Mazda Trucks 1972-1986 Repair Guide

Engine Disassembly

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See Figures 1 through 9

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Fig. Fig. 1: Removing the intake manifold



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Fig. Fig. 2: Removing the distributor



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Fig. Fig. 3: Removing the water pump



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Fig. Fig. 4: Removing the oil pump pick-up screen



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Fig. Fig. 5: Removing the eccentric shaft pulley



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Fig. Fig. 6: Removing the drive chain and sprockets



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Fig. Fig. 7: Loosen the tension bolts in the order shown



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Fig. Fig. 8: Removing the rear housing



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Fig. Fig. 9: Removing the seals from the rotor

Because of the design of the rotary engine, it is not practical to attempt component removal and installation. It is best to disassemble and assemble the entire engine, or, go as far as necessary with the disassembly procedure.

  1. Mount the engine on a stand.
  2.  
  3. Remove the oil hose support bracket from the front housing.
  4.  
  5. Disconnect the vacuum hoses, air hoses and remove the decel valve.
  6.  
  7. Remove the air pump and drive belt. Remove the air pump adjusting bar.
  8.  
  9. Remove the alternator and drive belt.
  10.  
  11. Disconnect the metering oil pump connecting rod, oil tubes and vacuum sensing tube from the carburetor.
  12.  
  13. Remove the carburetor and intake manifold as an assembly.
  14.  
  15. Remove the intake manifold gasket and two rubber rings. Discard them.
  16.  
  17. Remove the thermal reactor and gaskets.
  18.  
  19. Remove the spark plugs wires and distributor high tension leads, and remove the distributor from the front cover.
  20.  
  21. Remove the water pump and gasket.
  22.  
  23. Invert the engine on the stand.
  24.  
  25. Remove the oil pan and gasket.
  26.  
  27. Remove the oil pump screen and gasket.
  28.  
  29. Identify the front and rear rotor housing with a felt tip pen. These are common parts and must be identified to be reassembled in their respective locations.
  30.  
  31. Turn the engine on the stand so that the top of the engine is up.
  32.  
  33. Remove the engine mounting bracket from the front cover.
  34.  
  35. Hold the flywheel with a flywheel holder and remove the eccentric shaft pulley.
  36.  
  37. Turn the engine on a stand so that the front end of the engine is up.
  38.  
  39. Remove the front cover and gasket.
  40.  
  41. Remove the O-ring from the oil passage on the front housing.
  42.  
  43. Remove the oil slinger and distributor drive gear from the shaft.
  44.  
  45. Unbolt and remove the chain adjuster.
  46.  
  47. Remove the locknut and washer from the oil pump driven sprocket.
  48.  
  49. Slide the oil pump drive sprocket and driven sprocket together with the drive chain off the eccentric shaft and oil pump simultaneously.
  50.  
  51. Remove the keys from the eccentric and oil pump shafts.
  52.  
  53. Slide the balance weight, thrust washer and needle bearing from the shaft.
  54.  
  55. Unbolt the bearing housing and slide the bearing housing, needle bearing, spacer and thrust plate off the shaft.
  56.  
  57. Turn the engine on the stand so that the top of the engine is up.
  58.  
  59. If equipped with a manual transmission, remove the clutch pressure plate and clutch disc. Loosen the pressure plate bolts evenly in small stages to prevent distortion and possible injury from the pressure plate flying off. Straighten the tab of the lockwasher and remove the flywheel nut. Remove the flywheel with a puller.
  60.  
  61. If equipped with an automatic transmission, remove the drive plate. Straighten the tab on the lockwasher and remove the counterweight nut, while holding the flywheel with a flywheel holder. Remove the counterweight using a puller.
  62.  
  63. Working at the rear of the engine, loosen the tension bolts in the sequence shown, and remove the tension bolts.
  64.  

Do not loosen the tension bolts one at a time. Loosen the bolts evenly in small stages to prevent distortion.

