Finally found where rain water intrusion was coming from!

[Astrodokk]

The previous owner said it was a small leak and minor wood damage. NOT!

The preventive maintenance was nill.

I've been trying to locate the source of the small pond at the bottom step-well of our rear door after every rain, and have been inspecting any possible area of leakage. Upon inspecting the trunk space in front of the spare tire, I noticed that the trim was not quite flush with the body of the coach.
I had already taken out all of the MDF that was in there, and allowed the carpet to dry as well. But when it rained, it would all get wet again.

So as an experiment, I used a butyl type caulk (no silicone) and caulked the circumference of the trim. I first had to use two zinc plated screws to force the trim flush to the fiberglass. I don't like that the screws are there, but had to be field expedient. It rained for two days here and I'm happy to say, it's all dry inside!!!

When the summer starts, I will be removing the trunk trim, cleaning it well, and re-bedding the entire "flange" to the body. I think I will have to do the wood box inside first. There had been a piece of wood bonded to the inside of the trunk that some internal side screws had been used to hold it in place, but that rotted out long ago.

In the photo, you can see the two screws I used. The top right curve was where it was not flush.

[Astrodokk]

I will probably fix the clear coat later too.

[Blue~Go]

Happy day! The source has been found!

[Astrodokk]

Yes, I'm relieved. Now I can start thinking about getting the MDF/wood repaired/replaced after the trunk is done.

Actually, it doesn't really look so bad and I have tolerated the imperfectness of it. Function is not hindered and I have even thought that if it all gets dried out nicely, I may be able to just leave it for someone else to "rebuild" in a configuration they prefer.

Time will tell what I want to do.