Subaru Coupes/Sedans/Wagons 1985-1996 Repair Guide

Pistons, Connecting Rods, Crankshaft and Bearings

Print

All engines except the 1.2L are of the split case design. In order to remove any of the internal components, the case halves must be split. In other words, for the piston and connecting rod combination to be removed, the crankshaft must be removed and vise-versa.

REMOVAL



Except 1.2L Engine

See Figures 1, 2, 3, 4 and 5

Click image to see an enlarged view

Fig. Fig. 1: Cylinder block assembly-except 1.2L engine



Click image to see an enlarged view

Fig. Fig. 2: Removing the piston pins



Click image to see an enlarged view

Fig. Fig. 3: Removing the piston circlip



Click image to see an enlarged view

Fig. Fig. 4: Use a suitable ridge cutter to remove the ridge from the cylinder bore



Click image to see an enlarged view

Fig. Fig. 5: Carefully tap the piston out of the bore using a wooden dowel

  1. Remove the engine from the vehicle. Separate the engine from the transaxle.
  2.  
  3. Remove the intake manifold. Remove the oil pan and oil strainer. Remove the flywheel assembly.
  4.  
  5. Remove the timing belt, timing covers and related components.
  6.  
  7. Remove the cylinder head-to-engine bolts, in the reverse order of the torquing sequence. Remove the cylinder heads and gaskets.
  8.  
  9. Using an Allen wrench, remove the crankcase plugs of No. 1 and No. 2 pistons from the cylinder block.
  10.  
  11. Using a wrench on the crankshaft pulley bolt, rotate the crankshaft so that the No. 1 and No. 2 pistons are at the Bottom Dead Center (BDC) of the their compression stroke.
  12.  
  13. Using needlenose pliers, inserted through the crankcase plug holes, remove the wrist pin-to-pistons circlips.
  14.  
  15. Using a Wrist Pin Removal tool No. 399094310 or equivalent, through the rear service holes, remove the wrist pins through the crankcase plug holes.
  16.  

Keep the circlips and the wrist pins together for each cylinder so that they DO NOT become mixed up.

  1. In the same manner, remove the piston pins from the other cylinders.
  2.  
  3. Rotate the engine, so that the No. 1 piston side is facing upward, then remove the crankcase halve nuts and bolts.
  4.  
  5. Separate the crankcase halves. Remove the front oil seal, the O-ring and the back-up ring; be sure to replace them with new ones when reassembling the engine.
  6.  

Keep the pistons and the wrist pins together for each cylinder so that they DO NOT become mixed. Mark the pistons and the connecting rods so that the direction is not changed when they are installed.

  1. Remove the crankshaft together with the connecting rods, the distributor gear and the crankshaft gear as an assembly.
  2.  
  3. Remove the ridge from the top of the cylinder (unworn area), using a Ridge Reamer tool, to facilitate the removal of the pistons by performing the following procedures:
    1. Place the piston at the bottom of its bore and cover it with a rag.
    2.  
    3. Cut the ridge away using a ridge reamer, exercising extreme care to avoid cutting too deeply.
    4.  
    5. Remove the rag and remove the cuttings that remain on the piston.
    6.  

  4.  
  5. Using a hammer handle or a wooden bar, force the pistons out through the top of the cylinder block.
  6.  

1.2L Engine

See Figures 6 and 7

Click image to see an enlarged view

Fig. Fig. 6: Cylinder block assembly-1.2L engine

  1. Remove the engine from the vehicle.
  2.  
  3. Remove the timing belt, belt covers and related components. Remove the cylinder heads.
  4.  
  5. Remove the oil pan and the oil strainer assembly.
  6.  
  7. Stamp the cylinder number on the machined surfaces of the bolt bosses of the connecting rod and cap for identification when reinstalling. If the pistons are to be removed from the connecting rod, mark the cylinder number on the piston with a silver pencil or quick drying paint for proper cylinder identification and cap to rod location.
  8.  
  9. Examine the cylinder bore above the ring travel. If a ridge exists, remove it with a ridge reamer before attempting to remove the piston and rod assembly.
  10.  
  11. Remove the rod bearing cap and bearing.
  12.  
  13. Install a guide hose over the rod bolt threads; this will prevent damage to the bearing journal and rod bolt threads.
  14.  
  15. Using a hammer handle, remove the rod/piston assemblies through the top of the cylinder bore
  16.  

