Mazda 323/626/929/GLC/MX-6/RX-7 1978-1989

Crankshaft and Main Bearings

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REMOVAL & INSTALLATION



See Figures 1, 2, 3, 4, 5, 6, 7 and 8

  1. Remove the engine from the car, as described earlier in this section.
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  3. Remove the front crankshaft pulley and the flywheel. (The flywheel removal procedure is found later in this section.)
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  5. Invert the engine on a suitable workstand, then remove the oil pan and rear main oil seal. If so equipped, also remove the rear cover.
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  7. Remove the front cover, timing chain/belt, and oil pump.
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  9. Mark all main and connecting rod bearing caps for location.
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Fig. Fig. 1: Unfasten the main bearing cap bolts ...



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Fig. Fig. 2: ... then remove each cap and bearing



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Fig. Fig. 3: Measure the length of each main bearing bolt before installation, and replace any that are out-of-range-3.0L engine

You might want to check crankshaft end-play and main bearing oil clearances (as described under the installation procedure) at this time, before removing the bearing caps and crankshaft. In any event, be sure to check them when the crankshaft is reinstalled or replaced.

  1. Unfasten the cap bolts, then remove the caps and bearings. (On engines in which the rear bearing cap also retains oil seals, you'll have to use a puller.) Keep all bearings and caps in position (and in order).
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  3. If the engine uses a manual transmission and has reached the normal time for overhaul, remove the pilot bearing (which supports the transmission input shaft) from the rear of the crankshaft with an appropriate puller.
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  5. Carefully lift the crankshaft from the cylinder block.
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  7. Clean and inspect the crankshaft for wear and run-out, and the bearings for wear, as described below. Repair or replace parts as necessary.
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To install:
  1. Make sure all parts are clean and dry. Position the bearings in the engine block and bearing caps, then carefully lower the crankshaft into position. Install Plastigage® inserts on the main journals and crankpins, away from the oil holes. Assemble and torque the bearing and connecting rod caps (dry and in numbered order) with the arrows pointing forward. Be careful not to rotate the shaft. On the 3.0L engine, the main bearing cap bolts should be torqued in proper sequence to 14 ft. lbs. (20 Nm), then an additional 90 degrees and another 45 degrees after that. Also on the 3.0L engine, the connecting rod cap nuts should be torqued in proper sequence to 22 ft. lbs. (29 Nm), and then an additional 90 degrees. Paint reference marks on each bolt to assist with the angular torque. Remove the caps and check the bearing clearances by reading the width of the mark left by the insert in each case. Even if the crankshaft and bearings have passed their previous inspections, the crankshaft must be ground and undersize bearings installed, if clearances are improper.
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  3. Once the measured bearing clearances are correct, clean the insert marks off, thoroughly lubricate all wear surfaces with engine oil (bearing insert backs must remain dry), then reassemble and retorque all caps and cap bolts. On all GLC and 1979-82 2.0L engines, insert new side seals in the rear main cap grooves with their holes facing forward and backward, not side-to-side. On the 3.0L engine, measure the length of each main bearing bolt prior to final installation. The bolts are acceptable only if they are 3.35-3.37 in. (85.0-85.5mm). If any bolt length differs from this specification, replace that bolt.
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  5. Mount a dial indicator on the block with the pin resting against the end of the crankshaft. Push the shaft as far as it will go away from the indicator, then zero the indicator. Now, pull the crankshaft all the way toward the indicator and read the end-play. If excessive, adjust it with oversize thrust bearings (washers) or, in the case of 2.2L and 1983-87 2.0L engines, a standard undersize center bearing, including appropriate grinding of the center journal. The end-play check should be done in conjunction with a check of connecting rod side clearance, as previously described. Thrust bearings must be installed with the groove outward (toward the crankshaft thrust surface).
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Fig. Fig. 4: Main bearing cap bolt torque sequence-3.0L engine



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Fig. Fig. 5: Use a torque wrench to properly torque the cap bolts



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Fig. Fig. 6: Insert new side seals in the rear main cap grooves with their holes facing forward and backward-GLC and 1979-82 626 engines



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Fig. Fig. 7: Mount a dial gauge against the end of the crankshaft to measure end-play



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Fig. Fig. 8: Carefully pry the shaft back and forth while reading the dial gauge

  1. If applicable, tap the pilot bearing into the rear of the crankshaft using a piece of pipe the diameter of the outer bearing race. Be careful to apply pressure to the outer race only.
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  3. Install the rear main seal/cover, oil pump and oil pan, as described earlier in this section.
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  5. Install the timing chain/belt, front cover, etc. by referring to the appropriate procedures earlier in this section.
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CLEANING AND INSPECTION



