Preparing a Bus for Inspection: 9 Defects That Come Down to Parts
8 minute read · ·BAYKOÇ Technical Team
When a coach comes back from inspection the defect list looks much the same every time: no serious failure, just something small at part level. A dark marker lamp, a smearing wiper blade, a loose mirror. All of them jobs that would have taken half an hour the day before. The order below follows what we hear most often across the counter.
Lighting — the most frequent reason
Before the test, put someone outside and switch every lamp on one at a time. Dipped beam, main beam, indicators, hazards, brake lights, reversing lamps, fog lamps, number plate lamp and every marker lamp.
Pay particular attention to the marker lamps: because they are fed in series, corrosion at one point puts out the ones after it, and the driver never notices in daylight. If one is dark, test the run rather than replacing a single bulb and moving on.
Headlamp aim is a separate item. A lamp with a blistered reflector will not focus the beam properly even with a new bulb, and the setting will not hold.
Field of view: glass, wipers, mirrors
These three are assessed together, and each has a clear criterion:
- A crack in the windscreen within the driver’s field of view is a defect. A small crack at the edge usually passes; one in the swept area does not.
- If the wiper blade smears, replace it. Where the arm spring has tired, a new blade alone will not clear the smearing — the arm has to go too.
- Both exterior mirrors must be intact, secure and adjustable. A mirror that shakes or turns on its own is a defect, and the cause is usually the foot where it bolts to the body.
- A missing or broken wide-angle mirror is a defect; the glass can be supplied on its own without changing the housing.
Doors and emergency exit
The passenger door must open and close fully and the emergency release must work. If the door has slowed, you want to notice weeks before the test rather than the day before — the cause is usually the seal inside the cylinder, and sourcing that takes time.
Door rubbers must not be torn or lifting. That is both a defect item and the source of winter water ingress.
Suspension and body
A leaking shock absorber is visible: there is an oil trace down the body of it. Leakage is a defect, and replacement is always done in pairs per axle.
No damaged part may protrude from the body with a sharp edge. A broken bumper corner or a hanging wheel arch falls under this; usually the corner section is enough, not a complete bumper.
The day before the test
A short checklist:
- Switch every lamp on and off individually, with two people.
- Try the wiper blades on wet glass; if they smear, change them.
- Move the mirrors by hand; if there is play, tighten or replace the foot.
- Open and close the door five times; if it has slowed, postpone the test and source the part.
- Look over the shock absorber bodies for oil traces.
- Check whether any windscreen crack reaches into the swept area.
Part Categories in This Article
The parts discussed above are in stock in the following categories.
- Lighting (366)
- Mirrors & Mirror Arms (90)
- Shock Absorbers (77)
- Door, Rail, Luggage & Glass Seals (36)
- Wiper Systems (30)
- Glass & Glazing (10)
Related Makes
Frequently Asked Questions
What is the most common defect at bus inspection?
Lighting. Dark marker lamps, a dead number plate lamp and headlamp aim head the list. Most of it is caught by a simple check the day before.
Is a windscreen crack a reason to fail?
A crack within the driver’s field of view — that is, in the swept area — is a defect. Small cracks at the edge usually pass, though waiting is risky because a crack grows with driving vibration.
Does a leaking shock absorber count as a defect?
Yes. An oil trace on the damper body indicates leakage and is a defect item. Replacement is always done in pairs per axle; renewing one side alone leaves the damping unbalanced.
