97 E420 carbon build-up = $5600? - PeachParts Mercedes-Benz Forum

jbors · #1 04-30-2003, 07:19 PM

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.

#2 04-30-2003, 07:27 PM

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

blackmercedes · #3 04-30-2003, 07:32 PM

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...

royaiii · #4 04-30-2003, 09:08 PM

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.

william rogers · #5 04-30-2003, 11:29 PM

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

DuckMuck · #6 04-30-2003, 11:38 PM

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...

#7 05-01-2003, 11:06 AM

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.

stevebfl · #8 05-01-2003, 01:47 PM

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?

mbdoc · #9 05-01-2003, 04:07 PM

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

jbors · #10 05-01-2003, 04:21 PM

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.

aldedmon · #11 05-01-2003, 05:05 PM

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.

stevebfl · #12 05-01-2003, 06:15 PM

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.

blackmercedes · #13 05-01-2003, 07:12 PM

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

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

jbors · #14 05-01-2003, 07:34 PM

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

william rogers · #15 05-02-2003, 02:09 AM

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......