EGR Tube Location/Cleaning - PeachParts Mercedes-Benz Forum

96C280 · #1 03-05-2003, 04:04 AM

I've performed a search and read the threads, but I'm still in the dark on how to locate the egr tube to clean. What does it look like (diameter, length, connected where?) Where would I remove it to clean it out, etc. Do you access it from the top or do you need to get underneath the car? Also for reference what does the egr valve look like and where is it? I'm asking all these questions to demonstrate my cluelessness on this.

If I'm looking into the engine bay what side is the tubing on and do I have to remove anything to locate and/or see it clearly? Please note that I'm still a little vague on the engine layout and as to which side is the intake and exhaust side. Thanks.

suginami · #2 03-05-2003, 07:16 AM

I'm in a hotel in Atlanta right now, so I don't have my car in front of me, but the egr valve is at the rear of the passenger side of the engine.

It looks like sort of a flying saucer. It is reachable from the top of the engine.

It has a small diameter metal tube that exits the back of the egr valve, and goes around the back of the engine, between the engine and the firewall, and ends at the intake manifold.

You can ream it out with a cable attached to a drill motor, or simply replace the tube. Benzmac has posted that he usually just replaces the metal tube.

BTW, the blockage is usually right where the metal tube enters the intake manifold.

jsmith · #3 03-05-2003, 09:47 PM

Paul,

I'm thinking of performing this procedure. Do you have to disconnect the tube at the manifold? If not, what happens to all the gunk that you dislodge does it go in the manifold?

suginami · #4 03-07-2003, 12:15 PM

Yes, I would disconnect the tube both at the EGR valve and at the intake manifold. As Stevebfl has stated, the build-up is always at the opening of the intake manifold.

I cleaned mine out and replaced the egr valve. There was a TSB regarding the old valves sticking, and the part # changed.

My CE light still came on, so I actually replaced the metal tube.

Donnie (Benzmac) has also posted that he no longer reams these pipes out. It takes too much time, I guess, and it is more cost effective to just replace the tube.

BTW, I've always wondered where all that carbon goes if the pipe isn't removed. I guess it just gets sucked into the intake manifold...

96C280 · #5 03-07-2003, 10:46 PM

What's the procedure for removing the tube? What attachments hold the tube in place?

suginami · #6 03-07-2003, 11:28 PM

It's been over two years since I did it, and I don't remember.

I do recall that it wasn't that difficult...

96C280 · #7 03-08-2003, 05:33 PM

Well, I was able to disconnect the egr tube on both the exhaust and intake side and it was not easy. To access one of the two bolts on the intake side I had to disconnect the throttle assembly next to it to get access. There is one other attachment at the back of the engine compartment connected to the oil filter container. The tube was entirely loose at that point but no easy way to bring out the tube. It would have been nice to take it out and really examine it but since I couldn't, I examined the intake hole portion seen in stevebfl diy article and it was clear. The tube also was apparently clear as I used my liquivac and stuck it one end and put suction to it. Air easily move through the tube. So I put everything back. By the way, my car has just under 60k on it.

One thing I noticed before this procedure and confirmed after the procedure was that when I disconnected the thin rubber tube going into the EGR valve from the top of the engine under the plastic engine cover (after disconnecting the battery to clear the CE light) was that the CE engine light did not come back on. However, when I reconnected it, the CE light came on. Does this indicate the the EGR valve is bad? The EGR valve is supposed to be open at idle and closes at speed? How can I confirm without replacing it that the EGR valve is bad? I plan on getting the error code read but from what I've read it will not pinpoint to a certainty what part to replace and I may already be at that point. What happens if I keep this rubber tube unplugged? On a couple of short trips I have notice NO change in idle or running with this unplugged. Is the rubber tube part of the vacuum system? Many questions, hopefully, many answers. Thanks.

suginami · #8 03-08-2003, 05:40 PM

Actually, the EGR valve is closed at idle.

Also, the original EGR valves were defective and will stick. There is a TSB that addressed this issue.

There is a way to check if your EGR valve is not working due to a plugged up hot inlet pipe, or if the valve itself is sticking (sticking open or closed):

The ECU sends an electric signal to the switch-over valve which opens the EGR valve to engine vacum. The vacum pulls open the diaphragm on the EGR, allowing some of the exhaust gas to recirculate back to the intake manifold (thus the name, Exhaust Gas Recirculation), reducing emissions.

The ECU will not send this electric signal at idle or wide open throttle, or until the engine has warmed up. So, if you hand pull about 12" of vacum on the EGR at idle with a warm engine, you are creating a very lean condition (vacum leak) and the engine will attemp to stall and run very rough. This tells you not only that the EGR is opening, but also that the hot inlet pipe is not completely plugged up. If, when you pull vacum and nothing changes, then you know that either the valve is not opening up, or the hot inlet pipe is completely blocked.

Now, release the hand vacum and the EGR should snap shut. Engine should smooth out. If the EGR sticks in the open position, the engine will run rough at idle until the engine warms up.

There is another possibility that the diaphragm in the EGR itself may leak and cause an internal leak. The test for this is to see if the hand vacum will hold the EGR open for a period. It is common on vacum leaks to not be as noticeable with a cold engine as the engine is running rich and that helps off-set the added intake of air caused by the leak.

Since you are not complaining of an idle problem either when cold or hot, the EGR valve might not be functioning when in closed loop. In cases like this, the egr valve could be either stuck in the closed position or the pipe might be completely blocked.

By the way, I had a CE light problem when I first bought my car, and Arthur Dalton walked me through this process. I first reamed out the hot inlet pipe, but the EGR code still came up. He informed me of the TSB on sticking EGR valves, so I replaced it with the new one, changed the tube, and problem went away.

96C280 · #9 03-12-2003, 05:21 AM

Thanks for the info. I will try the vacuum test. Right now the CE light is gone and the car is running smoothly. I am not sure what I did to clear and keep clear the CE light. However, reading the other posts I know that it may come back eventually. I'll keep my fingers crossed until then. I also plan to have the code read eventually just to see what it was even if the light does not come back on. Thanks again.