I needed some help in finding out if my C220 Thermastat is still working properly. My car is also losing coolant and requires topping up every 10 days. I was wondering if anyone could help give me some tips on figuring out if the thermastat is fine. Where's it located on my car? and is it easy to change? Like the RAD hose that leads to the rad, usually their are pressure filled will coolant, mine can easily be squished and their is little coolant you can usually feel inside. Anyone know what's going on? and where my Thermastat is.

Thanks guys.

Don't take this the wrong way but, based on your description, go to a garage.

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2007 C 230 Sport.

your t-stat is on front of the engine at the opposite end of the top radiator hose. to the right of that plastic black cover with the MB Star molded on it.

With engine cold -sitting over night- start car and feel the top radiator hose, it should stay cold for a few minutes until the t-stat opens and then the hose gets warm - be careful of radiator fan coming on at any time

Do you see where the coolant is leaking? Have you checked and opened your coolant overflow tank to see what color the coolant is? should be yellowish, if it looks like chocolate milk post back here.

Also things like a new overflow tank pressure cap will make a big difference if it has never been changed.

Hey Ethan, thanks for your response. I drove my car from work right now, so I won't be able to test the hose and thermastat opening till later in the day or tommorow morning. However I checked the Resovoir right now, and it seemed very low again for having been filled up 4 days ago. I had the water pump done last year by an indy mechanic...But that's all he did. I tried looking for the thermastat, and couldn't find it right now. If I order a new one, is it easy to change, something I could do myself? Also I sqeezed the rad hose, and it seemed like little coolant sitting in it, easy to squeeze and you hear the coolant inside moving. Under neath the car I don't see any leaks either.

I took a flashlight to the resvoir and i see green coolant at the bottom...not choclate milk. But around the resvoir walls, it seems like someone just drank choclate milk and the sidewalls had dried....Also I think the cap is factory, do you think its seal is broken? Around my engine right now it smells like burning coolant mixed with something...but no leaks...please help, thanks

Hi there trueog,

Thermostat seldom give problem. It will cause the temp to rise to the red zone if it's stuck. However the radiator cap is more likely to cause problem if the rubber seal and spring tensioner fail. Anyway get it replace as it's relatively cheap.

Since you mention you need to top-up coolant every 10 days, I bet the radiator is leaking at the end tanks. The radiator is made from aluminium but the end tanks from plastic. Due to time and heat, the plastic can crack and cause coolant to leak. Inspect carefully as it is quite difficult to see. Happened to my 190E last time. The water pump also can leak at the rubber seal.

The trick is to start observing the suspected area the moment you start the car in the mornings from a cold engine. You will soon see coolant slowly seep out from the leak in a few minutes time just as soon as the thermostat opens.

On my case both the radiator end tank and the water pump leaked at the same time.

Hope this helps.

Cheers.

Thanks. I'm going to try that tommorow morning when the car's cold. Start it up and stand there and watch to see if their's any leaks. On my car its really tough to see the bottom of the radiator. ALso my car after a short fast ride, the temp sits quite high when you're in the city...that's why i was doubting the thermostat.

Thanks

Hi trueog,

Highly recommended that you bring along a Flashlight/Torchlight as well.
The crack on the radiator plastic ends are hairline cracks mind you, which is very difficult to detect.

Use the flashlight to shine on the sides of the radiator. You need to be patient to wait for the thermostat to open then only the coolant start to seep through the leak. However once the engine heats up the seeping coolant from the leak will evaporate due to the engine heat. So the timing must be right......

It took me quite a while to detect the leak on my radiator as the crack was not obvious at first ...but the crack grew bigger due to time....That is when I notice the coolant seeping out...

Be extra careful of the radiator fan though while you are at it....

Happy observing.

Cheers.

Trueog, don't dismiss Manny's advice about taking the car to a good garage.

An experienced MB mechanic through familiarity can hone in on the problem quick and will know how and what to repair.

I also admire your initiative to try and fix the car yourself, you may wish to purchase the Haynes manual for your C-class, it is a British spec book - but it is essential. T-stat replacement is a DIY job if you have complete instructions, which you'll find in the haynes manual, I think Amazon sells it, ISBN: 1859605117

Hey guys, another day of trying to figure out the coolant problem. So this morning I started my car up, watched the engine idle for about 10 minutes, and I saw no signs of coolant. However the hose to the Rad was still a little soft and easy to squeeze, but you could feel some of the coolant inside. I couldn't tell if my thermastat was or is working fine, I need some pointers on how to tell. I took it for a 15 minutes drive and came back and could smell little bit of burning coolant, however there were no traces. I'm going to change the cap on the resovior, but i'm still unsure about the thermastat. Anyone got suggestions on what else to try? Thanks

Hi trueog,

Since you were unable to trace any leak but can smell burning coolant...1 more suggestion.
This is from my experience on my 190E....

For a 4 cylinder 190E, located on the block just in between the headers, there are 4 stoppers or plugs for the water jacket as some call it. it's the size of an average coin. Mine was badly corroded and was leaking out coolant. But I'm not sure on the M111 engined c220.

Other possibilities include..leaking head gasket..which can allow coolant to seep into the combustion chambers..but if you are at this stage, i doubt that you could drive further without overheating the engine...

But to save you the trouble I agree with Manny's and Ethan's suggestion to bring the car to a good garage. Unless you really know what you're doing, it is not worth the risk to DIY. You might end up with a bigger bill.

However I still place my bet on the leaking radiator thou....

Cunix is refering to what I call freeze (core) plugs, and they can leak on some cars.

The theory of the t-stat is when car is cold and started up coolant only circulates throught the engine block. Once a temp sensor or t-stat detects enough heat the car starts to circulate coolant thorugh the radiator to be cooled by the air rushing through the radiator fins when the car is moving.

So when you start up car when cold the top hose should stay cool for a period then get hot. An infra -red thermometer is a good tool for taking temp readings of the radiator to see if it gets a rush of warm coolant from the t-stat opening.

If your driving and your temp gauge (working) reads as normal then your t-stat, radiator core and (hoses -are not collapsed) and are in good shape.

For leaking check out water pump seals, cracks in hoses, heater matrix all things that will leak when engine gets warm and you'll get either odor or drips.

Alos C-class cars have some heater hoses and components not found on other makes so be sure any garage you go to KNOWS Mercedes.

Is it a problem if the hose is a little soft after its been running for awhile and no pressure at the antfrreeze resoiver,except when the heater is turned on(only then dose the hose get tight too)?

BCM, how did you determine no pressure in the antifreeze reservoir?

after it had been running for awhile I took the top.

Thanks for the response. Yeah the problem continues, you can smell the coolant without a trace of a spill. I was wondering, if anyone thinks adding a coolant stop leak additive availble at fine automotive stores like WAL-MART...lol....is a good idea to use? has anyone used any stop leak items, and to what success or mess up...and what brands?...thanks