  1. Lift the rear housing off the shaft.
  2.  
  3. Remove any seals that are stuck to the rotor sliding surface of the rear housing and reinstall them in their original locations.
  4.  
  5. Remove all the corner seals, corner seal springs, side seal and side seal springs from the rear side of the rotor. Mazda has a special tray which holds all the seals and keeps them segregated to prevent mistakes during reassembly. Each seal groove is marked to prevent confusion.
  6.  
  7. Remove the two rubber seals and two O-rings from the rear rotor housing.
  8.  
  9. Remove the dowels from the rear rotor housing.
  10.  
  11. Lift the rear rotor housing away from the rear rotor, being very careful not to drop the apex seals on the rear rotor.
  12.  
  13. Remove each apex seal, side piece and spring from the rear rotor and segregate them.
  14.  
  15. Remove the rear rotor from the eccentric shaft and place it upside down on a clean rag.
  16.  
  17. Remove each seal and spring from the other side of the rotor and segregate these.
  18.  
  19. If some of the seals fall from the rotor, be careful not to change the original position of each seal.
  20.  
  21. Identify the rear rotor with a felt tip pen.
  22.  
  23. Remove the oil seals and the springs. Do not exert heavy pressure at only one place on the seal since it could be deformed. Replace the O-rings in the oil seal when the engine is overhauled.
  24.  
  25. Hold the intermediate housing down and remove the dowels from it.
  26.  
  27. Lift off the intermediate housing being careful not to damage the eccentric shaft. It should be removed by sliding it beyond the rear rotor journal on the eccentric shaft while holding the intermediate housing up and, at the same time, pushing the eccentric shaft up.
  28.  
  29. Lift out the eccentric shaft.
  30.  
  31. Repeat the above procedures to remove the front rotor housing and front rotor.
  32.  

INSPECTION Front Housing



See Figures 10 through 18

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Fig. Fig. 10: Check the housing for warpage along these lines with a straightedge and feeler blade



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Fig. Fig. 11: Indication of a normal wear pattern



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Fig. Fig. 12: Measuring stepped wear across the middle of the housing



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Fig. Fig. 13: Measuring the oil seal's stepped wear



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Fig. Fig. 14: Checking the housing for wear with a dial indicator



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Fig. Fig. 15: Checking the main bearing oil clearance



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Fig. Fig. 16: Removing the stationary gear



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Fig. Fig. 17: Installing the stationary gear in the rear housing



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Fig. Fig. 18: Checking the rotor housing width using a micrometer

  1. Check the housing for signs of gas or water leakage.
  2.  
  3. Remove the carbon deposits from the front housing with an extra fine emery cloth.
  4.  

If a carbon scraper must be used, be careful not to damage the mating surfaces of the housing.

  1. Remove any old sealer which is adhering to the housing using a brush or a cloth soaked in ketone.
  2.  
  3. Check for distortion by placing a straightedge on the surface of the housing. Measure the clearance between the straightedge and the housing with a feeler gauge. If the clearance is greater than 0.05mm (0.00197 in.) at any point, replace the housing.
  4.  
  5. Use a dial indicator to check for wear on the rotor contact surfaces of the housing. If the wear is greater than 0.10mm (0.00394 in.), replace the housing.
  6.  

The wear at either end of the minor axis is greater than at any other point on the housing. However, this is normal and should be no cause for concern.

Front Stationary Gear and Main Bearing

  1. Examine the teeth of the stationary gear for wear or damage.
  2.  
  3. Be sure that the main bearing shows no signs of excessive wear, scoring or flaking.
  4.  
  5. Check the main bearing-to-eccentric journal clearance by measuring the journal with a vernier caliper and the bearing with a pair of inside calipers. The clearance should be between 0.045-0.070mm (0.00177-0.00276 in.), and the wear limit is 0.010mm (0.000394 in.). Replace either the main bearing or the eccentric shaft if it is greater than this. If the main bearing is to be replaced, proceed as detailed in the following section.
  6.  

Main Bearing Replacement

  1. Unfasten the securing bolts, if used. Drive the stationary gear and main bearing assembly out of the housing with a brass drift.
  2.  
  3. Press the main bearing out of the stationary gear.
  4.  
  5. Press a new main bearing into the stationary gear so that it is in the same position as the old bearing before it was removed.
  6.  
  7. Align the slot in the stationary gear flange with the dowel pin in the housing and press the gear into place. Install the securing bolts, if required.
  8.  

To aid in stationary gear and main bearing removal and installation, Mazda supplies a special tool, part number 49 0813 235.

Intermediate and Rear Housings

Inspection of the intermediate and rear housings is carried out in the same manner as detailed for the front housing above. Replacement of the rear main bearing and stationary gear (mounted on the rear housing) is given below.

