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Toyota 4runner Engine Information

The following technical bulletins were published by AERA.


                                       Coolant In The Oil On
                                  Toyota 20R & 22R Engines

AERA members have reported instances of engine coolant mixing with the engine lubricating oil supply.

In some of these cases, pressure testing the cylinder block and head has not identified the source of the leak.  However, close inspection of the aluminum front cover revealed an area where the timing chain wore through into a water passage.  

In this engine the water pump is mounted to the front cover.  When the timing chain stretches and the automatic tensioner is no longer able to take up the slack, the loose chain can slap against the front cover.  Continuous contact will eventually wear a hole into the front cover, introducing engine coolant into the

                                                                      The AERA Technical Committee


                         Revised PCV Valve On
                   1984-87 Toyota 2.2L 4YEC Engines

The AERA Technical Committee offers the following information
concerning a revised PCV (Positive Crankcase Ventilation) valve on
1984-87 Toyota 2.2L 4YEC engines. The purpose of this revised
assembly is to improve the control of the PCV system in colder
ambient temperatures.

This revised system involves installing a new valve and hose
assembly as shown below. Installing the revised components seals and
meters the air flow through the system in all ambient temperatures.
If the PCV system is not completely sealed, it becomes ineffective
and may result in undesirable oil consumption.

Engines built beginning with serial number 4Y-0058330 have the
revised components. Parts are available with Part #12204-15022 for
the valve and 12261-73021 for the hose assembly to update older

                                         The AERA Technical Committee

October 1996 - TB 1387



                                Revised Crankshaft Caution On
                               1994 Toyota 2.2L 5SFE Engines

The AERA Technical Committee advises members of a revised crankshaft design on 1994 Toyota 2.2L 5SFE engines. This design change prevents the interchanging of old and new designs. The modified area is the drive gear for the engine balance assembly.

To reduce cold engine noise at start-up, the number of teeth on the balance shaft drive gear was reduced from 66 to 44. The change occurred with engine serial #55537901, which was built in July of 1994.

The balance shaft assembly gears also changed at the same time to accommodate the revised crankshaft. The first design used 32 teeth on each gear and the second uses 22 teeth. Those assemblies are not interchangeable.

For additional information see AERA Technical Bulletin TB 1347

                                                                            The AERA Technical Committee


                                        Oil Pump And Camshaft Changes On
                                            1984-85 Toyota 5M-GE Engines

Toyota has announced modifications for its 5M-GE engines built in 1984 and 1985 to improve the lubrication performance of the engine's camshafts.  This dual overhead camshaft 6-cylinder engine has suffered a lack of adequate oil to the camshafts in the past.

Toyota engineers have increased the capacity of the oil pump to increase the oil supply to the top end. This change also necessitated a change in the shape of the oil pan to provide adequate clearance for the new oil pump.  This change began with engine #5M-3581713 in August, 1984.  If the original oil pump
#15100-43010 is replaced with the new oil pump #15100-43020, oil pan #12101-43040 must also be used.

The diameter of the oil jet in the camshaft was increased from .048 to .056.  This change occurred in production beginning in May, 1985, with engine #5M-3675931 (see Figure 1).  Toyota allows the replacement of camshafts in engines built prior to May, 1985 with the new camshaft without changing the oil pump and oil pan.  The oil pressure switch should also be changed to the late model
switch.  The original camshaft #13501-43010 has been replaced by #13502-43030.  The correct oil pressure switch for use with the late model camshaft is #83530-14050.

                                                                           The AERA Technical Committee


                                          Camshaft Timing On 
                         Toyota 1.6L DOHC 4AF and 4AFE Engines

Timing the camshafts on 1.6L DOHC Toyota engines can be a source of frustration.  This popular DOHC, 16 valve engine is used in Corollas and Celicas

The cause of the frustration is two sets of timing marks on each of the integral camshaft gears (Figure 1).  Each set of marks has a particular purpose.  One set is used to time the intake with the exhaust camshaft when they are mounted to the cylinder head.  The other set indicates the TDC (Top Dead Center) for both

Mount the camshafts to the cylinder head using the following steps:

1)   Install the exhaust camshaft and torque the bearing caps in sequence to 
      108 in.lbs. (Figure 2).
2)   Rotate the exhaust camshaft to position the knock pin slightly past 
      9 o'clock (Figure 3).
3)   Mount the intake camshaft, aligning the installation timing marks and torque 
      the bearing caps in sequence to 108 in.lbs.
4)   Rotate the camshafts to ensure alignment of the timing marks. 
5)   Finish by aligning the TDC timing marks (Figure 1). 

The cylinder head is ready for installation on the cylinder block.  Align the crankshaft and camshaft sprockets before positioning the timing belt (Figure 4).  Aligning the through hole in the camshaft sprocket with the mark on the camshaft
bearing cap is the only tricky part.

