GM Astro/Safari 1985-1996 Repair Guide

Valve Springs and Stem Seals

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REMOVAL & INSTALLATION



See Figures 1 and 2



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Fig. Fig. 1: With the proper tools, valve springs and stem seals can be replaced with the cylinder head installed



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Fig. Fig. 2: A lever type or jawed spring compressor can be used with the head installed

If the valve springs are suspect, you may wish to measure the installed height BEFORE removing them. For details, please refer to the valve spring inspection information, later in this section.

Both the valve spring and stem seal must be removed if the valve is being removed from the cylinder head. If the cylinder head has been removed from the engine, then please refer to the Valve procedures found earlier in this section for details on spring or stem seal removal or installation. But unlike the valves which face into the combustion chamber (and therefore cannot be removed unless the cylinder head is off the engine) both the valve springs and the stem seals can be replaced with the cylinder head installed (if a special tool is used to keep the valves from falling into the combustion chambers).

The following procedures requires the use of GM Air Adapter tool No. J-23590 or equivalent, and a jawed spring compressor or a lever style spring compressor tool such as No. J-5892 or equivalent.

  1. For access, remove the engine cover from the passenger compartment. For details, please refer to General Information & Maintenance of this information.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the rocker arm cover.
  6.  

The cylinder on whose valves you are working must have its piston at TDC of the compression stroke in order to follow this procedure. On the compression stroke, the cylinder's valves will be closed allowing the air pressure to hold the valve in position. The engine must therefore be turned slightly for each cylinder's valve springs or seals.

  1. Remove the rocker arm and pushrod assemblies from the cylinders on which the valves are being serviced.
  2.  
  3. Remove the spark plug from the cylinder which is on its compression stroke and install a spark plug air fitting adapter with an in-line gauge set between the adapter and air compressor. Apply AT LEAST 100 psi (690 kPa) of compressed air to hold the valve in place.
  4.  


WARNING
If air pressure is lost while the valve keepers are removed, the valve will drop into the cylinder. If this happens, the cylinder head must be removed in order to recover the valve.

  1. Compress the valve spring using a suitable compressor tool and remove the valve key. Carefully release the spring tension, then remove the valve cap and spring.
  2.  

If the air pressure has forced the piston to the bottom of the cylinder, any removal of air pressure will allow the valves to fall into the cylinder. A rubber band, tape or string wrapped around the end of the valve stem will prevent this.

  1. If the seals are being replaced, remove and discard the old seal from the valve stem.
  2.  

To install:
  1. If removed, install the new seal using a valve stem seal installer or other suitable driver.
  2.  
  3. Install the valve spring and cap, then compress the spring and install the valve keys.
  4.  
  5. When the valve springs are properly installed, release the air pressure from the cylinder using the gauge set, then remove the spark plug adapter.
  6.  
  7. Install the spark plug and turn the engine sufficiently to work on the next cylinder. Repeat the above steps until all seals are replaced.
  8.  
  9. Install the rocker arm and pushrod assemblies.
  10.  
  11. Install the rocker cover and connect the negative battery cable.
  12.  
  13. Install the engine cover to the passenger compartment.
  14.  

INSPECTION



See Figures 3, 4, 5, 6 and 7



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Fig. Fig. 3: The first step in spring inspection is to measure the installed height



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Fig. Fig. 4: A special tool is needed to check valve spring pressure



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Fig. Fig. 5: Use a caliper gauge to check the valve spring free-length



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Fig. Fig. 6: Check the valve spring for squareness on a flat service; a carpenter's square can be used



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Fig. Fig. 7: The valve spring should be straight up and down when placed like this

  1. Before the springs are removed, check the installed height using a precision ruler. Compare the measurement to the specification found in the Valve chart at the beginning of this section.
  2.  
  3. Place the valve spring on a flat, clean surface next to a square.
  4.  
  5. Measure the height of the spring, and rotate it against the edge of the square to measure distortion (out-of-roundness). If spring height varies between springs by more than 1 / 16 in. (1.6mm) or if the distortion exceeds 1 / 16 in (1.6mm), replace the spring.
  6.  

A valve spring tester is needed to test spring test pressure, so the valve springs must usually be taken to a professional machine shop for this test. Spring pressure at the installed and/or compressed heights is checked, depending on the specification.

 
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