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As Ford Mechanic pointed out, the upper manifold bolts are a real monster to get out in one piece. When I picked up my M931A2, it only had 800 miles on the odometer; yet my exhaust manifold & its bolts looked worse than Ford Mechanic's pic above (have put around 11K miles on it since in past 3 years). So I soaked and I soaked and I soaked the bolts with almost a whole can of PB Blaster, but they wouldn't budge. Tried all kinds of heat, with various heating/cooling/tapping-with-hammer cycles. Applied more penetrating fluid (this time homemade 50-50 mix of acetone & ATF, as recommended by antique tractor guys), still no joy. Even tried heating & applying beeswax, but I got more beeswax on myself & surrounding parts than on the bolts themselves, and it still didn't work.
When I tried several short bursts from my impact wrench, the upper manifold bolts started snapping off. I even tried using a hand-held breaker bar with socket, and gently "rocking" an upper bolt back and forth....NOPE. After 6 straight days of everything I could try, I ended up with all six upper manifold bolts broken off in the block. The lower bolts came right out with the impact wrench, but not the uppers. On one I tried to drill through and remove with a "hardened" extractor....the extractor broke right off inside the stuck bolt remains.
So I took M543A2's advice. I picked up some thick square washers and larger 5/8-11 unfinished hex nuts (in the past I've found unplated square nuts in the concrete aisle at home improvement stores, but the hardware store I went to this time didn't have unplated square washers. Go figure). I countersunk the center holes in the washer to allow room for my welding rod to penetrate into the broken bolt. At first I tried to use my 110-volt wire-feed welder, but it just couldn't get the penetration needed and the washer-nut combo would break off.
So out comes my arc welder and 1/8" 7018 rod, and tried this on the first cylinder. It worked! The impact wrench spun the combo right off, and attached was the broken bolt with the extractor sticking through the other end. I cut off the bolt end and re-drilled the welded washer-nut combo to use again. I think there were 2 more times that this didn't work (one of them shown in pic below), so I drilled out the washer-nut combo and welded again; each time worked and removed the broken bolt. I made sure to let everything cool down before attempting to remove anything, hoping that the swelling-shrinking cycle of welding & cooling would loosen the seized threads.
The only time it didn't work was on the upper bolt for cylinder #6. 4 attempts kept breaking the bolt off farther and farther into the head, so I drilled it out as best as I could, and while contorted around the front tire, used a rat-tail file to slowly remove the remaining bolt steel until I could start to see the threads from the head/block. Then I finished up with some patient, tedious work with a tap to remove the metal fragments in the block/head threads.
I chased all 11 other threads with a quality tap to ensure that there wouldn't be any more drama, and when installing new stainless 8.8 bolts, liberally coated all threads with anti-seize.
The nice thing about the new gaskets (all metal, appear to be compressible like the turbo gasket) is that they have 3 small tabs per hole to grip the bolt threads, so that when you reinstall the exhaust manifold, the gaskets are already centered on the block/head and torquing them down according to the TM is a breeze.
Desperate times require desperate measures, someone once said...it took me more than 3 weeks straight to get this done. I'm just glad that it's over with.
Oh, almost forgot about the joy of trying to remove the thermostat housing: the bolt that is closest to the right-front corner of the truck was very difficult to remove. I could not get a crow's foot wrench into this small space, so I sacrificed a 10mm open-end wrench, heated it red-hot, and bent it as sharp as I could to fit into this spot. It did the trick, where I couldn't get anything else to fit. Reminds me of torquing Deuce head gaskets.
When I tried several short bursts from my impact wrench, the upper manifold bolts started snapping off. I even tried using a hand-held breaker bar with socket, and gently "rocking" an upper bolt back and forth....NOPE. After 6 straight days of everything I could try, I ended up with all six upper manifold bolts broken off in the block. The lower bolts came right out with the impact wrench, but not the uppers. On one I tried to drill through and remove with a "hardened" extractor....the extractor broke right off inside the stuck bolt remains.
So I took M543A2's advice. I picked up some thick square washers and larger 5/8-11 unfinished hex nuts (in the past I've found unplated square nuts in the concrete aisle at home improvement stores, but the hardware store I went to this time didn't have unplated square washers. Go figure). I countersunk the center holes in the washer to allow room for my welding rod to penetrate into the broken bolt. At first I tried to use my 110-volt wire-feed welder, but it just couldn't get the penetration needed and the washer-nut combo would break off.
So out comes my arc welder and 1/8" 7018 rod, and tried this on the first cylinder. It worked! The impact wrench spun the combo right off, and attached was the broken bolt with the extractor sticking through the other end. I cut off the bolt end and re-drilled the welded washer-nut combo to use again. I think there were 2 more times that this didn't work (one of them shown in pic below), so I drilled out the washer-nut combo and welded again; each time worked and removed the broken bolt. I made sure to let everything cool down before attempting to remove anything, hoping that the swelling-shrinking cycle of welding & cooling would loosen the seized threads.
The only time it didn't work was on the upper bolt for cylinder #6. 4 attempts kept breaking the bolt off farther and farther into the head, so I drilled it out as best as I could, and while contorted around the front tire, used a rat-tail file to slowly remove the remaining bolt steel until I could start to see the threads from the head/block. Then I finished up with some patient, tedious work with a tap to remove the metal fragments in the block/head threads.
I chased all 11 other threads with a quality tap to ensure that there wouldn't be any more drama, and when installing new stainless 8.8 bolts, liberally coated all threads with anti-seize.
The nice thing about the new gaskets (all metal, appear to be compressible like the turbo gasket) is that they have 3 small tabs per hole to grip the bolt threads, so that when you reinstall the exhaust manifold, the gaskets are already centered on the block/head and torquing them down according to the TM is a breeze.
Desperate times require desperate measures, someone once said...it took me more than 3 weeks straight to get this done. I'm just glad that it's over with.
Oh, almost forgot about the joy of trying to remove the thermostat housing: the bolt that is closest to the right-front corner of the truck was very difficult to remove. I could not get a crow's foot wrench into this small space, so I sacrificed a 10mm open-end wrench, heated it red-hot, and bent it as sharp as I could to fit into this spot. It did the trick, where I couldn't get anything else to fit. Reminds me of torquing Deuce head gaskets.