NCT brake testinig a 4wd car on rollers

peasant

The diesel smoke test does involve revving the engine to the limiter two or three times ...standard procedure.

Not a nice sound and engines with dodgy timing belts have been known not to survive the procedure (in rare cases). There is something to that effect on their paperwork, a big sign at the workshop and I think they make you sign a disclaimer as well.

But as long as your engine/injection pump and timing belt are in good condition there is nothing to worry about.

voxpop

They rev it to the redline! Didnt know that, thought they just gave it a bit of welly. You'd want to have the car nicely warmed up before putting it though that.

peasant

Not just warmed up ...you'd want to drive the nuts off it on the way to the test centre (and possibly for a few days previously)

Otherwise the collected soot and dust (the result of driving like a vicar in slippers for the last two years) will dislodge and come out in shovel-loads once they rev it and you'll fail the smoke test.

voxpop

or throw a bit of paraffin in *



*disclaimer: may cause problems

Johnny Utah

peasant wrote: »

Not just warmed up ...you'd want to drive the nuts off it on the way to the test centre (and possibly for a few days previously)

I will

peasant wrote: »

The diesel smoke test does involve revving the engine to the limiter two or three times ...standard procedure.

Not a nice sound and engines with dodgy timing belts have been known not to survive the procedure (in rare cases). There is something to that effect on their paperwork, a big sign at the workshop and I think they make you sign a disclaimer as well.

But as long as your engine/injection pump and timing belt are in good condition there is nothing to worry about.

The owner's manual says that you should "never allow the engine to run in the red zone of the revolution counter". Surely, it's bad for an engine to be redlined like that, especially a diesel engine?


I found something interesting on honestjohn, which questions the usefulness of diesel smoke tests:
http://www.honestjohn.co.uk/motoring_answers/index.htm?id=201



And to get back to what smokingman said above, how do I know that they will perform the diesel smoke test on my car as opposed to the emissions test for petrol cars? Is there an obvious difference in the procedure of these two tests which I can look out for?

voxpop

They dont do emission tests for diesels, only smoke test.


From that honestJonh link -> "remove the air filter immediately prior to the test." <- what that about ?

Johnny Utah

voxpop wrote: »

They dont do emission tests for diesels, only smoke test.

Yes, I know. When I was there before, I just saw them attaching a hose to the exhaust of cars. Is there an obvious difference I should look out for in the diesel smoke test?

voxpop wrote: »

From that honestJonh link -> "remove the air filter immediately prior to the test." <- what that about ?

Don't know how to do that.

gn3dr

Johnny Utah wrote: »

I have an NCT booked for next week, and I'm just wondering if there is anything I should look out for when they are testing my car- diesel RWD.

Would the RWD require the decelerometer as opposed to the standard brake test on the rolling road?






And if the OP is still here; how did you get on with your complaint?

Only thing I think with RWD (or FWD) is that they are not supposed to do the roller test if the car has a limited slip diff fitted.

As to my original complaint - I didn't get on too well. I got a letter back from NCTS in Dublin and basically it said something like .....we received your complaint, but we do notice that the car passed ......but thanks for the feedback anyway!

I did get a follow up call form someone in Limerick who was a bit more professional and he agreed that they would cover any costs if there was a problem with the car.

Yuppie

just found the old regs for smoke testing a diesel and it seems everything has to be done gently gently in terms of the reving.

also note that if they you havent asked you if the timing belt has been changed according to the manufacturing specified milage that they could be liable if the engine blows up, hopefully that wouldn't happen anyway

http://www.carlow.ie/sites/CarlowInternet/SiteCollectionDocuments/By%20Departmental/Motor%20Taxation/Miscellaneous/NationalCarTestManual.pdf

just about to buy and put through the Nct an 1998 citroen xantia 1.9TD stateside,

Fatfrog

peasant wrote: »

Not just warmed up ...you'd want to drive the nuts off it on the way to the test centre (and possibly for a few days previously)

Otherwise the collected soot and dust (the result of driving like a vicar in slippers for the last two years) will dislodge and come out in shovel-loads once they rev it and you'll fail the smoke test.

I personally disagree with the whole car revving thing at present it’s not accurate and basically bad for your car

1: If there checking the emissions they need to also dip your fuel tank to see exactly what’s in it! I mean you can have a dirty oul diesel running around for x2 years, throw a bit of petrol in the tank just before your test, gives a temporary good emission reading. As soon as the test is over it’s back to the same smokey grade fuel for another x2 years.

2: They rev your car when it’s in neutral? absolutely no load on the engine? Different story going up a steep hill in 3rd or 4th gear!

3: The car’s engine is not designed to sit on the spot while revving out!! Large fans should direct fast moving air over the engine (the water isn’t even going to get the chance to start cooling). If something was to fail during the test its “tough luck” as you would have signed a disclaimer, I’m sure the NCT’s process would not be covered under the cars warranty. So hypothetically if you went back to KIA with your 7 year warranty for a blown engine after the NCT it probably won’t be covered.

