Hi my 1999 ram 1500 318v8 used to run about 1/4 on the temp gauge it has recently started running about 3/8 to 1/2 and climbing grades it easily climbs to 3/4. but cools back down to 3/8 to 1/2 when the grade levels off. Going down steep hills it cools back to a 1/4 and then rises back to 3/8..
It seems like the longer I drive it slowly gets hotter (400 miles) and it was stuck on 1/2 when I pulled in my driveway.

I have/had a coolant leak on decompression (only when it is off)(I added stop leak) from either my water pump gasket or thermostat housing. I am running mostly water, (could this be the reason it is getting hotter)
I dumped out my overflow and cleaned it there was a lot of sludge in it. ( I am thinking of draining my radiator, & refiling it). It also does not seem like my heater is blowing heat as hot as it used to.

What could my problem be?
Could all of the little issues be related?
Is there a cheap fix?
Could it be a weak radiator cap?

Thanks Chad

OK, Chad. This all ties in together. You definitely have a flow problem. The stop leak is only making matters worse. You mention the sludge issue. All that is in the cores of your rad too! Ie: 60% of your rad is flowing. 40% stopped up. It needs 100% on hot days, inclines, long drives... ect.
No cheap fix here, except trying a good brand chemical flush first w/heat on full, then mix 20% coolant with distilled water and hope for the best.
In my opinion, the rad needs to be rodded out or replaced, and the leak permanently fixed, & new stat. Then next winter you might consider a new heater core. Don't forget to replace hoses. They're important too!