7745750_091 Volvo.Penta Tachometer sensor

Probable Causes
Oil cooler
Jacket water pump and auxiliary water pump (if equipped)
Water-cooled turbocharger (if equipped)
Cylinder head gasket
Cylinder head
Cylinder blockRecommended Actions
Table 1
Troubleshooting Test Steps Values Results
1. Check for leaks in the Engine Oil Cooler
A. Refer to the Testing and Adjusting manual for additional information.
Oil Cooler
Result: A leak was not found in the engine oil cooler.
Proceed to Test Step 2.
Result: A leak is found in the engine oil cooler.
Repair: Perform the following procedure:
1. Install a new oil cooler core. Refer to the Disassembly and Assembly manual for additional information.
2. Check the oil for coolant. If coolant is found in the oil, drain the crankcase.
3. Refill the crankcase with the proper oil after the leak has been repaired. Refer to the Operation and Maintenance Manual for the correct oil capacities and viscosity.
If the problem is not resolved, proceed to Test Step 2.
2. Check the Jacket Water Pump and the Auxiliary Water Pump
A. Check the weep hole of the jacket water pump for plugging. A plugged weep hole may cause coolant to be forced past the pump shaft seals into the crankcase.
B. Thoroughly inspect the water pump for damage and cracks. If internal leakage is suspected, remove the pump from the engine in order to perform a thorough inspection.
Pump
Result: The weep hole was not plugged and the pump is not damaged.
Proceed to Test Step 3.
Result: The weep hole was plugged.
Repair: Clear the plug.
If the problem is not resolved, proceed to Test Step 3.
Result: There was a problem with the water pump.
Repair: Perform the following procedure:
1. Install a new water pump. Refer to the Disassembly and Assembly manual for additional information.
2. Check the oil for coolant. If coolant is found in the oil, drain the crankcase.
3. Refill the crankcase with the proper oil after the leak has been repaired. Refer to the Operation and Maintenance Manual for the correct oil capacities and viscosity.
If the problem is not resolved, proceed to Test Step 3.
3. Inspect the Water-Cooled Turbocharger
A. Remove the oil drain line from the turbocharger and pressurize the cooling system. Refer to Testing and Adjusting, "Cooling System - Test" for additional information.
B. Check the turbocharger for coolant leakage.
Turbocharger
Result: The turbocharger is not cracked.
Proceed to Test Step 4.
Result: The turbocharger is cracked.
Repair: Perform the following procedure:
1. Replace the turbocharger. Refer to the Disassembly and Assembly for additional information.
2. Check the oil for coolant. If coolant is found in the oil, drain the oil.
3. Refill the oil after the leak has been repaired. Refer to the Operation and Maintenance Manual for the correct oil capacities and viscosity.
If the problem is not resolved, proceed to Test Step 4.
4. Inspect the Cylinder Head Gasket
A. Remove the cylinder head. Refer to the Disassembly and Assembly manual for additional information.
B. Check the cylinder liner projection. Refer to Testing and Adjusting, "Cylinder Liner Projection" for additional information.
Cylinder Head Gasket
Result: The cylinder head gasket and water seals are not leaking.
Proceed to Test Step 5.
Result: The cylinder head gasket and/or water seals are leaking.
Repair: Install a new cylinder head gasket and new water seals in the spacer plate. Refer to the Disassembly and Assembly manual for additional information.
If the problem is not resolved, proceed to Test Step 5.
5. Inspect the Cylinder Head
A. Perform a leak test on the cylinder head. Refer to the System Operation/Testing and Adjusting manual for additional information.
Cylinder Head
Result: A crack is not found in the cylinder head.
Proceed to Test Step 6.
Result: A crack is found in the cylinder head.
Repair: Repair or replace the cylinder head. Refer to the Disassembly and Assembly manual for additional information.
If the problem is not resolved, proceed to Test Step 6.
6. Inspect the Cylinder Block
A. Inspect the cylinder liner for cracks.
Cylinder Block
Result: A crack is found in the cylinder block or cylinder liner.
Repair: Perform the following procedure:
1. Repair or replace the cylinder block. Inspect the top deck. Refer to the Reuse and Salvage Guidelines manual for additional information.
2. Replace any cracked cylinder liners. Refer to the Disassembly and Assembly manual for additional information.
Verify that the repair eliminated the problem.
If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).