Diesel Emissions Test Havoc

Well the normal risk is the cambelt snapping. Head gasket failing is going to be pretty close to a coincidence, if the engine was warm then it was on the way out anyway, just change it before you warp something.

All the places I've been to there's a note _somewhere_ (normally very prominent) saying that before they do an emissions test on a diesel, you've got to be aware that they floor it for a while, and that the engine should be mechanically sound.

FWIW, red-lining a diesel shouldn't be a problem - the warning is normally about cam belts/chains.

IME, head gaskets normally "go" over the course of several thousand miles, and isn't caused by revving - don't forget that diesels have limiters to keep the revs inside a safe range.

Pete.

The message from snipped-for-privacy@clara.co.uk (BJ) contains these words:

Your engine has a rev limiter. Unless you've fiddled with it or it's not working properly the revs he's brought it up to are within the operating range of the engine.

It's part of the test...that's how it's done.

The message from Pete Smith contains these words:

The rays!

There is a standard leaflet that they should give out warning of the risks. Holding a diesel on the limiter with no load is a worse case condition.

Thanks everyone. The previous post is going to get me going to Trading Standards I think. The garage knew what stress they were putting the car under and only had to warn me. They knew the engine was cold, ie when I delivered the car, and knew it's age and mileage. What makes it worse is that it passed on a free retest, ie they overlooked advising me TWICE.

BJ

I don't think you'll have any success in claiming against them: the usual thing garages ask is whether the car has been serviced in line with the manufacturer's recommendations [particularly in regard of cambelt replacement interval]. The test-procedure does not involve operating the engine outside the manufacturer's design parameters [unless your injection-pump governor has been tampered with to change the rev- limiter setting]. It's not running the engine at higher load than it can expect to experience in real-world driving, after all. Indeed I'd say that if an engine can't be operated to its manufacturer-specified rev-limit then the engine is probably faulty already!

*If* they did it with a cold engine (most places monitor the oil temp before the run) then you might have them, equally if they held it their "for minutes" as you stated earlier. There's nothing in the test to suggest they'll hold it there for minutes and i would hazard a guess they were trying to clear it out, but with no load on it....ouch.

JH

The message from "JH" contains these words:

You sort of imply it'd be OK at the limiter under load but not without...why?

When an engine is operating at wide open throttle the gas pressure in the cylinders reduces the forces acting on the piston and rod as it goes over TDC. As soon as the throttle is closed the rod has to supply all the tension required to decelerate the piston. Race engines tend to let go just as the throttle is closed at the end of a straight. However diesels aren't throttled so this doesn't apply. A diesel always has full cylinders and.only the amount of fuel injected changes with load. In any case none of this would affect the head gasket. I think the failure was just one of those things and not the fault of the garage.

The above notwithstanding I think the diesel MOT test needs changing. An old engine that might soldier on quite happily for years if it never gets thrashed can easily be broken in a full rpm MOT test. The owner might never use those rpms in normal driving and the emissions at those rpms would then be irrelevant. 75% of the limited rpm would be a more reasonable test and quite adequate for the purposes of simulating most road use.

Dave Baker - Puma Race Engines

I'm not at all sure why women like men. We're argumentative, childish, unsociable and extremely unappealing naked. I'm quite grateful they do though.

The message from snipped-for-privacy@aol.comma (Dave Baker) contains these words:

I never do except when giving it a clear out...which it probably needs 'cos I don't run it at high revs.

Pottering round town I doubt I get it about 2000rpm, reaching perhaps

3000 on a dual carriageway. I'm not sure what the gearing is on the Maestro, but assuming a maximum of 80mph that's the highest it revs, 'cos I don't race up through the gears...I tend to hit 5th about about 30mph and "gather speed" rather than "accelerate".

It is a standard test if you want an MOT your vehicle has to pass it.

The engine oil must be at least 80c before the test can take place, if you look at the emission report it should give the oil temp?

Somewhere within the designated viewing area would have been a warning about the diesel emision test, you just did not notice it.

I just was not there. I was at work during both tests until near the end, the car was left there hours before each test. All the more reason I should have been warned verbally. I'm not even sure this garage has a viewing area - are they obliged to? BJ

The message from snipped-for-privacy@clara.co.uk (BJ) contains these words:

Then you wouldn't have seen the warning signs, would you!

Yes, and I'll bet you they have.

I have mot'd hundreds of diesels since the new smoke test was introduced and I have never had any breakages, BUT you do have a point about being warned that I was unaware of.

Read the leaflets section.

Thanks Fred, below is what an MOT station should have done whether or not I am watching the test:

"If you are presenting a diesel engined vehicle you should also receive the VI leaflet: Your diesel smoke check. This leaflet includes information about how the emissions check will be conducted on your vehicle."

I doubt very much if the garage can be held liable in my case bearing in mind all the above replies. It still remains that if I were forewarned as I should have been then I would have run the car up and down a nearby 60 mph road for half an hour and delivered it immediately prior to the test time. Like a poster above I do not thrash a car of this age in use. I know the gasket will go one day, I have no idea how old it is, but with the way I drive it may have lasted another year who knows? BJ

BJ