Here are the most likely causes:
* Power Steering Pump: This is the most common culprit. A failing power steering pump can't generate enough pressure to assist the steering. This often manifests as intermittent loss of assist, especially when the engine is under load or the fluid is low/hot. Check the fluid level – low fluid is a strong indicator. Listen for unusual noises (whining, groaning) from the pump itself.
* Power Steering Fluid Leaks: Leaks in the hoses, lines, or the pump itself will lead to low fluid and loss of assist. Inspect the entire power steering system for leaks – look for wet spots, fluid dripping, or shiny areas indicating fluid residue.
* Power Steering Gearbox/Rack and Pinion: Internal problems within the steering gearbox can cause intermittent loss of assist. This is more likely if you hear unusual noises (clicking, grinding) from the steering column area. A failing rack and pinion is a more serious and expensive repair.
* Power Steering Pressure Sensor/Switch (Less Likely): A faulty sensor could be sending incorrect signals to the power steering system, leading to inconsistent assist. This is less likely than the pump or leaks.
* Belt Issues (Less Likely): A slipping, worn, or broken serpentine belt (which drives the power steering pump) can also cause loss of assist. Inspect the belt for wear, cracks, or slippage.
What to do:
1. Safety First: Do not drive the truck until the problem is diagnosed and fixed. Loss of steering is extremely dangerous.
2. Check Power Steering Fluid: This is the easiest and quickest check. Locate the power steering fluid reservoir (usually a clear or translucent container). Is the fluid level low? Is it dirty or milky (indicating water contamination)?
3. Listen for Noises: With the engine running, listen carefully for any unusual noises coming from the power steering pump or steering column area.
4. Inspect for Leaks: Carefully examine all hoses, lines, and the power steering pump for any signs of leaks.
5. Professional Diagnosis: Because this is a serious safety concern, it's best to have a qualified mechanic diagnose the problem. They have the tools and expertise to pinpoint the exact cause and perform the necessary repairs. Trying to troubleshoot this yourself without experience could lead to further damage or injury.
Don't delay getting this fixed. Driving with intermittent power steering failure is extremely hazardous.
