Why do my cakes bulge in the middle everytime I do a fondant cake? Am I putting to much icing in between the layers? It never fails, the cake looks perfect at first, but then after a short time, presto--it's bulging--of course, after the other decorations are already on it and I can't fix it! It's times like this that make me want to quit all together!
I think maybe the filling is being squished out of the cake, if you don't use a dam before filling, then try that and see if it helps. And is your icing too soft? If it is then try using a stiffer icing to help keep everything from bulging out.
I suggest letting your cake settle for atleast 12 hours prior to covering with fondant. I level, damm, fill and place 2-3 tiles on top of my torted cake to allow any squishing of the filling to happen. If it is going to have several tiers on top then I add more weight. Once it has settled, then at that point I look for any bulging and remove any excess I see. It is much better for the bulging to happen now and not later. Then I proceed to covering with fondant. Also, I use a very thick buttercream (almost rolled buttercream) for my damm icing only. This really helps keep your filling inside and avoids that bulge.