I'm about to attempt removal of the Y-pipe on a '97 Taurus GL wagon (3.0 2V "U" engine Vulcan) to replace the oil pan gasket. Along with that I'll be replacing the front cover gasket and probably the valve cover, intake, and maybe even the head gaskets (all Felpro). I bought this car new in '98 and it's got 205.7k miles on it now. The exhaust nuts/studs have never been disturbed. In preparation for removal, I've been heating up the car to temperature, letting it cool, then spraying the nuts alternately with PB Blaster and Liquid Wrench. Four days of this now with two days left before the weekend. However, I may need to resort to using a torch and I'm just wondering what precautions I would need to take to safely do that. I've never used a torch before on anything and using one for the first time in the engine compartment of an automobile seems kind of crazy to me, but nonetheless - people do this safely so I'm hoping someone here can enlighten me as to how to do that. I'm not even sure exactly how I might be able to even GET a torch on the firewall-side flange nuts. They're well recessed from underneath and only one stud head is visible from the top. Maybe torch one nut from underneath and torch the other stud head from the top???

So what is the proper technique for using a torch safely (and effectively) on a car to remove fasteners???

 

This can be tricky and you are smart enough to ask. Heat will work. The question is can you do it safely and can you get a tool on the nut and bolts.

I can't recall what the under side of y pipes on the vulcan look like. Another non-heat option may be a nut splitter.

If you use heat you need MAP gas. A conventional propane tourch used for soldering copper will not get hot enough.

1 st. make sure you can get a 6 point socket or box wrench on the bolts. Sometimes they have rusted away too much. You need to scrape away any loose rust and hopefully you can still get a tight fit with a wrench.
The penetrating oil you spayed on will flair up. Just make sure there is not any rubber or plastic or wiring around this area that may melt.

I have only used a touch a handfull of times but you want to make sure you don't have any gas vapors aournd. Be smart and keep it away form your body. Have some water near by like a hose or spray bottle. Or even a fire extinguisher.

Lastly, wear eye protetion, long sleves and gloves.
best of luck

 

There is also something called Freeze and Release:
Freeze Your Nuts Off | Toolmonger

 

Freeze off may be worth a try too. Good idea. I have used the CRC version of it with out any luck. But I don't want to discourage you from trying it. The idea is that by contracting the metal it may break up any bonding between the fasteners. If the nut contracts faster than the bolt it will make it harder to remove. But any bonding may have been broken so when it returns to room temperature it may be easier to remove. Then soak it with penetration oil and try again.

I failed to mention earlier that Kroil is an excellent penetration oil. Many think it is better than PB Blaster. WD-40 is not a good penetration oil. You can only get Kroil from the manufacturer Kano labs. Some people sell it on ebay or craigslist. It is worth haveing a can around for such issues.

 

GRM (GrassRootsMotorsports) made a comparison and found that a 50/50 mix of acetone and ATF works best. The acetone goes into the cracks and carries some ATF along, the acetone evaporates. Caution: acetone is flammable and a solvent for paint.