Protocol for passing MOT emission test easier (TD5 2006)

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Stock_90_TD5_SW

Stock_90_TD5_SW

Active Member
Posts
156
Location
Estonia
Guys, do You have a way of delivering your trucks to the MOT exhaust gas test? The problem is the MOT people don't appreciate the amount of black powdery stuff that flies out of the exhaust at revving.

I usually do a longer drive on the highway, with engine hot, I rev it much more than I would usually do. Try to get the gunk out of the exhaust. I guess this is more or less correct?

My question is, how should I deliver the truck? Should I turn off the engine immediately after arriving at the MOT building? Or is it better to leave it running? Should I rev the engine before driving inside their building? Or rather avoid the acceleration pedal altogether and roll in on clutch power alone?

Any tips will be very much appreciate it, cause every time they see the black powdery smoke, they go extra-hard on everything else, picking on me on every pretence :)
 
Stock_90_TD5_SW said:
Guys, do You have a way of delivering your trucks to the MOT exhaust gas test? The problem is the MOT people don't appreciate the amount of black powdery stuff that flies out of the exhaust at revving.

I usually do a longer drive on the highway, with engine hot, I rev it much more than I would usually do. Try to get the gunk out of the exhaust. I guess this is more or less correct?

My question is, how should I deliver the truck? Should I turn off the engine immediately after arriving at the MOT building? Or is it better to leave it running? Should I rev the engine before driving inside their building? Or rather avoid the acceleration pedal altogether and roll in on clutch power alone?

Any tips will be very much appreciate it, cause every time they see the black powdery smoke, they go extra-hard on everything else, picking on me on every pretence :)
Click to expand...

You could try putting a couple of bottles of some kind of cleaner, like Comma Diesel Magic, or Wurth's fuel system cleaner in, and taking it for a good long run at high speed, that might clean it out a bit.

Obviously, I am not familiar with testing procedures in Estonia, but in the UK, they are supposed to test the oil temperature before the emissions test, so switching off the engine before test is unlikely to be a good idea, because it will cool down.

At the end of the day, these engines were not designed to cope with modern emissions testing procedures, so it will need a sympathetic tester, and that situation will tend to get worse over time.
 
Thanks, Turboman!

I will keep the engine running. The additive idea is also interesting , but I'm a little scared of such things :|

I am trying to understand what the mechanism for black gunk accumulation is. Is it just from engine idling and is simply unburnt fuel? And does it actually clear out at high revving or am I just creating additional smoke?

I have just replaced the MAF sensor, so the air delivery should be OK..
 
Make sure your air filter isn’t obscured by any debris, pull out your entire air box turn it upside and give it a jolly smack with your hand a lot of crap should come out
 
Stock_90_TD5_SW said:
Thanks, Turboman!

I will keep the engine running. The additive idea is also interesting , but I'm a little scared of such things :|

I am trying to understand what the mechanism for black gunk accumulation is. Is it just from engine idling and is simply unburnt fuel? And does it actually clear out at high revving or am I just creating additional smoke?

I have just replaced the MAF sensor, so the air delivery should be OK..
Click to expand...

I wouldn't worry about additives. Fuel contains them anyway, all you are doing is putting in a little bit extra a few days before the test.

Any engine, even if perfectly tuned, and using high quality fuel, produces a certain amount of combustion product in the form of soot, and unwanted gases. There is also water vapour, which will be visible in the air on a cold day, and condense inside the exhaust pipe, and be blown out when the engine is revved.

Not much you can do about it, it is the nature of the way engines work.
 
Rev the tits out of it before an emissions test..

if a derv fails an Emissions test i just tell the owner to rag the crap out of it and usually after 30mins of thrashing it passes ;)

Also as Turboman says the above additives also help.
 
Guys, thank You for the replies! The Italian tune-up worked. Passed on first accelleration.

BUT FAILED THE MOT ON THE REAR BRAKES :|

I've had this problem for some years, that the rear brakes were very weak. But as the front breaks were super strong, I would usually pass on the sufficient average braking power.

