Couldn't remove diverter stem

I was working on a very old 3 handle tub faucet, think it was either a Sterling or PP. The shower surround had failed big time and the leaky valve stems were extremely corroded. I managed with a great deal of effort to remove the hot and cold stems, and they work fine after I rebuilt them. But I couldn't budge the diverter stem. I was using a plumbing socket with my biggest crescent wrench for leverage. I felt that if I cranked on this stem much harder, it would snap and I'd be in deep doo doo, 'cuz the customer doesn't have the money for a whole new shower manifold. So, I stopped.

I've broken off shower stems in the past when I tried to remove a frozen-on handle, but I've never snapped one off way at the bottom using a socket. Is that even possible? Would a penetrating oil do any good? Should I have tried using a torch?

I can't believe that nobody has had experience with this.

With any regular shower stem or diverter stem like this, it is VERY important that you open the stem part way before trying to unscrew it. For the diverter, set it about 1/2 way between 'tub' and 'shower'

jimbo said:

With any regular shower stem or diverter stem like this, it is VERY important that you open the stem part way before trying to unscrew it. For the diverter, set it about 1/2 way between 'tub' and 'shower'

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Yes, the stems were all part way open. But as I mentioned, they were very very corroded and frozen on. I got two off. Any idea how to get the third off without snapping it? I talked to a local plumber and he thought I might have some luck once it's heated up.

Heat works well I would try it. Keep an extinguisher handy. Do you have the replacement diverter stem and seat? Is this diverter plastic?

Cass said:

Heat works well I would try it. Keep an extinguisher handy. Do you have the replacement diverter stem and seat? Is this diverter plastic?

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We're talking old brass stems here. I wouldn't consider putting a torch on anything plastic. If I pull the diverter and it needs replacing, I'll match it up at the hardware store. The hot and cold stems just needed rubber washers and some plumber's grease and they work perfectly.

If you can grab that stem real good, you'll be better off not pulling or pushing real hard, but you should be able to bump or jolt the wrench with the butt of your hand and make it loosen.

Hopefully the faucet assembly is firmly positioned.

Just don't be afraid to give it some real whacks.

You also may want to try some PB Blaster penetrant.