Possible diesel EGR bypass problem - might be worth checking by raistlin


User avatar
raistlin
I found a problem with the exhaust gas pipe which is connected to the blanking stub of my EGR (Exhaust Gas Recirculation Valve) bypass. Lyndon has had the same problem and I've since found out that several other people have seen this fault as well.

The background:-

The EGR system is designed to allow a certain amount of exhaust gas back into the engine cylinders via the inlet manifold. This is to reduce NOx emissions from the engine by replacing some of the oxygen in the pre-combustion mixture in a diesel engine.

An unfortunate side effect of this is to produce heavy carbon gunk build-up in both the EGR valve and the inlet manifold. Further, it is said that the mechanical part of the valve, directly in the line of intake air-flow, reduces the performance of the car as well as exacerbating the carbon contamination by providing a further surface for the crud to build up, thereby reducing, in a sort of vicious circle, the cross section of the air inlet tract at that point. The EGR is connected directly to the inlet manifold.

Some time ago, a bypass was designed whereby the EGR was replaced with a straight through tube and the exhaust gas pipe was blanked off. This certainly reduces the amount of contamination and is said to increase performance. Whether it does improve things is beyond the scope of this post though :)

The problem:-

There are two types of exhaust gas pipe (see attached diagram), with flanges at either end on the short pipe and at one end on the long pipe and these are separate items, secured to the pipe by either brazing, welding or some other process, to produce a gas tight pipe. The problem is that these flanges are separating from the pipe allowing some escape of exhaust gas.

The photograph illustrates the short pipe with flanges at both ends. The diagram illustrates the shape and location of both pipes, numbered 3 and 13 in the diagram.

If you have an EGR bypass on your car, it might be worth removing the engine cover and examining the pipe, whether it be the long or short pipe. However, the flange(s), even if broken away from the pipe appear to be secure owing to the tension between the pipe and the EGR bypass blanking stub so it might be as well to unbolt the EGR bypass from the inlet manifold to release the tension on the exhaust pipe and thereby positively to identify whether there is a problem or not.

On my car, there appears to be no indication of the problem in terms of engine performance or any other obvious symptoms so I would think that physical inspection would be the only way to be sure. Having said that, of course, exhaust gas escaping from the exhaust manifold can't be good, can it?

A probable, though not proven, reason is that the exhaust gas, with nowhere to go upon reaching the blanking stub, pressurizes the pipe beyond design limitations, causing failure of the flange joints.

Possible solutions

One solution to this is to replace the pipe or get the flange(s) re-attached but apparently the same thing will happen again. Lyndon came up with a permanent solution however, and it is the solution I am having done on my car.

Following installation of the EGR bypass, the exhaust gas pipe is redundant, so it can be removed completely from the EGR bypass to the exhaust manifold, and the port in the manifold can be welded over.

Lyndon tells me that although the pipe flange joints on his car failed on several occasions, he has never had a problem since the pipe was completely removed.

The time taken for the inspection, including removal and replacement of the engine cover and the EGR bypass, was less than 30 minutes, even for a mechanical numptie like me so in my view, a worthwhile investment in time and effort :)

A Caveat

I haven't heard of this fault occurring on cars which have a functioning EGR valve but, who knows? As I said before, there were no obvious symptoms. In fact, my car is in normal daily use at the moment until I get her into the garage next week for the welding to be done.

You do not have the required permissions to view the files attached to this post.

Paul

Cogito ergo sum... maybe?

Click the image to go to Nano-Meet Website
Image

Posted 05 Aug 2013, 18:15 #1 

User avatar
Trebor
Ill check mine out tonight Paul and get back to you

Rob
Robs Pictures at :

Robs Car Gallery

click below to access nano website
Image

Planning is an unnatural process, much better to just get on with things, that way failure comes as a complete surprise instead of being preceeded by a period of worry and doubt

Posted 06 Aug 2013, 05:18 #2 

User avatar
Trebor
i dont have the EGR bypass on mine so all is in its original state, it looks like this and all seems fine

Image

Image

Image
Robs Pictures at :

Robs Car Gallery

click below to access nano website
Image

Planning is an unnatural process, much better to just get on with things, that way failure comes as a complete surprise instead of being preceeded by a period of worry and doubt

Posted 06 Aug 2013, 17:28 #3 

User avatar
Arctic
(Trader)
User avatar
raistlin
Thanks Steve :) I understand it will be welded though.
Paul

Cogito ergo sum... maybe?

Click the image to go to Nano-Meet Website
Image

Posted 07 Aug 2013, 05:48 #5 

User avatar
ceedy
When I fitted a Bypass the small mounting for the flexi pipe didn't have quite the right profile , so it didn't seal the flexi right.
this cause a small leak. the worst aspect of this was the gooey muck that came out and spread around over the nearby area..
So that's a good way to check, stick your hand in and grope about , if it comes back black & sticky you have a leak somewhere.

Since I fitted the the bored out standard EGR ....no leaks, and its been in for a few years now..

:gmc:

Chris
Got one for Me , Then one for her, and now a big one for me again, All BLOO! Well saves on the touch up paint, Now Number one son's Spoilt it all by getting a Firefrost 1.8T

Posted 07 Aug 2013, 07:45 #6 

User avatar
Bermudan 75
So from Rob and Chris' comments, if you have the original EGR setup then there is no problem it would seem. So is it really worthwhile bypassing the EGR for the sake of cleaning it out on a regular basis?

Cheers

Mike
Image

Posted 07 Aug 2013, 08:00 #7 

User avatar
Arctic
(Trader)
Rover418275 wrote:So from Rob and Chris' comments, if you have the original EGR setup then there is no problem it would seem. So is it really worthwhile bypassing the EGR for the sake of cleaning it out on a regular basis?

Cheers

Mike


My opinion would be no as you know mike i carry three of these and i change mine over every winter then again when the spring starts bit OTT maybe but it suits me i also change the manifold once a year and the PCV (Positive Crankcase Ventilation Valve) twice a year oil filter and oil every six months again OTT :thumbsup: works for me ;)

Posted 07 Aug 2013, 20:24 #8 

User avatar
Bermudan 75
I have cleaned my EGR valve and have been wondering about the sludge in the manifold (inlet) and the hose to the intercooler.

My understanding is that the sludge starts to build up in the inlet manifold then to the EGR and then into the intercooler hose.

Does it then progress into the intercooler and beyond?
Does fitting the EGR bypass eliminate sludge formation?

Cheers

Mike
Image

Posted 14 Nov 2015, 18:05 #9 

User avatar
Colvert
Bermudan 75 wrote:I have cleaned my EGR valve and have been wondering about the sludge in the manifold (inlet) and the hose to the intercooler.

My understanding is that the sludge starts to build up in the inlet manifold then to the EGR and then into the intercooler hose.

Does it then progress into the intercooler and beyond?
Does fitting the EGR bypass eliminate sludge formation?

Cheers

Mike


Bump-------------- :wales:

Posted 30 Dec 2016, 20:55 #10 


Top