What did you end up doing homebound? Hope you found a solution to this Kohler vexation.

It's not yet resolved due to the holiday. I am likely going to jam a scraper tool in there to try to hold the anchor in place while I unscrew the bolt. If that doesn't work, I'll proceed to cutting off (or drill) the screw head with a metal blade. Then I'll figure out the anchor part afterward.

The same house has another problem toilet: a one-piece American Standard champion, but apparently an older model with an older flush valve. New flush valve parts are going to run me around $125 with shipping, which includes an adaptor to upgrade to the newer style flush valve. Insane.

Yea, that's a pity. I just changed out an AS toilet seat and can't believe what you have to do with that Kohler seat. Thanks for the heads up about the AS Champion. I know I'm going to be replacing a toilet soon if the eroded interior enamel bowl finish poses a general water leak problem and I'll be sure to read up on fix it problems ahead of time.

Hope you had a good break from work and enjoyed yourself.

I had the exact problem ! I used PB blaster & soak the bolts for two days, then finally I cut the caps off & pry screw + anchor out. Finally, I replaced new ones with normal #10 drywall screws + plastic anchors. Cost me 80 cents & 2 hours. Details instructions + pics here:

Here is a link that might be useful: Instructables toilet seat

Whenever you run across a replacement OEM auto or other kind of part with an outrageously expensive price tag on it, that is often a tip off that the trade has found a workaround and the item has almost zero demand. Always try to follow up or figure out such clues.

Thanks for the information ... :)

With the plastic anchors, using stainless steel screws will make the next replacement even easier.

I found that the Kohler-branded replacement anchors were exorbitantly priced @ $8.90 a piece. So, instead, I went to Home Depot and bought a box of 79 #14-16 1-1/2" green ribbed plastic anchors with pan-head combo drive screw, for a grand total of $6.58, incl. tax, based on a recommendation I had found elsewhere. My toilet is one of the one-piece, elongated, low-silhouette models, #K-3322, K-3489, K-14257, or K-14286, all of which are described in the same installation guide ... not sure exactly which one I have but they all take seat models #K-4636, K-4639, K-4713, or K-4732. Somehow, the seat had separated from this particular toilet some time ago and apparently the anchors had been lost or misplaced. So I snipped off about 1/8" or so off the tip of the Home Depot plastic anchors to shorten them a bit and gently tapped them into the two metal bushings embedded in the back of the porcelain toilet bowl. No problem, no damage thus far. Then, rather than using the pan-head drive screws that came with them, which seemed too wide, I used the bolts from the original seat installation which were present. While they, too, were a tight fit, they went in without a problem and without damage. I placed a metal nut under the head of each bolt to increase the standoff distance and everything now seems to fit snugly and securely. Time will tell whether this solution can be considered permanent or may have to be repeated, in which case I have plenty of replacement anchors.

For me one bolt just unscrewed and I drilled the anchor out. The anchor spun while trying to drill it, so I just placed a screwdriver between the porcelain and the anchor to prevent that. One bolt was frozen with the anchor so I took a Dremel tool, cut the head off the bolt and then drilled that one out. Both fell into the fixture. I tried to use Well Nuts per someone's suggestion, they did not work as a replacement. I bought a hollow wall anchor setup on Amazon, used the smallest anchors and they worked like a charm. Link: https://smile.amazon.com/gp/product/B07V6WM9CW/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1 It took longer trying to figure out what to do than actually doing it. Hope this helps!

This problem is caused by a basic design error. The anchor is made of aluminum and the bolt is stainless steel. These combination of metals is never supposed to be used together because it creates galvanic / bimetallic corrosion, which will 'freeze' the anchor to the bolt.

I managed to pry the anchors out and ordered an 84999 replacement set from Kohler - hoping that they fixed this problem. Nope! The anchor is still aluminum with the stainless steel bolt -- an Engineering 101 error! A photo is attached below. I was able to find one potential source for stainless steel molly / sleeve expansion bolts online.

Here is a photo of the bolt and cracked insert:

Kohler replacement set -- same problem!

Galvanic metal corrosion chart:

Thanks for all of the advice. If it wasn't for these tips I orobably would have ended up having to buy a new toilet and have it installed by a plumber. Probably would have dropped around $1,000 to do that where I live. But what a pain this was! I spent several hoursgetting the old bolts and anchors out. I had to use my Dremel reciprocating tool to cut off the heads of the bolts and then bought a set of cobalt drill bits to drill out the rest of the bolts and the anchors. Finally go it done but the anchors I had on hand were too small. I bought a pack of #14-16 1-1/4" plastic anchors and they worked perfectly with some wood screws I had on hand.