97 E420 carbon build-up = $5600?
 

Our E420 has only about 75K miles. The check engine/electronic light came on and the dealer's mechanic said I'd need to replace left and right oxygen sensors for $600.


After replacing those they told me that there was carbon build up in the air injection ports and that it was ~ $900 in parts and ~$4100 in labor to remove the cylinder heads and clean out the ports. While $900 sounds high for gaskets and connectors, $4100 in labor sounds real high.


Has anyone else ever encountered this type of problem on a car with so little miles? Any advice on alternatives that might be more reasonable?

Thanks for any information.

WOW. As a consolation, have you considered that carbon will turn into diamonds with some heat and pressure....
Before spending that kind of money on carbon built-up in such a new car, I'd:
1) Look for a second and third opinion.
2) try a heavy dose of fuel injector cleaner. (direct injection, in addition to through the gas tank)
3) Change oil for a very high detergent type
4) Try an engine flush
Good luck
jackD

If the diagnosis is correct, then I'd look for a "MotorVac" (I think that's the name of it) shop that does carbon evec without removing the heads. They have a machine that does it, but don't ask me how.

That said, $4100 labour at $80 per is 51 hours. FIFTY ONE HOURS? TO R&R two V-8 heads? That sounds REALLY high to me. I seem to remember someone having an M119 heads R&R's for around 16 hours. Do a search...

Did you regularly replace the air filters and keep up with maintenance. I have never heard of such a thing on this motor. Hows the driveability? Perhaps you might ask for a second opinion. 5600 seems through the roof for a head job. The only way I can think of such a thing happening is the engine overfueling for a long time as well as living in a very dusty or sandy location coupled with severe service conditions.

I must live in another world........
William Rogers............

I don't find the $5600 quote weird...neither do I find carbon buildup in your E420 weird either...considering the crap I've been goin' through with the dealership and my E420...I can pretty much believe anything now...good luck...if your car is as big of a ***** as mine, you'll need it...

I don't konw if there something special about the E420 on where the placemnts of them Oxygen Sensors, but i would have stopped right there when he said $600 to repair those, $200 for parts and another $400 for labor?!?
Find an independeant shop if your cars no longer under warrenty, much cheaper.

I have yet to fix a check engine light due to a carbon build-up. I have fixed a 600 for no compression due to carboned up (stuck) rings and the same on about six other late model BMWs and Jags.

I would be real interested in the concept behind this. What are we trying to accomplish by removing the carbon? Do we have a knock sensor problem? Just what is this carbon doing?

Is the check engine lamp ON? & codes P0 410 or P0 400 causing the engine to fail the emission test??

E420 background info
 

Dear Steve,

Thanks for your answer. I, too, had not heard of carbon problems in many years (at least since leaded gas was discontinued).

The car had no smoke, no rough idle, no hesitation, no driveablility issues BEFORE it was brought to the dealer. In fact, on a highway trip to Lake Tahoe last fall it averaged 25 mpg which I think is excellent, especially considering the elevation changes. The steady check engine / electronics light was the only reason for the visit to the dealer.

I have owned the car for about 12,000 miles and the motor has always run smoothly. During my ownership, maintenance was performed on schedule. It is driven in an 80/20% mix of suburban and highway driving in the SF Bay Area. No severe use conditions whatsoever (rare stop and go, no commuting).

I am hoping to pick it up today (with 2 new O2 sensors) but without the $5000 port cleanout. I have learned that $200 of the parts is for new oil tubes (they say this is precautionary for this engine). I have requested a copy of the diagnostic printout but don't know for certain if they will release it.

They say that the check engine light will still be on and that I won't be able to get it smogged legally while it is lit. They say only by cleaning the "carbon" can they get the light out. This apparently involves dis-assembly of the heads which is what requires lots of labor.

I'm hoping that regular use of Techroline and some long distance highway use may help clean out the bulk of the problem. If that doesn't do it I may have to succumb to today's version of highway robbery.

but wait
 

Before you drop 'em and bend over, do as others have suggested and find a local indie and let them have go at it. Even the Jedi Masters have shown skepticism of the diagnosis that you have been given. Do yourself a favor and run like hell away from those quacks(sorry DuckMuck) and find a shop that can properly diagnose your ailments.

There actually could be some merit to their diagnostics, I was only trying to get the angle and Doc does bring it up. I didn't read your post close enough the first time.

