Lukewarm water from your RV heater is typically caused by a failing heating element, sediment buildup, or thermostat issues. Most problems can be fixed by replacing the heating element, flushing the tank, or adjusting the thermostat.
Your RV sewer hose will likely freeze at 25°F, especially with the uphill section that creates standing water. The two-inch rise at your hookup point is particularly vulnerable to freezing.
Normal air suspension rise is 1-2 minutes. Taking 4-5 minutes suggests compressor issue, leak, or dirty intake filter. Check for leaks at fittings and inspect compressor.
Your Cummins 400's sudden power loss and throttle unresponsiveness, especially in hot conditions like Death Valley, could indicate ECM failure, fuel system problems, or turbocharger issues. Start with diagnostic scanning and check fuel filters.
Your story is a perfect cautionary tale about how ignoring gradual performance decline can lead to catastrophic engine failure. The combination of blocked exhaust flow and oil starvation from running 500 miles with severe backpressure absolutely justified your decision to replace rather than rebuild the engine.
Your RV's power steering leak that stopped on its own was likely caused by thermal expansion from an overfull reservoir. The excess fluid leaked out until pressure normalized, stopping the leak naturally.