300E Radiator Flush Results
 

Today I went ahead and flushed out my radiator on the '91 300E. I could not believe how much crud and sediment came out into the drain tubs. It literally looked like a sewage dump! The good news is that it did not take very long at all to get the clear water flowing out of the radiator drain plug or the engine block. I also disconnected the hoses from the expansion tank, removed it, and cleaned it all out with a hose sprayer and wiped clean with a few paper towels stuffed in and twisted around.
After adding the new coolant and running with the heater on, my engine temp was struggling to climb above 80c where it would usually quickly get up to 85c+ very quickly when at stop without the heater running! So, I guess the flushing and cleaning helped the coolant circulate better and become more effective. Any thoughts out there on my results?
I also changed out my differential oil which was black. I'm sure she appreciated that as well:)

Interesting results!

I think I need a new fan clutch as my fan rotates for a good 8 seconds after the engine is switched off. Might as well do a system flush like you did, hope to get similar results.

Thanks for sharing them.

P.S. I recently changed my differential oil (300E) at about 210,000 miles, the old fluid was golden in color, seemed brand new. I have no recollection of it ever being changed in the life of the car though. Eh, whatever, it is done now! :rolleyes:

Here is an excellent article on measuring the proper antifreeze ratio if you haven't already done so. http://www.k6jrf.com/MB_WW.html

M/B recommends new coolant every 3 years, barring the newer cars with extended life antifreeze.

Thanks for the info on the coolant! Will definitely heed that advice! Went to start the car today after work and my battery was dead! I ended up flooding it but what was really strange is that nobody could jump start me with their car batteries, not even the AAA guy! After he did everything he could to get it going, he noticed that the battery in my battery tray was about 4-5 inches short. He went to his truck and brought the other one and installed it. Whammo!!! My car has never turned over like that before! I am lucky I even ever got the thing started at all!!! Well, 154.00 later, I have the right size and powered battery finally installed. What a trip. And yes, your fan should not spin like that. It should be stiff when you try to spin by hand and only go a few inches. You probably need a new fan clutch.

A DIY write will be great on coolant flush and differential oil change.

Regarding the fan clutch, a warm spin test is not the correct way to determine if it is bad or not. It should spin freely when hot.

The only way to check is by physically seeing if it locks if the car gets hot, OR (my personal preference) when the car is cold, left overnight. In the AM, spin the fan by hand. It should turn no more than ~1/4 of a turn. If it spins 1/3, 1/2 or more of a turn, it is no go.

I got both the coolant flush and differential fluid change processes by searching this forum. There were several coolant flush threads. The Differential is pretty easy. On my 300E, the top plug was on the top left of the differential from the back facing forward. I made sure I could get that off first (if not, and you drain it, how would you fill it?). Once I did, I took the drain plug off on the bottom right and drained it. Put that plug back in and used a pump and hose I got from Autozone to pump in the gear oil back into the top left hole until it started coming out and put that plug back in. 10 minute job.