The fault code that you probably have is for secondary air injection causial chain. I think those last words are some Germans loose translation. Basically what it would mean is that everything about the air injection system is working but it doesn't get the job done.

The way you test this is to go to the activations screen on the scanner. One waits till the O2 sensors are closed loop and the scanner allows one to make the airpump work while monitoring O2 sensor voltage. When this happens the O2 sensor which has been floating between .2v and .8v must go to below .040v in 60 seconds. If it works it happens immediately. If there is a restriction the effect is reduced. The results of this test must be known.

I have heard of this restriction and maybe Doc can tell us a simpler way to clear it. I have read posts about this "fix" but don't remember what the answer was but I'm pretty sure it wasn't removing the heads.

Just because I have heard this problem doesn't mean it is the answer in your case. I have fixed a number of air injection problems that were flow related that weren't in the heads. The hosing must be tight and the vacuum check valve both must be applied and work. There have been problems with corrosion in some cars in that valve and in the pumps. If I am right about their concept the problem is lack of performance in the above test.

Great info Steve! Interesting! Amazing how complex the diagnostic systems have become.

jbors: Time for a looong road trip to FL to Dr. Brotherton!:D :D

now dealer syays he needs more time
 

Thanks again for the addional information, Steve.

Just heard from the dealer--despite my request to return the car with only the sensors replaced, they don't want to release the car tonight. They said they need more time to investigate and will call back later tomorrow.

This may yet turn into an interesting saga. Hope the ending costs less than the original estimate! I'm still inclined to look for a second "expert" opinion somewhere in N. California.

jbors

Yea Gads! what ever happened to the days when an engine carboned up you took off the air cleaner and sprayed a fine mist of water down the carb while a friend held engine speed about 2500 rpm's.that trick saved a lot of city driven only Cadillacs...... We seem to treat our modern cars especialy expensive German ones as if they were delicate atomic time pieces to be kept in vacum chambers, I do a lot of old Time Codger tricks to my MB's and they are all still running well......"knock on burl walnut"......
William Rogers......

it's called buy Fuel Injector Cleaner.......

you could get fancy German stuff from Performance Products (Ventil Sauber) or just Valveline Fuel Injector Cleaner from Autozone.

Run a few doses of that and go for a good hard drive on the freeway and you'll be good.


Get a second opinion as well. Sounds like these guys want you to grap your ankles.

I agree. Other varieties of fuel system cleaner include Techron (use the 'concentrate' form), Redline, etc.

Don't forget about an old-fashioned Italian Tune-Up...

If all else fails, do seek out an independent. N. California will have LOTS. Find out from your local Mercedes Benz Club of America (MBCA) president who everyone else takes their cars to (hint: it WON'T be the dealer).

A friend and I sat and discussed this over a couple beers last night. If I am right about what their theory is then normal decarbonization won't work. The problem is not in the combustion chamber but in the passages through the head that takes air injection into the exhaust.

We need a response here from someone that has viewed these passages. I remember there was a problem with an oil cap loosening and allowing oil to pass through the air injection castings and smoke like H*ll. I have read it but not seen it. My first concept on how to clean this would probably involve a reaming attempt after pouring something through the passages like x66p.

I will check the archives at a couple other sites, I know I have read the "fix" for this type of problem.

Seen it once. 140 with a 119. The air passages plug. No big deal. I find 5600 a bit stout to say the least. These heads aint that hard to pull and pullin a 119 is not any different than pullin a 113 out.

Can they determine which head?


I'd definatly look up a indy who has been into a 119 before and see what they price it at. I can see 3k maybe 4 if you did guides and a chain as well but 5600? Just in labour?




Joe

Combustion cleans out the combustion chamber, Fuel Injector cleaner helps loosen carbon and gunk from pretty much everything between the Injector and the chamber.


For $5 -$10 for a few doses of Fuel Injector cleaner you can't go wrong

The problem is not in the intake or combustion chamber or anywhere near the injectors. The only thing that should ever pass through these ports is air pumped by the air pump. It goes through passages in the head and comes out after the exhaust valve in the exhaust. The carbon should mainly be at the intersection unless the check valve has been bad and exhaust has bee going up the passages toward the valve and then the pump.

I believe Steve's theory is that the air injection ports which are plugged actually bring clean air (O2) to the exhaust stream to promote further/more complete oxidation of any unburnt fuel as it passes through the catalytic converter. If this is correct, than any cleaner, such as Techron, introduced through the fuel system will not be effective for this type of plugging.

