How to Use the FXTUL F603 Smoke Leak Detector
The FXTUL F603 is a basic automotive smoke leak detector with its own air source. For a controlled first test, keep the engine and ignition off, add only the specified smoke medium to the oil-level limit, seal one known low-pressure section, connect the unit to a charged 12-volt vehicle battery, start smoke, and follow the first visible exit point.
F603 has no pressure gauge, flow meter or flow-control valve. It can show where smoke escapes, but it cannot give you a pressure or flow reading, and smoke at one point does not automatically prove that the nearest component has failed. Confirm the test seal, designed vents and the vehicle’s service information before naming a repair.
Updated August 28, 2026.
In this guide
Make sure this is the correct F-series workflow
Look at the model printed on the front panel. F603 has a flat front with two indicator lights and a Start/Stop button; it does not have the round pressure gauge fitted to F703/F803 or the vertical flow meter fitted to F803.
The current F603 application list is narrower than the shared F-series product title. Use this guide for a bounded basic leak check, such as an intake path whose isolation method is known. Do not treat F603 as the F803 procedure for EVAP, turbo, crankcase or whole-vehicle sealing work. Those jobs need the correct model and the exact vehicle procedure for valve state, connection point and pressure limit.
| What is on your unit? | Correct next step |
|---|---|
| F603; no pressure gauge or flow meter | Continue with this guide and judge only visible smoke evidence |
| F703; round pressure gauge | Use the F703 workflow so the gauge check is interpreted correctly |
| F803; pressure gauge and vertical flow meter | Use the F803 workflow and its model-specific air/flow controls |
| Model label is missing, controls do not match, or the unit has been modified | Stop until the exact model and current instructions are confirmed |
Check the kit and prepare the work area
The current kit shows the F603 unit, hanging hook, smoke hose, 12-volt power lead, cone adapter, universal intake bladder with hand pump, replacement rubber, funnel and manual. Package contents can change, so identify the physical parts in front of you rather than relying only on a store image.
Work outdoors or in a well-ventilated repair area. Keep smoking, flames, sparks and other ignition sources away. Let the engine, exhaust and nearby components cool before routing the hose. Wear eye protection and gloves suitable for the smoke medium and any residue already present in the test path.
Have these items ready before connecting power:
- the exact vehicle service information for the section you will test;
- a charged 12-volt vehicle battery with accessible, identified terminals;
- the F603 hose, power lead, hook, funnel and correct sealing adapter;
- the smoke medium listed for the unit, with its container label readable;
- a bright inspection light, clean cloths and caps approved for the test section;
- a way to mark the first smoke exit without touching hot or moving parts.
Stop: Do not begin with a running engine, an unknown fuel-vapor procedure, a hot exhaust, a damaged cable, a leaking machine, an unidentified liquid or a system whose safe test boundary is unknown.
Know the F603 controls before adding fluid
The top of the unit carries the hook port and oil-fill port. The side oil-level window is the fill reference. The front has a power indicator, a working-cycle indicator and the Start/Stop button. The smoke hose and power lead connect at the side of the case.
The connector letters in different parts of the shared manual are inconsistent, so use the physical connector shape and the demonstrated cable fit—not an A/B letter. The smoke hose must seat on the smoke outlet, and the power lead must seat in the matching electrical socket without force.
Completion check: You can identify the oil-fill port, oil-level window, smoke outlet, power socket, two LEDs and Start/Stop button on your exact F603.
FXTUL F603 step-by-step smoke test
Step 1: Define one test section and its normal openings
Start with the symptom and the exact vehicle diagram. Decide which section is being tested, where smoke will enter, which openings must remain open by design, and which openings the service procedure allows you to cap. An intake path is a useful first example because its hoses, clamps, boots and joints can be inspected in sequence.
Do not seal an entire unknown system and hope smoke reveals the answer. A purge valve, vent, drain, throttle path or disconnected service port can be a normal route under one condition and a leak under another. If the service information does not define the test state, stop at that gap.
Completion check: The job note names the entry point, the bounded section and every intentionally open or capped path.
Step 2: Turn the vehicle off, cool it and inspect the path
Turn the engine and ignition off. Secure the vehicle against movement and remove the key or otherwise prevent an unintended start. Let hot parts cool before placing the hose, power lead or your hands in the work area.
Inspect the planned path before smoke is introduced. Look for a disconnected hose, split boot, loose clamp, missing cap, pinched seal or damage that already explains the opening. Correcting an obvious setup problem first makes the smoke result easier to interpret.
Stop: Do not route the F603 near a belt, fan, pulley, exhaust surface or terminal that could energize unexpectedly.
Step 3: Install the hook and keep the F603 upright
Thread or seat the supplied hook in the top hook port. Stand the unit on a stable surface or hang it from a support that can carry its weight without loading a hose, wire, hood insulation or moving panel.
