2003 E320 Sedan. Posted about my son's car a number of times. Ran into something that has finally stumped me completely. Short story, had to replace the coolant reservoir - broken nipple a while back, so we did that, refilled with the G40, pulled the vacuum - finished filling, and it was good to go. Did not do a full drain so did not drain the radiator nor crankcase - I did not have enough G40 to do that.

So flash forward, son is back for an extended visit so I finally have extended access to the car to take care of all that pending stuff. Have plenty of G40 on hand, so started this last night - figured it would be super easy. HA
Draining the radiator is simple. Re-read the WIS, looked at the EPC and realized I should have paid a lot more attention to it first. Three issues:

• EPC specifically calls out 2 of the 1129900901 drain screws (and two crush washers). These have a 6 mil hex head to remove. Two? Where the heck is the 2nd?
• So I go looking for the first one since even thou I see it in the EPC and the WIS just says to remove it and drain... I can't find it. Oh finally pulled out the inspection camera and I finally find it - driver side, above and just before the motor mount under the exhaust manifold. Now that I know exactly where it is - I look around from both the top and bottom and now I can see it. Very hard to see from the top but you can get to it. From the bottom, its behind the steering gear and steering wheel shaft - I give up trying to get to it from the bottom, No way I can get in there. From the top I can setup a 6mil hex head sock on a swivel and get to it - if your willing to let that exhaust manifold shield tear your hand up. But I can't loosen it.. Now its only a 6 mil hex head - I know that these type of soft screws don't like much torque - its spec is 11NM, and the last thing I want to do is break it off. By some miracle I am able to contort myself and my hands so I can get a small torque wrench on it. With the wrench set to 25NM - the absolute limit I want to apply to this - no way - not moving at all.
• I go back to the EPC and notice that crush washer 1129970144 is marked as no longer available. I go back and sure enough by getting that Depstech camera right on the screw - there is no crush washer. Ok. I get it - last time someone did this - way before we owned it - they could not get a crush washer or just did not have one so they torqued the crap out of it to stop it from leaking.

I have given up trying to loosen it. Its on way too tight and the crush washers are no longer available. Yes - I see some on EBay.
Where the heck is that 2nd drain plug? No mention of it in the WIS but the EPC has it...

So we will just fill knowing that about 1.5L is still the old stuff (from the radiator we drained about 6.5L of the 8L capacity).

Has anyone has any success recently with this drain screw? Has anyone found the 2nd one? If you have loosen it - what did you use for a replacement crush washer since its no longer available from MB?

 

I found the 2nd one. Here is how to find both: Find the top of the motor mount bolt - not the motor mount bracket, but the top single bolt that attaches the motor mount to the engine bracket. Now go directly to the crankcase. The drivers side crankcase coolant drain bolt is about 1-2cm in front of that point. The passengers side one is about 1-2cm back from that point on the passenger side. Both need a 6MM hex male socket to loosen. Visually - using the inspection camera - I can see on our car the passenger side one is not screwed in nearly as much as the drivers side. With better access I am confident I could remove the passenger side. Note that this location is not what the WIS shows - the WIS only shows what it looks like in the W202. The crush washer - I 'm not sure exactly where it goes, does it go inside the hole? Or outside?. I don't see any crush washers on our car but with one side so much more screwed in - I'm thinking they are inside and you would use a pick to remove them. Since the torque is only 11NM on them, the washers may be reusable since the WIS does not tell you to remove the screw - only to loosen it.

On the passenger side, if you remove the alternator it would be much easier to access and you will be able to get a torque wrench on it - just like doing that motor mount. Or you could remove the exhaust and remove the motor mount but I think access would be better coming through the top with the alternator and motor mount removed. Thus do the coolant replacement at the same time you do a motor mount.

For both - the easiest way would be when you are replacing the motor mounts, once a mount is removed - access the drain screws would be so much easier. So my recommendation is - wait to do this when you are replacing the motor mounts. With the old mounts removed you can see and access the screws from the top or bottom.

Side note - my daughters W210 (2001 E430) needs coolant replacement also, so I'll do a separate writeup on what I find there in those forums