2.5l 4-cyl - VIN [e] GMC Cab & Chassis R2500

ENGINE IDENTIFICATION

Note. For engine repair procedures not covered in this article, see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article in the GENERAL INFORMATION section.

Engine may be identified by the eighth character of the Vehicle Identification Number (VIN). VIN is stamped on metal tag, attached to left side of dash, near windshield. Engine identification number is stamped on machined pad on left rear of engine block below cylinder head.

ENGINE IDENTIFICATION CODE

ENGINE

See ENGINE REMOVAL - 4-CYL article.

Removal

1. Disconnect negative battery cable. Remove air cleaner. Unplug electrical connectors at intake manifold. Disconnect accelerator and throttle valve cables at bellcrank. Disconnect fuel and vacuum lines at throttle body and manifold. Drain cooling system.
2. Disconnect water pump by-pass hose at intake manifold. Remove rear alternator adjusting bracket. Disconnect alternator brace and move aside. Disconnect cruise control cable. Disconnect and label all vacuum hoses.
3. Disconnect vacuum line hold-down at thermostat housing. Disconnect heater hose at intake manifold. Disconnect coil. Remove intake manifold.

Scheme 1

Installation

To install, reverse removal procedure. Apply sealant to bolts No. 4, No. 5 and No. 6. (Scheme 1) Tighten bolts to 25 ft. lbs. (34 N.m).

1. Disconnect negative battery cable. Disconnect A/C belt. Remove A/C compressor and set aside. Remove rear A/C adjusting bracket. Raise vehicle. Disconnect exhaust pipe at manifold. Lower vehicle.
2. Remove air cleaner and heat stove tube. Disconnect oxygen sensor wire. Do not remove oxygen sensor from manifold unless exhaust manifold requires replacement. Remove exhaust manifold bolts. Remove exhaust manifold.

Scheme 2

To install, reverse removal procedure. Tighten bolts to specifications. (Scheme 2)

1. Disconnect negative battery cable. Drain cooling system. Remove air cleaner assembly. Disconnect PCV hose. Remove EGR valve. Disconnect spark plug wires at spark plugs. Remove A/C bracket and compressor and set aside. Disconnect vacuum line and wiring harness at thermostat housing. Disconnect and label all vacuum lines. Disconnect oil dipstick tube and oil filler tube. Remove valve cover bolts. Remove valve cover using Remover (J-34144-A).
2. Remove vacuum lines, fuel lines and wiring at intake manifold and throttle body. Disconnect accelerator, cruise control and throttle valve cables. Disconnect water pump by-pass and heater hoses at intake manifold. Remove alternator brackets and set alternator aside. Remove thermostat housing. Disconnect ground cable and wiring harness bracket at rear of cylinder head.
3. Disconnect exhaust pipe at manifold. Disconnect fuel filter and fuel line brackets at rear of cylinder head. Disconnect wiring harness connector at fuel filter. Disconnect wiring harness connectors at sensors at rear of head and thermostat housing. Disconnect coil wires and oxygen sensor wire. Disconnect upper radiator hose.
4. Loosen rocker arms and rotate to one side. Remove push rods. Remove head bolts. Remove head with intake and exhaust manifolds attached. Remove intake and exhaust manifolds.

Note. See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article to prepare head for installation.

Note. This procedure has been revised due to TSB Chevrolet 88-52, dated 09/23/1987.

1. To install, reverse removal procedure. Apply sealant to bolt No. 9. Tighten all head bolts to 18 ft. lbs. (24 N.m) in specified sequence. (Scheme 3)
2. Tighten all head bolts in sequence (EXCEPT bolt No. 9) to 27 ft. lbs. (35 N.m). Retighten bolt No. 9 to 18 ft. lbs. (24 N.m).
3. Draw a line across head of each bolt with a marking crayon to mark position of bolt.
4. Tighten all bolts an additional 90 degrees (1/4 turn) in specified sequence.

Scheme 3

VALVES

Note. New valves must not be lapped. Lapping will destroy protective coating on valve face. Use old valve (with face in good condition) if lapping is necessary.

VALVE ARRANGEMENT

I-E-I-E-E-I-E-I (Front-to-rear).

