Well here's my final report on fixing a leaking Thetford toilet. I hope it's not too long and boring
but might help someone else especially if their retaining clips/wedges/slides (I will use "wedges" from now on) were installed backwards as mine certainly were. It's hard to knock them loose working from the front of the toilet, if they are in backwards. I finally realized there was better access from the side of the toilet (especially on the right, where you can see right in there, see photo), so you can see where to place a long, flat-bladed screwdriver, or some other long blunt tool, and then tap with a hammer if you can hold it in position while doing so. It's very awkward laying there on your side trying to get your flashlight in the right spot, hold your tools, drink your beer, etc. The left side has even less room to maneuver as the shower wall is right there (on a 2004 3124KB) so you may need just the right length screwdriver or other long thin blunt device to reach in to the back of the clip from an angle, so you can hit the other end with a hammer and force the wedge out.
I had placed about 100 lbs. of books (had them stored in boxes nearby anyway) on the seat of the toilet (not on the lid, as Dave said, that could crack easily) hoping to compress the bottom donut/ring and reduce the amount of pressure on the wedges. It may have helped but they were still quite tight, but a few raps with hammer on the screwdriver (and a few &%#@@$ misses) and they finally popped loose. They may move back a bit with each "rap" and then pop loose. You can try to get a flat screwdriver aligned on the front of the clip (closest to toilet front, when clips are in backwards), but there's not much there to hit against, and the back of the clip is mostly hidden behind the nut. Its not easy.
On left side near the shower wall where space is tighter, I used a combination of first loosening the nut above the wedge through contortions with various wrenches/pliers, plus tapping the wedge with various items including a flat-blade screwdriver and an allen wrench that happened to be about the right length and blunt on the end. Eventually worked the clip loose on the left side also. A small piece of it, a lip of sorts which holds it in the metal track, broke off but this didn't affect re-installation, just made the wedge a little loose in the track.
Another idea: Before starting, take a magic marker and trace the front legs of the toilet, so you can see where it was originally in the re-install. Mine actually had the factory locator disc under the right leg, but it was still helpful to see the black line as I was lowering the toilet back into position. I also put a black mark on each nut before I began hoping to keep them in the same position for the re-install.
Whoever installed this toilet (at the factory) had used so much caulk that I had a somewhat hard time pulling up the toilet. I thought I had missed a screw and was a going to break something off while pulling up. I was not hitting agains the nuts at the clips/wedges (which is possible to do if you aren't lifting straight up). Finally gave it a good yank. At this stage of the operation I was about ready to go buy a portapottie anyway! It came loose, I put it outside, and then I spent a half hour cleaning out old caulk from the floor flange. I had a new valve/slide to replace the caulk-coated one (leaky also as it turned out), so I didn't have to clean it, just removed it. I took photos while taking off the old valve/slide in case of trouble but putting the new one on is a fairly simple task with 4 screws.
Earlier in this thread, the foam donut was discussed…the thin one that comes installed on the valve/slide, a thicker donut that you may receive if ordered separately for this toilet, and now I learned the original donut on the old slide was another variation…about as thick as the thinner one on the new slide, but it had silicone parts, little squares of silicone (visible in a photo here) built into it, that went up into recesses on the valve/slide. These recesses are present on the new valve/slide, but the new donuts don't make use of them. Upon reinstall, I used the donut that was already on my new valve/slide. I am guessing the thicker one would have been OK, but probably would have meant putting the adjustment nuts at a slightly higher level.
Tell you what, you get good at removing/installing those wedges the 2nd and 3rd time you pull the toilet but its far easier with the wedges not installed backwards! Use the right one as a guide to how far in the wedge needs to be tapped when replacing, then compare distance "in" with the left one (which you can't see from the side as well). I didn't have the nuts tightened down enough at first, so had some wobble so I pulled the toilet 2 more times (I'm slow, but I get there) and kept adding 1 turn tighter on the nut until there was no rocking of the toilet on install. As Bill's tutorial says, it looks like about 1 11/32 inches to the top of the nut was about right, or maybe 1/16 lower than that on my floor.
Oh yes, the leak?? It looks like the valve/slide itself had a leak behind the pull handle…there was dried blue fluid along the crack there, so the seal within the slide (which can be user-replaced, vs. buying an entire new slide like I did) was leaking a bit. Probably getting worse with age. As far as I could tell, the donut was not leaking anywhere. I did not add any caulk, as Bill said, I couldn't see how it would add anything here. I did caulk the edges of my vinyl flooring around the flange on the floor, just to seal things up in case of future leaks, hoping to keep the leak on the vinyl not underneath it in the wood sub-floor.
Put the pump assembly back together, power back on, charged the toilet, no leaks so far. I left the trim off the toilet base for our upcoming trip for ease of access to those clips in case something works loose in travel.
Many, many thanks to Bill and Dave for helping me through this! Also had one private message that was helpful.
quick question before re-install of toilet
my wedges were in backwards!
....boy was I hacked after trying to get those out for 45 minutes!!! 
Ditch that stinker and get real...toilet that is....it's the best thing you could do to your TM....don't make me write a note to the management! 
Linear Mode