4: You can’t really give your car a “warm up” run before the test, because they have to check the engine oil level when engine has cooled slightly (5-10 minutes of cooling time) oil level must be checked before revving/emissions test.

wailim_2002

Just seen this post and decided to throw my 10c in coz I've just got a part-time 4wd Ford Explorer.

My understanding is that AWD and Full Time 4WD both have center diffs which allow the rear axle to spin independently of the front and vice versa. So in principle if any of these were roller tested, its not the end of the world. However, it may cause havoc with the TC system (if equipped) and of course if there is a manual 'lock' which simulates part-time 4wd then big trouble!

Whereas with my 'truck' and similar eg, Landcruiser etc, its part-time 4wd. I have Low, High and Auto. But I do not have a center diff. If the system detects an axle slipping it will auto engage 4wd. In this case, without the center diff, the truck would jump off the rollers or the transfer case would explode. In any case, like a previous poster, if it jumped off the rollers I'd imagine damage WAS DONE to the drive train. Sure it may take a while for it to manifest!

I will bring a note for the check-in guy to sign stating I informed them it was part time 4wd and not to be tested on the rollers. Although I suspect it is not up to the owner to do this. It would be easy to prove negligence!

This is not like the timing belt issue on diesels where it can be tested but if proper maintenance has not taken place the belt can snap which is why they reverse the blame on the basis they could not have known.

E39MSport

wailim_2002 wrote: »

Just seen this post and decided to throw my 10c in coz I've just got a part-time 4wd Ford Explorer.

My understanding is that AWD and Full Time 4WD both have center diffs which allow the rear axle to spin independently of the front and vice versa. So in principle if any of these were roller tested, its not the end of the world. However, it may cause havoc with the TC system (if equipped) and of course if there is a manual 'lock' which simulates part-time 4wd then big trouble!

Whereas with my 'truck' and similar eg, Landcruiser etc, its part-time 4wd. I have Low, High and Auto. But I do not have a center diff. If the system detects an axle slipping it will auto engage 4wd. In this case, without the center diff, the truck would jump off the rollers or the transfer case would explode. In any case, like a previous poster, if it jumped off the rollers I'd imagine damage WAS DONE to the drive train. Sure it may take a while for it to manifest!

I will bring a note for the check-in guy to sign stating I informed them it was part time 4wd and not to be tested on the rollers. Although I suspect it is not up to the owner to do this. It would be easy to prove negligence!

This is not like the timing belt issue on diesels where it can be tested but if proper maintenance has not taken place the belt can snap which is why they reverse the blame on the basis they could not have known.

Not all landcruisers are part time 4wd.

Mycroft H

wailim_2002 wrote: »

Just seen this post and decided to throw my 10c in coz I've just got a part-time 4wd Ford Explorer.

My understanding is that AWD and Full Time 4WD both have center diffs which allow the rear axle to spin independently of the front and vice versa. So in principle if any of these were roller tested, its not the end of the world. However, it may cause havoc with the TC system (if equipped) and of course if there is a manual 'lock' which simulates part-time 4wd then big trouble!

Whereas with my 'truck' and similar eg, Landcruiser etc, its part-time 4wd. I have Low, High and Auto. But I do not have a center diff. If the system detects an axle slipping it will auto engage 4wd. In this case, without the center diff, the truck would jump off the rollers or the transfer case would explode. In any case, like a previous poster, if it jumped off the rollers I'd imagine damage WAS DONE to the drive train. Sure it may take a while for it to manifest!

I will bring a note for the check-in guy to sign stating I informed them it was part time 4wd and not to be tested on the rollers. Although I suspect it is not up to the owner to do this. It would be easy to prove negligence!

This is not like the timing belt issue on diesels where it can be tested but if proper maintenance has not taken place the belt can snap which is why they reverse the blame on the basis they could not have known.

Center Diffs aren't designed for +30mph difference between the front and real axel.

smokingman

smokingman wrote: »

If you've a turbo diesel then watch to make sure they don't do the smoke test for petrol cars. The last two times I've had an NCT, they've put the hose on the exhaust and revved the bejaybus out of it.
None of my protestations were heard in time and while the turbo wasn't blown afterwards, I was just very lucky. This also happened my neighbours Land Rover Freelander but his turbo didn't fare as well and was leaking when he left the center. They had put the smoke test on the results sheet though like with mine so at least we had proof of what was done.

If they heard your protestations you'd have been a tad embarrassed, the smoke test is at higher revs than the test done on petrol cars

You have the wrong end of the stick, the proof your buddy has is simply that they revved the diesel to the limit as per the declaration he signed.

vtiniall

Just coming in on the back of this thread. I have a 2000 Subaru Legacy Blitzen, Obviously 4 wheel drive. Just on what everyone else is saying about not testing cars on the rollers. I take it my Legacy should have been taken out of the test centre and ran on the other machine, with the Legacy being all wheel drive ?.

I know for certain that they didnt do that, as I was standing out front of the test lane and watched the car go through.

LIGHTNING

Dont drag up old threads. Start a new one