I'm about to begin changing fluids in my "new" 1981 300D. I have a few questions for those who've done it...

Differential: Where can I find the hex key necessary for this job? Is it a 14mm? I'm considering refilling with synthetic gear lube, any problems with that?

Transmission: any recommendation on off-the-shelve ATF? What standard should the fluid, at least, comply with?

Radiator: The stuff it has now is green...so I think is not the right one. I'm thinking on refilling with Texaco's phosphate-free ethyl-glycol antifreeze (red). That's what I've used in the Audi for over 2 years with no problems. They say it's good for 150.000 miles or 5 years. Even if it's half that, I think it's a good product.

Power steering: any advise on how to flush this system? I will replace the filter as well.

Brakes: I will change the fluid using Pentosin DOT 4.

Engine:I live in South Florida. I'll use Shell's Rotella 15W-40. It's very inexpensive and recommended for diesels. .

Thanks...

The rear diff. is in deed a 14 mm. I got one from my local NAPA auto parts. For the transmission, any Dextron III rated fluid will be fine. For the power steering I just siphoned out as much fluid as I could then added fresh fluid. I would drive for a couple of days and do it again. This gives the fluid that you didn't get, to mix with the new stuff.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

There are those who say the green stuff is OK for coolant, but I'd stick with the MB coolant. Just be sure to thouroughly flush the system, repeatedly as you don't want to mix the two. Also, stay away from the 150,000 mile coolant, especially if it is Dexcool.

Dexcool is what GM is running now, and it's supposed to be good for 5 years 150K miles. A friend has a shop and they have had to do complete cooling system jobs on 3 newer Chevy's at approximately 75K miles. The Dexcool stuff is corroding the fittings, anywhere there is a hose (heater hoses, by-pass hose at water pump etc). I got to see the effects when they were doing the heater hose on a 95 Suburban. The fittings crumbled in your hand.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

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