Hello all:

  We are trying to drop the oil pan on a very well used Cat 15.  The equalizer spring is out and the transmission is supported. All of the 3/8" and 1/2" cap screws that retain the pan are out yet the pan is on there tight. This engine was overhauled 12 years ago and sat ever since. The oil pan drain plug was left off to prevent accumulation of condensate. Somehow mice got into the oil pan and made a nest in the valve lifter area and probably everywhere else. Could the gasket be holding the pan on or are there any hidden bolts? Are there a pair of stuck dowel pins where the end of the pain bolts to the transmission? We don't want to get too rough with it and break something. Any thoughts would be greatly appreciated!     . 

I'm wondering if it was sealed with the #2 Permatex and is stuck pretty good. I did that to a D4 7U last year and hope I never need to pull the oil pan.
What if you put the spring back in with the track frame cradle bolts in and recoil bars attached and try jacking the engine up slightly not touching the oil pan to use the weight of the transmission to pull down the pan enough to break the seal? I can't remember if there's any dowels on that pan but I'll be finding out in the near future because I'm in the process of a complete tear down and rebuilding of a PV15.
Right now I'm reassembling the transmission.

Thank you for getting back. Father overhauled the engine and was not a fan of using Permatex on something that may ever need to come apart. If you need to rebore the engine check into using model T Ford pistons. They have a tall compression height, same bore diameter and come in oversizes and are reasonably priced. Father bored and sleeved this one.   Make sure that your oil fill and drain plug are in place lest you get critters. 

Thank you for getting back. Father overhauled the engine and was not a fan of using Permatex on something that may ever need to come apart. If you need to rebore the engine check into using model T Ford pistons. They have a tall compression height, same bore diameter and come in oversizes and are reasonably priced. Father bored and sleeved this one.   Make sure that your oil fill and drain plug are in place lest you get critters. 

  Success!  There was Permatex but only on one side.. After repeatedly counting the bolts and reviewing the parts book  a few good smacks with a 32 Oz. hammer and a block of wood it finally let go.