VALVE GUIDES

1. With cylinder head removed and disassembled, check valve stem-to-guide clearance. See, in the GENERAL INFORMATION section, «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article. Check clearance with valve head positioned .063" (1.6 mm) away from valve seat.
2. Use Valve Guide Cleaner (J-8101) for cleaning guides. Use Valve Guide Reamers (J-5830-01 or J-6621) to ream guides for installation of valves with oversize stems. Service valves are available in .003" and .005" (.08-.13 mm) oversizes.

VALVE STEM OIL SEALS

See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article for seal replacement.

VALVE SPRINGS

See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article for valve spring replacement

VALVE SPRING SQUARENESS

See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article to check squareness. Valve spring out-of-square service limit is .0625" (1.588 mm).

VALVE SPRING COMPRESSION PRESSURE

See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article to check compression pressure. Valve spring compression pressure service limit for both intake and exhaust when closed is 71-78 lbs. at 1.44" (32-35 kg at 36.6 mm). Valve spring service limit when open is 158-170 lbs. at 1.04" (72-77 kg at 26.4 mm).

VALVE SPRING INSTALLED HEIGHT

See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article to check installed height. Intake and exhaust valve spring installed height is 1.44" (36.6 mm).

1. Disconnect negative battery cable. Remove alternator and bracket. Drain cooling system. Disconnect lower radiator and heater hoses. Disconnect spark plug wires and bracket at intake manifold.
2. Disconnect fuel lines at side cover. Remove oil pressure sending unit. Remove wiring harness brackets from side cover. Remove 4 nuts from side cover studs.
3. Reverse 2 of the nuts (washers facing out) and screw them back onto the 2 inner studs. Install the 2 remaining nuts onto the same 2 inner studs (washers facing in).
4. Using 2 wrenches, hold the inner nut stationary, and jam the 2 nuts tightly together. Using a wrench on the inner nut, unscrew the studs until the cover breaks loose. Remove jammed nuts from each stud. Remove cover from studs.

Clean gasket sealing surfaces. Inspect studs and rubber washers for damage. Replace as necessary. Tighten studs to 90 INCH lbs. (10 N.m). Apply a 3/16" thick, continuous bead of RTV to side cover. Install side cover and tighten nuts to 90 INCH lbs. (10 N.m). To complete installation, reverse removal procedure.

Scheme 4

HYDRAULIC ROLLER VALVE LIFTERS

Note. For cleaning and inspection of hydraulic lifters, see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

Removal & Installation

1. Remove valve cover, intake manifold and push rod cover. Loosen rocker arm and rotate for clearance from push rod. Remove push rod, lifter retainer and guide plates. (Scheme 4) Using lifter remover or magnet, remove lifters.
2. Check lifter-to-bore clearance. Standard clearance is.0025" (.064 mm). Standard diameter of lifter is.8420-.8427" (21.387-21.405 mm). Standard lifter bore diameter is.8435-.8445" (21.425-21.450 mm).
3. To install, reverse removal procedure. If new lifter is being installed, sealer coating on inside of lifter must be removed. Coat lifter body and roller with engine oil. Ensure push rod seats properly in the lifter. Ensure lifter is installed on base circle of camshaft.

1. Disconnect negative battery cable. Disconnect power steering reservoir from fan shroud (if equipped). Remove upper fan shroud. Remove fan belts, fan and pulley. Remove alternator, brackets and brace.
2. Remove crankshaft pulley. Remove crankshaft hub bolt. Remove crankshaft hub. Disconnect lower radiator hose at water pump. Remove front cover bolts and front cover.

1. Clean mating surfaces of engine block, oil pan and front cover. Apply a continuous bead of RTV on cover. Install Front Cover Centering Tool and Seal Installer (J-34995) in front cover oil seal. Install front cover to block.
2. Install and partially tighten 2 oil pan-to-front cover bolts. Install front cover-to-block bolts and tighten to 90 INCH lbs. (10 N.m). Remove centering tool. Reverse removal procedure to complete installation.

Remove engine drive belts. Remove center hub bolt and slide hub and pulley(s) from crankshaft. Using large screwdriver, pry oil seal from front cover. DO NOT distort sheet metal timing chain cover.

