Valve Spring Caution For
                                             1995 Mazda 1.5L Z5 Engines

The AERA Technical Committee offers the following information regarding valve spring breakage and reuse for 1995 Mazda 1.5L Z5 engines. Some engines manufactured for the 1995 Protege model year may have inferior valve springs. Valve spring breakage has been reported on these engines, which prompted recall status from Mazda.

This breakage can cause engine chatter, damage to the engine pistons, and cause the engine to fail.

The wire rod used in the manufacture of the engine valve springs can develop small cracks causing breakage of the springs at any given moment.  It is AERA?s recommendation to replace all springs if the history is not known when doing a valve job for this engine.  

Replacement valve springs are available with Mazda part number Z50112125 for both intake and exhaust locations. 
 
                                                                         The AERA Technical Committee

                                               Crankshaft Thrust Wear For
                                            1999-2000 Mazda 1.6 & 1.8L Engines

The AERA Technical Committee offers the following information regarding excessive crankshaft thrust wear on 1999-2000 1.6 & 1.8L Mazda engines. This wear is usually accompanied by a rattling noise that worsens with time. 
 
APPLICABLE MODEL VEHICLES AFFECTED.
All 1999 Protege (1.6L) with VIN lower than JM1 BJ222* X0 140057
All 1999-2000 Miata with VIN lower than JM1 NB353* Y0 155947. 

DESCRIPTION:
A rattling noise may be heard from the engine when depressing the clutch or when revving the engine in neutral. In extreme cases, customers may experience noise at all times. This noise is the result of an improperly machined number 4 main cap of the cylinder block, which may result in premature wear of the thrust bearing.

If end play is .012 (.3 mm) or more on the above engines, the blocks should be inspected for the above condition. AERA members report block salvage machining operations can be done to re-establish proper main bearing bore dimensions.

                                                                        The AERA Technical Committee

     Oversize Crankshaft Thrust Washers On
	   1995-98 Mazda 1.5L Z5 Engines 


The AERA Technical Committee offers the following 
information on oversize crankshaft thrust washers for 
1995-98 Mazda 1.5L Z5 engines. This DOHC engine is 
used in the manufacturer?s Protege vehicles. Mazda 
offers four different size thrust washers, ranging 
from standard thickness to a .030 (.75 mm) oversize 
for this engine. 

This offering is somewhat uncharacteristic of 
automotive manufacturers and it allows for additional 
salvage operations of the crankshaft for engine 
rebuilders. Refer to the chart below to determine the 
washers required to obtain a crankshaft end play of 
.0032-.0111 (.080-.282 mm).

Part Number     Size    Crankshaft Thrust Width

B6Y1-11-SJO     Std.    .948-.950" (24.07-24.12 mm)     
B6Y1-11-SKO     .010"   .957-.959" (24.32-24.37 mm)
B6Y1-11-SKX     .020"   .967-.969" (24.57-24.62 mm)
B6Y1-11-SKY     .030"   .977-.979" (24.82-24.87 mm)     

AERA is currently unaware of an aftermarket supplier 
of these oversize thickness thrust washers. 

			  The AERA Technical Committee

May 1998 - TB  1573

##END##

                  Timing Chain Installation On
                   1979-85 Mazda 2.0L Engines


Correct installation of the timing chain on 1979-85 Mazda 2.0L
engines is critical to achieve the proper valve timing.

Rather than aligning the camshaft and crankshaft gears with marks
on the cylinder head or block, this engine uses marked plates on
the timing chain to set valve timing.  
Start the timing process by rotating the crankshaft and camshaft
sprockets until the keyways are facing straight up (12 o'clock). 
This should face the camshaft sprocket timing mark at 3 o'clock
and the crankshaft sprocket timing mark at approximately 5
o'clock looking at the front of the engine.

Locate the three marked links on the timing chain.  Two links
should be positioned at the crankshaft sprocket so that the
timing mark is between the links (Figure 1).  Position the chain
and camshaft sprocket so that the mark is in the middle of the
other marked link (Figure 2).  There should be 20 unmarked plates
between the two positions.

Be careful, some timing chains do not use marked plates to
indicate the correct timing positions for the camshaft and
crankshaft.  Use the old chain as a guide to make your own marks
on the new chain. 
 
                                     The AERA Technical Committee


August 1991 - TB 796

##END##

                                                  Valve Train Noise On
                                             1993-94 Mazda 2.0L Engines

The AERA Technical Committee offers the following information regarding a valve train noise on 1993-94 Mazda 2.0L engines. This noise can be associated with the Hydraulic Lash Adjusters (HLA).

This noise appears after the engine has been run at idle for a long period of time. The noise appears because air is entering the oil gallery. To prevent this condition from happening, Mazda had redesigned the oil pump plunger as shown in Figure 1.  

HLA noise will appear at the top of the engine and is several times faster than that of the engine speed. Verify the complaint by running the engine at idle for a period of time not letting the vehicle overheat. If the HLA noise is present, replacement of the oil pump plunger is required. 