See Figures 9, 10, 11, 12, 13, 14 and 15

  1. Inspect the crankshaft for any signs of scoring or cracks and for clogged oil passages. Also, inspect for signs of discoloration which indicate overheating has occurred. Clogged oil passages must be cleaned in a solvent tank or with solvent and brushes (steam cleaning is not a suitable alternative). After the crankshaft is removed from the solvent, it must be flushed with fresh water, dried completely and coated with a generous film of clean engine oil. Inspect the crankshaft for scoring and minor scratching. This type of surface damage means that the crankshaft should be machined and undersize bearings installed; cracks may indicate the shaft must be replaced. Consult a competent machine shop in the case of the latter two problems. If work on the crankshaft is suspended for any length of time, fabricate a set of wood V-blocks to support the crankshaft.
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Fig. Fig. 9: With the crankshaft mounted in V-blocks, run-out can be checked using a dial gauge



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Fig. Fig. 10: If you prefer, run-out can instead be checked with the crankshaft mounted in the engine block



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Fig. Fig. 11: Position the dial indicator against the crankshaft's center main bearing journal

  1. Support the crankshaft in metal V-blocks, mount a dial indicator on the center journal, and zero it. Now, rotate the crankshaft 360 degrees to check for runout. The reading of the indicator should not exceed 0.0012 in. (0.03mm) on the 1.5L, 1.6L and 2.2L engines, or 0.0016 in. (0.04mm) on the 3.0L engine. If it does, the crankshaft must be replaced.
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If V-blocks are not available, the crankshaft run-out may instead be checked with the shaft installed in the engine block.

  1. Using a caliper, check the diameters of all main journals and crankpins, in four places, as shown. If they are worn past the limit, they must be ground and undersize bearings installed. In addition, on 1981-89 engines, determine the elliptical measurement for each bearing journal by subtracting the smallest reading from the largest. This elliptical limit for both the main and rod journals is 0.0020 in. (0.05mm). If the wear is elliptical beyond the limit, the crankshaft must be machined and undersize bearings installed, regardless of the total wear.
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If the crankshaft is machined, the rolled fillet area must not be removed. Make sure the machinist is aware of the fillet "R" dimension of 0.12 in. (3mm) for gasoline engine crankshafts, or 0.102-0.118 in. (2.6-3.0mm) for diesels.

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Fig. Fig. 12: Turn the crankshaft slowly by hand while checking the dial gauge for run-out



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Fig. Fig. 13: Measure all the crankshaft wear surface diameters



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Fig. Fig. 14: Each wear surface should be measured at four places, including two perpendicular readings



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Fig. Fig. 15: If the crankshaft must be machined, do not disturb the rolled fillet areas

In addition, on 1983-87 2.0L engines, you must measure the front and rear oil seal sliding surface diameters. The rear seal surface must measure 3.5412-3.5434 in. (89.9-90.0mm). The front oil pump body assembly seal surface must measure 1.3371-1.3386 in. (33.96-34.00mm). Both must also be within the elliptical limit described above.

  1. Inspect the bearings for scoring, flaking, grooving, bluish color (due to heat), partial elimination of the overlay (appearance of a different color in certain areas), or a polished appearance. Replace if any such indications appear.
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COMPLETING THE REBUILDING PROCESS



Fill the oil pump with oil, to prevent cavitating (sucking air) on initial engine start up. Install the oil pump and the pickup tube on the engine. Seal the oil pan gasket as appropriate, then install the gasket and pan. Mount the flywheel and the crankshaft vibration damper or pulley on the crankshaft.

Always use new bolts when installing the flywheel. Inspect the clutch shaft pilot bushing in the crankshaft. If the bushing is excessively worn, remove it with an expanding puller and a slide hammer, then tap a new bushing into place.

Position the engine, cylinder head side up. Lubricate the valve lifters, and install them into their bores. Install the cylinder head assembly (or assemblies), and torque as specified. Install the rocker assembly (or assemblies) and cylinder head cover(s).

Install the intake and exhaust manifolds, the carburetor or fuel injection components, the distributor and spark plugs. Mount all accessories and install the engine in the car. Fill the radiator with coolant, and the crankcase with high quality engine oil.

BREAK-IN PROCEDURE



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 and adjust the ignition timing. Run the engine at low-to-medium speed (800-2,500 rpm) for approximately 1 / 2 hour, then retorque the cylinder head bolts. Road test the car, and check again for leaks.

Some gasket manufacturers recommend not retorquing the cylinder head(s) due to the composition of the head gasket. Follow the directions in the gasket set.

 
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