Systematic procedure to identify the source of fluid leaks on a 2014 Ram 2500 with 6.7L Cummins diesel engine using visual inspection, UV dye tracing, and pressure testing methods.

Warnings

Tools required

Parts

• UV dye for diesel engine oil × 1 — Use fluorescent oil dye compatible with diesel
• UV dye for coolant × 1 — Use compatible with OAT coolant systems
• Shop towels × 1 — Generic

Preparation

1. Park vehicle on level surface and allow engine to cool for at least 30 minutes
2. Engage parking brake and chock rear wheels
3. Document current fluid levels in engine oil, coolant, power steering, brake master cylinder, transmission, transfer case, and both differentials
4. Take photos of any visible staining or leak evidence before cleaning
5. Raise vehicle on lift or securely support on jack stands at all four corners for underbody access

Procedure

1. 1

   Initial visual inspection and documentation
   With vehicle raised, perform thorough visual inspection of entire underbody and engine compartment. Look for wet spots, staining, drips, or fluid accumulation. Check oil pan, transmission pan, transfer case, differential covers, coolant hoses, fuel lines, power steering lines, and brake lines. Note the color and consistency of any fluids found: engine oil (black/brown), coolant (purple), transmission fluid (red), gear oil (amber/brown), diesel fuel (clear/amber), brake fluid (clear/amber), power steering fluid (red). Document all findings with photos showing location and extent of leaking or staining.
2. 2

   Clean suspected leak areas
   Using brake cleaner and shop towels, thoroughly clean all areas where fluid residue or staining is visible. Clean a wide area around suspected leak sources to create a clean baseline for observation. For the 6.7L Cummins, pay special attention to: oil pan and drain plug area, rear main seal area at engine-to-transmission junction, valve cover gaskets, oil filter housing, oil cooler connections, fuel filter housing, injection pump seals, and turbocharger oil drain. For drivetrain: transmission pan and cooler lines, transfer case seals, front and rear differential pinion seals and cover gaskets. Allow cleaned areas to air dry completely.
3. 3

   Check fluid levels and top off if necessary
   After cleaning, recheck all fluid levels. Top off any low fluids to proper levels to ensure adequate pressure for leak detection. For engine oil, verify level is between MIN and MAX on dipstick with engine cold. Check coolant level in overflow tank (should be at COLD line). Verify power steering, brake fluid, transmission (with engine at operating temp in Park), transfer case, and differential levels according to specifications. Low fluid levels may indicate significant leakage and help narrow diagnosis.
4. 4

   Add UV dye to suspected systems
   Based on initial inspection and fluid types identified, add appropriate UV dye to suspected leaking systems. For engine oil leaks, add diesel-compatible UV oil dye through oil fill cap (typically 1 oz per 5 quarts). For coolant leaks, add UV coolant dye to overflow reservoir. For transmission leaks, add ATF-compatible dye through dipstick tube. For differential or transfer case leaks, dye may need to be added during fluid service. Follow dye manufacturer instructions for proper concentration. Note which systems received dye for later reference.
5. 5

   Operate vehicle to circulate dye
   Lower vehicle and start engine. Allow to idle for 5 minutes to reach normal operating temperature and circulate dye through systems. Check that coolant temperature reaches 180-200°F and oil pressure is normal (10+ PSI at idle, 30+ PSI at speed). Operate power steering lock-to-lock several times. If transmission leak is suspected, shift through all gears with foot on brake. After warm-up, take vehicle on 10-15 minute test drive including highway speeds, acceleration, deceleration, and turns to pressurize all systems and distribute dye throughout.
6. 6

   Inspect with UV light - engine compartment
   Return to shop and raise vehicle. Using UV inspection light in darkened area, carefully inspect all engine areas where dye was added. Fluorescent dye will glow brightly under UV light, clearly showing leak paths. On 6.7L Cummins, check: valve cover perimeter and bolt areas, oil filter housing and adapter, oil cooler lines and connections, front and rear crankshaft seals, oil pan gasket and drain plug, turbocharger oil feed and drain lines, fuel filter housing base and water-in-fuel sensor, high-pressure fuel pump, injector return lines, and EGR cooler connections. Trace glowing dye back to its highest point to identify actual leak source versus drip paths.
7. 7

   Inspect with UV light - underbody and drivetrain
   Continue UV light inspection of entire underbody. Check transmission pan gasket, output shaft seals, cooler line connections, and torque converter area (visible through inspection cover). Inspect transfer case input/output seals, shift motor seals, and vent. Check front differential pinion seal, axle tube seals, and cover gasket. Inspect rear differential pinion seal, axle seals, and cover. Look for glowing dye trails on frame, crossmembers, and skid plates that indicate leak paths from above. Check all brake line connections and wheel cylinders/calipers for brake fluid leaks (may not show with UV dye unless specific brake fluid dye was used).
8. 8

   Perform coolant system pressure test if needed
   If coolant leak is suspected but not clearly visible, perform pressure test. Ensure engine is cool, then remove radiator cap and install coolant system pressure tester adapter. Pump tester to 16 PSI (system rated pressure) and observe gauge. System should hold pressure for 5 minutes with less than 2 PSI drop. While under pressure, inspect all hoses, clamps, water pump weep hole, radiator end tanks and seams, heater core connections (check passenger floor for dampness), EGR cooler, CAC (charge air cooler) connections, and thermostat housing. On 6.7L Cummins, check the coolant-to-oil heat exchanger for external leaks and check oil for coolant contamination (milky appearance).
9. 9

   Check for internal leaks and cross-contamination
   Inspect for signs of internal leaks that may not be visible externally. Check engine oil dipstick and oil fill cap for milky residue indicating coolant contamination. Inspect coolant overflow tank for oil film on surface indicating oil-to-coolant leak. Remove oil fill cap and check for excessive white smoke from breather indicating blow-by. Check air intake tubing and intercooler boots for oil accumulation indicating turbo seal failure. Inspect exhaust for white smoke (coolant burning) or blue smoke (oil burning). For transmission, check for metallic particles in fluid. Check differential vent tubes for fluid being pushed out indicating overfill or excessive pressure.
10. 10

    Document findings and determine leak source
    Compile all inspection findings with photos clearly showing leak sources identified by UV dye or pressure testing. Determine primary leak source(s) requiring repair based on severity, location, and fluid type. Common 6.7L Cummins leak points include: oil filter housing gasket, front crankshaft seal, valve cover gaskets, oil pan gasket, rear main seal, turbo oil drain tube, and fuel filter housing. For drivetrain: transmission output seal, transfer case rear seal, and differential pinion seals are common. Prioritize leaks by severity: active drips requiring immediate repair, seepage requiring near-term repair, and staining from previous leaks already repaired. Provide customer with detailed report including photos, fluid type, location, severity, and repair recommendations.

Reassembly

1. Remove any pressure testing equipment and reinstall radiator cap
2. Clean any UV dye residue from exterior surfaces if needed (dye is generally permanent until leak is repaired)
3. Lower vehicle from lift or jack stands
4. Recheck all fluid levels and top off if necessary after testing
5. Clear any diagnostic trouble codes that may have been set during testing

Verification

• Confirm leak source has been positively identified and documented with photos showing UV dye trail or active leaking
• Verify all fluid levels are at proper specification after testing procedures
• Ensure customer report includes clear description of leak location, fluid type, severity, and recommended repairs
• If multiple leaks found, prioritize by severity and provide estimate for each repair
• For slow seepage, consider recommending customer return after additional drive time if leak source remains unclear

More procedures for this vehicle