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Main Bearing Housing Bore ForCaterpillar 10. 0 & 12. 0L C10 &

C12 Diesel EnginesOriginally published specificationsregarding the main bearing hous-ing bore for Caterpillar 10.0 and12.0L C10 and C12 diesel engineswere apparently inaccurate, soreview this information carefully.

Although some machine shopshave reported a discrepancy whilemeasuring main housing bores forthese engines, no apparent bearingdamage existed even though themeasured sizes were consistently.002 -.003 smaller than the pub-lished specification.

Caterpillar also offers .020 (.508mm) oversize OD main bearings forthese engines to repair severelydamaged bores. Refer to the chartabove to determine the propermachining dimensions for the aboveengines.

At this time, we are unaware ofan aftermarket source for main bear-ings for these engines.

Main Bearing Housing BoreCaution For 1997-2007 CaterpillarC15 Diesel Engines

Oversize main bearing bores havebeen reported during engine rebuild-ing operations on 1997-2007Caterpillar diesel engines.

To allow additional salvage opera-tions and block reclamation theCaterpillar Corporation does offer an

oversize .025 (.635 mm) outsidediameter bearing set. Caterpillar also

offers main bearing sets for oversizebore bearings in both standard and.025 (.635 mm) inside diameters (seechart below).

To determine if a block yourechecking has the oversize bores, usethe following procedures:

1) Install main bearing caps inoriginal positions.

2) Lubricate cap bolt threads andbolt head contact surfaces with a smallquantity of thread lubricant 2P2506.

3) Install and tighten main capbolts on the left side to 180-200 ft.lbs.(246-274 Nm).

4) Install and tighten main capbolts on the right side to 180-200ft.lbs.(246-274 Nm).

5) Tighten the main cap bolts onthe right side by rotating them anadditional 120.

6) Tighten the main cap bolts onthe left side by rotating them an addi-tional 120.

7) Measure bores with a dial boregauge which has a dial indicator cali-bration in .0001 increments.

8) Record your measurements andcompare to the standard main borediameter specification of 5.1133 -5.1143 (129.878-129.903 mm).

If the block you are checking islarger than the above standard specifi-cation, compare it to the oversizedimension of 5.1383 -5.1393

(130.513-130.538 mm). If there is aneed to resize, it is recommended togo to the oversize, rather than repair-ing by align boring back to standarddimensions.

Coolant Loss On 1985-2000Cummins 5. 9L Diesel Engines

The following information regard-ing coolant loss on Cummins 5.9L

diesel engines is known to apply to12 valve engines, but this condition

is certainly a possibility for 24 valveengines as well.

Cylinder porosity has been report-ed in the front cylinder toward theintake manifold side of the engine.This porosity concern was not a resultof an unconditioned cooling system.In this instance the condition was notrevealed until oversize cylinder bor-ing was performed. The amount ofoversize was the first oversize avail-able,.020 (.5 mm).

One way of determining if thiscondition is present on an oversizebore engine is to pressure test thecylinder block after all honing oper-ations have been completed.

Revised Cylinder Head Bolt For1985-1996 Cummins 10.0L, L-10Diesel Engines

A revised cylinder head bolt hasbeen introduced for for Cummins10.0L, L10 diesel engines.

This change has been imple-mented as a product improvementto address cap screw corrosion fail-ures.The cap screw (head bolt) wasfirst used with engine serial number35124397. The old and new capscrews can be intermixed within theengine.

The new cap screws have a greycoating on them and do not havethe

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Valve & Valve Guide Caution For

Cummins 11.0L ISM, M11 & QSMDiesel Engines

Engine builders are cautioned that11.0L M11, IAM and QSMCummins diesel engines have valvesand valve guides that may be incom-patible.As a condition of a productimprovement, Cummins imple-mented chrome intake valve stemsand a reverse scroll valve guide for alllocations beginning with engineserial number (ESN) 35135680 builtin July 2005.

These reverse scroll guides wereimplemented to prevent excessexhaust valve guide wear in thelower portion of the valve guideinside diameter. The reverse scrollguide has 50 percent more surface

area in the lower portion of thevalve guide inside diameter.

