GMC 4000 Series Service Manual page 317

Sec. 6B
Page 306
TORO-FLOW DIESEL ENGINE
POSSIBLE CAUSES
6. Worn oil pump assem bly.
7. E xcessive clearance at crankshaft, camshaft or
balance shaft bearings.
NOTE: In case of no oil pressure, the oil pump drive shaft or drive
gear teeth could be worn to point where oil pump is not driven. Inspec­
tion can be made by removing the oil pump and tachometer drive hous­
ing and gear at rear of engine.
A BN O R M A L ENGINE COOLANT TEMPERATURES
SYMPTOM A - ENGINE OVERHEATS
POSSIBLE CAUSES
1. Scale deposits in cooling system .
2. Air flow thru radiator restricted or clogged.
3. Loose fan drive belt (if used).
4. Low coolant level.
5. Hoses collapsed.
6. Defective therm ostats.
7. Combustion gases in cooling water.
8. Incorrect injection pump to engine timing.
SYMPTOM B - ENGINE RUNS TOO COOL
POSSIBLE CAUSES
1. Defective thermostat.
2. Wrong therm ostats installed.
G M C S E R V I C E M A N U A L
LOW ENGINE OIL PRESSURE (CONT'D)
REMEDY
6. Overhaul or replace engine oil pump assembly.
7. D isassem ble engine and replace bearings as
required.
REMEDY
1. Clean and flush cooling system .
2. Clean outside of radiator core.
3. Adjust belt to proper tension.
4. F ill system to proper level. Inspect cooling
system for leaks.
5. Replace defective hoses.
6. Remove thermostats, inspect, test, and replace
as necessary.
7. Determine point at which gases enter system .
Disassem ble and inspect cylinder head and gas­
kets. Replace gaskets, and if head is cracked,
replace head.
8. Set timing correctly.
REMEDY
1. Inspect thermostat and replace defective unit.
2. Install thermostats having correct opening tem ­
perature.