Use 6V6035 Hardness Tester On Crankshafts
Use the 6V6035 Hardness Tester to check crankshaft journal hardness before and after they are reground. It is important to check for hardness if the journal shows signs of high heat or if it has been ground to a new diameter. Do not use any other method to check for hardness. This can result in damage to the crankshaft.
The 6V6035 Hardness Tester has a hardened steel ball which “bounces” (hits) off the tested surface. The height of the bounce is read as a Rockwell “C” scale hardness reading.
Crankshaft journal hardness tolerances are given in “Crankshaft Measurement Specifications” in the Guideline for Reusable Parts, Form SEBF8041-01, Crankshaft Measurement.
The 6V6035 Hardness Tester can be used on any Caterpillar crankshaft if the journal diameter is at least 38 mm (1.5″), and is smooth. The journal must be polished and have no smeared bearing material on it.
To use the 6V3035 Hardness Tester, the surface finish must be .8 micrometers (20 microinches) or smoother and have a minimum surface thickness of 25 mm (one inch).
The 6V6035 Hardness Tester can be used to test most crankshafts for hardness.
Procedure To Clean Oil Passages In Crankshafts And Cylinder Blocks
All Engines
It is Caterpillar’s recommendation that the procedure that follows should be used to clean all new, used (crankshafts and cylinder blocks that are to be used again) and reconditioned crankshafts and cylinder blocks before they are assembled.
One reason for bearing failure after an engine overhaul is debris that was not removed from the oil passages in the crankshaft and cylinder block. Some of this debris (carbon deposits) is a product of fuel combustion that, over a long period of time, has mixed with oil and become thick. Most of the time this debris can not be removed completely when only a high pressure wash or a high pressure nozzle is used to clean the oil passages.
Debris (chips or abrasive material from the reconditioning operation) that is not removed after an engine or bearing failure or after a reconditioning operation can also cause early engine failure. It is important that all debris is removed from the oil passages in the crankshaft and cylinder block. Larger particles of debris can cause damage to the crankshaft journal and bearings when the engine is first started because the bypass valve can let unfiltered oil get in to the engine. See Illustration 1.
Illustration 1.
Use the following procedure to make sure the oil passages in the crankshaft and cylinder block are free of debris:
1. Remove all plugs. Allen head plugs may have to be drilled and removed with a 6.35 mm (.25″) Easy Out Remover. Most lightening hole core plugs are held in position with snap rings. These snap rings can be removed with two screwdrivers or can be cut in half with a cold chisel. Cylinder block plugs and similar plugs in older crankshafts can also be removed with a cold chisel.
2. Install one of the brushes from the chart in a variable speed drill. Use a brush that has a diameter that is just larger than the diameter of the oil passage to be cleaned.
3. Use a petroleum solvent and one of the brushes from the chart to loosen any debris or carbon (deposits) in all the oil passages in the crankshaft and cylinder block. See Illustration 2. Make sure the end of the brush goes to the end of each oil passage. Each oil passage must be cleaned from every possible direction. When the main oil passage in the cylinder block is cleaned, it will be necessary to weld a 3.18 mm (.125″) mild steel rod to the end of the brush handle. Make sure the rod is long enough to let the brush go all the way through the cylinder block. See Illustration 3.
Illustration 2.
Illustration 3.
4. Use the brush and a solution of detergent and water to “float” the debris out of the oil passages. Use water to wash the rest of the detergent and water solution out of the oil passages and then use an air hose to dry the cylinder block or crankshaft.
5. If the crankshaft and cylinder block are not going to be used immediately, put a rust inhibitor on the crankshaft and cylinder block to prevent damage.
6. Make sure the rust inhibitor is removed before the crankshaft is installed in the cylinder block.
7. Install all the plugs in the crankshaft and cylinder block. See the Specifications section of the Service Manual for the correct torques and procedures for the installation of the plugs in the crankshaft and cylinder block.
Crankshaft Failures
All Caterpillar Engines
There are two forces that act upon every crankshaft. Torsional forces are those forces which try to twist the crankshaft. These forces are the result of the rotating power that goes into the crankshaft when there is a power impulse (power stroke of the piston). Bending forces are those forces that act perpendicular to the centerline of the crankshaft and cause it to move towards the main bearing caps. This force is the result of the downward motion of the connecting rod when there is a power impulse.
Power impulses, which are the primary cause of both torsional and bending forces, occur at different times in the rotation of the crankshaft. For example, six cylinder engines will have a power impulse at every 120° of rotation. Eight cylinder engines will have a power impulse every 90° and twelve cylinder engines every 60°.
