Coolant Flush

[nokia8860]

It’s that time of year when the temps start hovering around 105 degrees Fahrenheit and a change of coolant is needed to insure adequate cooling of the engine while being fully loaded with the AC on 11 and not letting up on the accelerator.

While the manual has its own suggestion and it’s a good one to adhere to, I use my own concoction. Whatever you use the process of removing and replacing is the same.

http://www.bnzsport.com/gallery/coolant/CRW_8231.jpg

Ingredients are simple: Coolant, distilled water, water wetter (optional) and a new thermostat.

You will need to gain access to the drainage plug (shown in red) at the bottom of the radiator. This will require you to remove your skid plate. Once you have access to the drain plug make sure you have a large enough container to catch all the coolant that will flow out. Take a flat head screwdriver and loosen the plug.

http://www.bnzsport.com/gallery/coolant/CRW_8232.jpg

Once loosen (note not removed) undo the reservoir cap so coolant will start coming out. No the coolant isnt yellow. It just got captured that way.

http://www.bnzsport.com/gallery/coolant/CRW_8235.jpg

Edit: At this point you should flush out the radiator with water until it runs clean. This will require you to remove the upper and lower hoses attached to the radiator. A 7mm or flat head is all you need to remove the clamps to loosen the hose.

It’s a good time now to replace the thermostat since the radiator is now drained.

http://www.bnzsport.com/gallery/coolant/CRW_8233.jpg

The thermostat is housed in a metal casing held on by 3 star looking bolts (reverse security something… eh whatever) which can be undone with a 8mm socket. After removing the bolts, if you’re finding that it’s difficult to remove the housing, a swift whack with a rubber mallet will quickly free it. Once removed simply replace the old thermostat and gasket with the new one and reinstall the housing.

The next step is to drain the block. While underneath the car towards the middle of the passenger side block you will see a drain plug (M104 speaking)its made to attach a tube to it so you don’t spill coolant everywhere but if you have a large enough pan that wont been necessary. Loosen the plug and let the coolant run out.

http://www.bnzsport.com/gallery/coolant/CRW_8237.jpg

At this time I’ll also run the car with the HVAC on high heat to get the coolant out of the heater core as well.


Once coolant stops flowing out you can then tighten the plug and put back the skid plate as everything else will be from the top of the engine.

http://www.bnzsport.com/gallery/coolant/CRW_8238.jpg

If you’re doing the 50/50 method it’s rather simple to ensure the right amount of coolant for the right amount of water. However, if you plan on doing a 60/40, 75/25 (yep I use more distilled water than coolant in my mix) etc… having some empty containers will help you get the mixture just right.

http://www.bnzsport.com/gallery/coolant/CRW_8239.jpg

The best way I’ve found to put in new coolant without getting those nasty air bubbles inside is to have the engine running while adding the mixture. Once completed I’ll let the engine continue to operate for a bit with the cap still off, after I’ll cap it up and take it for a drive.

I’ll let the engine rest and recheck the reservoir and add more distilled water should I need to. But basically after that you’re all done.

And incase you’re wondering about my mixture this is what my temps are after some hard driving with the AC on 11.

http://www.bnzsport.com/gallery/coolant/CRW_8240.jpg

Dedicated to kameraguy and his hot running 3.6

[Brabus]

eXCELLENT!! Need to do this on my car... the temps are running pretty high in traffic.

[Luwin1026]

Great writeup!! And what a sweet garage bay - I can imagine some checker-floors with a built-in lift in the future!! :lol:

[Renn 208]

The burping's a key step in the process...so anyone else who decides to do the flush should not skip that step.

Also, while opinions may differ... I like using the stock MB coolant, which is clear/super faint yellowish.

Really though, it's the water that cools your engine...the "coolant" itself is really just antifreeze/anti rust, so mixes heavy on the water will help in warmer climates. Great write up Nokia! Everyone should be able to do their own coolant flushes.

[dshr]

Nice I've been planing to do this to one of our cars :). I need fluids all around.

[1998K]

Hey Nokia thank for the how to but please just a comment to this sentence:

"At this time I’ll also run the car with the HVAC on high heat to get the coolant out of the heater core as well."


To point out that you don't have to run teh engine, only to turn the key in order to activate the el. control of the HVAC system.

I'm quite sure that running engine without coolant in the circuit may damage the coolant pump.

Hi :)

[kameraguy]

Holy shsjfierycnodtrufyfgdh!! Your car returns to 85 degrees after a hard drive with AC in VEGAS heat???

Damn you need to patent that elixr! :P

Thanks doodster, this is what I definitely need!!

I know the thermostat is supposed to open full at around 87 degrees, so that explains why they say it's "normal" to have engine temps fluctuate between 90-100 degrees....but i'd rather have your kind of temperatures :P

BTW- how much watter whetter do you add? The whole bottle?

[benzmark23]

Does the Redline Watter Wetter really works

[Brabus]

Originally posted by benzmark23@Jun 6 2005, 08:35 AM
Does the Redline Watter Wetter really works
only on watter!!

[nokia8860]

Originally posted by kameraguy@May 30 2005, 10:08 AM
I know the thermostat is supposed to open full at around 87 degrees, so that explains why they say it's "normal" to have engine temps fluctuate between 90-100 degrees
I'll have to double check but I believe there are two stages to the thermostat. At 87 it is not fully open only 1/2 which allows some coolant to go to the radiator and allowing others not.

I forget at what temp is it fully open... well thats my understanding per the diagram i have on the 104 cooling. I'll double check and get back to you on that.

So kameraguy did you do the flush? Let me know if it helps.

[Vodka G]

i just did a flush the other day (since i was doing one on the TT i figure might as well)

but i did it a bit diff......i drained everything first....then i ran water to the radiator via the fill cap (with a hose) while the engine is running with drain plug open (heater on full blast) for about 3-5 min (yeah lots of water)

then fill

[BrabusCClass]

great writup! I think I should do this too...