I have a '99 E430 with 40K miles. I'm guessing that I'm probably delinquent in changing the anti freeze. Sure wish I had a manual! What is the recommended time / mileage to change anti-freeze?

I'm on the 2-year plan with all cars I take care of.

e430guy, Ph is the critical characteristic of Mercedes coolant . As the ph approaches 8.0 coolant should be changed as it erodes alloy engine components and makes plastic parts brittle. The ph of Mercedes coolant in the bottle is approximately 5.6 so that when it is mixed 50/50 with water the ph becomes 7.0 or neutral. The ph of other manufacturers' antifreeze can be as high as 9.0 or 10.0 straight out of the container which is an immediate problem. Swimming pool ph test strips can be used to check the ph of coolant and coolant/water mixtures.

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Fred Hoelzle

Every 2-3 years.

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Brian Toscano

The the owners manual for year 2000 recommends replacing it every three years.

Thanks for all the responses on the anti-freeze change schedule.

Does anyone know what the cooling system capacity is?

Another test to see if it is time to change antifreeze is using a digital volt meter. Connect the negative lead to the battery - terminal. Insert the positive lead into the coolant water. If you see a reading of .3volts or more, change the coolant. This not only helps protect the cooling system, but if you have a high voltage, it can alter the readings from coolent temp sensors etc and make the car run a little out of spec.
I know I will get some negative responses from this post, which is fine, but also I know it is correct.

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84 500 SEL (307,xxx miles)