The presence of these forces, when combined with torsional fatigue, bending fatigue, longitudinal cracking or bearing seizure can cause a crankshaft failure.
Torsional Fatigue
Torsional fatigue failures are usually the result of fatigue of the crankshaft which is caused by excessive torsional vibration. Under normal conditions, the vibration damper will keep this torsional vibration from becoming excessive. If the vibration damper has failed, this excessive vibration can cause a torsional fatigue failure in the crankshaft.
The failure usually begins on a journal at a point of stress concentration, such as a flaw, crack, oil hole or lightening hole. It then progresses into a torsional fatigue failure. The fracture is generally at a 45° angle through the oil hole. It usually occurs about 2/3 of the way down the crankshaft from the damper.
Illustration 1 shows two examples of a torsional fatigue failure. The fracture usually goes in one of two directions as shown by the lower illustration in Illustration 1.
Few crankshafts fail from true torsional fatigue, primarily because the vibration damper keeps the torsional vibrations within a safe limit. If the vibration damper does fail, normally the timing gears will fail before the crankshaft is damaged.
The following are some of the causes of crankshaft failures due to true torsional fatigue:
- 1. Defective or failed vibration damper.
- 2. Failed torsional coupling.
- 3. Improper applications of the engine. All engines in Caterpillar vehicles and packaged generator sets can be operated at approved loads and speeds without a torsional fatigue failure. Caterpillar engines in other applications will give acceptable operation if a torsional vibration analysis is made on the complete system before installation. This analysis can be performed by Caterpillar. For more information, see the Special Additions section of the Engines Price List.
- 4. A large inclusion or groups of inclusions (foreign material) in or under the journal surface. These inclusions are generally characterized by a short longitudinal fracture with 45° fractures at each end as shown in Illustration 2.
NOTE: Many inclusions are not harmful. For more information, see Guideline For Reusable Parts, “Inspection Of Crankshafts For Cracks,” Form No. SEBF8039.
- 5. Nicks, large scratches and cracks in the oil hole. See Engine Bearings And Crankshafts, Form SEBD0531, Section 5, for more information and illustrations on crankshafts with nicks, large scratches and cracks.
Illustration 1. Failure caused by torsional fatigue.
Illustration 2. Torsional failure because of large inclusions.
Bending Fatigue
Crankshaft failures that are the result of bending fatigue usually start at a point of stress concentration in the fillet. The bending forces on the crankshaft cause a small crack to form which moves through the web between the rod journal and the adjacent main journal. See Illustration 3.
The normal causes of a stress concentration in the fillet are:
- 1. Sharp nick, notch, or scratch.
- 2. Inclusion.
- 3. Grinder burn.
- 4. Wrong fillet (radius too sharp, incorrect finish).
- 5. Wrong or no shot peen operation after grinding. See Guideline for Reusable Parts, “Procedure to Grind Crankshafts,” Form SEBF8047.
- 6. Main bearing failure. The main journal is no longer supported correctly and the bending forces increase across the unsupported journal. The result is a bending fatigue failure.
- 7. Misalignment of the crankshaft in the block. This results when a crankshaft is used that exceeds the specifications for “bend” (total indicator reading). See Guideline for Reusable Parts, “Procedure to Measure and Straighten Bent Crankshafts,” Form No. SEBF8054.
- 8. Misalignment of the main bearing bores in the block. This can be caused by incorrect machining or by distortions from external forces, such as a bent engine base or improper alignment with the driven member. This driven member could be a marine transmission or a generator.
Additional information about the installation and alignment of Caterpillar engines, marine transmissions and generator sets is available in several Application and Installation Guides and Special Instructions. These publications are shown in the chart.
Illustration 3. Failure caused by bending fatigue.
Longitudinal Cracking
Crankshaft failures due to longitudinal cracking start with a momentary seizure of the bearing. This momentary seizure of the bearing is usually caused by a loss of oil film in a small area resulting in metal-to-metal contact with the journal. The metal-to-metal contact produces localized heat which causes small cracks (usually longitudinal) to form on the surface of the journal. These cracks eventually grow larger until the journal is weakened enough to permit a torsional fatigue failure. This torsional break often moves from the crack in opposite directions and at a 45° angle from each end of the crack. See Illustration 4.
One of the more common causes of momentary bearing seizures is excessively barrel shaped journals. Such journals carry a large portion of the load in the center of the journal and only a small portion on the ends. This high load condition in the center of the journal can result in metal-to-metal contact. Barrel shaped journals are usually produced during the grinding operation. The cause is normally a grinding wheel that has not been kept to the proper flatness. Such journals can also be produced by improper polishing.
