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2012 E550 Cabriolet 2011 VW Eos 1985 Pininfarina Spider
Coolant Leak
It looks like I may a small coolant leak. The warning light has come on a couple of times over the past 2 months and have had to add about 4-5 ounces of coolant each time. I can't see any leaks, the oil looks fine and no white exhaust. At first I thought it was the overflow tank, as the cap didn't seem to screw on tight. I put some teflon tape around the threads of the overflow tank and the cap seems to be more secure now. My usual Mercedes repair place can't get me in for a couple of weeks, anyplace I should look at on the car?
It looks like I may a small coolant leak. The warning light has come on a couple of times over the past 2 months and have had to add about 4-5 ounces of coolant each time. I can't see any leaks, the oil looks fine and no white exhaust. At first I thought it was the overflow tank, as the cap didn't seem to screw on tight. I put some teflon tape around the threads of the overflow tank and the cap seems to be more secure now. My usual Mercedes repair place can't get me in for a couple of weeks, anyplace I should look at on the car?
You are experiencing a acommon slow leak
You local MB Specialist will look at the RADIATOR seams for evidence of coolant salts.
Other candidates repairs are:
New Tstat + Hose + seals
New Water pump + Inlet
New tank CAP genuine MB
....
This leak is caused by extreme pressure after each engine stop. Saving gaz with ECO frequent stops makes this leak more productive.
The pressure relieving Cap does not appear to be very effective at protecting against high-pressure damages.
Last edited by CaliBenzDriver; Oct 18, 2025 at 04:27 PM.
Coolant leaks in the radiator can be difficult to see. If you can't find it, try adding some radiator coolant dye and use a black light to see if it shows up anywhere in the radiator or anywhere else in the cooling system.
If you are thinking about using a uv tracer dye I would use a black light and look around in the engine bay before adding it.
I used a uv dye in my oil first and then afterwards used the light and everything was glowing in there. Was pretty much useless. I then tested fresh oil vs used oil with the dye in it and they glowed the same. Very odd.
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