Rear Stationary Gear and Main Bearing

Inspect the rear stationary gear and main bearing in a similar manner to the front. In addition, examine the O-ring which is located in the stationary gear, for signs of wear or damage. Replace the O-ring, if necessary. If required, replace the stationary gear in the following manner:

  1. Remove the rear stationary gear securing bolts.
  2.  
  3. Drive the stationary gear out of the rear housing with a brass drift.
  4.  
  5. Apply a light coating of grease on a new O-ring and fit it into the groove on the stationary gear.
  6.  
  7. Apply sealer to the flange of the stationary gear.
  8.  
  9. Install the stationary gear on the housing so that the slot on its flange aligns with the pin on the rear housing.
  10.  


WARNING
Use care not to damage the O-ring during installation.

  1. Tighten the stationary gear bolts evenly, and in several stages, to 15 ft. lbs.
  2.  

Rotor Housings

  1. Examine the inner margin of both housings for signs of gas or water leakage.
  2.  
  3. Wipe the inner surface of each housing with a clean cloth to remove the carbon deposits.
  4.  

If the carbon deposits are stubborn, soak the cloth in a solution made for carbon removal. Do not scrape or sand the chrome plated surfaces of the rotor chamber.

  1. Clean all of the rust deposits out of the cooling passages of each rotor housing.
  2.  
  3. Remove the old sealer with a cloth soaked in ketone.
  4.  
  5. Examine the chromium plate inner surfaces for scoring, flaking, or other signs of damage. If any are present, the housing must be replaced.
  6.  
  7. Check the rotor housing for distortion by placing a straightedge on the areas illustrated. If the distortion exceeds 0.04mm (0.00157 in.) have the housing refaced or replace it.
  8.  
  9. Measure the clearance between the straightedge and the housing with a feeler gauge. If the gap exceeds 0.05mm (0.00197 in.), replace the rotor housing.
  10.  
  11. Check the widths of both rotor housings, at a minimum of eight points near the trochoid surfaces of each housing, with a vernier caliper. If the difference between the maximum and minimum valves obtained is greater than 0.06mm (0.00236 in.), replace the housing. A housing in this conditions will be prone to gas and coolant leakage.
  12.  

Standard rotor housing width is 70mm (2.7559 in.).

Rotors

  1. Check the rotor for signs of blow-by around the side and corner seal areas.
  2.  
  3. The color of the carbon deposits on the rotor should be brown, just as in a piston engine.
  4.  

Usually the carbon on the leading side of the rotor is brown, while the carbon on the trailing side tends toward black, as viewed from the direction of rotation.

  1. Remove the carbon on the rotor with a scraper or extra fine emery paper. Use the scraper carefully when doing the seal grooves, so that no damage is done to them.
  2.  
  3. Wash the rotor in solvent and blow it dry with compressed air after removing the carbon.
  4.  
  5. Examine the internal gear for cracks or damaged teeth.
  6.  

If the internal gear is damaged, the rotor and gear must be replaced as a single assembly.

  1. With the oil seal removed, check the land protrusions by placing a straightedge over the lands. Measure the gap between the rotor surface and the straightedge with a feeler gauge. The standard specification is 0.10-0.20mm (0.00394-0.00787 in.); if it is less than this, the rotor must be replaced.
  2.  
  3. Check the gaps between the housing and the rotor on both sides:
    1. Measure the rotor width with a vernier caliper. The standard rotor width is 69.85mm (2.75 in.).
    2.  
    3. Compare the rotor width with the width of the rotor housing measured above. The standard rotor housing width is 70mm (2.7559 in.).
    4.  
    5. Replace the rotor if the difference between the two measurements is not within 0.13-0.17mm (0.0052-0.0067 in.).
    6.  

  4.  
  5. Check the rotor bearing for flaking, wearing, or scoring and proceed as indicated in the next section, if any of these are present.
  6.  

The rotors are classified into five lettered grades, according to their weight. A letter between A and E is stamped on the internal gear side of the rotor. If it becomes necessary to replace a rotor, use one marked with a C because this is the standard replacement rotor.

Rotor Bearing Replacement

Special service tools are required to replace a rotor bearing. Replacement is also a tricky procedure which, if done improperly, could result in serious damage to the rotor and could even make replacement of the entire rotor necessary. Therefore, this service procedure is best left to an authorized service facility or a qualified machine shop.

