EGR and air recirculation? - PeachParts Mercedes-Benz Forum

rwthomas1 · #1 12-13-2002, 05:14 PM

Okay I have done searches on these topics but cannot come to any conclusion. I would like to disable the EGR by putting a BB in the line and also mounting a blockoff plate under the EGR valve to permanently disable it yet keep it looking stock. Any reason NOT to do this? Also, i have heard mention that the 84' 300D's from California, which would be mine, may or may not have "air recirculation" Whats this thing look like? Do I disable it too? Thanks, RT

billrok · #2 12-13-2002, 06:36 PM

I wonder if Mercedes put the EGR system on the 951... engines just for the appeasement of the DOT regulations when bringing them into the country. I disabled mine (for testing purposes only) (hehe) and have found pretty much no difference in mpg or driveability. I bought an extra EGR gasket for the day I fabricate a blank plate and close up the hole forever.

GregS · #3 12-13-2002, 08:48 PM

If you have an air recirc. valve, you will see it installed on the intake manifold right beneath and to the left of the EGR valve. It too will have a vacuum line running to it. There is no consequence to disabling it. When I bought my car (also an '84 cali version), it wistled like crazy. Turns out, the wistling was caused by the recirculation valve. When I asked around on the internet about it, I was told there used to be some kind of rebuild kit for the recirc. valve so it wouldn't wistle, but that most people just unplugged it and plugged the vaccum line. I've put around 23,000 miles on my car since unplugging it and have not noticed any consequence.

Many people say their car feels like it has more pep, and gains a couple mpg, when they disconnect the EGR. I noticed no difference in either pep or mpg, and another person out there with an '84 300D said their experience was the same as mine.

Greg
'84 300D

P.S., all w123 diesels have the air recirc. for '85. I was talking recently with a guy on this board with an '85 wagon, and he said the "wistling" didn't bother him. It drove me aboslutely crazy, so I'm glad I unhooked it (maybe its louder on some cars than on others?).

adamb · #4 12-14-2002, 08:24 AM

On my 1985 300D Cali model, the air recirc valve diaphram had a pin-hole leak which caused intermittent vacuum system failures, especially shifting troubles. This was the most challenging thing to troubleshoot, but when I finally disconnected that darn thing and got rid of all the vacuum lines for that and the EGR, the cars vacuum system is now in top-shape.
I would plug it and forget it.

Have a great day!
Adam Bush

#5 12-14-2002, 10:17 AM

The 617.951 blocks do have EGRs and I did plug mine. Jury is out on if it makes a difference. If not for performance, do it for morals alone. Do you want used gasses to be up in your motor? I think not!

MVK · #6 12-15-2002, 07:22 PM

I disabled EGR by BB methon on mine. Also disabled the air recirculation valve (ARV) which used to whistle like a boeing taking off. I liked the whistle for a while but then it was kind of annoying.

Disabling the EGR made my tranny shift much better. Very noticable difference.

ARV- disabling this made the cruise control very good. No more surges while on cruise control.

Its worth disabling both these culprits.

No difference in milage. A slight increase in power but excellent shift now.

MVK

rwthomas1 · #7 12-15-2002, 09:11 PM

Okay, finally looked at the car again today. There is a valve of some sort directly to the left of the EGR but it is actually mounted on the compressor outlet of the turbo. Not sure if this is the air recirculation valve or not. Looks like it may be a pressure sensing diaphram, maybe something to do with fuel enrichment? What am I looking at? Any pics? Thanks, RT

psychoman · #8 12-15-2002, 10:06 PM

I have an 85 SD and it whistles everytime you let off of the fuel. Like you said "it was neat in the begining, now it is annoying". Would love to no if the recirc valve is the one on the Compresser. Also should I disable all of the Vacum that feeds everything on that side of the engine. Hope it fixes my shift problem. And AC vent problems. Thanks