AGR Questions: Your Top 2 FAQs Answered

Hello everyone,

Currently, I am installing some sensors in the car. Today, it was a pressure sensor for the LDA. For this, I used the tip from Ulf (was it him? --> THANK YOU! ), which involved drilling a hole in the EGR valve.
To get to it, I had to remove it. While I was there, I took a closer look at the part. The EGR valve was intact for six months, but has been defective for two years. The vacuum hose is irreparably damaged and got clogged by a stupidly placed plug. On the side of the canister, a sintered silencer was installed to allow it to breathe. Two things caught my attention:

Here's the translation:

"Except for a few oily and carbon-like deposits on the valve lifter, everything looked much less severe than in the pictures in the technical articles. However, when looking at the sealing plate from the exhaust port side, there's a brownish-white, grease-like substance. How can something like that form? I would have expected soot, but not this. The plate itself is otherwise verschandeln and shiny."


2. The upper part of the plunger is clean, as if the valve, despite being defective, would still open. Is this normal? Could it be that during the last operation under normal conditions, it cleaned itself and didn't get clogged due to a lack of carbon buildup? When removed, the seat appeared to be fine. It also moves when you suck on the canister and seals properly. Perhaps it then forced the debris from point 1 into the engine.

joegolf wrote:

However, when looking at the diffuser plate from the exhaust gas inlet side, there is a brownish-white, grease-like substance present. How can something like that occur?

For example, when oil and (condensed) water mix, it forms an emulsion.
How that can occur on the exhaust side of the EGR valve ->

Quote:

The upper part of the plunger is clean, as if the valve, even though defective, would still open. Is this normal? Did the device get cleaned during its last operation under normal conditions, and did it not become clogged due to a lack of soot?

It could be.
To ensure that the part actually and consistently closes, I would verschandeln the inside of the pipe as thoroughly as possible and then check it again after a few thousand kilometers, or disassemble it. If it's still sooty at that point (despite the continued faulty control), then it's not closing properly.

Okay, I'll keep an eye on it. If in doubt, I'll insert a piece of metal into the gasket around the exhaust port. Then I can see if the sludge is being forced through the valve seat or if it's somehow forming in the exhaust system.

From what vacuum level should the valve open? This could be easily measured and would provide an indication of whether the spring force holding the valve closed is sufficient.

I can't provide you with precise data, only my own experience. In my case, the AGR valve also failed relatively quickly, after about 1500 km. Since I had already removed it, I cleaned it thoroughly, except for the back of the plunger. It still looks exactly the same now, after 55,000 km. The area within its adjustment range is quite clean, but a slight "carbon" buildup can still be seen underneath. Because the rest of the AGR valve is very clean, except for a little oil mist, I think this residue is from those initial 1500 km. Furthermore, the AGR valve itself can only open if there's significant back pressure in the exhaust system, as only that pressure could overcome the spring force (since there's no vacuum on the control side). This should be noticeable during normal operation.

Don't worry, I think everything is okay!