CLEANING AND INSPECTION




WARNING
Do not hot tank clean any aluminum parts or they will be ruined. Use carburetor solvent for cleaning.

Pistons

See Figures 7 and 8

Click image to see an enlarged view

Fig. Fig. 7: Use a ring expander to remove the piston rings



Click image to see an enlarged view

Fig. Fig. 8: Clean the piston using a ring groove cleaner

Using a piston ring expanding tool, remove the piston rings from the pistons; any other method (screwdriver blades, pliers, etc.) usually results in the rings being bent, scratched or distorted and/or the piston itself being damaged.

Clean the varnish from the piston skirts and pins with a cleaning solvent. DO NOT WIRE BRUSH ANY PART OF THE PISTON. Clean the ring grooves with a groove cleaner and make sure that the oil ring holes and slots are clean.

Inspect the piston for cracked ring lands, scuffed or damaged skirts, eroded areas at the top of the piston. Replace the pistons that are damaged or show signs of excessive wear. Inspect the piston ring grooves for nicks or burrs that might cause the rings to hang up.

Measure the piston skirt perpendicular to the piston pin axis and note this figure for the piston clearance check. If installing replacement pistons, follow the manufacturers recommendations on where to measure the piston.

Cylinder Bores

See Figures 9 and 10

Click image to see an enlarged view

Fig. Fig. 9: A telescoping gauge may be useful to measure the cylinder bore diameter



Click image to see an enlarged view

Fig. Fig. 10: Using a ball type honer is an easy way to hone the cylinder bore

Using a telescoping gauge or an inside micrometer, measure the diameter of the cylinder bore, perpendicular (90°) to the piston pin, at 1-2 1 / 2 in. (25-64mm) below the surface of the cylinder block. The difference between the two measurements is the piston clearance.

If the clearance is within specifications or slightly below (after the cylinders have been bored or honed), finish honing is all that is necessary, If the clearance is excessive, try to obtain a slightly larger piston to bring the clearance within specifications. If this is not possible, obtain the first oversize piston and hone the cylinder or (if necessary) bore the cylinder to size.

When measuring the cylinder bore, take measurements in several places. If the cylinder bore is tapered or is out-of-round, it is advisable to rebore for the smallest possible oversize piston and rings. After measuring, mark the pistons with a felt-tip pen for reference during assembly.

Boring of the cylinder block should be performed by a reputable machine shop with the proper equipment. In some cases, clean-up honing can be done with the cylinder block in the vehicle, but most excessive honing and all cylinder boring MUST BE done with the block stripped and removed from the vehicle.

Connecting Rods

Wash the connecting rods in cleaning solvent and dry with compressed air. Check for twisted or bent rods and inspect for nicks or cracks. Replace the connecting rods that are damaged.

Install the cap on the rod and torque to specification. Using an inside micrometer, measure the inside bore diameter perpendicular (90°) to the axis of rod and once again along the axis of the rod. If the two measurements are not within specification, have the rod resized by a competent machine shop.

It is normal for the inside diameter of the rod to be slightly larger when measured perpendicular (90°) to the axis of the rod.

Crankshaft and Main Bearings

See Figures 11 and 12

Click image to see an enlarged view

Fig. Fig. 11: Checking the bearing journal outside diameter with a micrometer



Click image to see an enlarged view

Fig. Fig. 12: After the cap is removed, use the scale supplied with the gauge to check clearances

Measure the bearing journals using a micrometer, to determine diameter, journal taper and eccentricity. If crankshaft journals appear defective, or do not meet tolerances, the crankshaft will require grinding.

Assemble the case halves with the bearings installed and torque to specification. Using a telescope gauge and micrometer, measure bearing I.D. parallel to piston axis and at 30° on each side of piston axis. Subtract journal O.D. from bearing I.D. to determine oil clearance.

