Hi. I may be of some help here. If you don't have oxy-acetelyne heat available to heat the nut ro a red color at least try it with a hot engine. If you've got some penetrating oil spray some of that on a couple times a day for a couple days with heating and cooling from running the engine.
Lots of people reccommend "PB Blaster" for a good rust penetrant. Something about a chemical reaction that eats rust.
You should rig up something to keep the pipe from turning. Hopefully something that'll not crush the pipe in the process. If you do get it to turn a little, add more penetrant and try to rotate the nut back and forth in the little space it turned the first time. If you rush it and try to turn it too fast the threads gaul or transfer metal from one part to the other in the threads. That's not a good thing. It's like welding them together.
Dave.

 

After 1979, everything must be looked up with a Calibration Code (CC). There are no more individual parts lists for EGR, T/E parts, carb and other emissions crappola. Add to the mix...squinting at microfiche.

The picture of the EGR setup (Section 94.1; page 7) shows the valve screwing into the EGR spacer plate, just as you said. The picture also shows another valve screwed into the manifold air supply tube that runs along the side of the engine....just as I said above. Please take a look and see how many of those air supply check valves your Bronco has.

Without the actual CC, it's a royal PITA to look thru the dozens of CC lists to find the parts that are correct...there's only 800 or so of those CC lists between 1980 and 1991!

 

Finally got the old one out. Unfortunately it took all the threads with it. FORTUNATELY, the old one was only put about 1/4" in so I still had about 3/4" of threads that I could easily tie into. New one screwed in and everything's hooked back up. For future reference if anyone needs it, the size on those is 28mm, roughly right in between a 1 1/16" and a 1 1/8".

 

Hi. Congrats and thanks for that wrench size.
Dave.

 

Hi AbandonedBronco,

I'm in your same spot. I already have the new check valve, but I can't get the old one off. Thanks for letting me know the wrench size. Let me ask you a couple questions - any tips on getting that thing off? I've soaked mine in PB blaster every day for a week and it still won't budge. Secondly - when you replaced your valve, did you notice anything different about your engine? My truck has a pretty decent exhaust leak coming from under the hood and I'm thinking this check valve is the culprit. I don't have the smog hoses on it now, so the valve is open to the air. Thanks in advance.

 

Hey fmc400, I'm not entirely sure, because as I said in my post, even after soaking mine for a while, the threads still came out. However, if you've been putting PB blaster on it every day for a week, you've put on a lot more than I did. I didn't have the strength of tools so I eventually went to a local tire shop and asked if they could just get it off for me. The guy just loaned me a two foot breaker bar and said have at it. With that much leverage, it came out pretty easy, although not without the threads. Hopefully, either you've soaked yours enough to where you won't have a problem, or you will have the same luck I did and the old one will barely have been put in that far and there'll be plenty of threads left.

I'm not sure if it'll fix your exhaust leak, I know with mine it had always made a little bit of noise, but when it went out, it went out. It melted my bypass valve in half, melted vacuum lines, and burned off the hose that was on it. Although it is possible that before it went out, it was still leaking, just not enough to cause some damage.
The way I got mine off was to rip the whole end of the valve off. It crumbled in my hands from rust. That way, just the nut was sticking out and I could get a socket around it, which gave me a bit more leverage.

Good luck with yours!