                                                                           The AERA Technical Committee


                                   Piston Pin Bushing Replacement On
                                          Toyota 2.8L (5MGE) Engines

The AERA Technical Committee has received reports of difficulties in the replacement of the piston pin bushings on the Toyota 2.8L (5MGE) engines.

The bushings that are provided by Toyota as well as most aftermarket manufacturers require only .0005 - .0015 of stock removal to finish the inside diameter to size.  If there are any irregularities in either the bushing's outside diameter or the receiver housing bore of the connecting rod, the bushing will be
out of round.  This out of round condition will not allow proper finishing of the inside diameter.

AERA is aware of at least one manufacturer that has an additional amount of stock in their bushing for easier finishing to the correct dimension.

                                                                         The AERA Technical Committee


                                            Oil in The Cooling System On
                                         1988 Toyota 3.0L, 3VZE Engines

AERA members have reported engine oil entering the cooling system on 1988 Toyota 3.0L 3VZE engines.  The most common source of this oil contamination has been a crack in the oil gallery of the cylinder block.  Some cracks can be seen with the naked eye and extend up into the cylinder bore.

This area of the block contains a vertical oil galley that feeds both banks oil to provide lubrication to the cams and valve train.  A crack in this area will connect the pressurized engine oil to the coolant passages of the block.  Pressure testing the cylinder block will confirm the defect.

The manufacturing process of the 4 motor mount bolt hole block, was modified toward the end of the 1988 production year to strengthen this problem area.  Later blocks castings with 6 motor mount bolt holes have not exhibited this problem.

Note: Other possible causes of oil in the cooling system may be the engine oil cooler, if so equipped, or either cylinder head.

                                                                      The AERA Technical Committee


                                              Engine Oil In Coolant On
                                            Toyota 2.4L (22R) Engines

Engine oil in the cooling system on Toyota 2.4L (22R) engine may be the result of an unusual occurrence.  While this condition is normally thought to be the result of a crack within either the cylinder head's or block's pressurized oil gallery, the 22R engine features another possibility.

This engine's cylinder head has two metric threaded plugs sealing the water jacket within the valve spring area.  The plugs are located directly below the camshaft where oil normally collects.  During engine operation as well as after shut-down, these plugs are completely submerged in oil.  If the plugs are not completely sealing the water jacket of the head, they will pull engine oil
into the cooling system as the engine cools down.

Pressure testing the cooling system of the cylinder head should reveal the leaking plugs, however heating the head slightly may be required.  While pressurizing the oil gallery of the cylinder head will not reveal a leaking plug.

                                                                        The AERA Technical Committee


                            Coolant Loss On
                      1981-92 Toyota 2.4L Engines

The AERA Technical Committee has received reports of coolant loss on 1981-92 Toyota 2.4L engines.  Depending upon the amount of loss, there may be evidence of white smoke coming out the tail pipe.  This problem has been seen on engines in use as well as engines that have been rebuilt.

This area of leakage has been in the exhaust ports of the cylinder head.  Over time continued hot exhaust gases may erode this area and create a hole into the cooling passage between the ports.  In some instances pushing on a suspect area with an awl or punch will expose the water jacket.  If the head is still on the vehicle, dropping the exhaust manifold will usually reveal coolant droplets hanging on the problem areas.  Of course pressure testing the head will also reveal the areas that are leaking.

Some AERA shops are successfully welding this area of affected cylinder heads.  There does not, however, seem to be a way of detecting heads that may leak in the future. 
                                                                            The AERA Technical Committee


                                       Valve Lash Adjustment For 
                                 1993-97 Toyota 1.8L 7AFE Engines 

The AERA Technical Committee offers the following information regarding adjusting valve lash for 1993-97 Toyota 1.8L 7AFE engines. The procedures and lifter type used for this engine is a little different than previous Toyota engines. Many previously built Toyota engines used a bucket style lifter with a removable hardened disc, which was available in different thicknesses. To adjust the valves in the 1.8L 7AFE engine, camshaft removal is necessary.

The Toyota 7AFE cylinder head uses a non-adjustable solid bucket type valve lifter, which is supplied in different thicknesses. There are a total of 35 lifters supplied to allow for valve adjustment. The area of thickness is measured as shown in Figure 1 below and ranges from .1992-.2260 (5.060-5.740 MM). Each lifter in the selection chart increases in thickness by an additional .0008" (.020 MM). Lifter selection is referred to as a number ranging from 06 to 74, increasing in increments of 2. As an example, lifter 06 is .1992 (5.060 MM) thick and lifter 08 is .2000 (5.080 MM) thick. 

Careful cylinder head disassembly and keeping lifters marked as to their original location can save a lot of time when it comes to reassembly and valve adjustment. The lash adjustment for this engine should be made while components are cold and should measure .006-.010 COLD (.152 TO .254 MM) for intake valves and .010-.014 COLD (.254 TO .356 MM) for exhaust valves. 

                                                                             The AERA Technical Committee

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