Saginaw Project (Arsh)

Saginaw Steering Gear Project

Lower Sector Shaft Seals

What does it do?

The lower sector shaft seals ensure that fluid is sealed and pressure doesn't leak when the steering wheel is turned to the left. They seal the pitman shaft into the housing. It separates the left turn chamber from the atmosphere and will act at all times but will seal most when the steering wheel is turning left.

What if it fails?

If the sector shaft seal fails then the fluid will leak past the seal from the sector shaft into the atmosphere. This would make steering difficult in both directions due to the low fluid level. A more severe effect would be experienced when turning left as the leak would be in the left turn chamber.

What would the customer concern be?

If the lower sector shaft seals failed, the customer concern would be that they experience difficulty turning the steering wheel left, or no assisted steering. The customer will also hear noises/whining from the engine bay as the power steering pump will be low on fluid. Due to the leak, the customer may also notice power steering leaks on the ground after parking their vehicle for some time.

Retaining Ring

What does it do?

The retaining ring is for the housing end plug and it keeps the end plug in place. The housing end plug separates the right turn chamber from the atmosphere. This ring is at work whenver pressure in the lower chamber increases past atmospheric 14.6959 psi. There is also an O-ring on the end plug that keeps the lfuid from leaking into the atmosphere.

What if it fails?

If the end plug retainer ring was to fail, it would essentially cause the end plug to pop out of the housing when the pressure difference arised. This would occur as soon as you begin to turn the steering wheel to the right and would result in a large loss of fluid very rapidly.

What would the customer concern be?

If the end plug retainer ring failed, the customer concern would be that they experience difficulty turning the steering wheel right, or difficulty turning in either direction due to the lack of fluid. The customer will also hear noises/whining from the engine bay as the power steering pump will be low on fluid. Due to the leak, the customer may also notice power steering leaks on the ground.

Flow Control Valve

What does it do?

The flow control valve maintains pressure at all engine speeds. With the engine on, the lfuid flows from the Venturi port to the steering gear. The chamber with the venturi port has low pressure and the valve port has high pressure. This difference in pressure overcomes the force of the spring and pushes the valve towards the lower pressure. Flow will increase as the engine speed increases. Eventually the increased flow will push the valve far enough to open the return port and excess fluid can now flow back at a constant rate.

Once we begin turning, flow becomes restricted and the pressure drops on one side as the venturi decreases. This results in a high pressure on the valve side, push the valve back with the spring force to block the return port. Once the return port is blocked, the pressures will equalize in both chambers. The equal pressure wilcause the spring to return the valve back to its fully closed position.

#3 Valve Body Teflon Seal

What does it do?

The third teflon seal on the valve body is responsible for separating the left turn chamber of the steering gear from the pump. It allows for a difference in pressure between the upper chamber (low pressure) and the lower chamber (high pressure). The seal also prevents the pump from over working because if a leak was allowing pressure from the pump to reacht the upper chamber, the pump would have to compensate by overworking itself.

What if it fails?

If the third teflon seal failed on the valve body, it would not allow for a difference in pressure between the pump and the left turn chamber. This would result in insufficient assist when turning right.

What would the customer conern be?

If the third teflon seal on the valve body failed, the customer concern would be that they experience extreme difficulty turning the steering wheel to the right. The customer will also complain of loud noises/whining coming from the engine bay upon turning right as the pump is over working itself due to the leak in the upper chamber.

Teflon Seals

What does it do?

The teflon seal on the rack piston ensures that the left turn chamber (Upper) and right turn chamber (lower) stay separated.

What does the separation allow?

It allows the two chambers to have a difference in pressure during left or right turns. This difference in pressure is what provides us with assist.

What if it fails? How does it fail?

If the teflon seal on the rack piston was damaged, it would not be possible to create a significant difference in pressure between the two chambers. It can fail by staying at full lock for too long as this heats up the fluid due to flow restriction. Contaminated fluid can also corrode the seal and make it fail.

What would the customer conern be?

The customer concern would be that they experience extreme difficulty in turning the steering wheel in any direction. There would be no assist.

#2 Valve Body Teflon Seal

What does it do?

The second teflon seal on the valve body is responsible for separating the right turn chamber of the steering gear from the pump. It allows for a difference in pressure between the right turn chamber (low pressure) and the left turn chamber (high pressure).

What if it fails?

If the second teflon seal failed on the valve body, it would not allow for a difference in pressure between the right turn chamber and the left turn chamber. This would result in insufficient assist when turning left. This is due to a higher pressure in the right turn chamber as the failed seal doesn't allow for a difference in pressure between the pump and the lower chamber.

