Free DPF Health Check

Worried your DPF is on its way out?

Our free DPF health check takes about 30 seconds. With the engine off and the exhaust fully cool, you wipe inside the tailpipe and compare the result with the examples in the tool below. It's a quick first DPF check, not a diagnosis, but it shows when testing is worth booking.

How the DPF Health Check Works

Watch the video. It shows what a normal and a heavily sooted tailpipe look like.
Do the wipe test. Run a clean finger or cloth around the inside of the exhaust outlet.
Pick your symptoms. Tick any warning lights, power loss or smoke you've noticed.
Check your area. The DPF checker then asks for your town or postcode to confirm whether you're within our usual mobile coverage.

If the checker says you're outside it, call anyway, as depending on the job and location we may still be able to help.

What Black Soot at the Exhaust Means

A DPF traps soot before it leaves the exhaust, so a working filter should leave little more than a light grey film. A finger coated in heavy, dry black soot can mean soot is getting past the filter.

That isn't proof of a fault, because some residue is normal and the tailpipe alone never gives a full answer, which is why the DPF health check is only a starting point.

Can a Cracked DPF Cause Black Soot?

Yes. Inside the DPF is a ceramic honeycomb structure, and if it cracks, melts or has been tampered with, soot can pass straight through. The wipe test can't confirm this, but filter pressure readings, calculated soot load and live data usually can.

Does Black Soot Mean It Needs Cleaning?

Not always. Chemical cleaning clears a blocked filter but can't repair a cracked one, and cleaning a damaged DPF simply wastes your money, so we check its condition first and tell you straight if it's beyond cleaning.

A clean tailpipe doesn't guarantee a healthy filter either. High DPF pressure, a sensor fault or a regeneration problem can all exist without any heavy soot at the exhaust.

Signs You Need More Than a DPF Health Check

Book proper DPF diagnostics if you notice:

A DPF warning light or engine management light
Limp mode or a loss of power
Regenerations that fail or happen far too often
Cooling fans running on after short trips
Higher fuel use or visible smoke
A previous clean that didn't solve the problem

Many of these come from faults elsewhere, such as a pressure sensor, a split pipe or an EGR problem. Our guide to a blocked DPF explains the common causes.

What Our Full DPF Test Covers

When we visit, our qualified VW master technician goes much further than the wipe test:

Fault codes plus live data, rather than codes alone
DPF differential pressure and calculated soot load
Exhaust gas temperature and pressure sensors
Pressure pipes, EGR operation, airflow and boost

If the filter is blocked but sound, we clean it on the vehicle and re-test. If the evidence points to a damaged DPF, you hear that before any cleaning is done. After a successful clean and repair, the vehicle carries on regenerating itself in normal driving.

Learn more about our mobile DPF cleaning, the other services we provide, or the experience behind DPF King.

Prices and Booking

The DPF health check is free. A visit with a 1-litre clean is £200, testing included, or £100 if the filter can't be cleaned. Our two-stage 2-litre clean comes with a 14-day guarantee. We cover Renfrewshire, Inverclyde, Glasgow and Ayrshire, and next-day visits are usually available. See real cases on our recent jobs page.

DPF Health Check Questions

Is the DPF health check a diagnosis?

No. It's a quick initial indication designed to help you decide whether professional testing is needed.

Can a blocked DPF damage the engine?

It can. Excessive back pressure reduces performance and efficiency, while repeated failed regenerations can dilute the engine oil with diesel, increasing wear on bearings and the turbocharger.

Can my DPF be blocked if the exhaust looks clean?

Yes. Only differential pressure and calculated soot-load readings, taken with diagnostic equipment, show how full the filter really is.

Will cleaning fix a cracked DPF?

No. A cracked filter usually needs replacing, and we'll explain our findings before you spend anything on cleaning.

Do you remove DPFs?

Never, because removing a DPF is illegal and an automatic MOT failure.

Can you check my DPF by registration?

Not online, as an accurate assessment requires connecting diagnostic equipment to the vehicle and reading its live data.

Not happy with your DPF health check result?

Call 07870 751782 or book a visit.