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Hi everyone.
It’s time for me to replace the coolant and fully flush the cooling system, and I’d like to do it myself.
I’ve read in many places that for a proper flush you should drain the coolant not only from the radiator, but also from the engine block.
The problem is that the block drain plug is very hard to access. I don’t have a lift, and doing this on jack stands in my driveway is extremely difficult, so I’m not confident enough to try it.
My question is is it possible to flush the system properly without draining the coolant from the engine block?
For example, would doing 4–5 flushes with distilled water be an acceptable alternative?
Pull the lower hose off to drain it its fast but messy. Once drained change all hoses if they are old now is the time to replace them all. To fill remove the coolant cap and fill. Then run the engine and bring it up to temp and run the heater too while keeping the tank full. After full and up to temp put on the coolant cap and let it build some pressure while running. You can tell by squeezing the top hose until you feel pressure. Now look for leaks and if no leaks your done.
To add, I wouldn't worry about whatever is left in the block after a lower hose pull. You're already better than 99% of the folks that have the same car.
I would, however, change the o-ring to anything you remove at minimum. And clean all mating surfaces.
What’s currently in the system looks like very old green coolant. I don’t think it’s been changed in a long time, if ever. The dealer sold me pink coolant, so I want to remove as much of the old stuff as possible before filling with the new one.
What’s currently in the system looks like very old green coolant. I don’t think it’s been changed in a long time, if ever. The dealer sold me pink coolant, so I want to remove as much of the old stuff as possible before filling with the new one.
Always change coolant every 2-3 years as it's cheap to do it now compared to the damage not changing it will do.
In my opinion I don't care what color the coolant is as long as you're not mixing colors. So after it's all drained fill it up with whatever color and never use tap water because it has to many minerals in it.
What does the WIS say to do for your engine? On my engines (M276) the procedure is to remove the lower radiator hose, drain the coolant, replace the hose, and further evacuate the coolant system using the vacuum method (search youtube).
The vacuum method does a few things: completely removes any remaining coolant, checks for leaks, and eliminates air pockets when you fill.
You don’t want to use tap water to mix with undiluted coolant, but to flush out the old stuff should not be a problem, depending on where you live. You will end up draining out the tap water, as well.
Here are some docs that may help. You don’t need an official Mercedes contraption to vacuum your coolant system. I have the Schwaben tool in the attachment, but you can find equivalent ones on Amazon. You will need an air compressor, though. A small “pancake” style will work. An air compressor is a good tool to have anyway.
For your M272 engine and year you should be using the 325.0 / 326.0 spec coolant. Zerex G48 coolant which is blue/green in color.
Why would the dealer sell you pink coolant, which im assuming is Zerex G40. This is coolant for 2014+ vehicles.
For replacing the coolant as part of the recommended maintenance it is just a drain and fill. No mention of a flush.
What is the color of the coolant in the car now? photo of what it looks like.
I would just do a drain and fill. Unless there is corrosion in the system I dont see the need to waste time and money on a flush.
But if you know the wrong coolant is currently in the car, or you plan to use the pink coolant, then sure flush away.
I like buying the premix 50/50. Zerex G48 coolant is usually on sale cheap at my local Napa auto parts store.
I lucked out and I needed to replace the oil filter housing gaskets on my M272 and it happen to be around 150,000 miles so time to replace the coolant anyways. I simply removed the oil filter housing and let everything gush out, didnt mess with drain plugs. then to fill i just poured the new coolant in the coolant reservoir until full, started the car and added more coolant as needed. No special steps needed, it is self bleeding. Topped off the reservoir once or twice the following days as I drove. Used around 6 liters which is 1-1/2 jugs of coolant.
Keep it simple. If you can get to the engine block drain great, if not oh well. Drain and fill what you can. Then do it again in another 5yrs. The coolant is only warrantied for 5yrs anyways.
Woow, thanks so much for such a great info, very much appreciated!
Originally Posted by TimC300
Why would the dealer sell you pink coolant, which im assuming is Zerex G40. This is coolant for 2014+ vehicles.
Hard to say. They have my vehicle (VIN) in their system, and that’s what they sold me. On the bottle it does say that it meets MB 325.5 specs.
Originally Posted by TimC300
For replacing the coolant as part of the recommended maintenance it is just a drain and fill. No mention of a flush.
What is the color of the coolant in the car now? photo of what it looks like.
The main reason I want to flush it is that I don’t know when it was last changed. Also, the coolant is green which (at least to my understanding) is an older type that Mercedes used a long time ago. On top of that, the manual says to replace it after 15 years or 250,000 km, so I’m assuming it may have never been changed for 15 years and I just want to be on the safe side.
Also I suspect the thermostat is failing (or already stuck in open position), so I’d like to do everything in one go.
As for the current coolant condition in the expansion tank it doesn’t look bad to me, green liquid, no visible contamination as far as I can tell, i can see the bottom of the expansion tank which is a good thing i guess .
My 1st thought seeing the reservoir photo is it looks like boilover staining. Or something has been spilled in there.
I dont think it matters, just stood out.
Is that jug of coolant unopened? If so it looks low, there should be 3.7 liters in there.
And the 325.5 spec confuses me because I cannot find it on the latest MB Bevo pages.
From a quick search it would appear the bottle you have is old stock. Me, I would want the latest product especially if paying a premium from the dealer. I know MB had updated there product labels the past recent years, must be at least 2yrs now because i remember buying MB brake fluid with the new label. Heres an article I came across about the various specs: https://www.fcpeuro.com/blog/engine-...-your-mercedes
I do agree you should do a flush to get all that green coolant out. If you have an air compressor then you can buy a vacuum adapter with cap which would make removing and refilling the coolant quick and easy. Steelman has a nice adapter and they offer free shipping though not sure about to Canada.
I cannot find any information on the above SI20.00-Z-0017A. That flyer mentions EU.
I had work done at my local Mercedes dealer last fall which involved adding coolant and they billed me for "Zerex G48 antifreeze".
That flyer is on a dealers wall in Maryland. It's a notice from Autonation on behalf of Mercedes. I went through the same line of questioning about fluids when my blue fluid was mixed with pink at the dealer a few months ago. Service centers have different regulations than consumers. This is the official Mercedes dealer position. There's a reason its on the wall of the workshop...probably tons of people have asked. You can buy whatever you want as a consumer at an autoparts store.
Last edited by Baltistyle; Dec 16, 2025 at 05:01 PM.
Hi everyone, I eventually replaced the coolant from green to pink. I did 7 cycles, maybe overkill, but I wanted to flush the green out of the system as much as possible.
I also replaced the thermostat. The reason was slow engine warm-up in freezing weather(-10, -15 C). At idle it would never reach 90°C(especially if heater is on), and while driving it takes about 10–15 minutes to get up to operating temperature. The temperature may even drop if I turn on the heater. In the summer works fine though.
I’m comparing this to a Kia Sorento, which warms up even at idle in about 7–10 minutes in freezing conditions.
After replacing the thermostat, nothing changed. Do you think the new thermostat could be defective, or is this normal for this engine?
Takes my car around 10 minutes of driving to get to operating temp. If I turn the heat on prior, like right away when starting the car the temp on the dash will noticeably lower and take a little longer to reach 90 on the display.
Seems normal to me.
I was going to question why do you want to replace the thermostat, probably working fine. Are you not getting heat from the vent?
I was going to question why do you want to replace the thermostat, probably working fine. Are you not getting heat from the vent?
Everything works as expected, except for how long the engine takes to warm up. That’s my only concern, it just doesn’t warm up the way I’m used to from other cars. When it’s freezing outside, it seems like it would probably never reach 90°C just idling, which really surprised me. That’s why I thought the thermostat might be bad and replaced it. I’m fine if that’s just how it works, I mainly want to make sure nothing is actually wrong.
The cabin heat does come fairly quickly, though, about 3-5 minutes after I start driving.
Someone in the W221 section was having issues with the heating and coolant so thats why I had been paying attention to what my car does. I have the m272 and it seems it takes 10 minutes for the dash to show 90 and it stays there for the most part.
From my understanding on start up the coolant is used to heat the oil to get it up to operating temp. So on cold start the heating circuit is kept closed, it only opens if the heat is turned on. Thats why if you turn the heat on you see the temp on the dash drop a little because the colder coolant in the heating circuit/heater core is allowed to cycle.
I would say your old thermostat is probably still fine and keep it just in case something happens with this new thermostat. Wahler makes the Genuine MB thermostat and its the brand I would have bought if I needed one.
Some additional info on the dash display. When the coolant temp is 80-115 the dash will show it as 90. Also the thermostat is not just opened/closed, there are a few settings de[ending on the operation.
I just re-read your other post. -15C is cold, especially at speed. I'm not surprised it takes a while to warm up. If you're not getting codes relating to temperature management, I'd call it good.
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