Pelican Parts
Mercedes-Benz Parts Catalog Accessories Catalog Mercedes-Benz How To Articles Mercedes-Benz Tech Forums
Call Pelican Parts at 888-280-7799
View Recent Cars  |Shopping Cart Cart | Project List | Order Status | Help

Pelican Technical Article:

Mercedes Benz Coolant Flush

Steve Vernon


30 minutes30 mins






Large flathead screwdriver, hose and water

Applicable Models:

Mercedes-Benz 190E (1984-93)

Parts Required:

Coolant, Distilled water

Hot Tip:

Don't burn your hands on the hot coolant

Performance Gain:

Proper engine temperature

Complementary Modification:

Replace hoses, clamps and thermostat

If you are replacing your coolant, it is a good idea to flush the system out while "you are in there." Flushing the cooling system will rid it of impurities, debris and assist in getting all of the old coolant out, giving the new coolant the best chance of protecting your engine and help your radiator last longer.

There are different thoughts on the use of tap water when working with your cooling system. Most tap water contains chlorine, fluoride and other impurities that are not friendly to your Mercedes-Benz radiator. While you should use distilled water when refilling the system, I see no problem in using a hose and tap water to flush the system out. Distilled water is expensive compared to tap water and you are going to be flushing the system not filling it. Please remember that when flushing the system the water coming out of the radiator is still toxic and must be disposed of safely and in the same manner as the coolant you initially drain.

Begin by parking your car on a level surface. If the car has been running or is still very hot, let it cool down for a while. Open the hood and remove the tow hook panel on the lower passenger side of the bumper by the drain plug. Place a large bucket or container under the drain plug. Once the system has cooled, use a large flathead screwdriver and turn the red radiator drain plug counter-clockwise. Coolant will begin to escape from the drain hole. Move to the coolant reservoir and remove the cap. This will break the vacuum in the system and allow the coolant to flow out quickly so make sure you place you bucket accordingly.

With your bucket still under the drain plug, insert your garden hose into the reservoir and turn it on. Allow the water to run until it comes out of the radiator clear. Close the drain plug and fill the radiator reservoir until full. You can squeeze the hoses a few times to burp the system. Put the cap back on the reservoir and start the car. Turn your heater to it's highest capacity. Don't leave the car as it will heat up quickly with just tap water in it. Once hot, stop the car let it cool a little and drain it again. If the water comes out clear you are good to go, if it still looks like it has impurities in it follow these procedures a few times until you get clear water out of the radiator. Now fill the system with distilled water, run the engine and heater, then drain when cool.

The coolant capacity of the 190E 2.3 is ten quarts but the heater core holds two. This means you will need to put in approximately eight quarts back into the system. Figuring that you want a 50/50 mix of coolant to distilled water and that you have 2 quarts of distilled water already in the system you need to add five quarts of Mercedes-Benz coolant and 3 additional quarts of distilled water. Make sure you squeeze or burp the hoses while filling to help get the air out of the system. With the system now full and burped, run the engine and heater, let the car cool and check the system level, top off as necessary.

Remove the tow hook cover on the lower passenger side of the bumper.
Figure 1

Remove the tow hook cover on the lower passenger side of the bumper. It just pulls straight out. Place a large bucket under the drain plug

Figure 2

With the car cool open the drain plug by inserting a large flat head screwdriver into the red plug and turn counter-clockwise

Open the reservoir cap.
Figure 3

Open the reservoir cap.

Flush the system by placing a garden hose in the reservoir and running tap water through the system.
Figure 4

Flush the system by placing a garden hose in the reservoir and running tap water through the system. Close the drain plug and fill the system. Run the car with the heater on maximum. Follow these procedures until the water runs clear. Fill the reservoir with the correct amount of 50/50 mixture of coolant and distilled water.

Comments and Suggestions:
Brad Comments: Hi, I just had to replace the coolant reservoir tank on my '87 190e 2.3, and just want make sure of something. After reattaching all the hoses, I realized there was a hose that connects directly under the radiator cap that seems to travel to nowhere. Is this the overflow tube, and does it just poke down into the wheel well/fender? I can not find anything anywhere that just says what it is, and I want to make sure that I'm doing this right before filling the car back up with coolant and completing the flush.

Thank you!
November 1, 2017
  Followup from the Pelican Staff: Yes, overflow drain. - Nick at Pelican Parts  
Naguar Comments: Hi, Nick. When refilling my 190e 1.8 after cold water back flushing etc. I disconnected the heater water pipe beside the reservoir tank, it's a rubber pipe onto a metal pipe. This is on the outlet side of the heater matrix. Clamped the rubber one and filled the reservoir tank until coolant flowed from the metal heater outlet pipe.
Once this happened I knew that the heater matrix was full and I didn't have any issues with air locks.

Just reconnected the rubber to the metal pipe , disconnected the clamp and continued filling.
January 9, 2017
  Followup from the Pelican Staff: Thanks for the tip, awesome advice. Appreciate you taking the time to share with us. - Nick at Pelican Parts  
SourwoodTom Comments: Hi. '95 SL500, M119 engine. Replaced T-stat, drained and flushed system. Everything seems fine, but I hear a gurgling in the dash when I run the heat. I suspect a bit of air in the system. It has been 500 miles or so, hasn't worked itself out. Any advice? Thanks.
December 19, 2016
  Followup from the Pelican Staff: Drain the coolant, then use a vacuum refilling system. That is only sure fire way to get air out. - Nick at Pelican Parts  
Al Comments: Thanks for the info, very helpful, take care !!!
June 20, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
Al Comments: Where is the A/C high pressure switch located on my vehicle and what does it look like.1993 Mercedes 190-E 2.6
June 17, 2016
  Followup from the Pelican Staff: I don't have a photo to share. It should be on a high side line. Be sure to evacuate and recover the refrigerant before removing the sensor. As the system will be opened when it is removed. - Nick at Pelican Parts  
Al Comments: I've got a 1993 Mercedes Benz 2.6 190E, auz fans never kick on, therefore causing the engine to run hot when the A/C is cut on. I've check fuses, jumped the fans with a jump wire they are good. What is suppose to kick those fans on? Thankyou !!!
June 15, 2016
  Followup from the Pelican Staff: The A/C High pressure switch does. - Nick at Pelican Parts  
MAV_GR1983 Comments: @Nick,thank you very much for making me clear how the radiator should work/cool,because i was not 100% sure what is going on with the temperatures there !!
Something else that i wanted mention is that my engine indicator rate,was jumping to 110c ,even at 120c If at 120c i close engineBy the way,thermostat is changed before almost month,Local service engineerfor the same reassons!
The temperature indicator until 80 to 85c moves smooth,with out any delay or fast heat up,while drive it for a ride inside town or high way.
Sometimes i see the indicator moves between 85-90-95c and all that in a matter of 2 seconds,and other times dont go more than a 85c ! I can provide more deatails if that is need !
I just worrie for my Lovely 190D !! Much Obliged.
Billy from Greece !
January 22, 2016
  Followup from the Pelican Staff: If you have erratic temp fluctuations, I would replace the thermostat. That may be the issue. - Nick at Pelican Parts  
MAV_GR1983 Comments: I am an owner of a 190D 2.5. Car has 300.000 kilometres and engine works as smooth as never before. The last weeks i had mentioned that my radiator when i touch it,it is cold,and only warm/hot at the right top where the hose comes ! Also,sometimes the radiator warm/hot in all places,as it should be. The hose that comes from the thermostat is not hot,maybe litle warm but nothing more ! Heater works fine with no problems at all ! Any suggestions could be much apreciated ! :
January 14, 2016
  Followup from the Pelican Staff: Sounds like it is cooling your engine correctly. The coolant should leave cool, not hot. That is likely what you are noticing. - Nick at Pelican Parts  
Jura Comments: Hey Nick, thank you for this great tutorial!
I want to do the same on my W201 1.8E, '93. but I can't find coolant drain plug behind tow hook cover like on your photo. Where else can it be?
October 12, 2015
  Followup from the Pelican Staff: Try same side of vehicle, on the back (engine) side of radiator. - Nick at Pelican Parts  
Al Comments: hi Nick, when trying to get the air out of the system by having the heater on; would it be better to leave the radiator cap off to allow air bubels escape??
August 11, 2015
  Followup from the Pelican Staff: Leave the cap on. Once hot, allow to cool then remove cap to bleed air. - Nick at Pelican Parts  
Abolsid Comments: It is working now - thank you Nick. It must have been an air pocket.
June 30, 2015
  Followup from the Pelican Staff: Great, thanks for the follow up. - Nick at Pelican Parts  
Abolsid Comments: Radiator fan stopped kicking in after coolant flush on my 93 190E 2.3. Does the new coolant Zerex 05 G affect the point where the fan kicks in?
June 22, 2015
  Followup from the Pelican Staff: Shouldn't. Could be an air pocket near the sensor. Try bleeding it again. - Nick at Pelican Parts  
bubba Comments: I change my let out tha water n put antifreeze in it now my car won't start
February 19, 2015
  Followup from the Pelican Staff: Most likely unrelated, the no start could be a coincidence.

I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
quesnoy Comments: Hey Nick. I wish I hadn't decided to flush my coolant. My car was running fine, but I felt like doing it since I just purchased the vehicle and didn't know how old the coolant was. After draining the radiator, I filled the tank back up with distilled water. Ran the engine until the fans came on with heater dial on full heat. Then drained the radiator again. Only water came out. I assumed the radiator must have been in pretty good condition. When I went to fill the tank back up, I could only fit two quarts of coolant and about a quart and a half of distilled water before the tank over flowed. I thought this was odd since the car is supposed to take around 9 quarts of coolant/water mix. I ran the engine and it runs hot. The fans come on wile idling. I shut the engine off before it gets too hot. But now I also notice that the heater isn't working. The fan works and the vent controls work. Even the recirculation works. Could it be that coolant is not even going into the heater core? Could this be why I couldn't fill up the vehicle with the full capacity of coolant/water mix? Any idea what I can check to get to the bottom of this? If the heater really is not working, what is the procedure for flushing and refilling the coolant so that the vehicle will run at normal operating temp? I'm pretty sure the thermostat is working just fine because the upper hose gets hot. Therefore, coolant is definitely going into the radiator...
January 17, 2015
  Followup from the Pelican Staff: You didn't mention what vehicle you have.

FIll the engine with coolant when it is off. If it still will not take the amount of collnt you drained, you may need to vacuum the system. Using a vacuum bleeder, pull the empty cooling (dry) system into a vacuum. Then use the vacuum tool to fill the system. RUn the engine, then top up as needed. - Nick at Pelican Parts
quesnoy Comments: Hi Nick,

Any advice on what type of coolant brand, color, spec. to put into my 190e 2.6. Keep in mind, milage is at around 260K if that matters. It currently has a green colored coolant mix in it, but I've been browsing the MB forums and everyone keeps mentioning Zerex G-05 in comparison to the MB brand coolant sold at dealerships. Your thoughts?
January 3, 2015
  Followup from the Pelican Staff: I always use what it suggested in the owners manual. No need to upgrade the coolant. Just use what is prescribed. - Nick at Pelican Parts  
quesnoy Comments: Thanks, Nick. As long as the engine appears to be running smoothly, I would think a rebuild would be a waste of money. I'm guessing that blow by residue in the intake had been accumulating for 260K miles worth of driving. I doubt if the previous owner had ever even taken the air box apart. If it doesn't start smoking again for another 260K miles, I will be fine with that. I just completed the recondition of the valve cover and inner baffle that separates the oil from the crank case ventilation ducts. The inner gasket was as hard as plastic. I'm guessing it was more than blow by that was getting into the air box. I'm pretty sure some oil from inside the valve cover was seeping into the baffle and getting blown into the air box as well. We shall see, though...
December 28, 2014
  Followup from the Pelican Staff: Good to hear. I tend to agree, if it runs well, do the least to keep it running well. - Nick at Pelican Parts  
quesnoy Comments: There was no water that I could see. Possibly some oil residue from the blow back coming into the air box via the crank case ventilation tube. The air box definitely had, what appeared to be oil in it. It may be a combination of oil and fuel. This engine has around 260K miles on the odometer, so I'm sure the piston rings are worn. But the engine runs very smooth, so I'm hoping a better/thicker synthetic oil might cut down on the blow by. What are your thoughts?
December 24, 2014
  Followup from the Pelican Staff: I haven't found thicker oil the be any help on worn engines. Only rebuilds can help. However, it may reduce the smoking a bit, until the oil wears and becomes dirty. Then it will return to smoking. It is worth a try if you want to avoid major repairs. - Nick at Pelican Parts  
quesnoy Comments: Hey, Nick. My brother and I were able to get to the bottom of my exhaust smoke. After removing the air box and giving the throttle body a very good cleaning, the smoke is completely gone. I mean, the exhaust was basically invisible right after the cleaning. Who would have thought that would make such a difference!
December 21, 2014
  Followup from the Pelican Staff: Was there water or oil in the intake air ducts? - Nick at Pelican Parts  
quesnoy Comments: Thanks, Nick.
December 19, 2014
  Followup from the Pelican Staff: No problem. - Nick at Pelican Parts  
quesnoy Comments: I have a '92 190e 2.6. Very high mileage. 260K miles on the clock. When I took delivery, I thought it might have a head gasket leak because it has a steady stream of what appears to be white smoke coming from the exhaust pipe when running it could be grey, I can't really tell. The vehicle does not overhead when left idling for quite a while and it does not appear to run rough. I conducted a block test using one of the test-tube turkey baster-looking things with the blue dye and the dye did not change color. It also appeared that the expansion tank had a good seal because the inflatable pump would not return to the inflated position very quickly. Am I doing the test correctly? Should I remove the thermostat to ensure that coolant is circulating all through the system? I felt the large hose going into the radiator and it felt like something was running through it. The coolant level has not changed, either. What could be causing this smoke? I often smell a strong fuel odor so I was thinking there may be a hole in the gas tank allowing condensation and moisture to enter the fuel system. Otherwise, I'm at a loss...
December 13, 2014
  Followup from the Pelican Staff: A small amount of white smoke can be condensation in the exhaust. if the block tester shows no co2 in the cooling system, your head gasket may be fine. To be sure, I would pressure test the cooling system. If the system will not hold pressure and there are no external leaks the head gasket may be faulty. - Nick at Pelican Parts  
Craig Comments: Nick, bought a 93 190E 2.3 and I noticed this rusted out pipe thing running along the bottom inside of the radiator. What is this and how do I put a new piece in? Thanks Craig in MD
October 13, 2014
  Followup from the Pelican Staff: Looks like a cooler pipe. You will have to detach it at each end to replace it. We don;t currently have a tech article for that procedure. Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
250TD Comments: Will it be the same procedure for W124 250TD?
September 24, 2014
  Followup from the Pelican Staff: I don't think so. The article applies to: Mercedes-Benz 190E (1984-93) - Nick at Pelican Parts  
exellerator Comments: I recently bought a '91 190E and as soon as I got home, I noticed that the low coolant light was on and that the temperature gauge was around the second middle bar. When I got to my driveway, luckily, coolant leaked out under my car. Do you know if my radiator, head gasket or anything is damaged because of this? I believe that the coolant was ejected from the tube below the coolant reservoir cap in Figure 3. Is that tube supposed to be connected to anything or is it there for coolant to come out in case something happens?
June 26, 2014
  Followup from the Pelican Staff: Being ejected from the cap is a sign of overheating. I would pressure test the cooling system and see if there are any externals leaks.- Nick at Pelican Parts  
Abolsid Comments: Thank you Nick for your prompt reply.
June 13, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
Abolsid Comments: I have a question: I was told that you need to change the thermostat when you replace the coolant in a 190E as it has a tendency to stick. Is this info correct or can I just use the existing thermostat without replacing it? Thank you.
June 9, 2014
  Followup from the Pelican Staff: If it is working normally right now, you should be Ok replacing only the engine coolant. - Nick at Pelican Parts  
Sandy Comments: Easy Peasy with these instructions. I flushed mine then filled it and run it to hot twice before flushing again and filling with 33% mix very rarely below -5c here in Bonny Scotland.
May 15, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
Jacky L. Comments: Hello, thank you for the DIY. The mercedes-benz radiator design is weird, how come we dont pour directly into the radiator but its using a external reservoir instead? I putted about 1.5L coolant and it was full until i drove a bit. Im still only up to like 2.5L. I don't know why you mentioned 8 quartz? Thank you.
March 21, 2014
  Followup from the Pelican Staff: All cars have an overflow reservoir. Most European makes utilize this as the reservoir for filling also. Just a design feature. If it is not taking the full amount, you may not have drained it all. - Nick at Pelican Parts  
emilve Comments: Amazing! Glad i found this site. Thank you for all the work you have put into creating this! Its very helpful.
January 13, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts

About Us
Pelican Parts, LLC
1600 240th Street
Harbor City, CA 90710
Order Online or Call:
Sign Up for Pelican Pit Stop News & Special Offers
Page last updated: Wed 2/21/2018 02:32:29 AM