The Van That Will Not Brake Straight
You drive a 2011 diesel panel van, 2.8 t laden, used for deliveries. Over three days you notice the brake pedal travels further before it bites, and the pedal slowly sinks if you hold it at a junction. The fluid level is just above the MIN mark; you have not seen a leak. This morning the van pulls to the right under braking on a dry road, and the ABS warning light stays on after the self-test. The front tyres are at 2.0 bar against a recommended 2.8 bar; the rears are correct. You have a 90 km delivery round with six stops, starting in 20 minutes. The weather is dry.
1. Diagnose the symptoms and decide whether the van should do the round.
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Symptoms and likely causes:
- Pedal sinks when held → internal leak past the master-cylinder seals or a fluid leak in the hydraulic circuit. A sinking pedal is never normal.
- Longer travel, fluid near MIN → fluid loss or air in the system; possibly a worn master cylinder or a leaking wheel cylinder/caliper.
- Pulls right under braking → a seized or weak caliper on one side, a contaminated pad/disc, or a collapsed flexible hose. The van brakes unevenly, which is dangerous in an emergency stop.
- ABS light on → the ABS is disabled; you have conventional brakes only, and the fault may also affect electronic brake distribution.
- Front tyres at 2.0 bar vs 2.8 → reduced grip, longer stopping distance, poor steering response, and increased risk of a blowout when hot.
Decision: do not drive the round. A sinking pedal plus uneven braking plus no ABS is a combination that can fail completely under repeated heavy use - exactly what a six-stop delivery round involves. The van should be taken out of service and inspected by a qualified technician. Arrange an alternative vehicle or reschedule.
2. The depot says 'just top up the fluid and go'. How do you respond, and what would a correct repair involve?
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Response: topping up masks the symptom but does not fix the cause. Fluid is being lost or bypassing internally; adding fluid restores the level but not the seal. The sinking pedal will return, possibly mid-braking, and the ABS and imbalance faults remain. Under load and repeated braking, a master-cylinder failure can mean no brakes at all. Refuse to drive it and record the refusal.
Correct repair path:
- Pressure-test the hydraulic system and inspect all lines, hoses, calipers and wheel cylinders for leaks and corrosion.
- Check the master cylinder for internal bypass; replace if indicated.
- Strip and inspect the front brakes; free or replace the sticking caliper, replace contaminated pads/discs as a pair per axle.
- Read ABS fault codes, repair the sensor/hydraulic fault, and confirm the light extinguishes after the self-test.
- Bleed the system with fresh fluid of the specified grade and check for a firm, non-sinking pedal.
- Set all tyre pressures to the manufacturer's figures (2.8 bar front here) and check tread depth and condition.
- Road-test at low speed in a safe area, including a controlled emergency stop, before returning to service.
3. What does the tyre pressure tell you about the van's handling and fuel use, and what else should be checked?
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Handling: at 2.0 bar instead of 2.8, the front tyres are about 29% under-inflated. The sidewalls flex more, the contact patch distorts, steering becomes vague and the front can wash out in a corner. Braking distance increases, and the already uneven braking is made worse. Under-inflation also raises tyre temperature at speed - a blowout risk on a loaded van.
Fuel use: rolling resistance rises with under-inflation. A 0.8 bar deficit on the driven/steered axle can cost a few percent in fuel, and more importantly it wears the shoulders of the tyres, shortening their life.
Also check:
- Tread depth (legal minimum 1.6 mm, but replace well before on a working van, especially for wet grip).
- Even wear across the tread - inner-edge wear suggests alignment problems.
- Age and condition: cracks, bulges, embedded objects, and the date code.
- Spare wheel pressure and tools.
- Wheel nut torque and bearing play, since the van pulls under braking.
- Load distribution: 2.8 t laden with a heavy rear load changes braking balance and tyre loading.