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Exhaust manifold connection to catalytic converter pipe leak

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Old 09-14-2013, 10:46 PM
Join Date: Jun 2007
Location: Virginia
Vehicle: 2006 Ford F150
Posts: 74
Exhaust manifold connection to catalytic converter pipe leak

Hi guys, I have an exhaust leak that I was looking for some opinions on how to fix. I had Banks Torque Tubes installed on the truck about 4 or 5 years ago that developed several cracks on the collector welds. They had to come of so I went back to the stock manifold that fortunately I had kept. About 15 hours later (manifold/headers on the 5.4L are no fun at all) and I have a leak at the ball joint connection between the manifold and the catalytic converter downpipe.

I have taken it apart many times and tried repositioning things in numerous ways just to try and get the joint to seal up but it still leaks. Visually looking at the two mating surfaces they look fine, no rough or rust pitted surfaces, smooth, round, no obvious dents. But it still leaks. I was hesitant to try and reshape the mating surface with a hammer because I do not see any obvious out of round areas.

Could I put any type of exhaust flange gasket or donut gasket in that joint? Stock configuration is no gasket, just metal on metal. I am afraid if she goes back into the dealership they are going to want to put a new catalytic/downpipe on it. That part from Ford is upward of $900.

2006 FX4
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Old 09-14-2013, 11:24 PM
Senior Member
Join Date: Jul 2012
Location: NH
Vehicle: 2004 Ford F150
Posts: 102
There is exhaust sealant sold at Autozone. Never tried it before but I happened to notice it.
'04 F150 supercab Pro Comp SS pro runners, K&N CAI w/ AFM dry filter, PHP Gryphon, Banks Monster Exhaust, Nfab steps, Mastercraft Coursers Axt P265/70r17
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Old 09-21-2013, 10:03 AM
Join Date: Jun 2007
Location: Virginia
Vehicle: 2006 Ford F150
Posts: 74
An update for those that may have a similar issue some day....

I fixed the leak. The manifold side of the connection has a stud screwed into it. The cat pipe flange slides over the studs and is held on by nuts. The studs are not threaded the full length plus they have a shoulder about half way up. That combination was preventing the cat pipe flange from moving closer towards the manifold and tightening the joint. Tightening the nuts on the studs more just clamped the flange tighter against the studs shoulder.

The solution was to use a dremel tool to grind off the shoulder and slightly drill out the bolt holes in the cat pipe flange so the flange can freely move up the studs closer to the manifold. Reassembled and torqued to 30 ft-lbs and no more leak.

Last edited by s27payne; 09-21-2013 at 10:05 AM.
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Old 09-21-2013, 10:19 AM
Bluejay's Avatar
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Join Date: Mar 2005
Location: Burleson/Athens/Brownsboro, TX
Vehicle: 2014 Ford F150, 5.0
Posts: 24,285
Glad you got it fixed and thanks for posting the cure.

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