Diesel mot

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Sat 10 Nov 2001 03:16
Diesel mot - Geoff
I've heard that I should take my passat tdi for a good run before it's MOT.
Is this true, what exactly should I do and why am I doing it?
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Sat 10 Nov 2001 09:43
Diesel Smoke Testing - David Lacey
Geoff,
Check the oil & coolant levels beforehand and take your car for a 15 - 20 mile run, preferebly on motorways and fast A roads. Make sure you stretch the engine to max rpm in perhaps 2nd and 3rd gears. This will dislodge any residual soot contained within the turbocharger and exhaust system. If this is not done, then when the tester comes to do the smoke test, excess soot will be ejected from the tailpipe and you will get a fail. All that is needed (usually) is a good fast run to rid the exhaust of this soot.
Cars which are poked around and not used at high speed (usually owned driven by older people.....wait for it!) seem to build up this soot and it can sometimes take 10-15 miles of hard driving to get rid of it.
Not very good for the environment, really - kinda defeats the object, methinks.
Company vehicles which are 'used' (read revved to within an inch of their lives) never have any trouble passing the MOT smoke test first time without any form of pre-test blowouts!!

Rgds

David
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Sat 10 Nov 2001 17:06
Re: Diesel Smoke Testing - Ian Cook
David

Your advice is very sound. This year, however, the C15D van (82K miles) had to go for its medical while I was on holiday (no chance for me to warm it up first and give it the traditional "blow through"). I knew the n/s front drive shaft boot wanted replacing so I arranged to leave "Sidney" with the local country garage for the week, to do the repair and MOT the van.

I was pleasantly surprised to find that it passed, no problem - especially as I didn't have time to do my usual trick of removing the air filter element.

Sometimes HE does smile on me, after all.

Ian
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Sat 10 Nov 2001 10:56
Re: Diesel Smoke Testing - ChrisR
I've owned a succession of old diesels and none of them has ever failed an MOT on emissions. No need to thrash it within an inch of its life. Just take it for a motorway run (half an hour?), and leave it in fourth until you're up to motorway speeds. Make sure it's fully warmed up when they do the test, and that the air filter is ok.

Chris
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Sat 10 Nov 2001 13:57
Re: Diesel mot - Geoff
Thanks for the replies.
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Sat 10 Nov 2001 18:01
Re: Diesel Smoke Testing - Guy Lacey
Hey Chris R - if you think there is no need to thrash your diesel to within an inch of its life then you can't have witnessed a smoke test being performed for an MOT.

Instructions for MOT: Rev the living hell out of the diesel and hold. Repeat x3.
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