8/1/2003
Click on a thumbnail to see the full-size image
Revised information for main bolt tightening on 1992-’95 Mitsubishi 4G and 6G series engines.
Engine Builders: The AERA Technical Committee offers the following revised information for main bolt tightening on 1992-’95 Mitsubishi 4G and 6G series engines. Information previously published in the OEM and aftermarket service manuals was incorrect and the following specifications should be used.
To install non-elastic main bearing bolts, the following procedure is applicable to all vehicle engines listed at right. Tighten the bolts on each main bearing cap equally until the specified torque is achieved. Use the bolt-tightening sequence if applicable.
Elastic main bolt tightening (plastic-angle tightening method). Before reusing main bolts measure the shank lengths of ALL the main bolts, if the measurement of 2.799˝ (71.100mm) is exceeded or the bolt has visual damage replace the bolts. Measure from the tip to the shoulder under the bolt head (not to the shoulder of the washer).
To tighten elastic main bearing bolts using the plastic/angle tightening method; the following procedure is applicable to all the engines listed.
1) Torque bolts in sequence (see Figure 2) to specification 18 ft.lbs. 2) Using a breaker bar (not a torque wrench), turn each bolt 90°. 3) Then turn each bolt an additional 90° with a breaker bar.
Engine Builders: The AERA Technical Committee offers this timing chain tensioner caution for 1998-2003 Chrysler 2.7L VIN R, U & V engines. The information should be considered any time a tensioner is being inspected for possible reuse during engine assembly. These engines use a combination of three tensioners per engine, two for the cam chains and one for the crank to cam chain.
Tensioner failure shortly after installation has been reported when reusing "good" tensioners. Reusing any tensioner is risky as tensioner failure can cause catastrophic engine damage. Apparently, determining tensioner condition by visual inspection is not a reliable procedure. It is therefore recommended that all three tensioners be replaced with new ones at time of service.
The engines use one long chain tensioner, called the primary chain tensioner, and two short secondary chain tensioners. Aftermarket tensioners are available and in high demand.
Engine Builders: The AERA Technical Committee offers the following information regarding a valve and valve seat problem for 1997-2003 John Deere 6105 and 6125 diesel engines. There have been reports of intake fracture and loose valve seats on these engines. The valve failures occur on engines built prior to 6105-003293 and 6125-008890. Loose valve seats have been reported during valve face machining.
Engines using the first intake valve design (R121803) are more prone to fail than the current Inconel®, valve p/n R122035. All intake valves in engines previous to the engine serial numbers listed above that have suffered an intake valve failure should be replaced with the current valve.
Failures typically occurred in the 800-1,400 hour range while valves in continuous service for over 1,400 hours are less likely to fracture with continuous use.
Engine builders have observed inserts with less than .003˝ interference fit and also report cracks between the intake and exhaust seats may leak coolant, as the casting in this area is very thin on early model heads. Intake valve seats with unknown interference fit should be replaced any time valve and valve seat service is performed.
One aftermarket valve and seat manufacturer says that the Inconel® valve should now be available.