1992/10/01 Caterpillar

3406B/C (8TC, 5YG, 3ZJ, 5KJ, 2EK, 4CK) Truck Engines

Reference: Truck Engine News, October 1991, Page 5, "New Piston Pin Retainer Used". Truck Engine News, March 1992, Page 6, Supplement, "Special Instruction, Wall Chart." Truck Engine News, April 1992, Page 2, "New Turbocharger Groups With Ceramic Turbine Wheels Used".

Reference: Service Manual, 3406B Diesel Truck Engine, SEBR0544-03, Specifications.

There have been several component changes in 3406 Truck Engines since 1991. Those changes are identified in the rest of this article.

Piston Pin

During 1992 a new larger diameter 7E1749 Piston Pin, which provides greater strength and fatigue resistance, is available. The new 7E1749 Piston Pin is 55.000 mm (2.1654 in) in diameter and 113.20 mm (4.457 in) long. The 8N1608 Piston Pin is smaller. It is 50.795 mm (1.9998 in) in diameter and 111.89 mm (4.405 in) long. The longer pin will reduce pin retainer groove wear caused by pin side impact.

Pistons

Two new pistons were used in 1991 models. Both pistons have an 8 mm to top ring distance and both have a low crevice volume (LCV) design for better emissions control. The 7E8656 Piston (15.6:1 compression ratio) is used in 285-330 horsepower engines. The 7E8700 Piston (15.2:1 compression ratio) is used in 350-425 horsepower engines. The 7E0489 Piston (14.5:1 compression ratio) used in the 460 horsepower engine is not changed. This piston has a 12 mm to top ring distance. The 460 horsepower piston requires a 7E3632 Piston Cooling Jet with two tubes secured by a 7E6479 Bolt. The second cooling tube sprays oil into a piston crown cavity for additional cooling.

The 7E8656 Piston (15.6:1 compression ratio) is used in all 1992 Mechanical ratings (310 to 425 hp). The 15.6:1 piston is used in the 310 hp rated electronic engine, while the 15.2:1 piston is used in the 350 to 425 hp ratings. The 14.5:1 piston continued on the 460 hp rating for 1992.

During 1992, the new 7E0292 Piston (15.6:1 compression ratio) was released to accommodate the new larger diameter 7E1749 Piston Pin and 7E1177 Pin Retainer. This piston is used in all engine rating except 460 horsepower.

NOTE: Pistons using different diameter piston pins should NOT be mixed in the same engine. The result could be excessive vibration.

Piston Pin Retainer

The 7E5665 Piston Pin Retainer is used with the smaller diameter 8N1608 Piston Pin. See Reference Article "New Piston Pin Retainer Used". The 7E5665 Piston Pin Retainer is in effect with 3406 Truck Engines 3ZJ6028, 5KJ7572, 2EK860, and 4CK1.

The new 7E1177 Piston Pin Retainer is used with the larger diameter 7E1749 Piston Pin. See the Effective Serial Number Chart.

Crankshaft, Bearings

The new 9Y7735 Rod Bearing (Wide) and 4P4334 Crankshaft are used on 3406 Truck Engines 5YG1 -Up, 3ZJ2830-Up, 2EK512-Up, 4CK1-Up, and 5KJ1-Up.

The 4P4334 Crankshaft can be retrofitted into any 3406B/C Truck Engine with the corresponding rod assemblies, bearings, and damper.

Mid-life Bearing Roll-in Recommendations

Engines with the new 9Y7735 Connecting Rod Bearings DO NOT require a mid-life connecting rod bearing roll-in unless the following severe service conditions are encountered.

* Extended operation at high load factors. Extended operation at high rpm (2100 rpm and above).

* Excessive lead or aluminum in oil samples. Reuse of crankshaft with marginal profile or surface texture.

* Engine overheating.

* Oil dilution by fuel or coolant.

* Rapid cold engine starts.

* Dry starts after an engine has set for 30 or more days without prelubing.

* Extended oil drain intervals causing excessive lube oil sooting.

* Plugged oil filters.

* Incorrect oil viscosity (too light during hot weather, or too heavy during cold weather).

