When and how do I replace my anti-freeze?

[Mercedes Guy]

My '92 190E 2.3 is about to turn over 90K miles. The maintenance manual suggests to change the anti-freeze at this time. Can anyone tell me how to do this? I would really like to do it myself if possible. Also, what brand of anti-freeze should I use? Thanks.

[Kestas]

This is the method I use for all my cars:

To flush, remove thermostat, reinstall housing, disconnect upper radiator hose at the radiator, and flush by inserting garden hose into radiator hose. Water flow should be opposite coolant flow during engine operation. Work the car's heater to flush that part of the cooling system also.

Flush overflow tank, then empty by siphoning off the fluid.

Once flushing is complete, turn off water and open all drain ports (block and radiator).

Reinstall thermostat, button everything back up, and refill with 50% antifreeze (calculated from your car's cooling system system capacity). Top off with water (preferably distilled). Use MB antifreeze from the dealer or Zerex G 05 antifreeze. Zerex G 05 is nearly identical to the stuff from the dealer, and is cheaper and more readily available at most auto supply houses, plus it is a product approved for use in MB coolong systems.

Tips:

If the coolant has oil in it, you should consider flushing with a non-abrasive and non-chlorinated detergent such as Shout, Spic & Span, or Dawn.

If the coolant is otherwise dirty, you should consider flushing with a citric acid-based flushant such as Prestone Super Flush.

Some people report that they run the engine a bit during flushing to help move all the old coolant from the engine.

Coolant is extremely toxic - and sweet. Keep your pets indoors if coolant is present outside. There have reports of horrible deaths to family pets drinking the stuff.

Dispose old coolant properly. Do not dump it on the ground, in the septic system, or in the storm drain that goes straight to the lakes and rivers.

[richard28]

Could you please clarify something I read in the Haynes manual. Re 300ce,it said to set the heater at full temp, disconnect the lower rad hose at the radiator & run the garden hose into the upper rad hose (thermostat removed) until the lower hose drained clear water. It said nothing about running the engine, so I assumed that wasn't necesssary. So, is the heater running off the battery alone? Once the drained water is clear, should the block be drained again & filled with antifreeze mixture, or should antifreeze just be added? I have never done this & don't want to mess up after I was able to replace the radiator from what I learned on this board & in Haynes. Thanks.

[Kestas]

I'm guessing there's residual vacuum stored on board for heater valve actuation. At least it's true on most other makes -- this is a safety feature to supply assistance for power braking at least once should the engine kick out.

After all the old coolant is flushed out, drain as much water as possible by opening the radiator and block drains and siphoning the overflow tank. This is to ensure you have enough empty space for the antifreeze charge, since you can never get all the water out. Add antifreeze according to the specified capacity, i.e., if your system capacity is 10 quarts, add 5 quarts antifreeze for the proper 50-50 coolant mix. Top off the remaining capacity with water.