Hi, this is my first post to the forum, I will introduce myself over on the new members page but I’m tearing my hair out at the moment with our C200 overheating.
The car has done around 32000 miles

We've had the electronic coolant pump and the coolant pump relay replaced and were still getting up to 120°c on the dash with message telling us to turn the engine off to prevent damage.

I don’t think it’s the temperature sensor as I have looked under the bonnet and seen dried coolant which has overflowed. Sometimes from the main header tank, sometimes from the one to the back of the engine bay, think this ones for the intercooler?

No problem with the radiator cooling fan, not on constantly but kicks in when temperature starts to go up. It sometimes feels like we’re about to take off it runs that fast.

Does anyone have any ideas or suggestions? It seems to be an intermittent fault, sometimes driving around happily for an hour and then all of a sudden it happens for no apparent reason.

 

I'm having the same problem. I hardly ever take the freeway and mostly drive around town because I work at home. Today, I was starting a 100 mile trip to Bullhead City, AZ and after a few minutes of driving on the freeway at 70 miles per hour, the temperature gauge quickly went in the red. I immediately pulled over to the side of the road, let the car cool down, then got off the freeway and took the surface streets back home. It didn't go back in the red at all while I was driving the 45 mph speed limit or idling at any stoplights and the temperature stayed at around the 80-90 mark. When I got home, I saw that the fan was running before and after I shut off the engine. An hour later, I checked the coolant level and it was normal. There were no codes thrown after running a scan. I did notice that there is a very small coolant leak (picture #1) so I'm thinking that it has a bad gasket and it seems that the thermostat is stuck on closed. I located the thermostat assembly (picture #2) on the FCP Euro website and the assembly and the 4 gaskets go for about $170 plus tax and shipping. The thermostat assembly looks a lot different than the one in the previous model year (W204) that my brother has and it definitely looks more complicated to swap out due to it's location under the charge air cooler in the engine bay (picture #3). Has anyone changed the thermostat on their W205 yet? I am just shy of 28k on the odometer and I didn't expect to have this replaced so soon. The connections at the top of the charge air cooler (picture #4) look manageable with the clip on the left, a bolt or 2 at the top, and the sensors on the right that need to be disconnected. I'm not sure how to remove the clips in picture #5 but they look like regular hose clamps. If you remove the clamps, do you recommend replacing them with new ones? And on the bottom right of the charge air cooler, once you pry off the plastic clips on the 2 metal lines in picture #6, how do you disconnect them from the plastic connectors that they are attached to? The sensor to the left of the metal lines can be easily pulled off of it's plastic place holder. Is it possible to just free up the top part of the charge air cooler and swivel it out of the way to get access to the thermostat assembly? If not, I'll probably just take it out completely to get maximum room. Any advice would be greatly appreciated so that I can avoid going to the dealership. The local mechanics here charge almost as much so I don't go there either.

Picture #1

Picture #2

Picture #3

Picture #4

Picture #5

Picture #6

 

I drove around town a few hours later to run some errands and this time it started going into the red at around 40-50. It's really frustrating that I haven't been able to find anything online so far. I'll try BenzWorld and see if anyone has a DIY on replacing the thermostat assembly.

 

Take it to the dealer.

 

If I wanted to take it to the dealer, then I wouldn't bother asking for help on this forum. Thanks for the helpful response.

 

Just trying to help. You will probably end up there anyway. Why wait. Seems like you're going in circles.

 

That's not helping by telling me to take it to the dealer when I'm asking for advice on how to fix this issue. If you have nothing to contribute then why respond to my post? You're the one going around in circles with your non-answers.

I've done all my own work on my ML500 and C300 and I've never taken either of them to the dealer or an independent mechanic. I've replaced many thermostats in several different vehicles. The one on the W205 is the most complicated looking one that I've come across but I'm sure it's something that I can do myself. So NO, I will not end up at the dealer anyway. Why wait? Because I like working on my own cars and I don't like throwing money away on things that I can do myself.