The valve guides are the same forthe intake and exhaust valves.Engines prior to ESN 35135680were built with chrome platedexhaust valve stems and non-reversed scroll valve guides. Toaccommodate the change in the

valve guides, it was required that theintake valve stems also be chromeplated to prevent excess wear on theintake valve stem.The chrome plat-ed intake valve stems were released amonth before the release of the

reverse scroll valve guides in order toprevent usage of non-chrome platedvalve stems with the reverse scrollguides. Do not use intake valvesfrom prior serial number engines incylinder heads with reverse scrollvale guides.

Intake valves with chrome platedvalve stems, p/n 4926069 or

4955239, must be used on cylinderheads which have the reverse scrolledvalve guides,p/n 4923471,or reversescrolled oversized valve guides, p/n4923473.

Either chrome plated intake valve,p/n 4926069, or non-chromeplated intake valve, p/n3417778, can be used oncylinder heads which have thenon-reverse scrolled valveguides,p/n 3328786.

Reverse scroll valve guides

can be identified by the innerthreading (spiral) of the guideat the top end, as opposed tono threads (spiral) on the non-reverse scroll guides.

Cylinder Head Installs For1986-2004 Cummins 14.0L

N, NT & N14 Diesel Engines

Because different cylinderhead bolts have been used inCummins, 14.0L N, NT andN14 diesel engines, theinstallation procedures maybe different depending onthe age of the head.

Thisservice partstopic pro-videsthe correct procedure totighten the cylinder head gasketcap screws(Figure 1,page 31).Information about the differentcylinder head bolts have beenused asdescribed previously inAERA Technical Bulletin TB

30 AERA TECHSOLUTIONSGUIDE |February 2008

Circle230for more information

New P/N Description Old P/N4926069, 4955239 Intake Valve 34177784923471 Standard Valve Guide 3328786

Valve Kit 38006364923473 Oversize Valve Guide 3417559

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683.There isa difference between pro-cedures of cylinder heads manufac-tured before and after January 1991.

Pre-1991 Cylinder HeadsWhen tightening the head bolts on NSeries engines built before January1991 and using head bolt, p/n209700 or 3013623, the followingprocedure should be used.

Head bolts part numbers 209700and 3013623 can be identified by anNT or NTC stampedon the head of the bolt.1991 and LaterCylinder Heads

When tightening the headbolts on N Series enginesbuilt in January 1991 and

later, and using head bolt,Part No.3071161,3068897,or 3068898, the followingprocedure should be used.

Head bolt part numpers3071161, 3068897 and3068898,can be identified bya

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are cautioned to check rod lengths

carefully.It is believed this occurred to

re-establish the intended center-to-center length (8.638 -8.642(219.405-219.507 mm) of the con-necting rod.The reported offset hasbeen to the rod big end,thus short-

ening the rod as measured without

the bushing installed.While it is common practice for

some machine shops to hone fitconnecting rod bushings afterinstallation. That process does notallow for adjustment of the center-to-center length of a connecting

rod.If this method of piston pin fitis used, excessive piston protrusionmay result, allowing piston tocylinder head contact if the engineis started.

Rocker Shaft Disassembly Caution

For 2000-2007 M ack 11.0L MP7 &MP8 Diesel Engines

When disassembling the rockershaft for 2000-2007 Mack 11.0LMP7 and MP8 engines you mustpay attention to engines equippedwith the PowerLeash engine

brake. In this system the exhaustrocker arm incorporates an integralengine brake valve and piston.

When removal of the rockershaft is necessary, the pistons mustbe retained to keep them fully

retracted in the bores.Suitable tie wraps ormechanics wire can be usedto secure the pistons in place.

Failure to secure theengine brake piston beforeremoving the rocker shaft

assembly will allow the pis-ton to drop from the bore asthe shaft is removed. Shouldthis occur, it may not benoticed,or it may be difficultto push the piston fully backinto the bore.

Additionally, plungers area match-fit to the rockerarm, and inadvertent mix-upof components must beavoided. Assembling therocker shaft to the engine oroperating an engine with theengine brake pistons notfully retracted will result inbreakage of valve train com-ponents and significantengine damage.

Note: The tie wraps ormechanics wire must beremoved only after the rock-er shaft has been reinstalledon the engine. TSG

32 AERA TECHSOLUTIONSGUIDE |February 2008Circle232for more information

Fi gure 2Cummins ISX 600 Series -

Old head gasket.

Fi gure 3Cummins ISX 600 Series -

New head gasket.

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