Keep the case upright through filling, operation and storage. Do not lay it on its front, back or side. Leave enough clearance for ventilation and for the hose and lead to curve without kinking.
Completion check: The unit cannot swing into the engine bay, tip over or pull on either connection.
Step 4: Connect the smoke hose and device-side power lead
Push the smoke hose onto the smoke outlet until it is fully seated. Connect the machine end of the power lead to the matching power socket. Hold the connector bodies rather than pulling or twisting the wires.
Leave the battery clamps disconnected at this stage. Inspect the smoke hose for a blocked nozzle, split wall, kink or loose end, and inspect the power lead for damaged insulation, exposed wire, corrosion or a weak clamp.
Completion check: Both machine-side connections are secure, the hose is open and the battery clamps remain isolated from the terminals.
Step 5: Add the correct smoke medium to the oil-level limit
With the F603 unpowered and upright, open the top oil-fill port. Use the funnel or a controlled-tip bottle to add only the smoke medium listed for the unit. The manual lists paraffin, baby oil or mineral oil; do not substitute fuel, solvent, coolant, brake fluid or another workshop liquid.
Watch the side oil-level window while filling. The manual says the level must not exceed 2 cm above the bottom of that window. Stop at the level reference rather than copying a fixed milliliter amount from a generic image. Close the fill port and wipe away any spill before power is connected.
If the machine was overfilled, keep it disconnected and follow the manual’s drain correction before use. Never invert a powered or hot unit.
Critical check: The correct fluid is present, the level is within the manual limit, the fill port is closed and the case is dry.
Step 6: Clean and seal the selected entry point
Remove only the intake connection or access point called for by the vehicle procedure. Wipe the inside contact surface so grit, a sharp edge or a clamp cannot cut the cone or bladder. Keep debris out of the open duct.
For a round opening, seat the cone squarely and deeply enough to seal without forcing it into the duct. For an irregular opening, place the universal intake bladder in the clean opening and squeeze its hand pump until the rubber is secure. Do not overinflate it, and keep it away from sharp or corrosive surfaces.
Insert the smoke nozzle into the adapter only after the adapter itself is stable. Support the hose so its weight cannot pull the seal sideways.
Completion check: The adapter stays in place with light hose movement and the nozzle has a direct path into the selected section.
Step 7: Connect the charged 12-volt vehicle battery
Confirm again that the ignition is off. Attach the red clamp to battery positive (+), then the black clamp to battery negative (−). Keep the clamps separated and clear of bodywork, tools and moving parts.
Use a 12-volt vehicle battery as specified for the F603. Do not substitute a generic switched DC power supply. When the connection is correct, the power indicator should illuminate and the built-in pump begins supplying air.
Stop: If the indicator stays off, a clamp sparks excessively, a lead heats, the case smells hot or polarity is uncertain, disconnect safely and inspect the power path before continuing.
Step 8: Check the air path without inventing a gauge reading
F603 has no pressure gauge or flow meter, so there is no F603 reading to record. Listen for the built-in pump, feel for an obvious kink in the smoke hose without pinching it closed, and check that the test adapter has not lifted out.
If air immediately escapes at the cone, bladder or an intentionally open port, correct the test boundary before starting smoke. Do not add shop air, clamp a hose until it is damaged or extend the test in an attempt to create an F803-style reading.
Completion check: Power is stable, the hose is open and the entry seal is not the obvious escape path.
Step 9: Start smoke and confirm it at the nozzle
Press the Start/Stop button once. The working-cycle indicator should illuminate and the unit should begin generating smoke. Keep the nozzle out of the test adapter just long enough to confirm a steady visible stream, then insert it into the sealed entry point.
The smoke cycle stops automatically after five minutes. You can stop it earlier by pressing Start/Stop again. A large cloud at the open nozzle only confirms that the machine is producing smoke; it does not measure the size of a vehicle leak.
Stop: If the unit has power but produces no smoke, do not repeatedly restart it. Stop the cycle, disconnect power, check oil level and hose routing, and let the unit cool before further inspection.
Step 10: Let smoke fill the bounded section
Keep the engine and ignition off while smoke enters the path. Watch the adapter first. Smoke escaping around the cone or bladder means the setup seal needs attention before any component can be judged.
Allow smoke to travel through the selected section without exceeding the five-minute cycle. The time needed for a visible exit depends on the section volume, isolation state and opening; do not convert a wait time into a leak-size measurement.
Completion check: The entry seal remains stable and smoke is moving through the intended path rather than spilling directly at the adapter.
Step 11: Inspect from the entry point outward
Use a bright light and begin at the adapter, then inspect each nearby joint, clamp, boot, hose, gasket edge and service port in path order. Look from more than one angle. A thin stream can follow a surface before it becomes obvious, while smoke already filling the area can make the real origin harder to see.
