Section 3.4
Oil Pressure Relief Valve

Oil leaving the pump under pressure passes into the pressure relief valve body. The spring-loaded valve opens when the pressure exceeds 724 kPa (105 psi) and directs the excess oil to the oil pan. The pressure relief valve is attached to the oil pump outlet tube (on 1991 and later engines), or the oil pump body (on pre-1991 engines). See Figure "Oil Pressure Regulator Valve Mounting" .‪

The pressure relief valve consists of a valve body, a hollow, piston-type valve, a spring, spring seat and a pin to retain the valve assembly within the valve body.‪

The relief valve assembly is composed of the same parts as the regulator valve assembly with the exception of the body. See Figure "Oil Pressure Regulator Valve Parts and Relief Valve Details" .‪

The valve is held on its seat by the spring, which is compressed by the pin in back of the spring seat. The entire assembly is bolted to the lower flange of the cylinder block and sealed against leaks by a gasket between the block and valve body. When conditions are such that the oil pressure at the valve exceeds 689 kPa (100 psi), the valve begins to be forced from its seat and oil from the engine gallery is bypassed to the engine oil pan. Thus, stable lubricating oil pressure is maintained at all times.‪

Section 3.4.1
Repair or Replacement of Oil Pressure Relief Valve

To determine if repair is possible or replacement is necessary, perform the following procedure. See Figure "Flowchart for Repair or Replacement of Oil Pressure Relief Valve " .‪

Figure 1. Flowchart for Repair or Replacement of Oil Pressure Relief Valve

Section 3.4.2
Removal and Cleaning of Oil Pressure Relief Valve

Remove the oil pressure relief valve as follows:‪

1. Remove the two bolts and washers securing the relief valve to the cylinder block.
2. Tap the oil pressure relief valve body lightly to loosen it from the gasket and cylinder block.
3. Remove the oil pressure relief valve and gasket.

Section 3.4.3
Disassembly of Oil Pressure Relief Valve

Disassemble the oil pressure relief valve as follows:‪

1. Clamp the oil pressure relief valve in the soft jaws of a bench vise.

   EYE INJURY ‪
   To avoid injury from flying debris when using compressed air, wear adequate eye protection (face shield or safety goggles) and do not exceed 276 kPa (40 psi) air pressure.‪

2. Remove the spring seat retaining pin from the oil pressure relief valve body. See Figure "Oil Pressure Regulator Valve Parts and Relief Valve Details" .
3. Remove the spring seat, spring and valve from the oil pressure relief valve body. See Figure "Oil Pressure Regulator Valve Parts and Relief Valve Details" .

Section 3.4.4
Cleaning the Oil Pressure Relief Valve

Perform the following steps to clean the oil pressure relief valve:‪

1. Clean all of the oil pressure relief valve components in fuel oil.

   EYE INJURY ‪
   To avoid injury from flying debris when using compressed air, wear adequate eye protection (face shield or safety goggles) and do not exceed 276 kPa (40 psi) air pressure.‪

2. Dry the components with compressed air.

Section 3.4.4.1
Inspection of Oil Pressure Relief Valve

Inspect the oil pressure relief valve as follows:‪

1. Inspect the oil pressure relief valve for movement. Check to see if the oil pressure relief valve moves freely in the valve body.
   1. If relief valve binds, replace it with a new part.
   2. If relief valve did not bind, reuse the component.
2. Inspect the components for wear or damage. Check to see if the valve or the valve body are scored.
   1. If the valve and valve body parts cannot be cleaned with a fine emery cloth, replace with new parts.
   2. If the valve and valve body parts can be cleaned with a fine emery cloth, reuse the parts.
3. Inspect spring for pitting or fractures.
   1. If spring is damaged, replace the component.
   2. If spring is not damaged, reuse the component.

Section 3.4.5
Assembly of Oil Pressure Relief Valve

The oil pressure relief valve body has two retaining pin holes. See Figure "Location of Oil Pressure Regulator Valve and Relief Valve Pin" . Install the pin in the outermost hole for the regulator valve. ‪

Figure 2. Location of Oil Pressure Regulator Valve and Relief Valve Pin

Assemble the relief valve as follows:‪

1. Apply clean engine oil to the outer face of the valve.
2. Slide valve into the oil pressure regulator body, closed end first. See Figure "Location of Oil Pressure Regulator Valve and Relief Valve Pin" .
3. Insert the spring in the valve and install the spring seat.

   NOTICE:
   The retaining pin must be positioned correctly so the proper valve opening pressure will be obtained. Although the same casting is used for both the pressure regulator and relief valves, the regulator valve has a slightly larger opening machined into the side. See Figure "Location of Oil Pressure Regulator Valve and Relief Valve Pin" .‪

4. While compressing the spring, install the retaining pin behind the spring seat.
5. Press the pin flush to 0.254 mm (0.010 in.) below the surface of the valve body.

Section 3.4.6
Installation of Oil Pressure Relief Valve

Install the oil pressure relief valve as follows:‪

1. Remove all traces of old gasket material from the mating surfaces of the oil pressure relief valve body and the cylinder block.
2. Place a new gasket onto the relief valve body.
3. Secure the oil pressure relief valve assembly to the cylinder block with two bolts. Torque the bolts to 30-38 N·m (22-28 lb·ft).
4. Refer to "12.3 Running" for verification of proper oil pressure relief valve installation.