tight, but that's what the books say. I can't see how you can tighten the nuts without a ball-end hex bit. Maybe better access with the fuel rail assy. off? Definitely something to check for tightness every once in a while. ------------------ Kevin 87 Carrera |
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04-09-2001, 11:31 AM
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I think the gaskets flatten. This is why they need re-torquing.
------------------ '83 SC |
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04-09-2001, 12:27 PM
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I just used a 3/8" drive 8mm socket and a bunch of extensions/elbows
It was one of those "I'm in here already and everything is apart" days. With the fuel rails, A/C stuff, heating stuff and air filter box off the bolts are barely accessable. 18 ft. lbs. is the torque recomended by the Bentley manual. I had a rough idle when cold, and a rich fuel condition in #6. I'm hoping my winter projects have eliminated any problems. I can't wait to get the car out of storage:-) ------------------ Dan Tolley 1987 911 Coupe http://www.cheaterswayside.com/911/gallery.asp?sort=0&userid=294 |
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04-09-2001, 12:59 PM
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carerra intake nuts should be tightened at full service intervals. 930s too. must be that phenolic spacer block and the two gaskets. carerras also blow out intake gaskets because of this.(that miss at idle and the high HC)
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04-09-2001, 04:47 PM
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Dan,
The ball-end hex key is the hot setup for tightening the manifold nuts. Get yourself an 8mm ball-end key and grind the bend off. Works great. ------------------ Kevin 87 Carrera |
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04-10-2001, 05:24 AM
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