--- title: Mount Pleasant: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/mount-pleasant-rhondda-cynon-taf/ location: Mount Pleasant county: Rhondda Cynon Taf latitude: 51.615640 longitude: -3.418810 service: AdBlue in a Diesel Tank updated: 2026-10-10 --- # How It Happens and How to Avoid It: AdBlue in a Diesel Tank in Mount Pleasant AdBlue already in your diesel tank? Then put this page aside for now, leave your ignition and engine off, and call 0333 366 0103. Normally, when the motor hasn't run, it is emptied and thoroughly cleaned where the car is in Mount Pleasant. If you're reading before it has happened, the rest of this page is about why it takes place and how to make sure it doesn't. ## AdBlue in a diesel motor, and its separate tank Plenty of modern diesels around Ynyshir, as well as Mount Pleasant, run on two liquids; the motor takes just your diesel. AdBlue goes to your exhaust, where it is sprayed into the gas to clean it, and it lives in a tank of its own. There's a filler for every tank. Some vehicles keep the AdBlue filler in your boot or under the bonnet; plenty of others have the two side by side behind one flap. At the pump, the diesel side gets filled constantly. A driver who has to stop and work out where it goes usually fills the AdBlue side, from a bottle, and far less often. It's in that gap that the error happens. ## How AdBlue in the diesel tank takes place in Mount Pleasant Three things tend to line up, and carelessness is rarely one of them. Haste follows from the warning. The car warns you as AdBlue runs low, and an empty tank sends it into limp mode — so the top-up gets done in a rush, before work on a drive off Cemetery Road, or on the way home in the car park outside Sports Bar. The old car's cap is where the hand goes — but a rental car, a new car or a company car puts the fillers elsewhere. That's the second thing: a new motor. Third, the bottle goes in: a diesel filler or AdBlue filler, it slides in as easily, and once the tip begins, no part stops it. The same few seconds decide it, in the middle of Mount Pleasant or out in Birchgrove. ## How to tell the AdBlue filler from the diesel one Before you pour anything, whether on a drive in Glynfach or a forecourt around Mount Pleasant, check these. They take a few seconds. - Blue and marking: an AdBlue cap is frequently blue, or says "AdBlue", where a diesel cap usually does not. Trust the cap, not where it sits. - The size. On many cars the AdBlue filler neck is the smaller of the two. - Open the flap and look for a label — plenty of vehicles show what belongs in each filler right there. - The handbook shows which it is when your filler isn't next to the diesel cap: your boot, or under the bonnet. - The person who drove the vehicle last. On a hire or company car collected from somewhere like the car park outside Porth, ask before you leave, not when the light comes on. ## AdBlue top-ups that never reach your diesel tank For the day the light comes on — wherever you are across Rhondda Cynon Taf — a routine to use. - Not in a rush on the side of Park Street, not on a slope, not with your motor running: park then switch off properly. - Find the AdBlue filler, read the cap, and speak the name "AdBlue" out loud while you unscrew it. It seems silly. It does the trick. - The two behind one flap? Then make sure the lid on your diesel side stays closed before raising the bottle. - Gently does it, through the bottle's own spout, till it is full or the bottle runs out. - Close the cap and check again. Make sure your diesel cap was never opened. Only then start the car. Find at stage two or three that it's already gone into your diesel side? So stop just there. Do not go on to step five. ## Mount Pleasant: already put AdBlue in your diesel tank? Then the order of things is short. Do not start your motor. Do not switch your ignition on; on plenty of diesels that alone runs the fuel pump. Topping up with diesel will not dilute it: instead, AdBlue sinks to the bottom of your tank, right where fuel is drawn from. The staff at Texaco, Shell or any forecourt will normally help to push your car clear if you ask. If you are on your own drive in Mount Pleasant, leave the car where it sits. Already started? Stop when it is safe, then turn off. Leave the M4 — under 10 miles out of Mount Pleasant — at the first exit. Roughly how far did it go? Crossing Mount Pleasant is smaller a job than a run of under 15 miles towards Cardiff, so tell us. ## What happens when we arrive around Mount Pleasant The van comes to your car anywhere it stopped — your own driveway, near Chapel, or by the local primary school. Both the work and the price rest on three answers — what liquid, what amount, and if it has run — so our engineers ask. You hear that price by phone, before anyone sets off. Next: a drain, then a thorough flush of the whole system. With AdBlue that matters more than with petrol: it crystallises and is corrosive to some of the metals in a fuel system, and so it does not wash out on its own. Testing comes at the end: before that, clean diesel is added, and the filter is flushed or changed as needed. We do not leave until it has been started and is running correctly. Using pumps fine on a busy forecourt and quiet enough to use outside a house at night, most jobs in which the engine has not run need about half an hour once our engineers are there. Paying happens on the day, not upfront, and you are given the paperwork an insurer asks for: an engineer report and a VAT invoice. Many insurance policies include misfuelling cover, so it's worth checking yours while we are on the way. ## About Mount Pleasant Mount Pleasant is a suburban area in Rhondda Cynon Taf, situated near the river and surrounded by other local communities such as Birchgrove and Dinas. Mount Pleasant sits at an elevation of 121 metres, with terraced housing being the predominant type of accommodation. Mount Pleasant is located near the town of Porth and is approximately 14 miles from Cardiff, the nearest city. Mount Pleasant is also relatively distant from London, at around 141 miles away. ## AdBlue drains in Mount Pleasant and across Rhondda Cynon Taf Throughout CF postcodes, our vans that cover Mount Pleasant — a residential suburb — work the surrounding places too, Porth and Dinas among them. The van reaches you fastest with a postcode starting CF39 0. The vehicle stays put. We drain it where it is — a side street near Cross of Sacrifice, a lay-by on the way to Bronwydd Park, a drive. Guessing won't help behind William Evans, close to a boundary, or somewhere awkward to describe; ring and check. ## For Mount Pleasant people, the short version Read the cap before you tip. If AdBlue has gone in your diesel tank regardless, leave the car off then ring 0333 366 0103. Petrol in Diesel empties it where it stands, anywhere across Rhondda Cynon Taf.