Oil Seal Inspection See Figure 19

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Fig. Fig. 19: Checking the oil seals for proper height and lip width

Inspect the oil seal while it is mounted in the rotor.

  1. Examine the oil seal for signs of wear or damage.
  2.  
  3. Measure the width of the oil seal lip. If it is greater than 0.8mm (0.0315 in.), replace the oil seal.
  4.  
  5. Measure the protrusion of the oil seal, it should be greater than 0.5mm (0.0197 in.). Replace the seal, as detailed below, if it is not.
  6.  

Oil Seal Replacement

Replace the rubber O-ring in the oil seal as a normal part of engine overhaul.

  1. Pry the seal out gently by inserting a screwdriver in the slots on the rotor. Do not remove the seal by prying it at only one point as seal deformation will result.
  2.  


CAUTION
Be careful not to deform the lip of the oil seal if it is to be reinstalled.

  1. Fit both of the oil seal springs into their respective grooves, so that their ends are facing upward and their gaps are opposite each other on the rotor.
  2.  
  3. Insert a new rubber O-ring into each of the oil seals.
  4.  

Before installing the O-rings into the oil seals, fit each of the seals into its proper groove on the rotor. Check to see that all of the seals move smoothly and freely.

  1. Coat the oil seal groove and the oil seal with engine oil.
  2.  
  3. Gently press the oil seal into the groove with your fingers. Be careful not to distort the seal.
  4.  

Be sure that the white mark is on the bottom side of each seal when it is installed.

  1. Repeat the installation procedure for the oil seals on both sides of each rotor.
  2.  

Apex Seals See Figures 20 through 24

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Fig. Fig. 20: Checking the apex seal height



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Fig. Fig. 21: Measure the apex seal spring free height



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Fig. Fig. 22: Checking the gap between the apex seal and the groove



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Fig. Fig. 23: Checking apex seal warpage



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Fig. Fig. 24: Seal clearance measurement points


CAUTION
Although the apex seals are extremely durable when in service, they are easily broken when they are being handled. Be careful not to drop them.

  1. Remove the carbon deposits from the apex seals and their springs. Do not use emery cloth on the seals as it will damage their finish.
  2.  
  3. Wash the seals and the springs in cleaning solution.
  4.  
  5. Check the apex seals for cracks and other signs of wear or damage.
  6.  
  7. Test the seal springs for weakness.
  8.  
  9. Use a micrometer to check the seal height. Replace any seal if its height is less than 7mm (0.276mm).
  10.  
  11. With a feeler gauge, check the side clearance between the apex seal and the groove in the rotor. Insert the gauge until its tip contacts the bottom of the groove. If the gap is greater than 0.15mm (0.0059 in.), replace the seal.
  12.  
  13. Check the gap between the apex seals and the side housing, in the following manner:
    1. Use a vernier caliper to measure the length of each apex seal.
    2.  
    3. Compare this measurement to the minimum figure obtained when rotor housing width was being measured.
    4.  
    5. If the difference is more than 0.3mm (0.0118 in.), replace the seal. The standard gap is 0.13-0.17mm (0.0052-0.0067 in.).
    6.  
    7. If, on the other hand, the seal is too long, sand the ends of the seal with emery cloth until the proper length is reached.
    8.  

  14.  


WARNING
Do not use the emery cloth on the faces of the seal!Side Seals

  1. Remove the carbon deposits from the side seals and their springs with a carbon scraper.
  2.  
  3. Check the protrusion of the side seals. It should be 0.5mm (0.0197 in.) or more.
  4.  
  5. Check the side seals for cracks or wear. Replace any of the seals found to be defective.
  6.  
  7. Check the clearance between the side seals and their grooves with a feeler gauge. Replace any side seals if they have a clearance of more than 0.10mm (0.00394 in.). The standard clearance is 0.05-0.08mm (0.00197-0.00315 in.).
  8.  
  9. Check the clearance between the side seals and the corner seals with both of them installed in the rotor.
    1. Insert the gauge against the direction of the rotor's rotation.
    2.  
    3. Replace the side seal if the clearance is greater than 0.4mm (0.0157 in.).
    4.  

  10.  
  11. If the side seal is replaced, adjust the clearance between it and the corner seal as follows:
    1. File the side seal on its reverse side, in the same rotational direction of the rotor, along the outline made by the corner seal.
    2.  
    3. The clearance obtained should be 0.05-0.15mm (0.00197-0.0059 in.). If it exceeds this, the performance of the seals will deteriorate.
    4.  

