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EGR Valve - What is it

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Having read posts about balnking this off i have tried to do a search for what this is and so far have come up with some many replies i thought i would ask than trying to confuse myself.

I have a 300tdi and would like to know what the EGR valve is, how i find it (if not blanked off already), what does it do and what does it do blanking it off..

Thanks all

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The EGR valve is on top of the exhaust manifold. It 'recycles' a percentage of exhaust gases into the intake air (the quantity of exhaust is controlled by vaccuum/engine revs). Later versions are done electronically, but they both have the same fault - the valve jams wide open and then too much exhaust gas is let into the intake at lower revs and the result of this is that the inlet manifold and part of the pipework becomes clogged with 'marmite'

Like this-


This has the effect of restricting air flow/increasing fuel consuption/reducing performance.

There are kits available for blanking off the EGR, but if the inlet manifold is heavily coked-up, then it has to be removed and cleaned, which is really messy job. The inlet ports have to be cleaned carefully as well - you have to be careful that lumps of the stuff doesn't stick partway through an already open valve. Some people have said that there is no noticeable difference in performance after doing this and others say it's a lot better. No problem with emissions come MOT time, so it's generally accepted that removal of the EGR is a good idea.


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Taken from my new website (only in draft form) - as done a bit of an explanation:

What is the EGR and what does it do??

EGR or Exhaust Gas Recirculation.

As its name suggests, the Exhaust Gas Recirculation (EGR) system allows a controlled amount of spent exhaust gas back into the air intake of the engine. On both Td5 and 300Tdi this is controlled by the vehicle ECU (Tdi has a standalone ECU for the EGR).

The purpose of recirculating a percentage of the exhaust gas is to reduce nitrous oxide emissions and combustion noise, recirculating a percentage of exhaust gas reduces the combustion temperature and slows down the fuel burn rate - which leads to reduced emissions, but also reduces performance. Although the EGR only works at certain part load conditions, removing it completely should make a difference in performance, and will possibly also lead to an improved mpg.

Why should I remove it??

As mentioned above, removing the EGR system completely will often make a big difference to performance, and can lead to improved mpg - however that is only part of the story.

When the EGR system works correctly, then it should only operate at part load, part throttle conditions - i.e. the times when you, as the driver, shouldn't notice its operation. But this isn't always the case. On both 300Tdi and Td5's it is very common for the solenoid valve to become clogged internally, which prevents it from sealing correctly. When this happens, performance and MPG will be substantially impaired... it is also very bad for the engine. If the percentage of EGR is too high, rapid engine wear (bore wear) will occur.

The EGR gas will also soot/clog up the inlet manifold as shown in the pictures below. On Td5's this can cause problems with the MAP (Manifold Absolute Pressure) sensor.

Looking at it from another point of view, removing the EGR basically means there is one less thing to go wrong!!

You should also remove the EGR if you regularly use high Sulpher diesel (in the UK, all diesel is low sulpher)

Does it cause any problems at MOT time??

The current 2008 MOT system for Diesel (i.e. compression ignition) vehicles only requires an Opacity test, (i.e. smoke) and not an actual emissions test as per petrol (spark ignition engine).

The EGR system (and the catalytic converter for that matter) does not actively affect smoke…. This differs from a diesel particulate filter (which is also exempt from testing at the current time). The only requirement is that the max smoke value for a turbo charged diesel is a mean (of the last 3 smoke tests) not exceeding 3.00m-1. For an initial 'fast pass' the smoke value must be below 1.50m-1.

In simple terms.... the only reason a modern diesel have CATs and EGR (along with other things) is to enable a manufacturer to meet the current EU legislation (for example EU4/5), but once a vehicle model has been type approved, and sold to the customer... the customer is technically free to do what they like regarding emissions, as long as they meet the requirements of their country, which in the UK is just the MOT test.

This can be confirmed by reading the MOT manual.

P.s . if you want a 'proper' EGR removal kit ;)




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Going off topic a bit but EGR is a swear word in our house at the moment!

My wife has a Saab 9-3 1.9TiD which is a very nice car to drive (if you like that sort of thing) but recently it has had to go in to the dealer due to a massive drop in power under 3K RPM.

Turns out the EGR valve is faulty but there are none available as they have been failing by the thousand and GM are having to redesign it (also affects the Vectra which uses the same engine). Luckily, being under warranty she has been given a hire car (a Vectra which is better than nothing I suppose). So far she has been without it for 4-weeks but she has been advised not to expect it back this side of May (only then if the manufacturing issues are resolved). As the problem is so widespread I understand even cars out of warranty are having the valves replaced (cost of each valve is about £180 plus fitting).

Getting back to Defenders and the EGR valve on the 300TDi, my 2004 model was not fitted with one from new so I don't have that particular item to worry about.

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EGR value was sticking on my 2006 Td5 90 was causing intermittent loss of power. Thought about bringing back to dealer under warranty but decided to take it off , replaced it with Devon 4x4 blanking plate , it now goes like s..t off a shovel. Also Has an Autologic tune.

Has DOE test next week hopefully it will sail thru.

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  • 2 years later...

Strange, I thought no 300tdi Defenders had the EGR fitted. Maybe you have a Disco engine. Later TD5s also had the thing not fitted at the factory as they didn't cut down emissions and just caused problems. So removing it will have no effect on your MOT.

As a moment of LR madness, my 300Tdi 110 csw has an engine number beginning in 21L (instead of 16L) which officially makes it an EDC auto Disco motor. Anyway, maybe the bits got mixed up somehow in manufacture :blink:

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egr's are a complete waste of time. they would be better spent as paper weights rather than adding weight to your motor. pull it out completely, or blank it off, either way you will be better off. just remember to blank off the tube to it if you remove it completely, aswell blanking as both holes left by removal of it on the inlet and exhaust manifolds.

if you leave it in situ and chose to blsnk it off that way, you can leave it all connected up still.


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