An alternate method is to measure the oil clearance on each crankshaft bearing by means of Plastigage®.

Wipe off oil, dust, etc. on the surfaces to be measured. Install the bearings in the crankcase and set the crankshaft in position. Cut the Plastigage® to the bearing width and place it on the journal parallel with the crankshaft axis. Be careful not to put it on the oil hole or groove. Bring together the crankcase halves and tighten the bolts and nut to the specified torque.


WARNING
During the work, the crankshaft must not be turned, nor the crankcase inverted.

Remove all the bolts and nut and separate the crankcase. Measure the Plastigage® width with the scale printed on the Plastigage® case. If the measurement is not within the specification, replace the defective bearing with an undersize one, and replace or recondition the crankshaft as necessary.

CHECKING RING END-GAP



See Figure 13

Click image to see an enlarged view

Fig. Fig. 13: Checking the piston ring end-gap with a feeler gauge

The piston ring end-gap should be checked while the rings are removed from the pistons. Incorrect end-gap indicates that the wrong size rings are being used; ring breakage could result if not corrected.

  1. Compress the new piston ring into a cylinder (one at a time).
  2.  
  3. Squirt some clean oil into the cylinder so that the ring and the top 2 in. (51mm) of the cylinder wall are coated.
  4.  
  5. Using an inverted piston, push the ring approximately 1 in. (25mm) below the top of the cylinder.
  6.  
  7. Using a feeler gauge, measure the ring gap and compare it to specification. Carefully remove the ring from the cylinder.
  8.  
  9. If the gap is smaller than specification, file the ring ends using an appropriate piston ring file. If the gap is greater, the cylinder bore must be honed to the next oversize or the piston rings are incorrect.
  10.  

CONNECTING ROD BEARING REPLACEMENT



Replacement bearings are available in standard size and undersize (for reground crankshafts). Connecting rod-to-crankshaft bearing clearance is checked using Plastigage® at either the top or the bottom of each crank journal. The Plastigage® has a range of 0.001-0.003 in. (0.0254-0.0762mm).

  1. Remove the rod cap with the bearing shell. Completely clean the bearing shell and the crank journal, blow any oil from the oil hole in the crankshaft; place the Plastigage® lengthwise along the bottom center of the lower bearing shell, then install the cap with the shell and torque the bolt or nuts to specification. DO NOT turn the crankshaft with the Plastigage® on the bearing.
  2.  
  3. Remove the bearing cap with the shell. The flattened Plastigage® will be found sticking to either the bearing shell or the crank journal. DO NOT remove it yet.
  4.  
  5. Use the scale printed on the Plastigage® envelope to measure the flattened material at its widest point. The number within the scale which most closely corresponds to the width of the Plastigage® indicates the bearing clearance in thousandths of an inch and millimeters.
  6.  
  7. Check the specifications chart in this section for the desired clearance. It is advisable to install a new bearing if the clearance exceeds specification; however, if the bearing is in good condition and is not being checked because of bearing noise, bearing replacement is not necessary.
  8.  
  9. If you are installing new bearings, try a standard size, then each undersize in order until one is found that is within the specified limits when checked for clearance with Plastigage®; each undersize shell has its size stamped on it.
  10.  
  11. When the proper size shell is found, clean off the Plastigage®, oil the bearing thoroughly, reinstall the cap with its shell and torque the rod bolt nuts to specifications.
  12.  

With the proper bearing selected and the nuts torqued, it should be possible to move the connecting rod back and forth freely on the crank journal as allowed by the specified connecting rod end clearance. If the rod cannot be moved, either the rod bearing is too far undersize or the rod is misaligned.

INSTALLATION



During installation, lubricate all moving components with oil. When the engine is first started, oil pressure will take time to build. The oil used to lubricate the engine during the first few seconds of operation must be placed on moving surfaces during installation.

