Loose Intake-Exaust manifold
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Elder User
Joined: Nov 1999
Posts: 796
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From: Anderson Northern Ca
Loose Intake-Exaust manifold
After rebuilding my inline-6 the intake-exhaust manifold bolts have been loosening up every six months or so.I tried to keep up on it but missed tightening it up for a few weeks(rain)and now after tightening it up I have a good leak in the exhaust part of the gasket.I have a new gasket and will be putting it on this weekend and would like to know if I can do anything to keep the bolts from coming loose again.I live at a place where I drive on a gravel road a lot and the vibration is high due to a stiff suspension setup,could this be causing some of my problems?Thanks for any suggestions.
"bowties in the rearview mirror"
"bowties in the rearview mirror"
Elder User
Joined: Dec 2002
Posts: 925
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From: Quaker Hill ,CT U.S.A.
Loose Intake-Exaust manifold
Use a torque wrench and the correct torque sequence and it wont loosen up again
http://www.cybrrpartspro.com/Chilton...6/85763099.gif
there you go torque to 26 foot pounds .
http://www.cybrrpartspro.com/Chilton...6/85763099.gif
there you go torque to 26 foot pounds .
Last edited by Chas1234; May 15, 2003 at 11:30 PM.
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Elder User
Joined: Nov 1999
Posts: 796
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From: Anderson Northern Ca
Loose Intake-Exaust manifold
Jon,I always follow the torque specks for these bolts as well as any other call out torque requirements.Thats why I can't figure out why the bolts keep coming loose.Do I need new bolts mabey?
"bowties in the rearview mirror"
"bowties in the rearview mirror"
Elder User
Joined: Dec 2002
Posts: 925
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From: Quaker Hill ,CT U.S.A.
Loose Intake-Exaust manifold
I wouldnt think new bolts would help unless the threads on the other bolts are really messed up .
I usually re-torque the intake/exhaust after the engine has been up to operating temp for the first time .
I havent had any problems yet ..
You may want to replace the bolts they may be stretched out .
How clean is everything ? that tend's to make a difference too
I usually re-torque the intake/exhaust after the engine has been up to operating temp for the first time .
I havent had any problems yet ..
You may want to replace the bolts they may be stretched out .
How clean is everything ? that tend's to make a difference too
Last edited by Chas1234; May 15, 2003 at 11:57 PM.
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Elder User
Joined: Nov 1999
Posts: 796
Likes: 3
From: Anderson Northern Ca
Loose Intake-Exaust manifold
Thanks Jon,The bolts have been in since 1971 so I think I will get new ones and follow your advice on retorquing after first warmup,thanks for the info.
"bowties in the rearview mirror"
"bowties in the rearview mirror"
Junior User
Joined: Aug 2002
Posts: 67
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From: Irvine
Loose Intake-Exaust manifold
Do the bolts still have the lock washers with them? My intake was missing a few and the same thing happend. If your getting new hardware dont forget those lock washers (blue loc-tite is also nice).
Joe B.
Joe B.
Post Fiend
Joined: Nov 2002
Posts: 9,987
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From: Memphis, TN
Loose Intake-Exaust manifold
Instead of threadlocker, use Anti-Seize Lubricant. It reduces thread friction, so you get an accurate torque reading. Too much friction on the threads will cause the torque to go up, even if the bolts aren't actually tightening down on the parts, so they ALWAYS need some kind of lubricant before being torqued. This stuff also prevents them from rusting or galling together, and can be used on everything from lug nuts to oxygen sensors. I use it on EVERY machine-threaded fastener on my truck. 
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Elder User
Joined: Feb 2002
Posts: 504
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From: Saddle Brook United State
Loose Intake-Exaust manifold
Just an FYI. I don't know when Ford started using them but the BOLTS on my 90 are special. The thread is an incomplete thread on the bolt and the hole. The bolt looks like it only has a 50% thread. This acts as a self locking thread, if you have these bolts, you don't want to run a tap in the hole as you will loose the locking ability. I bought all new bolts from FORD when I had the manifold off to replace a lower intake that had cracked a flange.
Don't buy stainless bolts either they are only a grade 2+ bolt, you need a grade 5.
stractor
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Postmaster
Joined: Jan 2003
Posts: 4,417
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From: Durham, NC
Loose Intake-Exaust manifold
You need to check your manifold ports, and make sure they are
flat. The cast iron has a tendency to warp. The best thing to
do is take it to a good machine shop, and have it planed.
flat. The cast iron has a tendency to warp. The best thing to
do is take it to a good machine shop, and have it planed.
Senior User
Joined: Aug 2000
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Loose Intake-Exaust manifold
I remember seeing a TSB or an update in a Ford shop manual about the updated bolts Stractor was talking about. I've had the same problem re-using old intake/exhaust manifold bolts...even when properly torquing them.
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