Need to replace exhaust flange gaskets, 175K, plenty of rust. Did SeaFoam induction, and a side benefit was easy detection of exhaust leaks (and death to mo'skeeterz for a 300 yard radius).

What would be best way to do this considering age and possibility of bolts shearing away?

 

Copious amounts of PB Blaster soaking for a few days in advance, possibly followed by the gentle persuasion of a propane torch...

 

Like the idea of several days of prep time. I think there are 3 bolts, two I can see the back of, and one that is threaded way up in the flange, so level of PB that will wick up is minimal.

 

The ways of the PB are beyond human comprehension.

 

best thing is to heat up the truck for a half and hour, take out the nuts and sometimes the other parts come with it. what ever doesn't then heat it up with a torch. its recommended you use acetaline and oxygen setup cause propane isn't hot enough. then you can use a pair of pliers or a eight mm stud remover. You will need a 8 mm thread chaser for the whole.

if you can't get access to a torch then just take them off and take them to a shop down the road that can torch them out.

 

But the PB just burns off when you drive the truck, so you spray the nuts today, drive to work tomorrow, and then what? Aren't you back to square one?

 

That's true, I have a spare truck to drive, my F250 is usually needed to go fetch parts for the Rover anyway.

 

I don't have a spare, if I cant fix my truck in 2 days then I ain't fixing it and I will pay to have it done.
But thats only happened once in the 4.5 yrs I've owned her.
The only other time I have paid for work is when I couldn't figure it out to save my life, hub seal on the rear axle kept leaking, install new one, leak next day.
Turned out to be a bad stub axle, it had a small burr that was tearing the seal.

 

I was thinking along the lines of PB it at night, allow to penetrate overnight, repeat the next night, etc. If it breaks loose the first 5mm of rust and corrosion the first night, I don't think you would be back to square one because that level of corrosion isn't going to return within 12 hours. The next night would do the next 5mm, and so forth. This is the process I used for 2 days in advance of changing my O2 sensors. After the second day they came out easily with an open end wrench without any hint of rounding the sensor. The first day they wouldn't budge with an O2 sensor socket.

 

Those things are always a pain. If you only have one day to do it, start soaking it with PB the night before, then again in the morning, then again at lunch and by the afternoon you'll be ready to give them a go. A tip though when trying to brake them loose, rust doesnt free up from slow steady pressure with a 3ft long breaker bar, it frees up from sudden impact. Slow steady pressure will more often then not break off a siezed nut. Contrary to recommendation, I take mine off with an impact. If they are going to break there's not much you can do about it but short bursts of instant pressure have a better chance of getting the nut to break loose. Sometimes it even helps to back it off and then retighten a few times, allowing a little more movement each time until the nut is off.

On the bright side if they break, drilling out the manifold and installing new hardware isnt that bad.