1. Install new seal with lip toward rear of engine. Drive seal into place using Seal Installer (J-34995). Coat oil seal contact area of balancer with engine oil.
2. Position hub on crankshaft and slide into position until it bottoms against crankshaft gear. Install center hub bolt and tighten. Install pulley-to-hub bolts using Loctite and tighten. Install belts and adjust tension.

Scheme 5

Scheme 6

1. Disconnect negative battery cable. Disconnect power steering reservoir from fan shroud (if equipped). Remove upper fan shroud. Remove fan belts, fan and pulley. Remove crankshaft pulley and front cover.
2. Remove valve cover. Loosen rocker arm bolts and pivot rocker arms aside. Remove push rods. Remove intake manifold. Remove push rod side cover and remove valve lifters. Remove distributor.
3. Remove radiator. Remove A/C condenser (if equipped) bolts. Raise and block condenser up high enough to clear camshaft. Remove alternator and bracket. Remove grille and filler panel.
4. Remove oil pump drive shaft retainer plate bolts. Remove bearing and shaft assembly. (Scheme 5)
5. Remove 2 camshaft thrust plate retaining bolts by working through holes in camshaft gear. (Scheme 6) Remove camshaft and gear assembly by pulling it through front of block. Use care not to damage camshaft bearings.
6. Place camshaft through opening in press plates on arbor press. Support gear (DO NOT support thrust plate) and press camshaft out of timing gear (if necessary). Position thrust plate so that Woodruff key in camshaft does not damage thrust plate during removal.

Inspection

1. Check camshaft journals for out-of-round condition. If journals exceed specification, replace camshaft.
2. Check camshaft end play. Replace thrust plate if clearance exceeds specification. Replace spacer ring if clearance is less than specification.
3. Check camshaft journal runout. If runout exceeds specification, replace camshaft. Check camshaft lobe lift. If not to specification, replace camshaft.

1. Support camshaft at back of front journal in arbor press using press plate adapters. Install gear spacer ring and thrust plate over end of camshaft. Install Woodruff key in shaft keyway. Install camshaft gear and press it onto camshaft until it bottoms against gear ring spacer ring. Check end play.
2. Coat camshaft lobes with GM Oil Supplement (1051396). Coat journals with engine oil and install camshaft in engine block. Be careful not to damage camshaft bearings. Align timing marks by rotating camshaft and crankshaft until timing marks on gear teeth line up. (Scheme 7)
3. Engine is now timed to No. 4 cylinder firing position. Install 2 camshaft thrust plate-to-block bolts and tighten. Install timing gear cover. Line up hub keyway to crankshaft key, install hub and tighten center bolt.
4. Install lifters, push rods, push rod cover, and oil pump shaft and gear assembly. To install distributor, turn crankshaft 360 degrees to firing position of No. 1 cylinder (timing marks aligned on balancer and timing pad and valves closed).
5. Install distributor in original position and align shaft with rotor arm toward No. 1 plug contact. Pivot each rocker arm over push rod and tighten rocker arm bolt (with lifter on base circle of camshaft). To complete installation, reverse removal procedure.

Scheme 7

With engine, flywheel and camshaft removed, drive out expansion plug from rear camshaft bearing. Remove by driving out from inside. Using Universal Camshaft Bearing Remover and Installer (J-33049), drive out front bearing toward rear of engine and rear bearing toward front. Drive center bearing out toward rear of engine.

Install each bearing on installer and replace in block in reverse order of removal. Ensure oil hole in camshaft bearings and cylinder block line up. Install front camshaft bearing with bearing recessed about 1/8" into engine block. This uncovers oil hole to timing gear oil nozzle. Reverse removal procedure to complete installation.

OIL PAN

See OIL PAN REMOVAL article.

PISTON & ROD ASSEMBLY

Note. See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article for removal, cleaning, inspection and installation of piston and rod assembly,.

1. When removing piston and rod assembly, ensure connecting rod, rod cap and piston are marked for proper reassembly into matching cylinder. When installing piston and rod assembly, ensure ring gaps are properly spaced. (Scheme 8) Ensure oil hole in bearing insert aligns with oil hole in connecting rod. NOTE: Notch on top of piston faces front of engine.
2. After installation, check rod bearing clearance using Plastigage method. Check rod side clearance after tightening rod nuts to specification. See «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article.