What would the customer conern be?

If the second teflon seal on the valve body failed, the customer concern would be that they experience extreme difficulty turning the steering wheel to the left. The customer will also complain of loud noises/whining coming from the engine bay upon turning left as the pump is over working itself due to the extra load from the lower chamber.

#1 Valve Body Teflon Seal

What does it do?

The first teflon seal on the valve body is responsible for separating the return port from the right turn chamber of the steering gear. The seal allows for a difference in pressure between the right turn chamber and the return port reservoir.

What if it fails?

If the first teflon seal failed on the valve body, it would not allow for a difference in pressure between the right turn chamber and the return port. This would result in insufficient assist when turning right. This is due to a lack of a higher pressure in the right turn chamber as the failed seal doesn't allow for a difference in pressure.

What would the customer conern be?

If the first teflon seal on the valve body failed, the customer concern would be that they experience extreme difficulty turning the steering wheel to the right.

Spool Valve O-Ring

What does it do?

The O-ring on the spool valve separates the pump from the return lines in the directional control valve. It also maintains pressure generated by the pump within the system.

What if it fails? How does it fail?

If the O-ring failed, there would be a leak from the pump back to the return port in ths system. Due to this the pump will be working overtime in order to try and compensate for the lack of fluid in the system due to the leak. Incorrect or rough assembly, and poor fluid condition could cause the o-ring to fail.

What would the customer conern be?

If the O-ring fails entirely, the customer will notice the steering wheel becomes much more difficult to turn than it used to be. The customer will also complain of loud noises/whining coming from the engine bay upon turning as the pump is over working itself.

Presuure Relief Valve

What does it do?

On most demand pumps, the outlet has to be restricted to create pressure that the pump can use. The higher the restriction gets, the less flow there is and that results in higher system pressure. The same goes for the opposite, with excessive flow, we will have a low restriction and that results in a lower system pressure. During full mechanical lock, we often block off the outlet completely, resulting in a 100% restriction. This creates we is known as hydraulic lock, which is a process of blocking the outlet, which in turn will stall the pump and damages components. In order to prevent damage to the components from hydraulic lock, a pressure relief valve was engineered to ensure the system pressure did not reach a harmful level. Once the pressure relief valve opens up, the pressure drops and this causes the flow control valve to move left. Once the flow control valve moves left, it unblocks the return port and the pressure begins to go down. Once low enough, the relief valve will close off the return port because pressure in the right chamber is low, which will allows the spring to push the control valve back to the right. This process continues to repeat itself until restriction to flow is removed.

Broken Torsion Bar

What does it do?

The torsion bar allows small relative motion between the inner and outer halves of the directional control valve when torque is applied to the stub shaft. This allows the directional control valve to direct pressure to the different chambers inorder to allow for a difference in pressure. The torsion bar also provides feedback to the driver as they turn the steering wheel. The wormshaft also have mechanical locks which will limit the amount the torsion bar can flex.

What if it fails?

If there is no torque on the stub shaft, the torsion bar keeps the two halves of the control valve aligned, and maintains pressure on both sides of directional control valve. This will not allow for a difference in pressure as without the torsion bar, the directional control valve will not be able to direct fluid into different chambers. There will be no more assist in turning the steering wheel.

What would the customer conern be?

If the torsion bar failed, the customer concern would be that they experience extreme difficulty turning the steering wheelin either direction. The customer may also complain of the steering wheel turning on its own as the torsion bar may be twisted and would result in the directional control valve open before it was supposed to.

• http://selectric.org/manuals/sag800/605.jpg
• 1981 Chevrolet Passenger Car and Light Duty Truck Unit Repair (Overhaul) Manual
• Hydraulic Assist Steering ILM

References

O-Ring (worm shaft to directional control valve)

What does it do?

The O-ring between the worm shaft and the directional control valve is responsible for sealing the left turn or upper chamber from the return outlet. The seal goes to work when we provide torque to the steering wheel to turn left. This causes the left turn chamber to pressurize and prevents pressure from leaking to the return lines.

What if it fails? How does it fail?

If the O-ring failed, there would be less pressure in the left turn chamber due to the fluid leaking past the O-ring back into the return chamber.

What would the customer conern be?

If the O-ring fails, the customer will notice the steering wheel becomes much more difficult to turn to the left. The customer will also complain of loud noises/whining coming from the engine bay upon turning as the pump is over working itself to increase pressure in the left turn chamber.

O-Ring in Wrong Groove

What would happen?

There would be an extreme difficulty experienced by the driver when turning the vehicle to the right side as fluid will leak past the o-ring right into the end plug.