Hi,
Can anyone point me in the right direction as to determin my recent MOT failure.
I have a Renault Megane 1.9 turbo diesel - 1997, 75k on clock.
It has failed the smoke test on the MOT - any ideas what could cause this.
It was only a five minute journey to the MOT centre so it has been suggested that I put "some kind" of additive in the diesel and take it for a good run before having the smoke test re-done. Will this work ??? If so, can anyone recommend a good additive. I'm thinking "worst case scenerio" of what the problem could be.
Any suggestions appreciated.
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A friend of mine had the same problem and was told (unofficially) by the tester to rev the engine to it's maximum a few times in succession just before taking it into the test station, also I believe it helps if the engine is warm.
Mind you, you'll die from embarrassment when you see what comes from the exhaust when you give it some welly!
PP
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Just a note to add, my friend's vehicle was a naturally aspirated Escort diesel, I don't know if your turbo would appreciate the same treatment.
PP
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I used to have a similar problem at MOTs with my turbo diesel.
However since using redex diesel additive in my turbo diesel, I have always passed with flying colours.
Definitely recommended.
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It happened to me with a Laguma 1.9dTi. Failed the smoke test. The bloke at the garage suggested I add a botttle of Redex additive, race it around the M25 at high revs for 30 minutes and come back for a retest. Did so and it passed no problems.
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It was only a five minute journey to the MOT centre.... Any suggestions appreciated
You've actually answered your own question. The short journey hasn't done you any favours. Take for an *Italian Tune*[1] prior to the re-test.
[1]search previous notes on Italian Tuning.
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The ATS test centre here has Forte diesel conditioner on the shelf at £10/can ready for all the smoke failures.
I don't think the car failed just because of the short run. I believe in using conditioner little and often, but the main thing is to get the engine revs up for a good draught through the system.
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Several years ago a friend had his diesel fail for the same reason. He bought a bottle of injector cleaner from the MOT garage, put half in the tank then started the engine, disconnected the fuel pipe near the filter, stuck it in the bottle and ran the engine as it sucked the cleaner out. It passed immediately! I always put a bottle in the tank the fill-up before the test and have never yet had a smoke test fail in 16 years of diesels. Another tip is that you leave the engine running if you have to wait for the test (obviously not if it is hours!) so that the engine is at a good temp when tested - or Italian tune up on the way to the test as others have suggested
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I had similar problems with a peugeot 405 diesel if I took it for an MOT with a cold engine.
I used to take it for a 20 mile drive using plenty of revs, and book a while-u-wait MOT, and it would always pass.
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How can you race up and down the M25 :-)
Had a similar problem with a 307 Diesel van once. Apparently its usually down to the injectors bieng partly blocked and not working properly.
I was sold a can of 'stuff' and the tester called it for a tenner and sent to the end of the A38 expressway and back. He didn't think it would make much difference, but I was happy to give it a try anyway.
The reading (not quite sure what it measured) went from something like 10 down to 2.45. Result - Passed.
Apparently it helps if you haven't got that much fuel in the tank.
I suspect I'll be using redex or similar on a regualr basis in both the Van and the Discovery.
Hugo
"Forever indebted to experience of others"
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Simple! Cold engines (or warm engines either....) don't pass the MOT smoke test as easily as hot engines. Part of the test prcedure is to check the sump oil temperature, so it is basic commonsense really.
The booked appointment MOT Test is a good idea here, as the engine can be warmed to temperature just prior to test by yourself.
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I saw a product called "Cataclean" on one of the sky shoppin channels the other evening. It *claimed* to reduce emisions within 5 mins of adding the product to the fuel tank. Works on petrol or diesel apparantly. Anyone ever used this stuff? Not snakeoil agian is it?
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Hi, Can anyone point me in the right direction as to determin my recent MOT failure. I have a Renault Megane 1.9 turbo diesel - 1997, 75k on clock. It has failed the smoke test on the MOT - any ideas what could cause this. It was only a five minute journey to the MOT centre so it has been suggested that I put "some kind" of additive in the diesel and take it for a good run before having the smoke test re-done. Will this work ??? If so, can anyone recommend a good additive. I'm thinking "worst case scenerio" of what the problem could be. Any suggestions appreciated.
When I had a Diesel VW passate company car that failed its first MOT on smoke, the garage telephoned the lease hire company to ask what they wanted to do about it. after half an hour driven out by one of the mechanics it was retested and passed without a hitch.When I enquired as to how come the reply was that the mechanic gave it a good thrashing to within an inch of its life.I was pleased it was not my car.
chris
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Except the test itself involves thrashing it within an inch of its life! First time I watched my (old) diesel being tested I thought it would blow up - they certainly used revs I would never have dreampt of!
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Except the test itself involves thrashing it within an inch of its life! First time I watched my (old) diesel being tested I thought it would blow up - they certainly used revs I would never have dreampt of!
Which is why it's also important to make sure the cambelt is in good order as well.
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and the reason the engine is thrashed to within an inch of its life on the MOT is because of some idiotic bureaucrats in Brussels. I queried this with the Govt dept responsible for MOT's when this test was introduced. Who ever revs their diesel under no load conditions to the red line? It is a totally unrepresentative test that gives meaningless results. The response I got was basically "Yes we agree, but Brussels told us to do it"!
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Buts it's not (is it?) The test is carried out with the accelerator fully depressed. With the way a diesel engine works, the fuelling will go to the maximum possible to accelerate the engine to maximum revs, albeit only for a fraction of a second due to the load of only the flywheel on the engine.
Ross
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But the load of the flywheel is nothing compared to putting to your foot the floor and expecting it accelerate the whole mass of the car, or pulling up hill at 60% revs with the accelerator hard down. Watching the MOT test on your own car makes you wince!
RichardW
Is it illogical? It must be Citroen....
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cant understand why fitting new fuel filter prior to mot
has'nt been suggested ...works for me
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My 220SDi failed on emissions the first time I put it in for it's MOT. It's was a police one (80K after 2 years), so my cure was:
Engine oil cleaner from Halfords - leave it running in the engine for 10mins or so. Gets rid of all the diesel oil debris/sludge.
Change oil, oil filter and air filter.
Spend 30 mins driving around so that the engine is nicely warmed up.
Remove air filter (more air in, dilutes what cack the exhaust might be throwing out), put it back after the MOT.
Passes with flying colours (I don't even think it's illegal to remove the air filter - but obviously you want it back in asap).
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jump in the car ,put on a helmet and hammer the pedal to the floor ,go as fast as you can up hills down hills and along pavements if you must,i gaurantee that you will clean out all those dust corners in your engine and turbo,due to the way a car is revved fro the mot it is very unlikley that you will generally do the same so just boot the jahookies off your car i think youll find it workds ,failing that take your inlet fuel pipe of the pump and the return ,drop them both in to a can of deisel conditioner and run it till the liquid in the return is filthy,then go for an mot.
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