SUBJECT: Diesel Engine Overheating
DATE: Dec. 11, 1998
NOTE: THIS INFORMATION APPLIES TO VEHICLES EQUIPPED WITH A 24 VALVE CUMMINS DIESEL ENGINE WITH AN ENGINE SERIAL NUMBER (ESN) 56512007 OR PRIOR.
Some vehicles may overheat or run hotter than normal. In some cases DTC P0217 - DECREASED ENGINE PERFORMANCE DUE TO ENGINE OVERHEAT may be set.
If a vehicle is brought in for an overheat condition, check the ESN to determine if the engine falls within the build range. If it does not, continue with normal cooling system diagnostics listed in the appropriate service manual. If it does fall within the range, perform the Repair Procedure.
Qty Part No. Description
1 05015090AA Thermostat
This bulletin involves replacing the thermostat with a revised part.
Replace the thermostat with p/n 05015090AA following all service manual Cautions, Warnings, and procedures.
Reimbursable within the provisions of the warranty.
Labor Op. No. Time
07-40-01-92 0.4 Hrs.
P8 New Part
INTERNAL LEAKAGE TEST
Remove engine oil pan drain plug and drain a small amount of engine oil. If coolant is present in the pan, it will drain first because it is heavier than oil. An alternative method is to operate engine for a short period to churn the oil. After this is done, remove engine dipstick and inspect for water globules. Also inspect transmission dipstick for water globules and transmission fluid cooler for leakage.
WARNING: WITH COOLING SYSTEM PRESSURE TESTER TOOL INSTALLED ON RADIATOR, DO NOT ALLOW PRESSURE TO EXCEED 110 KPA (20 PSI
) PRESSURE WILL BUILD UP QUICKLY IF A COMBUSTION LEAK IS PRESENT. TO RELEASE PRESSURE, ROCK TESTER FROM SIDE TO SIDE. WHEN REMOVING TESTER, DO NOT TURN TESTER MORE THAN 1/2 TURN IF SYSTEM IS UNDER PRESSURE.
Operate engine without pressure cap on radiator until thermostat opens. Attach a pressure tester to filler neck. If pressure builds up quickly it indicates a combustion leak exists. This is usually the result of a cylinder head gasket leak or crack in engine. Repair as necessary.
If there is not an immediate pressure increase, pump the pressure tester. Do this until indicated pressure is within system range of 110 kPa (16 psi
) Fluctuation of gauge pointer indicates compression or combustion leakage into cooling system.
Because the vehicle is equipped with a catalytic converter, do not remove spark plug cables or short out cylinders (non-diesel engines) to isolate compression leak.
If the needle on dial of pressure tester does not fluctuate, race engine a few times to check for an abnormal amount of coolant or steam. This would be emitting from exhaust pipe. Coolant or steam from exhaust pipe may indicate a faulty cylinder head gasket, cracked engine cylinder block or cylinder head.
A convenient check for exhaust gas leakage into cooling system is provided by a commercially available Block Leak Check tool. Follow manufacturers instructions when using this product.
COMBUSTION LEAKAGE TEST - WITHOUT PRESSURE TESTER
DO NOT WASTE reusable coolant. If solution is clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE CYLINDER BLOCK DRAIN PLUGS OR LOOSEN RADIATOR DRAINCOCK WITH SYSTEM HOT AND UNDER PRESSURE. SERIOUS BURNS FROM COOLANT CAN OCCUR.
Drain sufficient coolant to allow thermostat removal. Refer to Thermostat Replacement. Disconnect water pump drive belt.
Add coolant to radiator to bring level to within 6.3 mm (1/4 in) of top of thermostat housing.
CAUTION: Avoid overheating. Do not operate engine for an excessive period of time. Open draincock immediately after test to eliminate boil over.
Start engine and accelerate rapidly three times, to approximately 3000 rpm (2000 rpm for diesel) while observing coolant. If internal engine combustion gases are leaking into cooling system, bubbles will appear in coolant. If bubbles do not appear, internal combustion gas leakage is not present.