How do you remove coupler loop on MTH truck blocks

I'm not sure what you mean,, Engine trucks?  What's a coupler loop? F-3s?

The diecast truck block coupler loop on Diesel engines. 

Sorry  I don't get it.   If It's what I think it might be you'll have to remove the motor. Give us the engine or perhaps a pic.

Jeff,

   Pictures please, not quite understanding just what you are doing?

PCRR/Dave

Do you mean the round mounting hole for the coupler on the ends of the trucks? If so the only way I know how is to cut them off

Yes the round mounting hole on engine truck blocks. Someone posted they unbolt but those posts were all deleted. Need to know how, thanks....

All the ones I’ve ever seen are cast into the truck block.  I usually remove the outboard axle, put the cover plate back on, cover all the holes then cut it off.  A zona saw is a little less messy than a dremel, but you can use a dremel too. 

Jeff, I've always cut them off as once I fix a pilot and/or ready to mount the standard kadee gearbox I cut them.  I've used a dremel, I've also used a set of diag cutters and cleaned cut.  The cutters are the fastest way I've found and require very little prep or cleanup.

Not that I have seen every possible way Lionel, Williams, MTH, etc use to mount couplers I wonder if the person who gave the impression that the coupler mounting boss unbolts was referring to the mounting of the coupler itself. Some use a rivet some a snap-ring and a couple of other methods. I have never seen a mounting boss that was not cast as part of the truck casting. I have cut a couple of them off when converting to Kadee couplers I usually use my band saw and then clean up with a file.  J

I know they can be unbolted as long as the truck block is the be 3-2-3 unit, meaning you can switch out hi-rail and scale wheelsets. Unscrew the roller if applicable, then unscrew the truck block cover plate. Remove the axle closest to the mounting hoop. Look inside where the axle was and you will find a screw. Undo that screw and lift out the mounting hoop. I run 3RS so I remove these when I convert to fixed pilots and Kadee’s not only for clearance but also looks, it looks kinda silly hanging in there. 

Thanks Ben that's what I need. Thanks to all for your comments too. I will check this out for sure. 

I should have looked first, as it appears from my fleet that this is only possible on 4-axle units. My SD35’s are definitely cast into the block. Here’s a few pics of a U25B I just did. 

 I don't get why you people are cutting the block when it would be easier to just cut the back of the KD box off IMO??

Joe, I too cut the back of the Kadee box off and round it. A little trick I learned for Doug AKA Laidoffsick!