iamno1

Help! Supposed MB master mechanic is telling me to change radiator and transmission because of a recent issue with car occasionally going into limp mode. I understand that there was a radiator problem back in 2003 but this is a 2006. He also said that some seal near or at the transmission was gushing (?) fluid. Would it make more sense to flush the transmission, replace the fluid, change the seal and pray? Is he confused on the radiator issue for 2003? Any help is appreciated.

ambit

The rear main seal can sometimes leak (at the back of the tranny where the driveshalf connects) but its a pretty 'simple' fix.
Can he clarify which seal he's talking about?
Your car is new enough to not have the valeo radiator problem.

iamno1

Thanks ambit, that's a little encouraging. With lack of information an concern that I was changing parts that didn't need to be changed I opted to flush the tranny and change the seal and pray.

Rudeney

Your car has an early version of the 722.9 transmission and it is going to be more problematic. They tended to blow the main fluid pump and had problems with the speed sensor. Both problems are expensive ($2K+) to repair, but the good news is that the fix is permanent.

Patton001

Has he ruled out the conductor plate issue in the trans causing it to go into limp mode? He should be aware of this. That is about $800-$1,000 to replace

Is he seeing trans fluid in the coolant system and coolant in the trans? If so I would say they both need replacing. It sounds like the trans fluid cooler built into the raditor has been compromised. It will be pretty obvious if the 2 are mixing.

Glyn M Ruck

The conductor plate issue is the speed sensor issue. Read codes & post. If code is speed sensor data implausible then you need a new conductor plate. Very early 722.9 transmissions require the entire valve body replaced. Newer transmissions require that you flash the calibration data from the old TCU to the new one when changing the conductor plate/TCU. Conductor plate issue will put the transmission into limp.

Your car is way out of the coolant leakage problem in crap Valeo radiators.

Your car likely has a Behr radiator.

tcuz4

Rodney, just how early is early for the 722.9 problems.
My 2006 Clk350 isn't showing any signs of a problem at 100k km. I can't track the VIN number on the available forums as it doesn't come up as a recognized number. Maybe because it's Australian.
The engine number however does come within the range for troubles.
Thanks
Tom

Rudeney

There doesn't seem to be a distinct range of problematic transmissions as with engines and the balance shaft problems. Basically, the earlier the transmission, the more problems they seem to experience. The 722.9 was introduced in calendar year 2004 in select MY2005 vehicles (mostly the V8's) then went fleet-wide for MY2006 (except for some AMG models). Sometime during the MY2006 build, there were some changes made to the transmission where the pan was redesigned to help with fluid flow. This solved some problems. The two main problems are with the speed sensor and the main fluid pump. These were revised sometime during the MY2007 build, which again improved quality. Later, there was another change to support stop/start and that has seemingly help, too. Again, it's just that as they continued to build these and solve problems, the continued to improve quality.

tcuz4

Thanks for that.
I tried to gain some information form the MB dealership in Melbourne and was told that they had no knowledge of any issues with this trans, or TC oil changes ('no, the converter has no drain') and only a very limited knowledge of the balance shft problems.
At that point I gave up on them. There's more useful info here on this site.

Glyn M Ruck

To save repeating things you will find considerable information on the 722.9 & failing Siemens conductor plates etc. etc. on the W203 & W204 forums.

iamno1

Thanks for all the information. I did have the mechanic flush out the transmission and repair the leaking rear seal. I've driving the car about 2000 miles since then which included a long trip from Georgia to Missouri and back. Once on the way up and once on the way back the transmission seemed to be in 5th gear instead of 7th gear. I pulled over and restarted the car and it went away. Has not done it at any other time. I'm suspecting that my speed sensor is going out and that I'll need a valve body to fix this. How can I check if I have a coolant leak into transmission fluid or visa versa. I'd hate to put a new valve body in and then find that it was a coolant leak issue and have to start over at considerably higher costs. Happy Holidays everyone.

Patton001

Coolant in the trans fluid should be obvious by inspection of the trans fluid

Rudeney

I still say this is the typical early 722.9 problem - most likely the speed sensor. And the symptom isn't that it stick in 5th - it sticks ion 3rd and won't shift at all. Mine has done this twice, and always was fine after a restart. But I smell a new valve body/conductor plate in my future...

iamno1

Just wanted to post an update on how the transmission faired after flushing and putting the new gasket in. About 3 months later the car started to go into limp mode again, obviously not a good sign and so I had the car taken to a Mercedes Dealer for review. I was told that it was not the transmission but the valve body was bad and needed to be replaced. $2300 later the car is running like new again with the moral of the story being, don't necessarily trust all Mercedes repair shops even if highly recommended. The recommended shop in Atlanta that was suppose to do a great job and costs much less than the dealer turned out not to be true in this case. Saved about $5000 by taking to the dealer and I got free Cappucino while I waited. I have to give kudos to the Mercedes Dealer in Creve Coeur, MO who treated me right and got the job done. Buyer beware when it comes to repairs for sure. Now if I can find someone to repair a small defect in my convertible roof. Cheers