Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Pinpoint Test B: Loss Of Coolant
- Possible Sources
- Seal
- Coolant hose
- Engine oil cooler
- Coolant pump
- Radiator
- Heater core
- Engine front cover
- Head gasket
- Cylinder head
- Cylinder block
Visual Inspection and Pre-checks
- Check for engine coolant leaks around sealed areas, such as the coolant pump, intake manifold and cylinder heads.
- Check the coolant hoses and tubes for damage.
- Check the coolant hose and tube connections and make sure they are securely connected.
- NOTE: A sweet odor accompanying white smoke is not considered normal and is indicative of coolant in the exhaust.
- B1 CHECK FOR OBVIOUS SIGNS OF CONCERN
- Ignition OFF.
- Inspect the engine and cooling system for signs of coolant leaking externally. REFER to the Diagnosis and Testing procedure in the appropriate Engine Cooling System article for the engine being diagnosed. Refer to the appropriate Engine System article for the procedure.
Are any external coolant leaks detected?
Yes REPAIR as necessary. No GO to B2 - B2 CHECK FOR EXCESSIVE SMOKE FROM THE EXHAUST
- Start the engine.
-
NOTE: Coolant intrusion in to the cylinders will cause white smoke from the exhaust.
Allow the engine to reach normal operating temperature. Inspect the exhaust for excessive white smoke.
Does the exhaust emit excessive white smoke?
Yes GO to B6 No GO to B3 - B3 CHECK FOR COOLANT IN THE ENGINE OIL
- Ignition OFF.
- Remove and inspect the engine oil level indicator for signs of coolant in the oil.
Is coolant present in the engine oil?
Yes If equipped with an engine oil cooler, GO to B4 If not equipped with an engine oil cooler, GO to B5 No GO to B6 - B4 CHECK THE ENGINE OIL COOLER
- Inspect the engine oil cooler and seals for damage.
Are the engine oil cooler and seals free of damage?
Yes GO to B5 No REPAIR as necessary. - B5 CHECK THE ENGINE FRONT COVER
- Remove the engine front cover. Refer to the appropriate Engine system article front cover procedure for the engine being diagnosed. Refer to the appropriate Engine System article for the procedure.Check the front cover seals for damage and signs of coolant passing in to the engine oil.
Are the engine front cover seals or sealing surfaces damaged causing coolant to leak in to the engine oil?
Yes Install new engine front cover seals or a new engine front cover. Refer to the appropriate Engine system article front cover procedure for the engine being diagnosed. Refer to the appropriate Engine System article for the procedure. No GO to B6 - B6 CHECK COMPRESSION AND CYLINDER LEAKAGE
- Ignition OFF.
- Remove the spark plugs. Refer the appropriate Engine Ignition System article for the engine being diagnosed. Refer to the appropriate Engine System article for the procedure. Perform a compression test and cylinder leakage test. Check the test results for signs of a damaged head gasket or cylinder head sealing surfaces. Check the coolant for bubbles caused by air entering the cooling system from compression. REFER to: Compression and Cylinder Leakage Test - Diesel .
Does the compression test or cylinder leakage test indicate a loss of compression or excessive cylinder leakage in to the cooling system?
Yes GO to B8 No GO to B7 - B7 CHECK FOR COOLANT INTRUSION
- Using a bore scope, inspect the cylinders and pistons for signs of coolant intrusion.
Do the cylinders show signs of coolant intrusion?
Yes GO to B8 No The source of the concern is not coolant intrusion in to the cylinder. Check for other possible sources for coolant loss. REFER to the Diagnosis and Testing procedure in the appropriate Engine Cooling System article for the engine being diagnosed. Refer to the appropriate Engine System article for the procedure. - B8 CHECK THE ENGINE
- Remove the cylinder heads. Refer to the appropriate Engine System article cylinder head procedure(s) for the engine being diagnosed. Refer to the appropriate Engine System article for the procedure. Inspect the head gasket(s) for signs of damage or failure. Inspect the cylinder block and cylinder head(s) for damage. REFER to: Cylinder Block Distortion . and REFER to: Cylinder Head Distortion .
Are the cylinder head gasket(s), cylinder head(s) or cylinder block head damaged?
Yes REPAIR as necessary. No Install a new long block.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.