C280, Check Engine light, EGR Valve
 

94 C280- check engine light came on. Mechanic says gotta change EGR valve, $900. Seems pretty steep. ANybody have any suggestions to get to the bottom of this? What are the codes? Do Codes point to exact problem?

Thanks.

On this particular engine, there is a real well-known EGR problem. On the EGR valve, there is a pipe which channels the exhaust from the exhaust manifold (through the EGR valve) and around into the intake manifod. These pipes are just notorious for plugging up with soot. They can either be cleaned out or replaced, I prefer to replace this pipe, as the new pipes are modified. I would almost bet that this is the real problem. Are you taking the car to a Mercedes or at least European specialty shop?

Gilly

PS The codes will point usually to the "general" problem, not exact. There is no code that says "EGR Valve is bad", the code will read something like "EGR system, incorrect flow" and it can be anything with the EGR system, such as the vacuum line that operates the EGR valve is disconnected (or the EGR pipe is plugged solid with soot;) ). Same thing say with an engine misfire. The code may say "Misfire Cyl. 1", so what do you do, replace #1 cylinder? No, you figure out the reason for the misfire. Hope this helps clear things up a little.

Yes, the place I go to does only Merc, BMW, etc.
$900 sounds high but they say half is for labor because it's hard to get to it! Any thoughts?

Thanx a bunch!

$900 to replace the EGR valve on a 104? Yeah, i have a few thoughts.
#1 thought: I wonder if they will ask you to squeal like a pig.
#2 thought: It probably isn't the problem
#3 thought: Where else can you take this car.
$900 is totally outrageous, it's less than 1 hour of work, even if you have problems, which sometimes does happen if the pipes won't break free. Lets say $200 worse case scenario, but that's if they notify you there are stuck pipes, they should be quoting about $100 labor. How much is the valve itself?

Gilly

PS (again) You can go out to the car, raise the hood, and SEE the EGR valve. There are 2 bolts holding it down, and a pipe attached to each side, and 1 vacuum hose. NOT THAT TOUGH.

I hear you! I looked up the part online- $200. I assume they will mark it up. I think I have some questions to ask in the morning before they touch anything.

Thanks.

There is a TSB about the original EGR valves sticking, but 95% of the time, the problem is a plugged up pipe, where it connects at the intake manifold. I think you'd be wasting your money replacing the EGR valve when the problem is probably a plugged up hot inlet pipe. I'd try reaming out the pipe before I dropped $200 on an EGR valve.

Steve Brotherton (stevebfl) has written an article with a picture that shows where the pipe gets plugged up.

http://www.peachparts.com/Wikka/EngineControls

And like I said, it's probably (with lets say 80% certainty) not even the problem. I HAVE replaced some valves, it's not like it's an impossibility, put a plugged pipe is more likely the problem.
If you activate the valve (which is possible either by using the "activations" screen with their computer or by applying vacuum directly to the valve) the engine should almost die. If they apply vacuum to the valve and almost nothing happens, the pipe is plugged, simple as that.

Gilly

Many thanks for your help.
Any other probing/challengin questions I need to ask (and I am not shy!)?

Thanks.

Yeah, well, the guy/guys in the shop all just love it when the owners come in the next day and say "So, I was on the internet last night...............", but what else can you do? And the tough part for anyone here is just the "approximately" 20% margin that they COULD have correctly diagnosed the problem.
Maybe you can just ask about how they know the EGR valve is bad, what the test steps were, just tell them you're concerned about spending $900 for it, etc etc. If they just say "well, that's what the code says it is" and never mention that they actually tested the valve or anything, then I'd be suspicious. Can you just pay whatever they say they have in it for diagnosis and walk away, or do you REALLY like these guys? The valve itself just usually isn't the problem, they need to attach a vac pump, like a mityvac, to the valve and open it and see if the engine runs like real crap or not. If it's opening (which they can just observe) and the engine pitch hardly changes, then it's a fair bet it's that tube, in which case my "personal" recommendation it to replace it with the updated one, but a "quickie fix" is to do what Steve B recommends in that link given above, which is to ream/clean it out with an old speedo cable on a drill. Look over that link by the way, it's one of the last items on that page. Maybe you could print that out and take it with you and show it to them (I don't really want them to read my "3 thoughts" I gave;) ). (PS maybe that means I'm a little shyer than you:confused: )

Gilly

Already had Steve's article this morning!
I have printed what I need to take with me! Not to worry- they won't see your comments.

I am so looking forward to talking to these guys tomorrow!

Thanks.

OK, sounds good. Go easy at first though, sometimes that "20%" will get ya. But the $900 is still crazy. I take it you don't do the DIY thing?

