W205 Overheating Gauge Problem – White Goo in Radiator?
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C300
W205 Overheating Gauge Problem – White Goo in Radiator?
I recently picked up a 2016 Mercedes C300 (W205) from auction with about 85k miles. The car drives like new. I drove it about 50 miles home from the auction with no overheating issues at all.
The next morning, as soon as I started it, the temperature gauge jumped all the way to hot. I opened the hood and didn’t see any boiling coolant, so I figured maybe the thermostat was the problem. I replaced the thermostat and flushed the system. While doing that I noticed some kind of white goo/sludge in the radiator — there was quite a bit of it, with chunks, but I did my best to flush it out.
Unfortunately, the issue is still happening. The gauge immediately shows overheating, but the engine doesn’t seem like it’s actually running that hot.
So far I’m thinking it could be:
Has anyone run into this before on a W205 with the M274 engine? Any advice on what to check next would be a huge help.
Thanks
The next morning, as soon as I started it, the temperature gauge jumped all the way to hot. I opened the hood and didn’t see any boiling coolant, so I figured maybe the thermostat was the problem. I replaced the thermostat and flushed the system. While doing that I noticed some kind of white goo/sludge in the radiator — there was quite a bit of it, with chunks, but I did my best to flush it out.
Unfortunately, the issue is still happening. The gauge immediately shows overheating, but the engine doesn’t seem like it’s actually running that hot.
So far I’m thinking it could be:
- Bad coolant temp sensor or cluster issue
- Water pump not circulating properly
- Cooling fan problem
- Air still trapped in the system
- Or worst case, head gasket/coolant contamination from previous owner
Has anyone run into this before on a W205 with the M274 engine? Any advice on what to check next would be a huge help.
Thanks
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C220d 2019
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First thing you might wanna do is check for exhaust gases in your coolant. Make sure this thing wasn’t sent to auction due to a bad coolant and oil mixing issue. If you find that that is not the case, and you just need to flush everything, it’s time to get out the garden hose and flush out your entire cooling system of that goo. You will want to run the water in the reverse direction of the normal water flow.
