Slight Loss of Coolant or Low Coolant Light Coming On with No Signs of External Leaks (Perform Service Procedure in this Bulletin)

Some customers may comment that the low coolant light is coming on and/or the coolant level is low with no external leaks visible. Low coolant may be accompanied by one of the following when the engine is cold:

This condition may be caused by porosity in the aluminum of the cylinder head casting.

Follow service procedure in this bulletin.

Diagnostic Checks

1. Verify low coolant level.
2. Inspect all coolant hoses and connections for coolant leaks.

•	If leaks are found, replace hoses and/or tighten clamps as necessary and return vehicle to the customer.

•	If no leaks are found, check engine oil for signs of coolant contamination. Add black light dye (SA9176NE) to the cooling system and start engine. Run engine until it is at normal operating temperature 180°F (82°C) to allow the dye to circulate through the system.

3. Pressurize cooling system to 25 psi (172 kPa) and monitor gauge for pressure loss during remaining inspections.

•	Inspect complete cooling system hoses and connections for visual signs of external leaks using the black light (J42220).

•	Remove spark plugs and inspect threads for wetness from coolant and check with black light (J42220).

•	Using a flashlight, inspect combustion chambers for any sign of wetness from coolant.

4. If no pressure loss and no signs of internal or external leaks, return vehicle to customer.
5. If pressure gauge shows loss of pressure and there is evidence of external leakage from hoses or other external cooling system components, correct the leak using the appropriate service manual procedures.

•	If coolant is present on any spark plug thread or visible in a combustion chamber, replace the cylinder head. (Refer to the "Cylinder Head Replacement" procedures in the appropriate 2.2 (L61) Engine Mechanical Service Manual for the vehicle being repaired.)

•	If pressure gauge shows loss of pressure and no external leaks, remove cylinder head and inspect cylinder liner height to block deck surface for flushness.

-	If a cylinder liner is not flush with the block (lower than block surface), replace the cylinder block. (Refer to the "Cylinder Block Replacement" procedures in the appropriate 2.2 (L61) Engine Mechanical Service Manual for the vehicle being repaired.)

-	If all cylinder liners are flush with the block surface, replace the cylinder head. (Refer to the "Cylinder Head Replacement" procedures in the appropriate 2.2 (L61) Engine Mechanical Service Manual for the vehicle being repaired.)

6. Verify leaks have been corrected.

To receive credit for this repair during the warranty coverage period, submit a claim through the Saturn Dealer System for J3010 (Cooling System Lean - Analyze) and/or J0518 (Head, Cylinder - Replace) or J1810 (Block, Engine Cylinder - Replace).