For a while now, I've been meaning to replace my original, yellowed coolant tank on my 500E. I did it last year on my 560SEC and it really brightened up the underhood area. So, I finally bit the bullet and added one (as well as a new coolant level sensor) to my latest parts.com order.
I received the new tank and sensor today, and commenced to replace them. The entire process took less than one hour in my driveway/garage.
Tools needed on hand include the following:
- Phillips head screwdriver - normal size/length
- Philips head screwdriver - stubby
- Flat-head screwdriver - normal size
- 1/4" ratchet with medium extension, and 8mm and 10mm sockets
- magnetic picker-upper tool (in case you drop hardware)
- snap-ring pliers
Parts for the job include:
- 124 500 15 49 (coolant tank)
- 124 540 02 44 (coolant level sensor)
Here's the procedure for the job:
Here's an overall view of the coolant tank before I got started.
Notice the three hoses + electrical connection attached.
Next up, remove the radiator cap. Make sure you do this when the car is cold so coolant doesn't spew everywhere and/or burn you !
Next, siphon out the tank as best you can. I used a spare length of hose, and an old clear-glass vase of my wife's (don't tell her!).
Next, unplug the electrical connection to the coolant level sensor, and move the plug aside.
The plug ends may break off in your fingers, so it's a good idea to replace this (and other like plug housings) underhood.
Use your regular Philips-head screwdriver to loosen the top hose clamp.
Remove the clamp by sliding it down the hose away from the end of the hose.
Next, carefully shimmy/pull the end of the braided hose to the overflow tank off the nipple.
These hoses tend to get VERY fossilized, so it may well be a good time to replace this hose.
Use your stubby Philips head screwdriver to loosen the lower (larger diameter) hose.
You can use the larger Philips screwdriver if you remove your airbox and air tubes. I was lazy so just went with the stubby guy....
Use your 10mm socket on a 1/4" ratchet with extension to remove the two nuts holding down the opposite end of the tank.
These nuts are both pretty accessible.
This is where the 8mm socket comes in handy ... in case you need to loosen one side of the plastic belly pan encapsulating the bottom of the engine, to let out a stray nut that fell down into the engine because you dropped it !!!
Your extensible magnetic tool can reach in there on top of that belly pan and retrieve the stray nut.
After removing the hoses and the nuts, you can gently but firmly pull the tank straight up.
It is embedded into the top of the fender liner with a small extension that fits into a rubber bung plug ring.
You'll see it on the bottom of the tank after you remove it from the vehicle.
Here are the old and new tanks, side by side.
Whoever believes that new tanks aren't as white as snow when new, can definitely change their belief NOW.
Here's the area underneath the tank. You can see the hole where the extension on the bottom of the tank, and the rubber bung plug fits, near the center of the photo.
Take some quick detailer and clean this area out with a rag, as it's gonna be a LONG time 'til you're back underneath here.
Next, remove the circlip that retains the coolant level sensor in the hole on the side of the tank.
Here's the procedure.
Next, get out the new sensor (if you choose to install a new one.
Here is the new one and the old one, side by side.
Next, insert the new coolant level sensor. The different-sized tangs on the sides guarantee that the sensor will only go into the hole one way.
Push the sensor down all the way (so that the black o-ring is against the inside of the hole) and replace the circlip with the pliers.
Next it's time to transplant the rubber bung plug ring from the bottom of the old tank to the new tank.
You can see that here.
Next, replace the new tank into position, putting the bolts at the ends through the holes in the ends of the tank.
Gently push the bottom extension of the old tank (with the bung plug ring around it) into the hole in the inside fender wall.
Use even but firm and increasing pressure. This should push the rubber plug ring into the hole where it's molded lip
will retain it and seal the hole.
Then, re-install the two 10mm nuts that you removed earlier.
Re-install all hoses and tighten the clamps
Re-install the electrical connection for the coolant level sensor.
Lastly, put the coolant that you siphoned out of the coolant tank, back into the tank.
I also added a bit of pre-mixed coolant I keep on hand to the tank, to bring it up to the proper level.
This replaces the small amount of coolant that leaked out when I removed the lower hose (I had rags handy to absorb most of it).
Start the car and get the cooling system under pressure to ensure that the hoses you replaced are indeed properly clamped into place and not leaking coolant.
That's it .. you're done. Enjoy your new white, underhood coolant tank !!