Download: Mercedes W204 C Class Transmission Service ATF Fluid Oil Change 7GTronic 722.9 Test 0-60 mph

By Scott Elliott


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A video of how I performed the automatic transmission fluid change and oil cooler flush. Improvisation was the name of the game. Also a 0-60 mph run of 6.30secs. You do need a compressor but any serious DIY'er must have compressor in his/her garage ... right? .

There appears to be a lot of mystique and misinformation about the subject of doing your own transmission service on these cars ... or indeed any work at all.

There's a feeling these transmissions are such a complex mechanical/electronic component that us mere mortals should not approach closer than a 3 metre radius from this marvel made from "unobtanium". It's a load of nonsense.

Doing the service is straight forward and I would think any automobile DIY'er with reasonable skills and tools prepared to take his/her time and logically work through the process will do a better more thorough job. The key is to do some planning first. Watch the video and note the equipment you need and get it all organised first.

All the stories about special tools, the oil temperature only being read by the special software system are urban myths in my book ... and the story about the oil level being absolutely critical ... so critical it has to be within an oil atom's diameter of the correct depth or the transmission will explode like an IED the instant you start the engine! Think through the logic of this. The oil level is set using the overflow method. The overflow pipe snaps onto a fitting inside the pan over the drain hole. You overfill and bring the oil up to temperature and then let the excess drain out until you get a "spitting intermittent flow" according to the technical workshop data. That's the best subjective test I've ever heard. Every person will have a different measure of what a "spitting intermittent flow" is. But it's a very simple and effective way of setting the level so the Germans were clever with that one.

So don't be scared of these things.

Sure the transmission is sophisticated but the service is very straight forward. The 6 speed German ZF transmission in my last Ford was also quite sophisticated.

In Australia the dealers want a small fortune to do the service. My understanding is all they do is drain the oil from the pan, remove it and change the filter. I've heard even draining the TC is sometimes considered optional. I'd be surprised if they flush the old oil from the oil cooler. I did using a very special tool ... a sports drink bottle ... and I got to drink it first!

There's also this notion they have specially trained Bavarian Technicians raised in the German Alps and bottle fed Mercedes ATF from 6 months of age. Most times the work will be done by an 18 year old apprentice. No disrespect to apprentices because they have to learn.

I do all the servicing myself now as it's just too expensive at the dealers.

The Mercedes C Class W204 is a well engineered car but they still have problems like many other European vehicles. Toyota's and Hyundai's usually have less problems than a Mercedes. I bought mine as a demonstrator at 10,000km and it now only has 48,000km. While doing this transmission service I noticed the engine sump oil pan is leaking. I'm probably going to have to drop the oil, take it off, clean the surfaces and apply a new sealant. I wasn't expecting these sorts of problems with the German marque. However, I still really enjoy driving the car and it certainly has a nicer feel than the run of the mill Toyota's.

Once you get all the plastic covers off underneath and take off the fancy clothes and expose the components it's no different to a Ford or any other rear wheel drive car. It's an automobile with a whole bunch of components bolted together so therefore it can be pulled apart. They've got a lot of electronics ... so what. So do Toyota's and Hyundai's and their electronics are better and more reliable.

1. You may wish to remove the rear exhaust bracket that sits slightly over the rear of the oil pan (C320CDI). In the video I point out the tubular cable holder at the front to remove and pulled clear. It's only two bolts. The rear exhaust bracket is easier to get to and has four bolts. I'll probably do it that way next time.