Coolant problem

Jacqui Canter Anderson

Asked by Mar 30, 2016 at 08:33 AM about the 2007 Mercedes-Benz R-Class

Question type: Maintenance & Repair

A few months ago my CEL came on, went to
autozone they came back with thermostat temp too
low and flapper stuck. We changed the thermostat
and filled the reservoir to the max coolant line with
undiluted antifreeze. The CEL light went off. A week
or so later I got a "coolant level too high" message.
Took coolant out until it was back at max fill line. I
have had to do this 2 more times now. Each time
it's overflowing when I open the reservoir tank. Also
the radiator fan is running at high, sounds like a jet
taking off. HELP!!!!

5 Answers


Not a Mercedes guy, but have you noticed that your fans remain on for a while after the car is shut off? On the newer vehicles the fans will stay on for a few minutes to cool the radiator. If this is not occurring, that may be why your bottle is full all of the time. Just something to consider.........

Jacqui Canter Anderson

It does stay on but only for a couple seconds. The fan never ran at high like it does now before the thermostat was replaced.


Okay, well that's probably the reason the coolant keeps going to the bottle. You may need a new Engine Coolant Temp sensor. Some vehicles also have a radiator temp sensor. Not a Mercedes guy so I can't really say for sure how many sensors your car has. But I would start there. You may also want to check your fan. It may be failing which is why it sounds so loud. Try to free spin it with your fingers. See if it rotates freely or if it sticks.

Jacqui Canter Anderson

I'll check into the sensors, thank you! I've been asking around and quite a few people think I should check out the water pump.?

Pawan Chopra

Your coolent sensor is dirty, just clean it or your mechanic will do , it is few seconds job, may be without cost.

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