Defender 300tdi 1994

I have had a new two part exhaust fitted to the old manifold exhaust, which has a catalytic converter. Seemed fine for a couple of weeks, local driving. Took it for a run from London to Cambridge on the M11 and the sooty smoke coming out of the exhaust was unbelieveable. It looked like it was on fire. I stopped and checked on the hard shoulder and really could not see anything wrong. The performance was the same, running fine. I wonder if when breaking the seal between the exhaust manifold pipe to fit the new rear sections, soot had been disturbed and dislodged if it had to be hit by a hammer, which had been laying 'dormant' until a good 'blast through' with a long run? I checked with the exhaust supplier and fitters and they said it may be a split turbo pipe, can't see it though. In my manual it said it can be because of an ill fitting exhaust or broken exhaust brackets. Any ideas anybody?

Any soot dislodged probably got burnt off before it even left the garage as they would have to 'light up the cat' as part of the job. If it's dense black smoke it's likely to be further up the line, valves or injectors starting to clog and the nature of an old diesel sucks a bit of oil up and burns that instead. Run some injector, cylinder and engine oil cleaner though (not all at the same time though!). Many short, low speed easy going trips would likely cause this, where a motorway blast highlights it. Willing to bet the old cat got burnt up as a result too, now the new one is on there producing the correct restrictions and pressures the hot gasses are finding other things to burn off.

Thanks for your valued advice Dan. Been to Benbecular and Ive toured the Outer Hebrides in my Landy, great fun and great place too! Live on the outskirts of London.