Additional information is available in the Guidelines For Reusable Parts, “Crankshaft Measurements,” Form SEBF8041-01, “Procedure To Polish Crankshafts,” Form SEBF8042-01 and “Procedure To Grind Crankshafts,” Form SEBF8047.
Illustration 4. Longitudinal cracks.
Bearing Seizures
Crankshaft failures caused by a bearing seizure are different from longitudinal cracking failures because the oil film is lost over the entire journal. This causes the bearing to seize to the journal. High temperatures are generated during the bearing seizure. This tempers (softens) the journal and weakens the fillet. The result is a bending fatigue failure. The fracture usually starts in the fillet and progresses through the web to the adjacent main journal. See Illustration 5. In a failure of this type, there are usually several small cracks in the fillet or journal. These small cracks are an indication of a seizure in a large area.
Crankshaft failures due to bearing seizures can be caused by:
- 1. Plugged oil passages because of dirty oil or sludge.
- 2. Not enough bearing clearance. It is recommended that the bearing bores and the crankshaft journals be measured to determine if the bearing clearance is within specifications.
- 3. Not enough oil to the rod bearings because of momentary seizure of the main bearings. The momentary seizure can be caused by excessive main bearing clearance or a dry start after an overhaul. If there isn’t any oil in the oil cooler, oil filter or oil passages, the bearings can be damaged in the time it takes for these components to fill with oil. A shortage of oil to the bearings can also be the result of operating the engine at too high an rpm when the oil is still cold.After an engine overhaul, always pressure lubricate the engine before starting.
After an oil change, always crank the engine, without fuel, until the engine has some oil pressure.
- 4. Lubrication problems such as fuel dilution of the oil, anti-freeze contamination of the oil, excessive oil temperatures or improper oil cooling.
- 5. By not changing the oil at the correct interval.
- 6. An improper surface finish on the journals. See the Guideline For Reusable Parts “Crankshaft Measurement,” Form SEBF8041-01 and “Procedure To Polish Crankshafts,” Form SEBF8042-01.
- 7. Improper journal profile. An improper journal profile can cause a loss of oil film where the clearance is the smallest. For more information, see Engine Bearings and Crankshafts, Section 3, Form SEBD0531.
- 8. Engine overspeed.
- 9. No oil.
- 10. Improper assembly.
Illustration 5. Failure caused by a bearing seizure.
Remanufactured Undersize Crankshafts Are Available
All Caterpillar-built Engines
Remanufactured crankshafts are now available for almost all Caterpillar-built engines. These remanufactured crankshafts have had both the rod and main journals ground undersize the same amount. All these crankshafts can still be ground to the next undersize dimension in the future, if needed. With all remanufactured crankshafts it is now necessary to return a core. Remember remanufactured crankshafts are not serviced with bearings, so it will be necessary to order the correct bearings for the crankshaft.
Publication Date -11/04/1984
Why Choose Caterpillar Remanufactured Crankshafts? Because We Offer More …
A crankshaft is a crankshaft, right? WRONG! With a Caterpillar Remanufactured Crankshaft you get more. For instance, no one else but Caterpillar can offer you a guarantee of receiving the crankshaft you need for your Caterpillar engine. If necessary Caterpillar will fill your stock order for a Caterpillar Remanufactured Crankshaft with a new one to assure your order is filled.
Compare this deal with anyone in the industry and you’ll find we’re hard to beat. Our commitment to assuring availability along with Caterpillar’s proven quality, firm prices and the fact that Caterpillar crankshafts come with the crankshaft gear adds up to value that you shouldn’t pass up.
Did you know about these new crankshaft options from Caterpillar? “Upgrade to New” Crankshafts and Remanufactured “Undersize” Crankshafts from Caterpillar now offer you exceptional value. If you’re not familiar with these options, do yourself a favor and read the following article for complete details.
Remember, there are no bargains, only cheap imitations. So stay with genuine Caterpillar quality parts. Contact your Caterpillar dealer and find out just how much more we offer.
