A1 ENGINE REPAIR // FLAGSHIP DIAGNOSTIC
2014 4-Cyl Sedan
2.4L I4 · 96,000 mi · P0301 misfire · coolant disappearing
Customer concern
"Coolant disappears every week or so. I'm topping it off and there's white smoke at startup that smells kinda sweet. Engine runs OK but the temp gauge creeps up in traffic."
Pre-checks
DTC: P0301 — CYLINDER 1 MISFIRE DETECTED (intermittent) P0128 — COOLANT TEMP BELOW THERMOSTAT REG TEMP (pending) OIL LEVEL: Full, clean — OK OIL CONDITION: No milkshake, no coolant intrusion — OK EXTERNAL LEAKS: None at hoses, water pump, radiator — OK RESERVOIR: Low, refilled. No visible oil film — OK
External cooling system passes inspection. The coolant is going somewhere. Find it.
Step 1 · Scan data + cooling pressure test
Read the live data, then pressure-test the cooling system. If it holds and you see no external drop, the coolant is leaving some other way.
FixedIntel Scan Tool · Live data
ECT climbing toward 215°F · MAP at idle
Cooling system · Pressure test
Target 16 psi · hold 15 min
Pressure holds at 16 psi. No external drop. No visible leak.
Where is the coolant going?
Step 2 · Combustion gas (block) test
Draw vapor from the coolant reservoir through the chemical. If hydrocarbons are present, the fluid changes color — combustion gas is crossing into the cooling system.
Block tester · over reservoir
Fluid: blue — negativePOSITIVE — combustion gases detected in coolant.
What does this confirm?
Step 3 · Compression test · all four
Crank each cylinder and snapshot the reading. Combustion gas is in the coolant — now find out which cylinders are leaking.
Two adjacent cylinders read low. What does this pattern point to?
Step 4 · Cylinder leakdown · cyl 1
TDC compression on cyl 1. Apply 100 psi shop air.
Leakdown tester · cyl 1
62%
Leakage · out of spec
Listening points
Listen at each location to find where the air is escaping. Click each hot zone.
Bubbles in the coolant reservoir during leakdown on cyl 1 confirm what?
Step 5 · Root cause
Block test positive, adjacent cylinders 1 and 2 both low, leakdown bubbling into the coolant. Call it.
Final root cause for the misfire, coolant loss, and combustion gases in the reservoir:
Diagnosis Closed.
Blown head gasket between cylinders 1 and 2 — pulled the head, surfaced it, replaced gasket and head bolts.
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A1 · ENGINE REPAIR
Flagship cleared
Step breakdown · aced first try