This hypothesis would explain why there are no symptoms of driveablility problems as the engine doesn't care what you do the exhaust stream after it exits the cylinder (at least not on the molecular level).

Yet wouldn't it be reasonable that one could add some sort of solvent to the line(s) feeding these air injection ports to see if that could reduce the plugging which is suspected?

IF you car fails the emission test & has either code P0 410(air injection) OR P0 400 (EGR flow) then the inner passages inside of the cylinder might be plugged.
Here in the Atlanta area we see this problem ALL of the time!
IN some "extreme cases" the cylinder heads MUST be removed to solve the problem.
NO solvent added to the fuel system can get into these passages.
NO miracle in a can will help.

Yet another STEALERship story! I went to my local stealership for a coolant leak. My trusted mechanic is now somewhat difficult to get to being that my new job takes me far in the opposite direction. So I though I'd give my local dealership a try. They said I needed an new radiator - this I did need, but then they told me that I needed a new power steering pump as well as coolant overflow tank (which I did not) as well as saying that my throttle cable was loose (which it was not) - anyhow there estimate was $1200 just to do the radiator! So I took the time to go back to my trusted mechanic who did the job for $800.00 (not cheap but still saved $400!) and also confirmed that I did not need the other items mentioned above.

If you are ever in the SoCal area I highly recommend swining by Mr MB Motors in Tarzana. Enrique is honest and knows his stuff - MBZ mechanic for over 40 years!

PO 410 it is
 

After replacing the two O2 sensors (for $825 including the diagnostic charge), the car was hooked back up to the diagnostic computer and revealed a PO 410 code. As Steve had suggested earlier, this translates to insufficient air coming from the air injectors located after the exhaust valve. Apparently, the only way to restore the flow is to tear down the heads and rod out the offending carbon from the passages.

The MB shop foreman told me that by refusing to have the repair performed, the engine computer would likely try to lean down the mixture slightly in order to try to get the oxygen content up to the sensors. Then the engine would potentially run hotter.

Although I was told by the foreman that my check engine light would be lit when I picked up the car, the light was actually not lit. I guess it will be going back on if the sensors foul again due to insufficient fresh air in the exhaust. I'm hoping to try some long distance cruising anyway in hopes that keeping the engine hot for an extended period might help unplug something.

I will be looking for an independent shop to rip down the heads if it comes to that. But it sounds like one hell of an expensive project and I wonder how how got so lucky.

Re: PO 410 it is
 

I think you mean "unlucky".

Sometimes in cases like this, I think you can chalk it up to the old addage, "sometimes bad things happen to good people".

OK, I may be talking way out of my MB reach here, but I wouldn't expect this to cause any real world issues. The system's going to normally run the air pump to allow fresh air into the exhaust at startup to help with emissions. After the engine is warm, it shouldn't have to run; hence, your exhaust composition will only be "off" on cold starts. Not enough pollution to be a worry, and no impact towards "poisoning" your O2 sensors... Too bad that it appears that the people's republic of the leftist coast there will bust you on the emissions check for the check engine light. You can't disconnect the batt. before going in for testing because it will show that the OBD II monitors haven't run yet. :(

The test described is run specifically to test the air pump system--it can't be run while then air pump is actually NEEDED. Just can't think of a way around it!

M119 Carbon Build up Could be true
 

Hi Guys,

I too have had this diagnosis. It seems like 25 of m119 owners have heard of this issue and the others haven't. My mechanic told me it doesn' affect performance and that is is a smog related issue more than anything.

THe only way I have heard of clearing the passages in the head that have build up is via mechanical means, which means the heads have to be removed.

I would really be interested in that procedure that cleans the passages without having to have the heads removesd. Please pm me with address and info. Thanks

Ive had to clean out an m 111 4 cylinder with same issues, used mechanics wire to force thru passeges after removing head, used carb cleaner to help soften up carbon, ive done the same on 119 motors, its tedious work ,no carb cleaner with heads on is going to clean these passages

dousing with MOPAR CC cleaner would do its job perfectly here. Careful dripping with a pipe/funnel system would work - IDK how the ports are shaped or accessed but pretty sure this remedy could work.

I have seen a mitsubish GDI engine being decoked with it by leaving it overnight in the engine, that engine refuses to run if it gets carboned.