If these or similar conditions cause marginal lubrication to an engine, Caterpillar recommends the bearings be inspected and/or replaced if necessary.

Truck engines built with the 1W7524 or 9Y9497 Rod Bearing have a mid-life crankshaft bearing inspection required as part of the preventative maintenance schedule. This inspection consists of removing the connecting rod bearings only. The bearings are inspected for any sign of dirt and debris that have been passed from the main bearings. If the connecting rod bearings do not show any of these signs, Caterpillar recommends that the main bearings be left alone and only the connecting rod bearings be replaced.

Connecting Rod

Illustration 1. 9Y6054 Connecting Rod Assembly (A), Crankshaft bore diameter 96.2 mm (3.79 in), Pin bore diameter 55.0 mm (2.17 in). 7E5996 Connecting Rod Assembly (B), Crankshaft bore diameter 96.2 mm (3.79 in), Pin bore diameter 50.8 mm (2.00 in). 9Y6400 Connecting Rod Assembly (C), Crankshaft bore diameter 96.2 mm (3.79 in), Pin bore diameter 50.8 mm (2.00 in). 8N1726 Connecting Rod Assembly (D), Crankshaft bore diameter 103.5 mm (4.07 in), Pin bore diameter 50.8 mm (2.00 in).

During 1992, a new larger piston pin for the 3406C Truck Engine created the need for a new connecting rod. The new 9Y6054 Connecting Rod Assembly is compatible with the larger diameter 7E1749 Piston Pin. The connecting rod assembly contains a piston pin sleeve bearing with side relief which retains more oil and reduces bushing wear. This rod assembly also utilizes the simpler bolted rod cap retention method. It uses the same tightening procedure as the 7E5996 Connecting Rod Assembly.

In the first quarter of 1991, the 7E5996 Connecting Rod Assembly was phased in for all 3406 Truck Engine ratings. This rod replaced the 8N1726 Connection Rod Assembly. On the 7E5996 Connecting Rod Assembly, the rod cap is attached with bolts that thread into blind tapped holes in the rod assembly to simplify the joint. This is similar to 3176 Truck Engines. The torque for installing the rod caps is different from earlier rods. See Illustration 1 and the chart and the Reference.

The 5YG engines and some earlier 3ZJ and 2EK engines use a 9Y6400 Connecting Rod Assembly. This rod uses bolts and nuts to fasten the rod cap to the bottom of the rod. See Illustration 1 and the chart.

The 9Y6400 and 7E5996 Connecting Rod Assemblies are interchangeable and CAN be mixed within the same engine. But, be sure to note the different tightening specifications when installing the rod caps. The 7E5996 Connecting Rod Assembly also has side reliefs in the rod eye bushing. This retains more oil in the pin/bushing joint for reduced bushing wear. The 9Y6400 and 7E5996 Connecting Rod Assemblies have different tightening specifications.

* In the 7E5996 and 9Y6054 Connecting Rod Assemblies, lubricate the threads and seating faces of the rod cap with 4C5590 Thread Lubricant/Anti Seize Compound. The bolts should be tightened to 90 ± 8 N·m (60±6 lb ft), and then the bolts should be tightened an additional 1/4 turn (90 degrees).

* In the 9Y6400 and 8N1726 Connecting Rod Assemblies, lubricate the threads and seating faces of the rod cap with engine oil. The nuts should be tightened to 80 ± 8 N·m (60 ± 6 lb ft), and then the nuts should be tightened an additional 1/3 turn (120 degrees).

NOTE: Large and small diameter piston pins and rod assemblies should NOT be used within the same engine. The result could be excessive vibration.

Dampers

When the wide bearing crankshaft is installed, torsional vibration control is achieved with either the bonded rubber or visconic type damper depending upon the engine rating. All 460 hp truck engines use the 7E9520 Visconic Damper. Other ratings use the 4P4297 Bonded Rubber Damper or the 7E9520 Visconic Damper.