After doing further research by looking at some pictures of the charge air coolers for sale online, it looks pretty simple to remove it to get access to the thermostat assembly. If I get the assembly delivered this week, then I'll install it this weekend.

 

Just wanted to share my overheating experience.

My 2015 Mercedes C300 was overheating after at least 8-9 miles of driving:
1. When I drove over 65 mph (with and without AC on).
2. When I drove below 65 mph but only with the AC on.

How would it look when it would overheat:
The coolant temperature gauge would start rising and reach 120 degrees celsius and the aux fan would start running at the highest speed. No high temperature red light and no messages. As soon as I let go the gas the temperature would start coming down to the normal temperature (90-95 degrees celsius) and the aux fan would slow down.

Solution for my car:
After all the research I got the water pump replaced and it solved the problem. Seems like the water pump is the culprit in most of the cases. The water pump is vacuum actuated. In my car the vacuum line was fine.

As per the repair guy - the water pump in W205 models has been updated by Mercedes and seems like having some manufacturing defect. Mercedes takes the water pump back and re-manufactures it.

I got the repair done at a local shop. Cost is as follows:
1. Water pump: $230 (from Mercedes with 2 years warranty)
2. Coolant: $25-30
3. Labor: $375 approx. (3.5 hours of labor)

Hopefully this is helpful!





This is the old water pump.

2015 Mercedes C300 W205 overheating at highway speeds.

 

That's exactly what the problem turned out to be with my 2015 C300. It was not the thermostat as I originally thought and I returned the brand new thermostat that I purchased. No one on this forum bothered to respond to my questions about replacing the thermostat except for that idiot member "places". Luckily, this mechanic friend of mine had access to some kind of Mercedes Benz database and printed out the attached Mercedes-Benz Campaign No. 2016030001 which came with instructions. What a joke, the Service Campaign Bulletin says this at the bottom of the page: "Approximately 48 vehicles are affected". I'm positive that this faulty water pump affects a lot more than 48 vehicles. I took my car to Mercedes-Benz of Henderson (worst dealership ever) who refused to fix my vehicle because my VIN number wasn't on their "list". I called Mercedes-Benz USA which was a complete waste of time because they too were not willing to assist me in resolving anything. It should be a recall not a service campaign bulletin but they can get away with it because it's not a safety issue if your car overheats and ruins your engine. I bought a genuine MB water pump (part number 274-200-15-07-85) for $200 from the Mercedes-Benz Parts Store website. The instructions were very helpful and I was able to replace the water pump myself which took a couple of hours. The problem with the water pump is that the coolant pump control lever is made of some cheap plastic that breaks and gets stuck inside the water pump which causes the overheating issue. The stealership that refused to cover the repair wanted about $1000 or so to replace it even though this is a known issue. C'mon Mercedes, own up and actually stand by the cars that you manufacture.

So far, as the second owner of my vehicle I have only had 2 issues with it. A faulty spark plug and overheating caused by the water pump. Other than that, the car has been very dependable and I'm also very happy with the great gas mileage that I get in the city which is 25 to 37 miles per gallon depending upon whether you don't hit too many stop lights and the weather conditions. I tend to get less gas mileage in the hot vegas summers. In the winter time though I consistently get 35 to 37 mpg. The turbo prefers cold air and of course you can't drive it like a race car to get this kind of gas mileage. I only have about 34k miles on the odometer and I do all the scheduled maintenance on it myself including oil changes every 5000 miles instead of the recommended 10,000 mile intervals. Mobil 1 currently has their yearly promotion where you get a $10 VISA card for each 5 quart jug that you buy, limit 2 per household. Walmart sells the Mobil 1 0W-40 European Car Formula for just under $25 (tax included) so you're getting each jug for about $15. Not a bad deal, but beware though, Mobil 1 won't honor the rebate if you buy the oil from Amazon which they sell for the same price as Walmart. It's stated under their terms and conditions.

 

Lvbatteryguy no reason to call out members who respond to your posts like that. A little more civility would be appreciated.