I was going clockwise round the M25 Saturday morning on my way from Park Royal to Enfield, when just after J23 I noticed about half a mile in front, a tanker with a noticeable cloud of blue smoke coming from the rear end, and as I was slowly closing on him I detected the smell of burning rubber!
I was within 200 yards of him when I had to leave at J25 and he was still smoking like a good un.
Tyre failure?, brake seized on? I’m surprised the driver hadn’t seen anything in his mirrors or no one had flashed the driver, I’ve heard nothing on the news since to the effect that a tanker had gone up in flames!
It may have been an over fill on the Adblue tank , as it leaked and got on the exhaust causing the smoke to flow past the unit to the back of the tanker .
Hence why he kept going .
Should’ve put a call into plod, they’d soon catch him.
I had a brake chamber fail on me and despite having 26t of Coca Cola on the back the truck never even dropped a single click. There was a lot of spray on the road so I failed to notice the smoke. Fortunately a brother rubber came past and wound his window down to tell me what was going on. When I finally stopped the smell was terrible. Much further and this would’ve happened …
I was always surprised at the number of times there would be a breakdown on my maiden trip for a new client when on agency… You’d think that if you only drive at a place “rarely” or “Never before” - that the chances of having a mis-hap would be small - not so!
Left the yard on my first trip for Brum in a palletliner with that client - got to the first steep uphill, and didn’t have the guts to get up there (59 plate tractor I think in 2013) I pulled over to the side, and only then did I notice the smoke pouring off the back axle of the trailer… It was the MIDDLE of the three that was practically catching fire though, the smoke just billowing backwards making it look like it was coming from the rear axle. The mechanic (in house) who came out to put it right wasn’t impressed that I’d called him out on a friday night and all - but you’d think the regular full time driver might have noticed something slowing him down over the days and weeks beforehand…
I find it hard to believe that a seizing axel just “happens”. The mechanic didn’t say anything about “Chamber Fail” when he was fixing it, which took him about 2 hours to do…
Yet another palletliner shift that ended up being a 15 hour job!. At least I got paid though, and therein lies the argument perhaps as to “why the full timer didn’t report it”… 
Of the other “first time out” breakdowns - electrical failure was most often the cause. A wire had snapped or frayed away on the underside, and I suddenly found myself either with no electrics at all, and a conked-out truck I’m trying to steer into the side verge with arms like popeye or having all the lights go out in the middle of the night on a B road somewhere on my way to a farm pickup… A bit tricker dealing with that one!