Captdave Posted January 22 Share Posted January 22 Not so long ago the engine management light (EML) was on most of the time on my 2004 2.5 TDI C5 allroad. It would go off occasionally but would very soon come back on again. I tested it with my Launch OBD11 reader and it came up with the following faults PO401 and P0402. P0401 means insufficient exhaust gas recirculation P0402 means excessive exhaust gas recirculation So having some idea of what the problem was I decided to carry out a few tests around and on the EGR valve. First test I did was to check I had a vacuum going to the EGR valve. I did this by getting the car warm and then pulling off the vacuum pipe and putting my finger over the end and it had a good suction. Next test was to disconnect the electric plug to the EGR Solenoid valve (this is controlled by the ECU and tells the Solenoid valve when to open and supply vacuum to the EGR valve) With the plug disconnected no vacuum at the end of the pipe so that proved the solenoid valve was working as it should. Third test was to use a little vacuum tester (20 euro from Amazon) on the EGR valve itself. I found the EGR valve was unable to hold a vacuum at all and rapidly returned the gauge to zero telling me that the diaphragm inside the EGR valve was faulty. The next step was to order a new EGR valve from Autodoc and proceed to change the valve which at first sight looks a bit tricky but it is quite straightforward once you get into it. TOP TIP to remove the two allen headed set screws you will need a six mm allen key on a socket I used a quarter inch square drive allen Key with a very small extension around 2 inches otherwise you will really struggle to get the screws out. You will need to remove the Turbo heat shield first which is only help in place by a couple of screws. Once the allen screws are out you need to remove the inlet manifolds so you can gain access to the two 13mm bolts that hold the EGR valve onto the bypass pipe. They come off very easily again with a socket driven allen key and extension. Now you need a 13mm combination spanner to undo the two 13mm bolts you may need to twist the EGR valve a little to get at them and off it comes. At this point I used my vacuum tester on the new EGR valve which help the pressure perfectly where the old one would just open and then close straight away. To my horror I discovered there was a real filthy mess inside the inlet manifolds and inlet ports on the cylinder heads in some cases restricting the flow by around 40 percent YES 40 percent at least. So I had to clean all this mess out and this is a dirty filthy horrible job. I used brake cleaner and rags in my garage but still made a hell of a mess much better to do it in a parts washer or take it to the car pressure wash YOU HAVE BEEN WARNED. When it is all cleaned up you can reassemble in the reverse order which does not take long and give it a try. My EML light did not go out straight away but after a few minutes before I even got the car out of the garage it was off and has not been back on since so a great result. Incidentally the car has never run better which is unsurprising considering all the gunk that was in the manifolds and the EGR valve being unserviceable. Hope this helps I was just a bit bored today so thought I would post about my EGR valve work. All The Best Capt Dave 1 Quote Link to comment Share on other sites More sharing options...
Steve Q Posted January 22 Share Posted January 22 9 hours ago, Captdave said: Not so long ago the engine management light (EML) was on most of the time on my 2004 2.5 TDI C5 allroad. It would go off occasionally but would very soon come back on again. I tested it with my Launch OBD11 reader and it came up with the following faults PO401 and P0402. P0401 means insufficient exhaust gas recirculation P0402 means excessive exhaust gas recirculation So having some idea of what the problem was I decided to carry out a few tests around and on the EGR valve. First test I did was to check I had a vacuum going to the EGR valve. I did this by getting the car warm and then pulling off the vacuum pipe and putting my finger over the end and it had a good suction. Next test was to disconnect the electric plug to the EGR Solenoid valve (this is controlled by the ECU and tells the Solenoid valve when to open and supply vacuum to the EGR valve) With the plug disconnected no vacuum at the end of the pipe so that proved the solenoid valve was working as it should. Third test was to use a little vacuum tester (20 euro from Amazon) on the EGR valve itself. I found the EGR valve was unable to hold a vacuum at all and rapidly returned the gauge to zero telling me that the diaphragm inside the EGR valve was faulty. The next step was to order a new EGR valve from Autodoc and proceed to change the valve which at first sight looks a bit tricky but it is quite straightforward once you get into it. TOP TIP to remove the two allen headed set screws you will need a six mm allen key on a socket I used a quarter inch square drive allen Key with a very small extension around 2 inches otherwise you will really struggle to get the screws out. You will need to remove the Turbo heat shield first which is only help in place by a couple of screws. Once the allen screws are out you need to remove the inlet manifolds so you can gain access to the two 13mm bolts that hold the EGR valve onto the bypass pipe. They come off very easily again with a socket driven allen key and extension. Now you need a 13mm combination spanner to undo the two 13mm bolts you may need to twist the EGR valve a little to get at them and off it comes. At this point I used my vacuum tester on the new EGR valve which help the pressure perfectly where the old one would just open and then close straight away. To my horror I discovered there was a real filthy mess inside the inlet manifolds and inlet ports on the cylinder heads in some cases restricting the flow by around 40 percent YES 40 percent at least. So I had to clean all this mess out and this is a dirty filthy horrible job. I used brake cleaner and rags in my garage but still made a hell of a mess much better to do it in a parts washer or take it to the car pressure wash YOU HAVE BEEN WARNED. When it is all cleaned up you can reassemble in the reverse order which does not take long and give it a try. My EML light did not go out straight away but after a few minutes before I even got the car out of the garage it was off and has not been back on since so a great result. Incidentally the car has never run better which is unsurprising considering all the gunk that was in the manifolds and the EGR valve being unserviceable. Hope this helps I was just a bit bored today so thought I would post about my EGR valve work. All The Best Capt Dave This is a fantastic guide, thanks so much Dave 🙂 I've, pinned this post for other members. Quote Link to comment Share on other sites More sharing options...
alpha omega Posted January 22 Share Posted January 22 well done david.....though no eml light has come on i know with having high mileage i need to do my inlet maifold and is it possible to clean the egr valve on my audi a4 tdi 2011 avant rather than buy new. and does anyone have a guide to do this with pictures all the best everyone Quote Link to comment Share on other sites More sharing options...
Captdave Posted January 23 Author Share Posted January 23 12 hours ago, alpha omega said: well done david.....though no eml light has come on i know with having high mileage i need to do my inlet maifold and is it possible to clean the egr valve on my audi a4 tdi 2011 avant rather than buy new. and does anyone have a guide to do this with pictures all the best everyone Hi Steve, Yes it is possible to clean the EGR valve, I did mine with brake cleaner rags and a tooth brush and its quite easy however you should test it with a little vacuum pump to make sure it holds pressure (mine did not) Quote Link to comment Share on other sites More sharing options...
alpha omega Posted January 23 Share Posted January 23 great stuff david.thank you.i just need a guide now and pictures lol😁 Quote Link to comment Share on other sites More sharing options...
audia4b5kev Posted February 1 Share Posted February 1 I LEAVE MINE IN TFR OVERNIGHT COME UP LIKE NEW AD RATHER TAKE IT OFF LIKE INSTEAD THE SPRAY EGR CLEANER KEV 1 Quote Link to comment Share on other sites More sharing options...
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