'99 C230K Mass Air Flow Sensor

[Mott]

I recently took my c230K Sport in for a 'B' service. The car has about 42k miles. In addition to needing new brakes & rotors on both axles, the car needed new front lower ball joints, transmission work(valve body work and new control module) and a new mass air flow sensor. I am somewhat concerned about the air flow sensor. What could cause a problem that would require replacement at on 42,000 miles? This was done on warranty as was the transmission work, but I am still concerned. There was no sign of this such as check engine light, fuel economy drop off or hard starting. I have never had to replace this even on my American cars. From another thread on this board, it sounds like it could be an expensive repair. I have kept to the factory maintenance schedules. The transmission work is somewhat troubling too...

Thanks for your help. I am a new member and this is my first post. This is a great site!

[blackmercedes]

I have no idea of why they would replace the MAS without any reason. Generally, a faulty MAS trips the CE light, causes rough running and driveability problems.

Perhaps there were stored codes? You might want to query the ealer a little closer.

Your 722.6 tranny is subject to some updates, and that's normal.

[blackmercedes]

Soory, missed your question about MAS's in general. Most new cars use a sensitive MAS to meet the latest emission standards and OBD-II regulations.

All manufacturers are having some problems with their MAS's. That said, MB's failure rate is pretty low, and the part is inexpensive compared to most makes. Our Mazda 626's MAS is $1300...

[ILUVMILS]

A faulty MAS will not necessarily turn on the check engine light overnight! The air mass quantity becomes more inaccurate over a period of time. The engine control module(ME-SFI)adjusts fuel"TRIM" to compensate for the erroneous air quantity data. When the MAS degrades to the point where the ME-SFI control module can no longer compensate for the inaccurate air mass data, the CHECK ENGINE light comes on. This data can be checked to determine the efficiency/function of the MAS, well before the CE light comes on. It sounds like the technician who did the "B" service on this car took the time to check this, and probably saved the owner a trip back to the dealer. As for the transmission work, it could be the dealer was making sure that the transmission was good-to-go while it's still under warranty.

The mass air sensor was replaced in my wifes 2000 C230K about 2 years ago with 16000 miles. The C/E light came on and the supercharger wouldn't engage. At this time my service rep. told me that it wasn't uncommon with the C series as he had replaced approx. 30 of them the month before!!

Fortunately that was the first and last time it was replaced, the car has 47k miles on it now with no problems since. KNOCK on Wood!!!

It really has been a great car with loads of part throttle power and great gas mileage.

Dale

[Gilly]

Smells real real fishy that they would replace the MAF sensor without the owner stating the check engine light is on, and doing transmission work without a complaint in the operation ie rough shift or a slip, etc. Raer rotors at 42000 would concern me too.
The ball joints at 42000 may be normal if the car is driven on real poor roads ALL the time, but other than that it's hard to believe, but possible.
Has the dealer ever flushed the brake fluid or coolant? Should have both been done by now, the brake fluid probably twice actually. It's nice to have a dealer give it a good going over before
the warranty runs out, but this is really odd.

Gilly

[Mott]

Thank you for your help. The service advisor did say that there were some codes regarding the MAS and that it would be a good idea to replace it under warranty. They also replaced some other items under warranty that I did not even notice. So I guess they we doing due dilligence. As for the rotors, I don't expect them to last much more than 40k. I also do a fair amount of stop and go driving which probably accelerates their wear.

Nice job by DC and Kimi today in Melbourne!

[blackmercedes]

Gilly,

I had front lower ball joints done on my C230 at about 100,000 km's (62K-miles) after driving on our pot-holed sorry excuses for roads. They were slightly worn, but nothing to get too uptight about. The dealer happily replaced them under warranty.

I have talked to other W202 owners in Canada (terrible roads) that have replaced them as early as 60-70K (50-45K-miles).

I wonder about those rear rotors though! That is pretty low mileage. I'm on my third set of fronts, but the rears are original, just a set of pads. And I'm far from easy on my brakes. I do know some dealers that don't install new pads without new discs, and his dealer might take that approach.

However, Mott's comments about stop and go driving might wear them down much faster. I'm pretty easy on them in town, but work 'em like crazy given the chance in the mountains.

Glad to hear the dealer caught the codes early before running problems came up.

Mott,

My sister-in-law and her husband live in Sydney. They bought a Renault 306 drop-top, and love it. When they told me what they paid, I nearly fell over. "Why didn't you get a Mercedes" I wondered aloud. Then they told me the prices of Mercedes in Oz. YOUCH!

[DR.DIESEL]

Mott,

Your car got a "Going out of warranty sale!!!!" I am just suprised that they didn't reseal the rear axle too.
At our dealership, we schedule all out clients in around 45k for a final inspection where we go over the car with a fine tooth comb.
Any updates, faults, or known problems are addressed then so the client won't have to flip the bill later down the road.