Two MOT'S, But

[Brian]

Both my BX's have just passed their MOTs with no advisories Yipee,
one is a TD the other is N/A.

But the smoke test results for the N/A car was unusual.

Results:
1. 1.10
2. 5.37
3. 2.71
4. 2.18
5. 2.13 Test Result 2.34 Pass

Normally the first result is high, then lower with each test.
The tester could not suggest a reason for this strange result.

Has any one come across this before ?, or can it just be put down to the testers right foot !!!...

[Vanny]

should always ignore the first reading! atmosphere interferes with the machine, and you'll probably find it was a cold day, maybe even the first run of the day so the piping into the machine gets damn, and water picks up the particles like you wouldn't believe. Blast of hot air will clean it out and thus the rest of the readings are fine!

When i took the 1.7td engine with the blown head gasket for MOT the results where sub 1 for all 5 runs because the amount of water going into the exhaust was holding in all the particulates! Hence giving rise to the notion that oil dirven particle filters on exhuasts shoudl work really really well!

[Brian]

Hmmm, that's interesting.

Water misting into the inlet manifold for the MOT then !!!.

But I would have thought that with all the compression pressure seeping into the cooling system, not a great deal would find it's way into the exhaust.
Most would escape past the rad pressure cap or into the engine bay depending where the gasket/head defect actualy was.

[tom]

Vanny is almost certainly right. Mine always passes on the first run because it arrives (very) well warmed through.

[Brian]

Hi,

I also always warm my car prior to MOTs, at least for 10 miles min, and on the governor in places, to blow out some of the crud.

This result was most unusual, and the MOT tester !!! (having years of experience to relate from), had not come across this situation before, nor had I... Strange...