Two years ago we bled the system and replaced the brake fluid. Last autumn replaced the discs and pads and the things has gotten worse. The mot test registered 48% efficiency for both axles as an average (needed 50% to pass); around 20% on the rear. My front discs are perforated Britpart ones with OK pads (don't remember the brand, but googled before buying).

The mechanic says the calipers are OK. He suspects the pressure pump? I'm confused as this smells of my standard 'replace all parts' technique.

Can You help me with the logic here? What are the usual suspects in this case and how to go about determining the cause without replacing everything?
 
Last edited:
Stock_90_TD5_SW said:
Guys, thank You for the replies! The Italian tune-up worked. Passes on first accelleration.

BUT FAILED ON THE REAR BRAKES :|

I've had this problem for some years, that the rear brakes were very weak. But as the front breaks were super strong, I would usually pass on the sudficient average braking power.

Two years ago we bled the system and replaced the brake fluid. Last autumn replaced the discs and pads and the things has gotten worse. The mot test registered 48% efficiency on thr front and around 20% on the rear. My front discs are perforated Britpart ones with OK pads (don't remember the brand, but googled before buying).

The mechanic says the calipers are OK. He suspects the pressure pump? I'm confused as this smells of my standard 'replace all parts' technique.

Can You help me with the logic here? What are the usual suspects in this case and how to go about determining the cause without replacing everything?
Click to expand...

By pressure pump, do you mean the brake servo? Or the vacuum pump that activates it?
 
Brake biasing is done in the master cylinder on TD5s. There is no separate reducing valve for the rear brakes. If there was a problem with the vac pump it would affect both front and rear brakes. Same with the servo. The OP says it's had new discs and pads so that would leave the calipers or master cylinder as the culprits. Just my logic given the information presented anyway.
 
DefenderPilot said:
Brake biasing is done in the master cylinder on TD5s. There is no separate reducing valve for the rear brakes. If there was a problem with the vac pump it would affect both front and rear brakes. Same with the servo. The OP says it's had new discs and pads so that would leave the calipers or master cylinder as the culprits. Just my logic given the information presented anyway.
Click to expand...

I am not that familiar with Td5s, but I had assumed it would have bigger calipers on the front than on the rears?

In which case, if there was no servo assistance at all, the front might have enough braking power to scrape through the test, and the rears not.

Maybe that is not the case, I do not know.
 
Turboman said:
In which case, if there was no servo assistance at all, the front might have enough braking power to scrape the test, and the rears not.
Click to expand...

True. The numbers are quite low for both front and rear. Add the servo and vac pump back on to the list of possible suspects.
 
Thank You for the replies!! Really appreciate them!

I meant the vacu pump.

The chronology of brake problems was like this: 3 times in a row the rear brakes were below acceptance at the MOT, but the front efficiency compensated and let me pass. Last summer I replaced rear disks and pads and the MOT didnt register any improvement. In the autumn I replaced the front disks and pads and felt that the front brake got weaker. Now that feeling was confirmed by the MOT with the efficiency of the front brake droping significantly.

What do You think would be the most reasonable line of action? Checking for leaks (brake fluid level is good and not much topping needed)? Start replacing parts?(that's what I usually do). Or taking the truck to the independent LR people here, who are cheaper than the stealer, but still a little over-hyped.
 
Stock_90_TD5_SW said:
Thank You for the replies!! Really appreciate them!

I meant the vacu pump.

The chronology of brake problems was like this: 3 times in a row the rear brakes were below acceptance at the MOT, but the front efficiency compensated and let me pass. Last summer I replaced rear disks and pads and the MOT didnt register any improvement. In the autumn I replaced the front disks and pads and felt that the front brake got weaker. Now that feeling was confirmed by the MOT with the efficiency of the front brake droping significantly.

What do You think would be the most reasonable line of action? Checking for leaks (brake fluid level is good and not much topping needed)? Start replacing parts?(that's what I usually do). Or taking the truck to the independent LR people here, who are cheaper than the stealer, but still a little over-hyped.
Click to expand...

Test the servo, as I described above. If it isn't working, try and find the vacuum pump, and try and find out if it is working, you should be able to pull off the pipe, and see if it is creating any vacuum. If it isn't, replace or repair it, if it is, replace or repair the servo.
 
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