Cylinder Block

The upper liner area of the new cylinder block has been changed to allow a higher coolant path because of the new 8 mm top ring distance LCV pistons. The new cylinder block also provides increased top deck stiffness for added block and head gasket durability. The new 4P3720 Cylinder Block is direct replacement for the former 2W6039 Cylinder Block. The former cylinder block is canceled. The new cylinder block is effective with 3406 Truck Engines 8TC13672, 4MG96903, 5YG570, 3ZJ1, 5KJ1, 2EK1, and 4CK1. The former block is not compatible with the new 8 mm top ring distance LCV pistons due to insufficient top ring cooling.

Illustration 2. Upper liner area of new 4P3720 Cylinder Block. Location of machined undercut cooling passage (E) for full circumference of liner bore.

Illustration 3. Upper liner area of former 2W6039 Cylinder Block. Location of cast cooling passage (F) for partial circumference of liner bore.

Cylinder Liner And Liner O-Rings

The former 7W3550 Cylinder liner has been replaced with the new 2W6000 Cylinder Liner. The new liner has lower O-ring locations relative to their installed location in the bore in the cylinder block. The new location will help prevent rolled and cut O-rings that can lead to liner distortion and possible piston seizures. This change also eliminates the tendency for the liner to pop-up and protrude above the top of the block after assembly. The top liner O-ring now resides below the lower bore chamfer in the cylinder block. This should also prevent trapping the filler band under the liner flange since the liner will remain in place following assembly. Final liner/ cylinder kit assembly and liner projection measurement is simplified.

The former 6V5121 Liner O-Ring is replaced by the new 3E6777 Liner O-Ring. The new 3E6777 O-Ring is made of material which is more durable and oil resistant. The previous O-ring deteriorated with long term exposure to oil. A result of the improved durability is an increase in material stiffness. This makes the liner more difficult to install in the block. The use of soap on the new O-rings may not provide sufficient lubricity for ease of installation. The new liner O-rings require the lubrication with clean engine oil plus the use of a 2P8260 Liner Installer Tool for efficient installation.

Turbocharger

A TV75 turbocharger (see Illustration 4) has replaced the former TV71, TV72 or TV78 turbochargers (see Illustration 4) on 400 and 425 horsepower family engines. The 310 and 350 horsepower family engines use the S3B turbocharger. Both the TV75 and S3B turbochargers have radial recirculation grooves in the compressor housing. This helps prevent surge in deep engine lug. The TV75 turbocharger has a larger hub diameter on the turbine side for the oil seal ring to run in. This reduces the amount of oil going to the seal ring. The TV75 turbocharger uses a single, sintered iron, thrust bearing with tighter end clearance. The former turbochargers used a rotating collar and two individual steel backed aluminum bearings.

Illustration 4. TV75 Turbocharger cartridge.

Illustration 5. TV71, TV72, or TV78 Turbocharger cartridge.

Jake Brake (Model 346D)

The Jake Brake slave piston lash setting has changed from 2.03 mm (.080 in) to 1.70 mm (.067 in) to maintain acceptable push rod loads. The Jake Brake output has increased by 30 horsepower due to higher boost levels on the 1991/92 engines. See nameplate for correct setting for each engine.

Pacbrake (Model P36)

In October of 1991 the P36 compression brake became available as a factory install option. It is set at .067 in. at the factory and should be reset to .070 in. at the first valve lash check to maximize performance.

Tu-flo® Air Compressor (Model 550/750)

The Tu-Flo model 550 air compressor is the new standard model that replaces the former model 501 air compressor. The use of the model 550 air compressor increases the air flow from 11.75 cfm to 13.2 cfm. The models 550 and 750 share the same cylinder block, head, and connecting rod. The block is a one piece casting which strengthens the structure and eliminates a gasketed joint and runs cooler. The unloader valve has also been improved. The model 750 replaces the model 700 as the optional air compressor. The model 750 delivers 16.5 cfm, while the former model delivered 15.5 cfm.

Fuel Injection Nozzles

The nominal valve opening pressure (VOP) specification on nozzles for 1990 and earlier truck engines is 15200 kPa (2200 psi) with an acceptable VOP reuse range of [11024-1600 kPa (1600-2350 psi)]. The nominal VOP for 1991-Up truck engines, with nozzle part numbers 7W7040 through 7W7045 is 17000 kPa (2500 psi) with an acceptable VOP reuse range of [13790-18270 kPa (2000-2650 psi)].