Broad Availability For Caterpillar Remanufactured Crankshafts
Caterpillar has a comprehensive offering of Remanufactured Crankshafts to suit your needs. “Upgrade To New” crankshafts are NEW cranks offered through the Remanufactured Products Program at 55 to 65% of new prices with the return of a core. Two choices of Remanufactured “Undersize” Crankshafts are also available. They are priced at 20 to 35% of new and are ground to .025″ and .050″ undersize (.020″ for 3200 and 3300 Series Engines, .030″ for 3300 Series Engines). Whichever repair option you choose, you are assured:
- … Immediate availability-Crankshaft repairs are now available “off-the-shelf” at your Caterpillar dealer. No more waiting for your crankshaft to be repaired or for an exchange crankshaft to be delivered from a distant location.
- … “Same as new” warranty-six months, unlimited mileage/hours.
- … Performance, service life, and reliability “like new” from a crankshaft remanufactured to new specifications by people who KNOW the new specs.
- … Core acceptance policy which is the simplest and most liberal in the industry-no measurements required. Virtually ALL crankshafts are acceptable for full credit.
- … Timing (crankshaft) gear included.
Caterpillar Remanufactured Crankshafts-a competitively priced, off-the-shelf alternative for your crankshaft repairs. Refer to the chart for details on the Remanufactured Crankshafts available.
Checking Crankshaft Journal Surface Hardness On Remanufactured Crankshafts
3200, 3300, And 3400 Families Of Engines
Some Remanufactured crankshafts have been hardened by a Meloniting heat treat process. This process provides a thin surface hardness. DO NOT attempt to measure the surface hardness of journals on these crankshafts with a mechanical hardness checking instrument, such as a Sclerometer. A mechanical hardness checking instrument will indicate a low hardness level and may damage the journal.
Remanufactured crankshafts that have been hardened by the Meloniting process are stamped “MHT” in the same area the Remanufactured part number and date code are stamped. Be sure to check for the “MHT” mark before attempting to take any hardness measurements. If the Remanufactured crankshaft is stamped “MHT”, DO NOT use a mechanical hardness checking instrument to check the journal hardness.
Publication Date -01/01/1991
New Front Crankshaft Seal Used
3300 Family Of Engines
A hydrodynamic front crankshaft seal is now being used in the 3300 Family Of Engines. The 9Y9895 Crankshaft Seal Group is a direct replacement for the 5S6296 Seal. A 4C8982 Installer must be used to correctly install the 9Y9895 Crankshaft Seal Group.
Publication Date -01/03/1991
A New Type of Main Bearing is Available
- Generator Set:
- All 3304
- All 3306
- Industrial Engine:
- 3304 Diesel
- 3306 Diesel
- Marine Engine:
- 3304
- 3306
Engine News SEBD9345, March 2005, “A New Type of Main Bearing is Available”. Disregard this article. See the article that follows.
The 4W-5738 Main Bearing is cancelled for all 3300 engines. The replacement bearing for 4W-5738 Main Bearing is 232-3233 Main Bearing. Do not use the 4W-5738 Main Bearing. Use the 232-3233 Main Bearing. This is available for all 3300 engines.
The material for the main bearing has changed. The old main bearing was a copper bonded aluminum alloy with a lead tin overlay and a steel back. The new 232-3233 Main Bearing has an aluminum alloy and a steel back.
Installation Of 8N628 Service Replacement Bearing For Rear Of Injection Pump Camshaft In Sleeve Metering Fuel Injection Pump Housing
All Sleeve Metering Fuel Injection Pump Housings
(1) The 8N628 Bearing (1) can be installed as a service replacement for the rear bearing of the camshaft in the fuel pump housing for sleeve metering fuel systems. Joint (A) (contact point of bearing ends) and notch (B), on the inside diameter of the bearing, must be put in a specific position when the bearing is installed in the fuel pump housing.
(2) Remove the camshaft rear bearing from the fuel pump housing. Be careful to hot damage the bearing bore in the housing.
(3) Install the new 8N628 Bearing (1) in the 4 or 6 cylinder pump housing (2) or the V8 cylinder housing (3), as follows:
1. Use bosses (4) on 4 or 6 cylinder pump housing (2), and bosses (5) on V8 cylinder pump housing (3) to find the vertical and horizontal centerlines of the bearing bore.
2. The correct installed location of joint (A) is shown on each of the above illustrations and notch (B) must be within the 10° location.
(4) Install bearing (1) into the bore so dimension (C) [dimension from outer edge of bearing to face (D) of pump housing] is 0.114 ± 0.025 (.0045″ ± .0010″).
(5) Check to see that the camshaft will turn freely. With the new 8N628 Bearing (1) in the pump housing, clearance between the camshaft bearing journal and the bearing is 0.038-0.140 (.0015″-.0055″).
(6) Assemble all parts to the fuel pump housing amd make all necessary tests and adjustments.
