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Engine Depollution Failure - Warning light
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gmerry   
Thu Feb 25 2016, 12:14pm
Joined: Dec 11 2009
Member No: #21
Location: Scotland
 Yes, 5 hours would be spot on (with prior experience, everything to hand and a few modified hand tools to work around all the obstructions, ie that lots of 8mm and 10mm spanners maybe 6 of each size to reach all the different combinations of depth, arc length, handle obstruction. And don't forget to replace the existing studs that hold the EGR valve to the cylinder head with the revised mechanic friendly design. Also you will need at least 3 different hose clip pliers to access all the different hoses.

Regards

PS, my 1st off time was at least double the above.
FraserG   
Thu Feb 25 2016, 08:59pm
Joined: Jan 05 2015
Member No: #2011
Location: Auckland
 Excuse me for sounding stupid, but why did they make this procedure so difficult to action? Did they not expect that the EGR valves would need replacement? Throw the car away after three years? It seems ridiculous that such an expensive repair would be designed into the cars maintenance requirements. I'm not looking forward to needing to explain this to my wife when it needs doing to my car. I can imagine he reaction but I don't want to buy a [%*^#@!] Toyota!
David Hallworth   
Thu Feb 25 2016, 11:58pm

Joined: Apr 16 2010
Member No: #90
Location: Glasgow
 You can see and touch the front EGR valve but there is a lot of stripping down to do to actually be in a position to remove the valve itself.

The rear valve that you cannot see and have to change by feel is much easier to do and takes half the time apparently.

I've got no first hand experience of changing either and can only repeat what I've heard from other people. G has changed both of his, he'll be able to give a much better idea of time taken then I can.

David.
Bishop   
Mon Feb 29 2016, 09:30am
Joined: Apr 16 2012
Member No: #868
Location: Harpenden
 FraserG - I am afraid that there are a lot of repairs to individual components that require many hours work to take the car apart to get at the said component and then rebuild it again. I have had 2 such instances since the turn of the year - the hydraulic power steering pipe/ hose (7 hours work) and the left rear ABS sensor (3 hours to drop the fuel tank.
FraserG   
Mon Feb 29 2016, 11:31pm
Joined: Jan 05 2015
Member No: #2011
Location: Auckland
 Bishop,
Yes sadly I am sure you are right. As a designer it does however upset me because I know that things don't have to be designed this way. For instance why would the rear ABS sensor be above the fuel tank? You can tell I'm not a engineer can't you! Hopefully my car continues to behave itself as it has done so far in our happy life together. Cheers
userpco   
Tue Mar 01 2016, 10:33am
Joined: Sep 15 2011
Member No: #622
Location: Ascot, Berkshire
FraserG wrote ...

For instance why would the rear ABS sensor be above the fuel tank?


It's my understanding that although the sensors are on the wheels they are connected above the fuel tank.
gmerry   
Tue Mar 01 2016, 10:58am
Joined: Dec 11 2009
Member No: #21
Location: Scotland
 Hi Userpco, yes the rear ABS sensors are conventional and accessed through the back of the hub. The connections between the flying leads of the sensors and the fixed vehicle wiring are on top of the tank in a very good dry location. Actually, these connections are very easy to access, there is a nice little flap under the rear right seat and its the same access point for the in-tank fuel pump and sensor.

Now having changed both rear ABS sensors, the overall design looks very sensible and the job is not nearly as bad as one fears. Actually, the only part that was a pain in the proverbial was some minor corroded up fasteners on things like the wheel arch liners. Oh well.G
JPV   
Tue Mar 01 2016, 04:58pm
Joined: Sep 04 2011
Member No: #606
Location: Norwich
gmerry wrote ...

Hi Userpco, yes the rear ABS sensors are conventional and accessed through the back of the hub. The connections between the flying leads of the sensors and the fixed vehicle wiring are on top of the tank in a very good dry location. Actually, these connections are very easy to access, there is a nice little flap under the rear right seat and its the same access point for the in-tank fuel pump and sensor.

Now having changed both rear ABS sensors, the overall design looks very sensible and the job is not nearly as bad as one fears. Actually, the only part that was a pain in the proverbial was some minor corroded up fasteners on things like the wheel arch liners. Oh well.G


This confuses me. Why do Main Agents charge for dropping the fuel tank when replacing these? You seem to be indicating that it is not necessary.
e3steve   
Wed Mar 02 2016, 01:42pm
Joined: Jan 21 2013
Member No: #1163
Location: Warsash, Hants & Palma de Mallorca, Spain
 It's necessary to first drop the exhaust to allow the tank to be lowered, albeit by only 15-20cm; then the sensors' cables can then be pressed home into the channels (moulded into the tank top itself) by feel.

Both ABS sensors are the same, as are their cable lengths. This means that the r/h sensor cable snakes back & forth in order to lose some of that excess cable length.

[%*^#@!] ridiculous!
ChrisW   
Mon Aug 29 2016, 09:46am
Joined: Jun 18 2013
Member No: #1335
Location: Surrey
 Fascinating thread - thank you to all. My Engine Management Light came on about 4 years ago with a depollution faulty message. First intermittent, then all the time. Car ran well. I asked the MOT inspector if this would be a problem. No, as long as the emissions test is ok. The EML is not part of the MOT. It has passed 3 times since with the EML lit. The last MOT was at a Citroen main dealer. It would have cost £96 to read the fault code! The mechanic agreed with me to ignore the light as the car is running well. He said that people can spend a lot of time and money trying to chase-down warning lights. If it ain't broke don't fix it.

The lit EML was a minor irritant but, as a result of this thread, I now welcome it! Here's why. All things being equal, the power output of an engine depends on the rate it burns fuel. This is limited by the availability of oxygen in the cylinder. A turbo boosts this but also heats the air, which reduces its density and the amount of oxygen. That's why big engines often have turbo intercoolers.

When the EGR valve opens it dilutes the oxygen with hot exhaust gases. It counteracts the benefit of the turbo. This reduces the power and probably the efficiency of the engine. But the reduction in oxygen reduces the combustion temperature and the amount of NOX. Blanking-off the EGR is popular because it avoids this power loss. I fully agree with gmerry's diagnosis that, if one EGR fails shut, the EMS is designed to shut the other EGR because otherwise the EMS would have the impossible task of trying to operate 2 sets of cylinders with different combustion conditions.

Although the EGR reduces the combustion temperature it has little or no effect on the exhaust gas temperature. It is an urban myth that blanking the EGR could damage the turbo. In any case, the EMS closes the EGR when under heavy load to maximise the power, so the turbo will be subjected to high temperatures regardless of whether the EGR is working or not.

It would appear that my car has been running for the last 4 years with both EGRs shut. This will have improved the performance of the engine for zero cost. That's why I am now happy that the EML is lit and I will continue to ignore it!
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