I'm having a problem with my Adblue whereby the info has been saying 3500 miles for 2 months, didn't go up with a top-up and after 2000 miles I can't get a drop to go in.

 

Apart from the implications and Skoda's verdict on it all there was one thing that the service desk manager couldn't quite explain well.

 

Basically, the mechanic said the tank was full but the plug-in diagnostic reading was 34%. Apparently, the 34% doesn't measure quantity but something else.

Any ideas? 

Could it be that Halfords/Sainsbury's etc Adblue vary in quality (urea content???) and the 34% gives some sort of quality/usability reading?

This could only happen if none is being injected into  the exhaust? Faulty pump? But I would expect an error code when checked.

They just said all is normal.

 

They had no answers to my questions like how can it go 2000 miles (ie nearly half the tank normally) without seemingly using a single drop?

How is it fuller now than after my last top-up?

If it really is full how come it is only reading 3500 miles? That is like filling your diesel/petrol tank to the brim and the gauge pointer only going to ¾ full.

Their plan now is to keep the job open and let me do another 2000 miles and take it back without adding a single drop.

I suspect a sticky level sensor.

1 minute ago, weasley said:

I suspect a sticky level sensor.

I thought that a month or 2 ago but it doesn't explain how I could have driven 2000 miles and still have a full tank.

I tried topping it up before contacting the garage a couple of weeks ago but couldn't get a drop in.

If the level hasn't changed that would seem to suggest that either a) The dosing pump isn't working b) the exhaust gas probe isn't giving the correct reading and the dosing computer therefore thinks it doesn't need to inject any adblue c)The dosing computer is faulty.

 

A simple test would seem to be available that would confirm there is a problem without driving 2000 miles first. i.e. to shove an MOT exhaust gas tester up it's backside and see if the emissions are within spec.

widdershins

 

Thank you very much for that, much appreciated. Not that I understand it that much!

 

But, if you don't mind, I will print that off and get them to pin it to the job sheet when I next take it back.

This youtube video pretty much explains how the whole emissions thing works.  Basically sensors in the exhaust gas pipework check how much Nitrogen Monoxide the engine is putting out and pass this information to a computer.  Sensors in the adblue system detect the percentage of urea in the adblue solution (I'd guess in your case that's what the 34% is, the video suggest typical values are around 32.5%).  That sensor is to get round people being crafty and filling the tank with 50/50 adblue and water (or even 100% water) to save money.

 

The computer then calculates how much adblue to dose the exhaust gases with given both the amount of pollutants entering the SCR system and also the strength of the adblue solution.  It squirts this into the gases, they do their magic in the SCR catalyst chamber and cleaner emissions come out the other end to go out the tailpipe.

 

It follows that if any part in the adblue system is broke and isn't doing it's job then no reduction in Nitrogen Monoxide emissions from the tailpipe would happen.  So any test of the exhaust gases should quickly confirm if it's working properly without waiting 2000 miles.  However the next question is how environmentally friendly are you?  If it's running fine and you don't need it working to get through an imminent MOT you could just let it stay broken in the meantime and save on AdBlue.  If however you have an MOT in the next month or two then you'd probably be better getting onto it just now as it will fail the MOT if the emissions are outside tolerance.

 

 

Edited 25 May, 20197 yr by widdershins
Typo

Thanks again for a great and helpful post. Still another year to its 1st MOT.

Are you using the correct filling kit?

I assume so, just the container of Adblue and the hose that comes with it. Not had a problem before and the garage couldn't get any in.

My car is back in the garage for attempt no. 2 to fix this. 

They are saying that they have done some tests and are claiming I have over-filled it which I very much doubt.

Is that even likely to cause the problems I have had?

 

Regarding MOT testing; NOx isn't part of the test, so the machines are unlikely to be capable of measuring it.

'Claiming the owner overfilled' is common, funniest is when the owner does not tell them the AdBlue was refilled at another Main Dealership by a Tech or Fitter.

 

Because they claim it does, does not mean they are correct and the system is not at fault.

Edited 28 August, 20196 yr by Roottootemoot

But how do I defend it when they charge me £100 to refill and set it all up again on the computer as they are saying?

I've asked the receptionist what specifically did they find to be able to blame me but no answer.

1 minute ago, Ashaz said:

I've asked the receptionist what specifically did they find to be able to blame me but no answer

Take it up the chain of command until you do get an answer.  They'll struggle to come up with anything believable. Ask for whatever is said in writing, they may back down at that point.

Roottoot is the man for this stuff really though.

On 25/05/2019 at 13:38, widdershins said:

Sensors in the adblue system detect the percentage of urea in the adblue solution

They do on the cars in the vid, but I'm not convinced that the Yeti has such a composition sensor.  Can't see it in the wiring diagrams. There's level and temperature, but nothing leaps out at me for 'quality' of urea.

Thanks 👍

Ashaz, "But how do I defend it when they charge me £100 to refill and set it all up again on the computer as they are saying?"

 

Your kidding.

How can they charge you to refill, when they cant get any in????

And £100...Are they having a larf.