  12.  


WARNING
There are four different types of side seals, depending upon their location. Do not mix the seals up and be sure to use the proper type of seal for replacement!Corner Seals

See Figure 25



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Fig. Fig. 25: Checking the corner seal groove

  1. Clean the carbon deposits from the corner seals.
  2.  
  3. Examine each of the seals for wear or damage.
  4.  
  5. Check the corner seal protrusion from the rotor surface. It should be free to move under the finger pressure and protrude 0.5mm (0.0197 in.) or more.
  6.  
  7. Measure the clearance between the corner seal and its groove. The clearance should be 0.045-0.048mm (0.00177-0.001889 in.). The wear limit of the gap is 0.08mm (0.00315 in.).
  8.  
  9. If the wear is between the corner seal and the groove is uneven, check the clearance with the special bar limit gauge (Mazda part number 49 0839 165). The gauge has a go end and a no go end. Use the gauge in the following manner:
    1. If neither end of the gauge goes into the groove, the clearance is within specifications.
    2.  
    3. If the go end of the gauge fits into the groove, but the no go end does not, replace the corner seal with one that is 0.03mm oversize.
    4.  
    5. If both ends of the gauge fit into the groove, then the groove must be reamed out as detailed below. Replace the corner seal with one which is 0.0072 in. oversize, after completing reaming.
    6.  

  10.  

Take the measurement of the groove in the direction of maximum wear, i.e., that of rotation.

Corner Seal Groove Reaming See Figure 26

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Fig. Fig. 26: Reaming the corner seal groove for an oversized corner seal

This procedure requires the use of special tools; if attempted without them, damage to the rotor could result.

  1. Carefully remove all of the deposits which remain in the groove.
  2.  
  3. Fit the jig (Mazda part number 49 2113 030) over the rotor. Tighten its adjusting bar, being careful not to damage the rotor bearing or the apex seal grooves.
  4.  
  5. Use the corner seal groove reamer (Mazda part number 49 0839 170) to ream the groove.
  6.  
  7. Rotate the reamer at least 20 times while applying engine oil as a coolant.
  8.  

If engine oil is not used, it will be impossible to obtain the proper groove surfacing.

  1. Remove the reamer and the jig.
  2.  
  3. Repeat Steps 1-5 for each of the corner seal grooves.
  4.  
  5. Clean the rotor completely and check it for any signs of damage.
  6.  
  7. Fit a 0.2mm oversize corner seal into the groove and check its clearance. Clearance should be 0.02-0.05mm (0.000787-0.00197 in.).
  8.  

Seal Springs

Check the seal springs for damage or weakness. Be exceptionally careful when checking the spring areas which contact either the rotor or the seal.

Eccentric Shaft See Figures 27 through 31

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Fig. Fig. 27: Measuring the eccentric shaft rotor journal diameter



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Fig. Fig. 28: View of the eccentric shaftarrow points to oil jet plug; remove it to check the spring and ball



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Fig. Fig. 29: Using a dial indicator to check eccentric shaft run-out



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Fig. Fig. 30: Blind plug location



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Fig. Fig. 31: Exploded view of the roller bearing and oil jet

  1. Wash the eccentric shaft in solvent and blow its oil passages dry with compressed air.
  2.  
  3. Check the shaft for wear, cracks, or other signs of damage. Make sure that none of the oil passages are clogged.
  4.  
  5. Measure the shaft journals with a vernier caliper. The standard specifications are:

    Main journals43mm (1.6929 in.)
     
    Rotor journals74mm (2.9134 in.)
     

  6.  

Replace the shaft if any of its journals show excessive wear.

  1. Check eccentric shaft run-out by placing the shaft on V-blocks and using a dial indicator as shown. Rotate the shaft slowly and note the dial indicator reading. If run-out is more than 0.06mm (0.00236 in.), replace the eccentric shaft.
  2.  
  3. Check the blind plug at the end of the shaft. If it is loose or leaking, remove it with an allen wrench and replace the O-ring.
  4.  
  5. Check the operation of the needle roller bearing for smoothness by inserting a mainshaft into the bearing and rotating it. Examine the bearing for signs of wear or damage.
  6.  
  7. Replace the bearing if necessary, with the special tool, Mazda part number 49 0823 073 and 49 0823 072.
  8.  

 
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