Fluid Leak Diagnosis

Systematic diagnosis of fluid leaks on a 2023 Chevrolet Bolt EUV electric vehicle, identifying source and type of fluid loss from cooling system, brake system, windshield washer, or drive unit.

Warnings

Tools required

Parts

• Shop towels × 1 — Use as needed

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow vehicle to sit for at least 10 minutes to let any active leaks drip and collect
3. Note the location of any puddles or stains under the vehicle before moving it
4. If possible, place clean cardboard under vehicle overnight to identify leak location and fluid type
5. Ensure vehicle has been powered off for at least 5 minutes before beginning inspection

Procedure

1. 1

   Identify Fluid Type and Location
   Examine any fluid puddles or stains under the vehicle. Orange/pink fluid indicates DEX-COOL coolant. Clear/blue fluid indicates windshield washer fluid. Clear to light brown fluid indicates brake fluid or drive unit fluid. Note the approximate location of the puddle relative to vehicle (front, center, rear, driver side, passenger side). Take photos for reference.
2. 2

   Raise and Support Vehicle
   Safely raise the vehicle using a floor jack at the designated lift points. Support with jack stands at all four corners for complete undercarriage access. Never work under a vehicle supported only by a jack. Ensure vehicle is stable before proceeding.
   ⚠️Never work under a vehicle supported only by a hydraulic jack. Always use properly rated jack stands.
3. 3

   Inspect Underbody for Active Leaks
   Using a flashlight, inspect the entire underbody starting from the suspected leak area. Look for wet spots, dripping fluid, or fresh fluid trails. On the Bolt EUV, pay particular attention to: drive unit area (center front), coolant lines running to battery thermal management system (under floor pan), brake lines at all four corners, and windshield washer reservoir (front driver side).
4. 4

   Inspect Cooling System Components
   Check all coolant system components including: radiator (front of vehicle), coolant reservoir (passenger side engine bay), heater core hoses (firewall area), battery thermal management coolant lines (under vehicle floor), coolant pump connections, and all hose clamps. Look for wet spots, corrosion, or staining that indicates a slow leak. The Bolt EUV uses coolant for both the electric drive unit and battery thermal management.
5. 5

   Inspect Drive Unit and Reduction Gear
   Examine the electric drive unit housing (front center of vehicle) for fluid seepage around seals, particularly at the axle output shafts and where the unit bolts to the motor housing. Check the drive unit fill/drain plugs for wetness. Fresh oil indicates a recent leak; dried oil with dirt indicates an older leak. ATF from the drive unit will appear red or amber.
6. 6

   Inspect Brake System
   Check brake fluid level in master cylinder reservoir (driver side rear of engine bay). Inspect all brake lines, flexible hoses at each wheel, brake calipers, and the master cylinder for signs of leakage. Brake fluid is hygroscopic and will attract dirt, appearing as dark wet spots. Check area around ABS module and brake booster connections.
7. 7

   Inspect Windshield Washer System
   Examine windshield washer reservoir (front driver side of engine bay) for cracks or loose connections. Check washer hoses running to front and rear nozzles. Washer fluid leaks are typically clear or blue and will be obvious in the front driver side area or along the hood or roof line.
8. 8

   Check for Condensation vs Actual Leaks
   Distinguish between normal air conditioning condensation and actual fluid leaks. Clear water dripping from the center front underbody is normal A/C condensation. This will have no odor and no color. Actual leaks will show fluid accumulation, staining, or will be located away from the A/C drain area.
9. 9

   Perform Dye Test if Necessary
   If leak source cannot be visually identified but fluid loss is confirmed, add UV dye to the suspected system (coolant or brake fluid). Run vehicle through normal operation cycle for 50-100 miles. Re-inspect with UV light to identify exact leak source. Follow dye manufacturer instructions for proper concentration.
10. 10

    Clean and Monitor
    Clean the suspected leak area thoroughly with appropriate cleaner and dry completely. Apply oil dry or absorbent material below the suspected area. Lower vehicle and run through appropriate test (drive cycle for drive unit, operate climate control for coolant, apply brakes for brake system). Re-inspect after test to confirm leak source and severity.

Reassembly

1. Lower vehicle from jack stands using floor jack
2. Remove jack stands and lower vehicle completely to ground
3. Clean any spilled fluids from garage floor or driveway

Verification

• Confirm exact source of leak has been identified or ruled out
• Document leak location, fluid type, and severity for repair planning
• Check fluid levels in all systems and top off if necessary to safe operating level
• If no leak found but fluid loss confirmed, schedule additional diagnostic time or pressure testing
• Advise customer of findings and provide repair estimate for leak correction

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