Scheme 8

FITTING PISTONS

1. Check cylinder bore taper and out-of-round. Refer to «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article. Cylinder bore out-of- round should not be more than .0010" (.025 mm). Cylinder bore taper should not be more than .005" (.13 mm).
2. Measure diameter of cylinder bore parallel to crankshaft at a point 2.25" (57.2 mm) from top of cylinder bore. Measure outer diameter of piston at centerline of pin bore, 90 degrees to pin bore axis.
3. Determine if piston-to-bore clearance is acceptable. If not acceptable, determine if a new piston can fit cylinder bore. If not, cylinder bore must be reconditioned.
4. Before cylinder reconditioning, ensure that main bearing caps are in place and tightened to specification to avoid distortion during reconditioning operation. Pistons are available in standard size, .005", .010", .020" and .030" oversizes.
5. Measure new piston and hone cylinder to correct clearance. After reconditioning operation, allow bore to cool, then clean bore with hot soapy water and oil cylinder walls.

FITTING PISTON RINGS

Note. See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article for measuring piston ring side clearance and end gap.

1. Ensure manufacturer's marks face up when rings are installed. DO NOT use ring expander on side rails. Use ring expander to install intermediate and upper rings. Ensure ring gaps are staggered at proper intervals.
2. If new piston rings are to be installed and no visible cross-hatch marks remain on cylinder walls, remove cylinder wall glaze using spring-type hone. After honing, clean bore and block with hot soapy water and oil cylinder walls.

1. Mark pistons and pins to assure assembly with same rod. Press piston pin from piston and connecting rod using Piston Pin Remover and Installer Set (J-24086).
2. Inspect and replace any piston pin showing signs of fracture, etching or wear. Check piston pin diameter. Standard piston pin diameter is .938-.942" (23.83-23.93 mm).
3. Check piston pin-to-piston pin hole clearance. If clearance exceeds specification, replace both piston and piston pin. Piston and pin are a matched set and are not available separately.

1. Raised notch on rod must face opposite notch on top of piston. Press pin through both piston and rod until pilot hub bottoms on support fixture and/or pin is centered in piston.
2. After pilot hub bottoms, DO NOT exceed 5000 lbs. (2275 kg) pressure with press. Ensure piston floats during pin installation operation.

CONNECTING ROD BEARINGS

Note. Precision insert bearings are used in this engine and shimming is not acceptable for adjustment. Always replace bearings in pairs. DO NOT file or grind connecting rods or caps when fitting bearings.

1. Remove connecting rod bearing caps and mark rods and caps for proper installation. Inspect each bearing for peeling, melting, seizure or improper contact. Replace defective bearings.
2. Measure outside diameter of crankshaft connecting rod bearing journals to determine if out-of-round or tapered. Replace crankshaft if measurement exceeds specification.
3. Use Plastigage method for bearing clearance check. See «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article. Bearings are available in standard and .0010" (.025 mm) undersize. NOTE: If clearance cannot be brought within specifications with service bearings, replace crankshaft. DO NOT grind or recondition the crankshaft. It is a rolled fillet type.
4. Check connecting rod side clearance. If excessive, replace connecting rod and cap. If side clearance is less than specification, remove rod and cap. Check for scratches, burrs, nicks or dirt between crankshaft and rod. Dress minor imperfections with oil stone. Recheck side clearance.
5. During assembly, ensure oil hole in bearing aligns with oil hole in connecting rod. Ensure bearing tangs are seated in appropriate slots in rod and cap. Ensure connecting rod bolt heads are properly seated in connecting rod.

MAIN BEARINGS

Note. Precision insert bearings are used in this engine and shimming is not acceptable for adjustment. Always replace bearings in pairs. DO NOT file or grind connecting rods or caps when fitting bearings.