Except 1.2L Engine

See Figures 14 and 15

Click image to see an enlarged view

Fig. Fig. 14: Piston ring end-gap alignment-except 1.2L engine



Click image to see an enlarged view

Fig. Fig. 15: Installing the piston into the bore using a ring compressor and a handle of a hammer

  1. Install the connecting rods onto the crankshaft and tighten the cap bolts to specification.
  2.  
  3. Install new crankshaft bearings into the cylinder blocks and the crankshaft assembly into the left-hand cylinder block.
  4.  
  5. Using Three-bond® 1215 sealant or equivalent, apply it along the mating surface of the cylinder block. Install the right-hand cylinder block onto the assembly. Tighten the cylinder block bolts to 17-20 ft. lbs. (23-26 Nm) for the 8mm bolts and 29-35 ft. lbs. (39-47 Nm) for the 10mm bolts.
  6.  
  7. Using a dial indicator, check the crankshaft thrust clearance. If not within specification, the crankshaft thrust surface must be corrected.
  8.  
  9. Using a piston ring expander tool, install new rings onto the pistons. Position the piston rings gaps as shown in the illustration.
  10.  
  11. Using engine oil, lubricate the piston assembly. Turn the crankshaft so that the No. 1 and No. 2 connecting rods are positioned at BDC.
  12.  
  13. Using the Piston Ring Compression tool No. 398744300 or equivalent, compress the piston rings into the piston assembly. Then, using a hammer handle, drive the piston assembly into the cylinder block.
  14.  
  15. Using the Piston Pin Guide tool No. 399284300 or equivalent, install the piston pin and the circlip through the service hole.
  16.  
  17. Repeat this procedure to install the remaining pistons.
  18.  
  19. Apply fluid packing to the piston pin plugs and tighten to 46-56 ft. lbs. (62-76 Nm).
  20.  
  21. Install the front and rear oil seals using a driver.
  22.  
  23. Install the oil strainer and oil pan.
  24.  
  25. Install the cylinder heads and torque to specification.
  26.  
  27. Install the timing belt, belt covers and related components.
  28.  
  29. Install the intake manifold and tighten to specification.
  30.  
  31. Join the engine and transaxle. Install the engine in the vehicle.
  32.  

1.2L Engine

See Figures 15 and 16

Click image to see an enlarged view

Fig. Fig. 16: Piston ring end-gap alignment-1.2L engine

  1. Install the crankshaft lower bearings and place the crankshaft into the cylinder block after lubricating it with oil. Install the crankshaft so that the chain connecting the balance shaft and oil pump sprocket is as shown in the illustration.
  2.  
  3. Install the upper bearings in the main caps and install the caps on the engine. Tighten the main bearing cap bolts/nuts to specification.
  4.  
  5. Check the crankshaft end-play. If not within specification, the thrust surface of the crankshaft must be corrected prior to assembly.
  6.  
  7. Install the rod bearing on the connecting rod. Install the piston rings on the piston using a ring expander.
  8.  
  9. Position the piston rings as shown in the illustration and install the ring compressor. Install rubber boots over the rod bolts.
  10.  
  11. Install the piston into its cylinder with the Fuji Industries mark facing the front of the engine and tap into place using a wooden hammer handle. Remove the rubber boot, install the rod cap so that the protruding ridge faces the front of the engine and tighten the bolt/nut to specification.
  12.  
  13. Install the oil strainer assembly and oil pan.
  14.  
  15. Install the cylinder heads.
  16.  
  17. Install the timing belt, belt covers and related components. Adjust the valve lash.
  18.  
  19. Install the engine in the vehicle.
  20.  

BREAK-IN PROCEDURE



1 / 2 hour, and retorque the cylinder head bolts. Road test the car, and check again for leaks.

Start the engine, and allow it to run at low speed for a few minutes, while checking for leaks. Stop the engine, check the oil level, and fill as necessary. Restart the engine, and fill the cooling system to capacity. Check the point dwell angle and adjust the ignition timing and the valves. Run the engine at low to medium speed (800-2,500 rpm) for approximately

Follow the manufacturer's recommended engine break-in procedure and maintenance schedule for new engines.

 
label.common.footer.alt.autozoneLogo