the op was referring to a coolant flush which was why i didnt expand on it.
the slk has an aluminum block and heads. after 3 yrs you would be amazed at the oxidation that comes out of the engine, which is why i use the vinegar flush. its very inexpensive and easy to do. prior to the flush i take a sample have a glycol contamination test done. any m/b shop will do the test.
any oil in the system will flushed with the vinegar. then reflush with pure distilled water.
while the benz manual gives specific parameters for fluids they also initally stated the transmission fluids were lifetime in the 722.5 trans. only after getting a number of failures did they start req. a flush at 40k.
when considering the cost of replacing the parts on a benz early preventative maintenence is a cheap and easy way to prolong the life of any auto. while the car gets older the prices of the parts dont!!
Yeah, I was initially thinking "What the hell is he thinking - flushing his engine with water and vinegar."
There are some guys that talk about pouring water into their carbs to flush their engine. I was trying to figure out how you would do that on an SLK.
The oil (there shouldn't be any in there in the first place) that is floating around in the coolant would be flushed out, but the oil that is sticking to the sides of the coolant passages won't necessarily be removed. That's why the deoil mixture is required. Mercedes makes their own product for it, but some folks just use Liquid Tide and water and it seems to work fine. Same with the citric acid. Mercedes has their own product, but you can pick it up at a pharmacy, canning store, etc. for a lot cheaper.
Let me tell you about flushing the cooling system on my ponton. The manual calls for flushing it with P3 soda, i.e. lye, to deoil it. So I bought some lye and dumped it in. The thing started to heat up, boil and bubble up - scared the hell out of me.
But it apparently worked with no ill effects. Cooling system has been good for fifteen years since I did that. I won't be using lye in the SLK.
I agree on the transmission - it's the 722.6. I've got the same transmissions in my SLK and my 210 diesel. I do the transmission in the 210 every 50,000 miles. I'm not positive, but the last I heard, Mercedes required a one time only transmission fluid change at 60,000 km, i.e. 39,000 miles. Haven't heard that they now are requiring them every 39,000 or 40,000 miles? With as little mileage as I'll be putting on the SLK, I'm thinking that I might do it at ten year intervals - haven't decided on that yet. It is interesting that our transmissions are still "filled for life," but the identical transmissions in later cars require servicing the transmission. BTW, my '99 210 has a drain plug on the torque converter which makes is nice to get almost all of the old fluid out. My SLK doesn't have a torque converter drain plug. I think the torque converter drain plug was eliminated in September, 1999.
The coolant on my SLK is an every 150,000 miles or ten years. I have heard no reports yet that that interval is an issue, but I certainly am monitoring both the coolant and the traffic on lists like this one. Distilled water might be overkill too, but I do the same thing.
Sounds like we both do a bit of overkill on maintaining our cars.