Mark the first point where smoke exits into open air. If the area becomes saturated, stop smoke, ventilate, let the cloud clear and repeat a shorter observation rather than guessing through the haze.
Common mistake: Following the largest cloud instead of the first smoke trace. The largest cloud can be where smoke collects, not where it began escaping.
Step 12: Decide whether the exit is a setup leak, normal path or fault candidate
Check the adapter and every cap you installed. Then compare the smoke exit with the vehicle diagram: is it a designed vent, drain or open valve in the current key-off state? If so, correct the test state only through the service procedure and repeat.
If smoke repeatedly starts at the same unintended joint with the entry seal confirmed, record that location as a fault candidate. Do not replace the nearest component only because smoke is visible there; inspect the hose, seal, mating surfaces, fasteners and connected parts that can create the same path.
Pass condition: The same unintended exit can be reproduced after the test setup and normal openings are ruled out.
Step 13: Stop the cycle and clear residual smoke from the machine
Press Start/Stop if the working-cycle indicator is still on; otherwise confirm that the five-minute auto-stop has ended. Remove the nozzle from the adapter and let the machine discharge the residual smoke remaining in its hose, as directed by the manual.
Do not open the vehicle section while the F603 is still adding smoke. Keep the unit upright and allow nearby smoke to disperse before disconnecting or reaching deeper into the bay.
Completion check: The working-cycle light is off, no new smoke is being generated and residual smoke has cleared from the nozzle.
Step 14: Disconnect power and release the adapter
Remove the battery clamps without allowing either clamp to contact the other terminal or bodywork. Disconnect the F603 power lead and place the clamps where they cannot spring back onto the battery.
Pull the smoke nozzle from the cone or bladder. If the universal bladder was used, hold it securely and press its relief valve until the rubber is fully deflated before removal. Do not pull an inflated bladder through the opening.
Restore caps, ducts, clamps and connectors using the vehicle procedure. Keep smoke residue and adapter debris out of the intake.
Critical check: Vehicle and F603 power are isolated before the test path is reassembled.
Step 15: Verify the finding after repair
Repair the confirmed cause with the specified part, seal preparation, fastener order and torque. Then rebuild the same test boundary and run a shorter confirmation smoke check.
A successful verification has three parts: the original unintended smoke exit is gone, the test adapter still seals, and no new exit has appeared nearby. Finish with the vehicle’s required operational, scan or drive-cycle checks; a smoke test alone does not prove every related symptom is resolved.
Pass condition: The repaired path remains smoke-tight under the same controlled setup and the vehicle passes its separate service checks.
Store and maintain the F603
Let the unit cool, then inspect the hose, nozzle, lead, clamps, hook and adapters. Wipe the exterior and clean the bladder without using corrosive liquid. Coil the hose and lead without tight bends and secure them with the straps.
Store the F603 standing or hanging upright—never on its side. The manual calls for draining the old smoke medium and refilling with fresh medium every three months. Check the level and condition again before the next job rather than assuming stored fluid is ready.
Troubleshoot the test without forcing a result
| Symptom | Check first | Safe decision |
|---|---|---|
| Power indicator stays off | Battery state, red-to-positive/black-to-negative polarity, clamp contact and lead damage | Disconnect before moving a clamp; do not bypass the lead or use another power-supply type |
| Power is on but no visible smoke appears | Oil level, closed fill port, open hose, Start/Stop state and unit temperature | Stop, disconnect and inspect; do not run repeated full cycles without finding the cause |
| Smoke escapes around the cone or bladder | Clean contact surface, adapter position, bladder inflation and hose side-load | Reseal the entry before judging any vehicle joint |
| Smoke exits at an expected vent | Vehicle diagram, valve state and the defined test boundary | Use the exact service procedure; do not improvise a cap or energized valve command |
| Engine bay fills with smoke but the origin is unclear | Entry seal, inspection order, lighting and accumulated haze | Stop, ventilate and repeat a shorter observation from the entry point outward |
| No vehicle leak is visible | Intended openings, caps, isolation boundary and whether the symptom is present in this static state | Do not raise pressure or extend cycles; reconsider the test method and symptom conditions |
| Fluid appears at the case or smoke outlet | Possible overfill, tipped storage or internal leak | Disconnect, keep upright and correct the fluid condition before reuse |
What a complete F603 job looks like
A complete job is not “smoke came out.” You identified the exact F603, chose one supported test section, recorded its normal openings, used the correct smoke medium and oil level, powered the unit from a 12-volt vehicle battery, kept the engine off, ruled out adapter leakage, reproduced one unintended exit, repaired its confirmed cause and repeated the same check.
That sequence is the value of the F603: a simple visible path from a sealed section to an opening. Keep the model boundary clear, and the smoke becomes useful evidence instead of a reason to guess at parts.
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