To replace the oil pump plunger, remove the snap ring at the bottom of the pump as shown in Figure 1. Remove spring seat, pressure spring and the plunger. Replace the old plunger with the new plunger, Part #JF01 14 115. Reassemble the bottom of the oil pump in the reverse procedure of disassembly

NOTE: Follow instructions in the service manual for disassembly and assembly of the engine to get access to the oil pump for replacement of the plunger.

                                                                        The AERA Technical Committee

                                          Coolant In The Oil On
                                     Mazda 1.5 & 1.6L Engines

AERA member machine shops should carefully inspect the cylinder head when resolving engine oil contamination complaints.

The cylinder head carries two cup type freeze plugs on the valve spring side of the cylinder head.  Leaking freeze plugs will accumulate a black residue during operations.  Pressure testing the cylinder head confirms that the plug or plugs were leaking.  

Successful repairs include replacement of the plug or peening the metal surrounding the plug over it.  Be sure to re-pressure test the cylinder head after repairs are completed.

                                                                              The AERA Technical Committee

                                               Oil Consumption On
                                    1989-94 Mazda 3.0L VIN JE Engines

The AERA Technical Committee offers the following information on oil consumption on 1989-94 Mazda 3.0L VIN JE engines. The area of concern causing this oil consumption is the cylinder head. At this time, only the single 
overhead cam (SOHC) heads have been affected. It appears this cylinder head is prone to cracking on the valve spring side of the head as mentioned in AERA Technical Bulletin TB-1260.

In at least some of the instances reported a dissimilar crack as described in TB 1260 has been observed. These cracks have allowed oil to enter the combustion process around either valve guide. These cracks create a passage 
for hot engine oil to seep through the openings or voids created. Engine oil collects in this area of the head, allowing ample amounts of oil to pass. There have been reports of one quart of oil consumed in 50 miles driven.

The extent of these cracks in most instances has been too excessive to warrant successful welding repairs as some have been reported to be longer than 6 inches. In other instances where the cracks have not been so severe but 
leakage was detected, welding has provided a successful repair.

                                                                            The AERA Technical Committee

                                                   Engine Over Cooling 
                                   On 1994-97 Mazda 2.3L VIN A Engines

The AERA Technical Committee offers the following information on engine over cooling on 1994-97 Mazda 2.3L VIN A engines. Some customers have complained there is insufficient heat coming from the heater in the cab of the vehicle.

One cause of this type of condition may be a casting slag from the cylinder head that has become lodged in the thermostat housing. When this occurs, the 
thermostat is unable to close completely. That opening allows the engine to over cool or never warm up to the correct operating temperature. To repair this problem, flush the entire cooling system (engine and radiator) to remove any slag that could be left in the engine.

To cure this problem at the factory, Mazda revised the cylinder head casting process during the 1997 model year. 

                                                                The AERA Technical Committee

                                           Valve Spring Identification On
                                              Mazda 1.6L DOHC Engines

Mazda uses a different valve spring for the intake and the exhaust valves on their 1.6L DOHC engines.  The difference is often not noted until after the cylinder head components have been cleaned.  This engine uses a rectangular spring design for intake and a common round design for exhaust valves.   

The valve spring specifications are also different for each of the springs.  Refer to the chart below to identify and test the valve springs for reuse.

Description              Intake (Rectangular)   Exhaust (Round) 

Valve Spring                   1.890              1.902
  Free Length
Test Pressure                49-55 lbs.           40-44 lbs.
                                     @ 1.555             @ 1.555
Installed Spring               1.555               1.555
  Height

Both springs use the same retainer and keepers.  Remember to replace worn or defective keepers in pairs.

                                                                          The AERA Technical Committee

                                 Main Bearing Installation Caution On
                                    1983-91 2.0 & 2.2L Mazda Engines

AERA members report occasional difficulties when installing main bearings on Mazda 2.0 & 2.2L engines used in automotive and industrial applications.  The problem arises when a  technician attempts to install the lower bearing shell into the main bearing cap.  

Normally the bearing will snap into place, so that the bearing tang is fully seated into the cap's receiver groove.  However it appears that some main bearing caps were inadvertently manufactured with an insufficient groove length.  This will not allow the bearing tang to fully seat into the cap and may cause the crankshaft to lock up when the main bearing caps are torqued to specification.

In this situation, you may be tempted to simply replace the main bearing set.  Unfortunately,  the problem lies with the main bearing cap, not the main bearing itself.  Further, there has been no consistency with this problem,  which makes it very difficult to anticipate.  The bearing tang length of both OE and aftermarket bearings measure .137-.138 (3.480-3.505mm).  The bearing tang requires .005-.008(.127-.203mm) end clearance for proper installation.

If this problem occurs, consider these two solutions: increase the length of the receiver groove in the cap, or decrease the length of the bearing tang.

The preferred method is to remove metal from the main bearing cap.  This may be accomplished by the use of a hand grinder and a small stone or disc.  Some shops have also made effective repairs with a small hand file.

                                                                               The AERA Technical Committee