The Check You Do Before Handing Over Cash: Independent Mobile Pre-Purchase Inspection
Buying a used car in the UK is essentially a trust exercise between you, a stranger on the internet, and a vehicle with a past it may not be keen to disclose. The seller wants you emotionally attached before you look too closely. The private ad is professionally lit and taken from the flattering angle that hides the rear quarter rust. The service history is "mostly there." The engine is warm when you arrive because the seller "just got back." And that light on the dash? Oh, that's nothing, had it for months. A pre-purchase inspection from SOS CarFix sends an independent mobile mechanic to the seller's location — not yours — to crawl over the car before your money changes hands. We scan the ECU for hidden fault codes, assess the bodywork and chassis for crash repair and corrosion, check the mechanicals, and take it for a test drive with professional eyes and ears. We work for you, not the seller, which means we have no incentive to be polite about what we find.
Don't buy a used car blind. SOS CarFix sends a mobile mechanic to the seller — full check, diagnostic scan, no garage faff. Get a quote today.
How it actually works
A used car is a box of unknowns. The question is how many of those unknowns you want to discover after you've signed the V5C rather than before. Our inspection covers four main areas. First, the diagnostic scan: we plug into the OBD-II port and pull every stored and pending fault code from every module on the car — engine, gearbox, ABS, airbags, emissions — including the ones a seller has conveniently cleared the morning before your visit. (Cleared codes leave traces. We know what to look for.) Second, structural and bodywork assessment: we check panel gaps, paint depth if the equipment supports it, and look for signs of filler, respray, or welded repairs that suggest the car has been in a significant accident that didn't make it onto the HPI. Third, a thorough mechanical inspection — tyres (including tread depth against the UK legal minimum of 1.6mm across the central three-quarters of the tread), brakes, suspension, steering, fluid levels and condition, oil sludge, coolant colour, belts and timing systems, exhaust, lights, and anything else that's accessible without a ramp. Fourth, a test drive where we listen for the noises that disappear the moment a seller gets in the passenger seat. After all of that, you get a straight-talking written report — red, amber, green — covering what we found, what it will likely cost to fix, and whether this car is worth what they're asking. We don't get a commission from the seller. We are constitutionally incapable of being motivated to say it's fine when it isn't.
“The private ad is professionally lit and taken from the flattering angle that hides the rear quarter rust.”
Sound familiar?
So what's behind it?
What we do — at your door
We travel to wherever the car is being sold — a private driveway, a dealer forecourt, a Tesco car park — and carry out a thorough independent inspection on your behalf. You don't need to be there if geography makes that tricky, though most customers are because they find it instructive to walk round the car with a mechanic who is freely narrating what they're poking at and why. We bring our own diagnostic equipment, connect directly to the vehicle, pull codes from every available module, complete a structured physical inspection from bonnet to tow bar, and take it for a proper test drive rather than a gentle loop of the estate. The written report we produce is designed to be actionable: what's wrong, how serious, what it would roughly cost to put right, and a clear steer on whether the car represents fair value at the asking price — or whether the seller should be doing a lot more explaining. We work exclusively for the buyer. We've never met the seller before and won't see them again. That independence is the entire point.
What affects the price
The cost of a pre-purchase inspection reflects the mechanic's time and travel to the seller's location, the comprehensiveness of the diagnostic scan and how many vehicle systems are accessible, and any specialist equipment used. A basic visual and mechanical check is naturally quicker than a full multi-system diagnostic sweep with a written report, so what you pay depends on the scope you book. Travel distance to the vehicle matters too — we're a mobile service, and reaching a seller further afield takes time we account for honestly rather than pretending is free. The inspection cost should always be weighed against what you're buying: on a £15,000 car, even a modest inspection fee is trivial if it surfaces a hidden fault worth thousands to fix. On a £2,000 banger, you still want the check — but the scope might be leaner. What we will not do is invent a list of faults to justify the fee. If the car is solid, we will tell you it's solid.
Random knowledge you didn't ask for
Questions you're probably asking
Can't I just use an HPI check instead?
An HPI or similar data check tells you whether the car has outstanding finance against it, whether it's been written off by an insurer, whether it's stolen, and whether the mileage looks plausible against MOT records. It tells you nothing about the condition of the engine, the state of the brakes, the rust hiding under the sills, or the fault codes the seller cleared yesterday. The two are complementary — not alternatives. Do both.
Does the seller have to let me do a pre-purchase inspection?
No, and that's the most useful answer you'll read today. A seller who refuses a reasonable independent inspection request is, in our experience, a seller with something to lose from you finding out what it is. You can't compel anyone to let a mechanic inspect their car — but you can walk away, and usually you should.
What happens if you find something serious?
You get it in writing in the report, with a clear explanation of what it is and a realistic sense of what it would cost to address. Then you decide: walk away, use it to negotiate a lower price that reflects the repair cost, or proceed anyway with eyes open. That's your call to make. Our job is to make sure you're making it with accurate information rather than the seller's optimistic interpretation of 'runs fine.'
Can you inspect a car at a dealer, not just a private seller?
Yes. Dealers generally can't refuse a pre-purchase inspection — it would be commercial suicide to do so visibly. Independent inspections at dealers are slightly rarer because consumers (incorrectly) assume dealer cars are therefore safe, but a used car on a dealer forecourt can still have undisclosed issues, unresolved warning lights and wear that the consumer rights clock doesn't start ticking on until after you've bought it.
What if the car fails and I don't buy it — was the inspection a waste?
This is the question that reveals a slightly inverted way of thinking about it. The inspection working is precisely when it saves you from buying a problem. You've spent a relatively small amount to avoid potentially spending thousands more on a car that would have cost you far more in repairs, or that would have needed work before your next MOT. The inspection where we find nothing and you buy with confidence also has genuine value — it just feels less dramatic.
The Check You Do Before Handing Over Cash — sorted at your door
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