Help - Brakes lock up on 1997 3500 van

I have a 1997 Dodge Ram 3500 van that I use to haul my llamas and equipment in to shows, pack trials, etc. I bought this vehicle used last year and had Mechanic #1 replace the worn front brake pads soon after I got it. The first time that I used it heavily loaded with llamas and gear in warm weather the left front brake started to lock up, heat up and smoke. I managed to limp into the shop of Mechanic #2 who took the wheel apart, cooled down the brake with water, bled some of the brake fluid, and sent me on my way for the price of a few sodas. Nice guy.

This seemed to do the trick, until I was coming back from an event, loaded with couple of animals and gear, descending a steep winding mountain road. The brakes again heated up and the left front locked up. This time I sprayed water on it until it was cool enough to release. I took the van back to Mechanic #1 who checked the brakes and said he couldn't find anything wrong and sent me on my way. No charge. Nice guy.

The van worked fine for a while, but then scenario number two happened again on the same mountain. Both front brakes seemed to be involved this time.

In a couple of weeks I will be traveling with a big load down some steep grades, and really want to have this problem fixed. I'm about to take the van to a mechanic to get the brakes worked on, and I'd like to have a clue about what might be wrong so that I don't end up replacing the entire system, piece by piece. Anyone have experience with this or at least a suggestion for where to start?

I'm going to cross-post this to the Ram 3500 pickup forum, too, as I think a lot of the equipment is the same on the trucks as on the vans.

Thanks for any help you can offer,
LlamaLadySG

i had a similar problem with a dodge caravan, turned out to be the hoses going to the calipers, they have a check valve in them or they let go from the inside and it acts as a check valve. i hope this helps.
Pat.