EGR Valve vacuum testing - fault code P0401

[Manske]

A few weeks ago the engine warning light came on. Last month I already spend near £1000 pounds on a cambelt + waterpump replacment and glowplugs replacement. I was feeling poor so I set out finding what the problem was myself. It appeared to by fault code P0401 - EGR flow unsufficient. I asked my local dealer what they would suggest doing about it and they quoted me £260 for an EGR valve replacement. In this topic I wanted to share my experiences in finding a solution for this problem.

 

Just a bit of background: I spanner a bit on my motorcycle but in my 5 years of Skoda ownership I have never lifted the rubber engine cover. So I am pretty much a novice at this. 

 

To get started I purchased a cheap OBD2 bluetooth dongle (£5.95) and the Torque Pro app for Android (£3). Bluetooth pairing the two devices was easy. There is a menu that says "Fault Codes" and when selected will scan for fault codes.

 

 

 

This gave P0401 with an option to read what that means. There are many good threads on this forum about P0401 and possible ways of tackling this fault. 

[Manske]

I will show you how I did the vacuum test of the EGR Valve. I used a Sealey vacuum tester which is the same as a mityvac. 

The reason I do vacuum testing is that the valve is operated by a vacuum hose. This is not a valid way of testing an electrically operated EGR Valve (obviously!)

 

I disconnected the vacuum hose and connected the Sealey vacuum tester. No matter how hard I pumped, the valve would not hold vacuum.

 

 

Here is the result (after much toiling) with a new EGR Valve. You can see that the valve holds good vacuum at -550 m Hg which would be ~0.3 bar.

 

 

Vacuum testing the new valve on the bench:

 

 

Note the metal rod moves up, opening the pathway to let used exhaust fumes into the air intake.

[Manske]

So there you have a condensed version of the useful bits that I learned from two Saturday afternoons. 

I read many EGR topics but I found this topic of particular help for dismantling the EGR valve and throttle: http://www.briskoda.net/forums/topic/212548-egr-valve-cleaning/

 

Here some photos:

 

Throttle or "Intake Manifold Flap" after 135k miles

 

 

EGR Valve after 135k miles:

 

 

This is how the EGR Valve fits with the Intake Manifold and the EGR pipe:

 

 

The IMF and EGR are connected to each other and to the Manifold with 5 mm Allen bolts. The EGR pipe is connected with 6 mm Allen bolts.

[Manske]

After a few hours of cleaning: 

 

Inlet Manifold Flap or Throttle Body (part number 036128063 / A2C53099815)

 

 

EGR Valve 

 

 

I know that it was pointless to clean the EGR valve. The truth is that I had no idea how to vacuum test the valve until I saw it mentioned on this forum, someone saying mityvac and when I looked it up I saw something that looked like the vacuum pump in my motorcycle brake bleeding set. That is when I made the connection. Duh!

[Manske]

Old EGR Valve:

 

 

Part number 038129637D

 

 

Wahler WAO Germany

 

New EGR Valve (£64)

 

 

Note: the VW mark has been cut out for some reason

 

 

and the Wahler box:

 

[Manske]

So there you have it. This job took me longer than needed because I had to figure out how things hang together in this car. I am glad I have a few socket sets with suitable extensions. I also used a short stubby Allen key to access the 6 mm Allen bolts. All very fiddly. I also found it hard to get the electric connector to the IMF off. Mmmm. I removed the rubber air hose and then found it hard to push it back in again. Somehow it has to "click". 

 

 

For the cleaning I used a toothbrush stick first, then paraffin and finally carb cleaner. The man at the garage had suggested that "some customers" use Mr Muscle degreaser. 

So the first afternoon was spend cleaning and reassembling, then I reset the fault codes but the next day the fault came back of course. Then I bought a new EGR valve to replace the old one (as suggested by the garage). The next Saturday I was meant to fix the new valve but the mityvac and vacuum testing idea came to me. 

 

I can't put a price on my time here. Obviously a cleaning job like this makes everything dirty, hands, clothes. It takes effort to  get it all off. So perhaps the £260 that the garage was going to charge me does not look so bad after all. Plus they collect and return the car to my house. All good service from the local Skoda dealer. 

 

But we learned something...

[cheshire_cat]

welcome to the black hand gang :sun:

[Grumbee]

Fantastic post.... I tried to clean the valve in situ but have so far been unsuccessful so I'll certainly use this info to help me to correctly diagnose and fix the problem with my 05 Occy......

 

THANKS

[Manske]

I wouldn't clean the valve in-situ because

1) you can't really get all the muck out that way

2) any muck or carb cleaner might roll via the manifold into the engine. 

 

This brings me to question why there is so much muck in the first place? I guess in 9 years a lot of it can accumulate. Cleaning it should be a service task, like every 60k miles or so. 

It looks to me that there are two contributors to the EGR Valve muck:

 

1) Engine oil vapour flows back into the air intake. 

2) Sooth from the exhaust gas via the EGR pipe

 

The two mix together and pollute EGR Valve, IMF and Manifold. I tried to scrape some muck out of the manifold and squirted carb cleaner in it. That was a bad idea. I am thinking of ways to get the manifold off for cleaning. Another lovely project.

[cheshire_cat]

No3   heat