Hummer H2. Manual - part 66

Fig. 19: Measuring Bearing Clearance 

Micrometer & Telescopic Gauge Method 

A micrometer is used to determine journal diameter, taper and out-of-round dimensions of the crankshaft. See 
CLEANING & INSPECTION under CRANKSHAFT & MAIN BEARINGS in this article.  

With crankshaft removed, install bearings and caps in original location on cylinder block. Tighten bolts to 
specification. On connecting rods, install bearings and caps on connecting rods. Install proper connecting rod 
cap on corresponding rod. Ensure bearing cap is installed in original location. Tighten bolts to specification.  

Using a telescopic gauge and micrometer or inside micrometer, measure inside diameter of connecting rod and 
main bearings bores. Subtract each crankshaft journal diameter from the corresponding inside bearing bore 
diameter. This is the bearing clearance.  

CRANKSHAFT & MAIN BEARINGS 

REMOVAL 

Ensure all main bearing caps are marked for location on cylinder block. Some main bearing caps have an arrow 
stamped on them. The arrow must face timing belt or timing chain end of engine. Remove main bearing cap 
bolts. Remove main bearing caps. Carefully remove crankshaft. Use care not to bind crankshaft in cylinder 
block during removal.  

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

CLEANING & INSPECTION 

Thoroughly clean crankshaft using solvent. Dry with compressed air. Ensure all oil passages are clear and free 
of sludge, rust, dirt and metal chips.  

Inspect crankshaft for scoring and nicks. Inspect crankshaft for cracks using Magnaflux procedure. Inspect rear 
seal area for grooving or damage. Inspect bolt hole threads for damage. If pilot bearing or bushing is used, 
check pilot bearing or bushing fit in crankshaft. Inspect crankshaft gear for damaged or cracked teeth. Replace 
gear if damaged. Ensure oil passage plugs are tight (if equipped).  

Using micrometer, measure all journals in 4 areas to determine journal taper, out-of-round and undersize. See 
Fig. 20 . Some crankshafts can be reground to the next largest undersize, depending on the amount of wear or 
damage. Crankshafts with rolled fillet cannot be reground and must be replaced.  

Fig. 20: Measuring Crankshaft Journals 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

Crankshaft journal runout should be checked. Install crankshaft in "V" blocks or bench center. Position dial 
indicator with tip resting on the main bearing journal area. See Fig. 21 . Rotate crankshaft and note reading. 
Journal runout must not exceed specification. Repeat procedure on all main bearing journals. Crankshaft must 
be replaced if runout exceeds specification.  

Fig. 21: Measuring Crankshaft Main Bearing Journal Runout 

INSTALLATION 

Install upper main bearing in cylinder block. Ensure lock tab is properly located in cylinder block. Install 
bearings in main bearing caps. Ensure all oil passages are aligned. Install rear seal (if removed).  

Ensure crankshaft journals are clean. Lubricate upper main bearings with clean engine oil. Carefully install 
crankshaft. Check each main bearing clearance using Plastigage method. See MAIN & CONNECTING ROD 
BEARING CLEARANCE .  

Once clearance is checked, lubricate lower main bearing and journals. Install main bearing caps in original 
location. Install rear seal in rear main bearing cap (if removed). Some rear main bearing caps require sealant to 
be applied in corners to prevent oil leakage.  

Install and tighten all bolts except thrust bearing cap to specification. Tighten thrust bearing cap bolts finger 
tight only. Some models require that thrust bearing be aligned. On most applications, crankshaft must be moved 
rearward then forward. Procedure may vary with manufacturer. Thrust bearing cap is then tightened to 
specification. Ensure crankshaft rotates freely. Crankshaft end play should be checked. See CRANKSHAFT 
END PLAY .  

CRANKSHAFT END PLAY 

Dial Indicator Method 

Crankshaft end play can be checked using dial indicator. Mount dial indicator on rear of cylinder block. 
Position dial indicator tip against rear of crankshaft. Ensure tip is resting against flat surface.  

Pry crankshaft rearward. Adjust dial indicator to zero. Pry crankshaft forward and note reading. Crankshaft end 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

play must be within specification. If end play is not within specification, check for faulty thrust bearing 
installation or worn crankshaft. Some applications offer oversize thrust bearings.  

Feeler Gauge Method 

Crankshaft end play can be checked using feeler gauge. Pry crankshaft rearward. Pry crankshaft forward. Using 
feeler gauge, measure clearance between crankshaft and thrust bearing surface. See Fig. 22 .  

Fig. 22: Checking Crankshaft End Play 

Crankshaft end play must be within specification. If end play is not within specification, check for faulty thrust 
bearing installation or worn crankshaft. Some applications offer oversize thrust bearings.  

CYLINDER BLOCK 

Block Cleaning 

Only cast cylinder blocks should be hot tank cleaned. Aluminum cylinder blocks should be cleaned using cold 
tank method. Cylinder block is cleaned in order to remove carbon deposits, gasket residue and water jacket 
scale. Remove oil gallery plugs, freeze plugs and cam bearings before cleaning block.  

Block Inspection 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures