Systematic procedure to identify the source of fluid leaks on a 2016-2024 Hyundai Tucson 2.5L AWD by visual inspection, UV dye tracing, and pressure testing.

Warnings

Tools required

Parts

• UV dye for engine oil (if not included in kit) × 1 — Use OEM specification
• UV dye for coolant (if not included in kit) × 1 — Use OEM specification
• UV dye for transmission fluid (if not included in kit) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and allow all fluids and components to cool completely (minimum 2 hours)
2. Place wheel chocks behind rear wheels
3. Clean undercarriage and engine bay with degreaser to remove existing oil and fluid residue for accurate leak identification
4. Check fluid levels: engine oil, coolant, transmission, brake, front differential, rear differential, transfer case, and washer fluid
5. Document current fluid levels and note any that are low as potential leak sources
6. Raise front of vehicle with floor jack and secure on jack stands at manufacturer lift points
7. Remove front wheels if needed for better access to suspension and drivetrain components

Procedure

1. 1

   Initial visual inspection from above
   Open hood and inspect engine bay with flashlight. Look for wet spots, stains, or drips on: valve cover, front engine cover, oil filter housing, oil cooler lines, power steering pump area (note: this vehicle uses electric steering, so no fluid here), coolant hoses, radiator, expansion tank, thermostat housing, brake master cylinder, and firewall. Take photos of any suspect areas.
2. 2

   Inspect underside - front section
   Position yourself under the front of the vehicle with work light. Inspect: oil pan and drain plug area, front engine cover lower section, transmission pan and cooler lines, front differential housing and axle seals, CV axle boots, transfer case housing and seals. Look for fresh fluid, wetness, or crystallized residue indicating older leaks.
   ⚠Verify vehicle is stable on jack stands before positioning yourself underneath
3. 3

   Inspect underside - rear section
   Move to rear underside area and inspect: rear differential housing and pinion seal, rear differential cover, driveshaft connections and boots, rear axle seals, fuel tank and fuel lines, rear brake calipers and lines, exhaust system hangers for fluid drips from above. Note any wetness or staining.
4. 4

   Inspect cooling system
   Examine entire cooling system: radiator end tanks and core, upper and lower radiator hoses, heater hoses at firewall, water pump weep hole (located at front of engine), thermostat housing, coolant reservoir and cap. White or green crusty deposits indicate coolant leaks. Check ground under vehicle for green coolant puddles.
5. 5

   Identify fluid type by characteristics
   If fluid is present, identify by color and consistency: Engine oil (amber to dark brown, slick), ATF (red or pink, slick), Coolant (green, sweet smell), Differential/transfer case fluid (amber, gear oil smell), Brake fluid (clear to amber, very slick), Washer fluid (blue or green, watery). This helps narrow down the leak source.
6. 6

   Apply UV dye if leak source unclear
   If visual inspection does not clearly identify leak source, add appropriate UV dye to suspected system. For engine oil: add dye through oil fill cap. For coolant: add to expansion tank when cool. For transmission: add through dipstick tube or fill port. Use manufacturer-recommended dye quantity. Run engine to operating temperature and drive vehicle 10-20 miles to circulate dye.
   ⚠Only add dye to cool systems. Never open cooling system when hot
   ℹ️Some UV dyes may require 24-48 hours of operation for best results
7. 7

   UV light inspection
   After dye circulation period, use UV light to inspect all suspect areas in darkened conditions. The UV dye will fluoresce brightly at the leak source. Trace the leak upstream to find the actual failure point, as fluid may run along components and drip at a location away from the leak. Take photos under UV light for documentation.
8. 8

   Pressure test cooling system if applicable
   If coolant leak is suspected but not visually confirmed, perform pressure test. Remove radiator cap when cool, attach coolant pressure tester per tool instructions, and pressurize to system rating (typically 1.1-1.3 bar or 16-19 psi). Monitor pressure gauge for drop and inspect all cooling components for seepage. External leaks will appear as drips; internal leaks may show no external evidence.
   ⚠Do not exceed cooling system pressure rating marked on radiator cap
9. 9

   Check for internal leaks
   Internal leaks are harder to detect. Check engine oil dipstick for milky appearance (coolant in oil). Check coolant for oil film or contamination. Inspect exhaust for white smoke (coolant burning). Check for excessive oil consumption without external leaks. White residue on spark plugs may indicate coolant entering cylinders.
10. 10

    Document findings
    Record all leak locations, fluid types, and severity. Note whether leaks are active (wet/dripping), seeping (damp), or residual (dried stains). Estimate leak rate based on how quickly fluid accumulates. Take clear photos of leak sources. This documentation will guide repair procedures and parts ordering.

Reassembly

1. Reinstall front wheels if removed and torque lug nuts to specification in star pattern
2. Lower vehicle from jack stands
3. Clean any degreaser or inspection materials from engine bay and undercarriage
4. If UV dye was added, label systems with dye type and date for future reference

Verification

• Confirm leak source has been positively identified and documented
• Verify fluid levels are still within safe operating range
• If UV dye was used, verify fluorescence clearly indicates leak point
• Review photos and notes to ensure all information needed for repair is captured
• Place clean cardboard under vehicle overnight to monitor active leak rate if needed
• Test drive vehicle if safe to do so and recheck for new fluid accumulation

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