B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 002-020   Valve, Cylinder Head

Valve Sealing

If the compression is low on one or more nonadjacent cylinders and the pressure can
not be increased by oiling the rings, poor valve sealing is to be suspected.

Valve leakage is often audible from the intake and/or exhaust manifold.

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

• Turn off the vehicle’s main fuel shutoff valve.

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

• Disconnect the battery cables, negative (-) cable first.

WARNING  Coolant is toxic. Keep away from children and pets. If not reused, dispose of in accordance with local environmental regulations.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

• Remove the cylinder head. Refer to Procedure
  002-004.

The following disassembly and assembly procedures are provided for inspection purposes
only. Refer to the Shop Manual, Bulletin 3810206, for complete rebuild instructions.

Mark the valves to identify their location.

Valve Spring Compressor, Part Number 3375962

NOTE: If the valve springs, collets, retainers, and valve guide seals are to be used again, they
must be installed in their original location.

Compress the valve spring using the valve spring compressor, Part Number 3375962, and remove the valve stem. Remove the collets.

Release valve spring and remove the spring retainer and spring.

Remove the remaining collets, retainers, springs, and valves.

NOTE: Keep the valves in a labeled rack for a correct match with companion seats while making measurements.

Remove the valve stem seals.

WARNING  Wear protective eye covering when cleaning the valves. Failure to do so can result in injury to the eyes.

Clean the valve heads with a soft wire wheel.

NOTE: Keep the valves in a labeled rack to prevent mixing prior to making measurements.

WARNING  Do not mix gasoline, alcohol, or gasohol with diesel fuel. This mixture can cause an explosion.

WARNING  When using solvents, acids, or alkaline materials for cleaning, follow the manufacturer’s recommendations for use. Wear goggles and protective clothing to reduce the possibility of personal injury.

WARNING  Use skin and eye protection when handling caustic solutions to reduce the possibility of personal injury.

Polish the valve stem with a Scotch-Brite™ pad, or equivalent cleaning pad, and diesel fuel or solvent.

Inspect the valve guides for scuffing or scoring.

Measure the valve guide bore.

If the inspection reveals damaged valve guides, refer to the Alternative Repair Manual, Bulletin 3666109.

Inspect the valve seats for cracks or burned spots.

Refer to the following reuse guidelines for any cracks discovered. Service valve seats are available for seats with burned spots that will require more than 0.254 mm [0.010 in] of grinding to clean up. Refer to the Alternative Repair Manual, Bulletin 3666109, for valve seat installation procedures.

Inspect for abnormal wear on the heads and stems.

Measure the valve stem diameter.

NOTE: If the valve is
not within specification, it
must be replaced.

Check the valve stem tip for flatness.

Inspect for bent valves.

Measure the rim thickness to determine if there is enough stock to grind the valve.

If the valves are determined to be suitable for resurfacing, refer to the B Series Shop Manual, Bulletin 3810206.

Inspect the valve springs.

Measure the valve spring.

A load of 289.13 to 321.26 N [65.0 to 72.2 lbf] is required to compress the spring to a height of 49.25 mm [1.94 in].

NOTE: Clean all cylinder head components before assembling.

Install new valve stem seals.

The intake and exhaust seals are the same.

Lubricate the stems with SAE 90W engine oil before installing the valves.

Install valves into their original location.

Valve Spring Compressor, Part Number 3375962

Install the valve spring and retainer.

Use the valve spring compressor, Part Number 3375962, to compress the valve spring and retainer assembly.

Install new valve collets and release the spring tension.

WARNING  Wear eye protection. If the collets are not correctly installed, they can fly out when the stems are hit with a hammer.

After assembly, hit the valve stems with a plastic hammer to make sure that the collets are seated.

Install the cylinder head and gasket. Refer to Procedure
002-004.

Install the push tubes. Refer to Procedure
004-014.

Install the rocker levers. Refer to Procedure
003-008.

Adjust the valve lash. Refer to Procedure
003-004.

Install the rocker lever covers, and tighten capscrews.