Power steering just stopped working over night

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If there is no noise and no assist, the first thing I would do is check the pump for flow and pressure. Here are the directions for doing it. I'm adding these directions just in case you want to check it. Also, you should be able to see the fluid circulating in the reservoir. So check that. If there is no flow, replace the pump.

Here is a link that talks about different issues with PS pumps.

https://www.2carpros.com/articles/power-steering-problems

https://www.2carpros.com/articles/how-to-replace-a-power-steering-pump

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Pump Flow and Pressure Test

WARNING: Do not touch the flowmeter during the test procedure, or severe burns and serious injury can occur. Failure to follow these instructions may result in personal injury.

1. CAUTION: Make sure that the connection point will not interfere with any of the engine accessory drive components or drive belts.

Install the power steering analyzer at the high pressure port of the power steering pump. Make sure the power steering analyzer gate valve is fully open.

2. Place a dial thermometer in the power steering pump reservoir.
3. Check the power steering fluid level. If necessary, add specified power steering fluid.
4. Install a digital tachometer.

5. CAUTION: Do not hold the steering wheel against the stops for more than 3 to 5 seconds at a time. Damage to the power steering pump can occur.

Start the engine. Place the transmission in NEUTRAL. Set the parking brake. Raise the power steering fluid temperature to 74 - 80°C (165 - 175°F) by rotating the steering wheel fully to the left and right several times.

6. With the steering wheel in the straight-ahead position, set the engine speed to 2,100 rpm. Record the flow rate and pressure readings.
- If the flow rate is below the flow rate specification, continue with the test procedure.
- If the pressure reading is above the maximum pressure specification, check the power steering hoses for kinks and restrictions.

7. Partially close the gate valve to obtain 750 psi. Set the engine speed at idle. Record the flow rate.
If the flow is less than the specified flow rate, install a new power steering pump.

8. CAUTION: Do not allow the gate valve to remain closed for more than 5 seconds.

Completely close and partially open the gate valve 3 times. Record the pressure relief valve actuation pressure reading.
If the pressure does not meet the relief pressure specification, then install a new power steering pump.

9. Set engine speed to 2,100 rpm. Record the flow rate.
If the flow rate varies more than 3.785 liters/minute ( 1 gallon minute) from the initial flow rate reading, install a new power steering pump.

10. CAUTION: Do not hold the steering wheel against the stops for more than 3 to 5 seconds at a time. Damage to the power steering pump can occur.

Set the engine speed at idle. Turn (or have an assistant turn) the steering wheel to the left and right stops. Record flow rate and pressure readings at the stops.
- The pressure reading at both stops should be nearly the same as the maximum pump relief pressure.
- The flow rate should drop below 1.9 liters/minute (0.5 gallons/minute).
- If the pressure does not reach the maximum pump relief pressure or the flow rate does not drop below the specified value, excessive internal leakage is occurring. Install a new steering gear as necessary.

11. Turn (or have an assistant turn) the steering wheel slightly in both directions and release quickly while watching the pressure gauge.
- The pressure reading should move from the normal back pressure reading and snap back as the steering wheel is released.
- If the pressure returns slowly or sticks, the rotary valve in the steering gear is sticking or the steering column is binding. Check the steering column and linkages before repairing the steering gear.

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Here are the directions specific to replacing the pump. Most likely, you will need to rent a tool for pulley removal and replacement. Here is a link that shows how it is done.

https://www.2carpros.com/articles/remove-reinstall-power-steering-pulley

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Power Steering Pump-4.6L (2V)

Special Tool(s)
Pic 1

CAUTION: While repairing the power steering system, care should be taken to prevent the entry of contaminants or premature failure of the power steering components can result.

1. With the vehicle in NEUTRAL, position the vehicle on a hoist.
2. If removing the power steering pump, remove the LH front wheel.
3. If removing the power steering pump or pulley, remove the air cleaner.

Pic 2
Part 1 Of 2
Pic 3
Part 2 Of 2
Pic 4

4. Remove the parts in the order indicated in the illustration and table.
To remove individual parts, only carry out the listed steps:
5. To install, reverse the removal procedure.
6. Fill and leak test the system.

Item 17: Pulley Removal Note

Pic 5

1. Using the special tool, remove the pulley.

Item 21: Pump Bolts Removal Note

Pic 6

1. Remove the nuts and position the bracket and cable aside.
- Remove the pump bolts.

Item 21: Pump Bolts Installation Note
1. Make sure to align the bracket and pump before tightening the bolts.

Item 20: O-ring Installation Note

Pic 7

1. Using the special tool, install a new Teflon seal on the pressure line fitting.

Item 17: Pulley Installation Note

Pic 8

1. Using the special tool, install the pulley.

Item 16: Drive Belt Installation Note
1. Rotate the tensioner clockwise and remove the belt from the power steering pump pulley.

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Here are the directions for bleeding the system.

Power Steering System Purging

Special Tool(s)
Pic 9

CAUTION: If the air is not purged from the power steering system correctly, premature power steering pump failure can result. The condition can occur on pre-delivery vehicles with evidence of aerated fluid or on vehicles that have had steering component repairs. Failure to follow these instructions may result in personal injury.

1. NOTE: A whine heard from the power steering pump can be caused by air in the system. The power steering purge procedure must be carried out prior to any component repair for which power steering noise complaints are accompanied by evidence of aerated fluid.

Remove the power steering pump reservoir cap. Check the fluid.

2. Raise the front wheels off the floor.
3. Tightly insert the stopper of the vacuum pump into the reservoir.
4. Start the engine.
5. Install the vacuum pump and maintain maximum vacuum, 68 - 85 kPa (20 - 25 in-Hg).

6. CAUTION: Do not hold the steering wheel against the stops for more than 3 to 5 seconds at a time. Damage to the power steering pump can occur.

Cycle the steering wheel fully from stop to stop 10 times.
7. Stop the engine.
8. Release the vacuum and remove the vacuum pump.

9. CAUTION: Do not overfill the reservoir.

Fill the reservoir.
Use approved transmission fluid.

10. Start the engine.
11. Reinstall the vacuum pump. Apply and maintain maximum vacuum, 68 - 85 kPa (20 - 25 Hg).

12. CAUTION: Do not hold the steering wheel against the stops for more than 3 to 5 seconds at a time. Damage to the power steering pump can occur.

Cycle the steering wheel fully from stop to stop 10 times.

13. Stop the engine, release the vacuum, and remove the vacuum pump.

14. CAUTION: Do not overfill the reservoir.

Fill the reservoir as needed and install the reservoir cap.

15. Visually inspect the power steering system for leaks.
16. Lower the vehicle.

17. CAUTION: Do not overfill the reservoir.

Fill the reservoir as needed and visually inspect the power steering system for leaks.

18. Install the reservoir cap.

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Let me know if any of this helps or if you have other questions.

Take care,

Joe