1. Inspect each bearing for peeling, melting, seizure or improper contact. Replace defective bearings.
2. Measure outside diameter of crankshaft main bearing journals to determine if out-of-round or tapered. If measurement exceeds specification, replace crankshaft.
3. To check main bearing clearance, use Plastigage method. See «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article. Bearings are available in standard and .0010" (.025 mm) undersize. NOTE: If clearance cannot be brought within specifications with service bearings, replace crankshaft. DO NOT grind or recondition the crankshaft. It is a rolled fillet type.
4. If engine is in vehicle, position jack under counterweight adjoining bearing being checked so weight of crankshaft will not compress Plastigage and provide an incorrect reading. DO NOT position jack under crankshaft pulley. Crankshaft post damage will result.
5. During assembly, ensure main bearing cap arrows face front of engine.

CRANKSHAFT END PLAY

See ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article to check crankshaft end play. Replace No. 5 thrust bearing if not to specification.

REAR MAIN BEARING OIL SEAL

Note. Rear main bearing oil seal can be removed and installed without removal of oil pan or crankshaft.

Remove transmission assembly. On manual transmission, remove pressure plate and clutch disc. Remove flywheel retaining bolts and flywheel. Remove rear main bearing oil seal. Take care not to scratch crankshaft or seal surface. Clean block-to-seal mating surface.

Coat outside surface of new seal with engine oil. Using Installer (J-34924), install seal with lip toward engine. Ensure that seal is firmly in place. Install flywheel. On manual transmission, install pressure plate and clutch disc. Install transmission.

Disconnect negative battery cable. Drain engine coolant. Remove all accessory drive belts. Remove lower radiator hose at water pump. Remove water pump attaching bolts and remove water pump.

If installing new pump, transfer pulley from old pump. Apply continuous bead of sealer to clean pump sealing surface. Install water pump while sealer is still wet. Tighten attaching bolts. Install lower radiator hose and drive belts. Connect negative battery cable. Fill cooling system and check for leaks.

Note. For further information on cooling systems, see ENGINE COOLING SYSTEM article.

CRANKCASE CAPACITY

Crankcase capacity is 4 qts. (3.7L) with oil filter change; 3 qts. (2.8L) without filter change.

NORMAL OIL PRESSURE

Normal oil pressure is 36-41 psi (2.53-2.88 kg/cm 2 ) at 2000 RPM.

OIL PRESSURE REGULATOR VALVE

Oil pressure regulator valve is located in oil pump body. Valve is nonadjustable.

ENGINE OILING SYSTEM

Oil pump draws oil from pan, feeding it through the oil filter and into passage along right side of the block where it intersects lifter bosses. Oil is then routed to camshaft and crankshaft bearings through smaller drilled passages.

Oil is supplied to rocker arms through hydraulic lifters. By-pass valves are located in pick-up screen, oil filter mounting and oil pump. Oil returns to pan through return holes in head and block.

Removal & Disassembly

Remove oil pan. Remove 2 flange mounting bolts and nut from main bearing cap bolt. Remove oil pump and screen as an assembly. Do not disturb oil pick-up tube on screen or body. Mark teeth for proper indexing during reassembly. Disassemble pump and inspect for excessive wear or cracks. (Scheme 9)

Scheme 9

Reassembly & Installation

1. Install drive gear and shaft. Install idler gear with smooth side toward cover. Fill oil pump cavities with petroleum jelly to ensure immediate oil pressure. Install cover, tighten retaining bolts and ensure shaft turns freely. Install regulator valve plunger, spring, retainer and pin.
2. Align oil pump shaft to match with oil pump drive shaft tang. Install oil pump in block. Position flange over oil pump drive shaft lower bushing. No gasket is used. Tighten bolts. Pump should slide easily into place. Install oil pan with new gaskets and seals.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

VALVE SPECIFICATIONS

VALVE SPECIFICATIONS

PISTON/PIN/RING SPECIFICATIONS

PISTONS, PINS & RINGS SPECIFICATIONS

BEARING SPECIFICATIONS

CRANKSHAFT MAIN & CONNECTING ROD BEARINGS SPECS

VALVE SPRING SPECIFICATIONS

VALVE SPRINGS SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

See also:
• ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION
• ENGINE REMOVAL - 4-CYL
• OIL PAN REMOVAL
• CYLINDER HEAD