Gilly

PS (I'm PS crazy tonight): If you plan on keeping the car for quite awhile, then consider the new tube if it does end up being plugged. If maybe only a couple more years, then you persomally would probably do OK with the speedo-cable trick.

PPS:rolleyes: : And also it's possible it's not the tube OR the valve, OK? There's a switchover valve, which needs a vacuum source, and the switchover valve is controlled by the engine control module, etc etc, so it's not a case where it "has" to be the valve or the tube, just a heads up.

Logical diplomacy is the approach!
I used to do DYI but time is the issue.
I am an aerospace engineer and enjoy getting into things.

OK, hopefully you saw both of my add-ons to that last post. Wish we had a chatroom here, sounds like they don't want it here.
Let us know how it turns out for you.

Gilly

Saw everything.
Will post outcome tomorrow.

Thanks.

Honestly, they were a bit surprised and Mike-the-mechanic got a bit defensive when I asked my first question: what did the codes tell you? And from there it was interesting to hear the mumbo jumbo about special test, it could be the EGR valve but the air flow goes up, down, around downtown, then a miracle happens, ... and he couldn't be sure until he opened everything which seems fair. He also claimed that taking the pipes out was tedious.

The mechanic knew of the vacuum tube test but he didn't do it. He said he used some Merc test "something" called SDS or something like that.

Anyway, where we have left it is that my bet is it is the pipe (he also thought it was very likely) and he can open he valve and we go one step at a time. But I will wait until next week until Iget a second opinion.

Funny thing is when I talkd to the owner, his response was if it was up to him he'd just disconnect the check-engine light and keep driving the car for a while!!!!!!

The info you all provided last night was EXCELLENT.

Thanks a bunch.

OK, the test he mentioned, where he mentioned the "SDS", that's "sort of" positive news. SDS is Star Diagnosis System, it's a Mercedes test computer, so it's good to see they apparently have that shop tool, that's an encouraging sign. As I mentioned, they can use this to go "into" the engine control unit and as a test, activate the EGR valve. At that point, what's being done is this EGR switchover valve directs vacuum to the EGR valv (no need to use a mityvac then, at least not at this point). If they simply observe the valve while they do this, they can see if the valve is opening or not. If it is, you've just eliminated a whole lot of testing. The main thing is: "Did the engine start to run terribly or not?" If NOT, then more than likely it's the tube. I can't even think right now WHAT ELSE it could be. If it DOES run like crap, then something else is going on, possibly the engine control unit has some error in it preventing the EGR system from activating under "normal" driving circumstances, but will work OK with the shop computer (SDS) telling it to activate. You're an aerospace engineer, I'm sure this isn't over your head. If however they did this test with the computer, and the EGR valve DIDN'T open, then you have more work to do, either no vacuum to the switchover valve (which in many case means you have a vacuum leak, which means even MORE trouble codes) or a bad switchover valve, or the computer output to the valve isn't working, or hey, guess what? *Bad EGR valve*! So that's kind of the whole run-down of the system, you should have a fairly good working knowledge of the system, maybe as good as the guy working on it, (except all the principals of when the control unit activates it and all that stuff, I don't need to get into that, do I?:( ).

YES it's sort of a tedious job, it's quite a it more work than replacing just the valve, for sure. That's why you want to really think about your plans for the car (couple more years? a decade? want to will it to your relatives?). Again the new pipe should "fix" the problem, the part that goes inside the intake is longer. Cleaning it out? That's only going to last awhile, my opinion is if the car is an 89, it took 14 years to plug up (assuming it is), it'll probably plug up again in alot less than 14 years, they won't be able to make it as clean as it was in 89 and it'll reaccumulate faster. This tube does run from the exhaust manifold on the right side (passenger side), around the rear of the block, and to about the middle of the intake manifold. Once you've replaced one 3 or 4 times you get the hang of it and can do it in maybe around an hour, hour and a half, those first few times were taking me I believe over 2 hours though.

Here is a pic of EGR pipe we replaced few weeks ago

Other one

Nice photo! Like clogged arteries!

I just did this job on my 1995 C280 - 141,000 miles. The last 20-25mm of the pipe was plugged solid. I don't know how anything was getting through it and yet I hadn't gotten a code. I took Gilly's advice and replaced the tube. I did try cleaning it on the engine using Steve B's method and another suggested on this forum - a copper tube guide with a cable forced through on the intake manifold side. I wasn't satisfied that I did a satisfactory job. Replacing the tube is tedious, but there are worse jobs. One note, you can see the intake manifold end of the tube by blocking open the throttle plate and using a small mirror.

Good point Vince, I shoulda pointed that out.

Gilly

C280 Check Engine Light
 

It was the EGR Pipe. It was clogged.
I just took a digital photo and will post it (if I can) so others can see it. EGR valve was oK. Pipe cost $130.