Neptune36

New to me 2016 E550 conv. After turning the engine off there is a carry on what sounds like an electric motor that runs for 10-15 seconds then it shuts off and winds down. Also it starts up when when unlocking doors. Just curious what this is. Maybe something to do with the fuel pump?

Chevota

Mine does it too. Not sure what it is but it's normal.
Also, as of a couple weeks ago, I did the intercooler pump mod which causes it to kick On the same way and run for a bit after shutting down. So someone might have done that as well. If it matters I can tell you how to check if the mod was done. If it's not done I can tell you how to do it

Neptune36

Is the way to tell to see if there is a short wire from a relay near the coolant reservoir to ground? I saw that on a U Tube. I don't what what that buys me in performance however.

Chevota

I know I posted a reply to this a day or two ago. It's happened to me many times here on mbworld. Not sure wth.
Anyway, yes, you can see the wire in most cases. Just find the relay and it's likely right there attached with a big ugly connector. You can do it elsewhere where you can't see it but it's much harder so I bet very few people do it. Or you can just unplug the relay and see if the noise stops. The housing should have a couple snap connectors on the sides, mine were brittle and I broke one fyi. Then slide the guts out and there's a common relay which is a black cube ~1" square. Just pull it out.

I did the mod and yes I think it's worth it. Mine doesn't have a brown wire like you see online, it's yellow and I'd imagine yours is too. It's the relay coil ground just the same but I'd verify regardless of wire color because who knows what a wrong connection might do. I'm sure nothing more than a blown fuse but with these cars who knows.
I also did it a bit different so it doesn't look as ugly. I hate those clamp-on wire taps and I've never used one, ever. The mod does trigger a code because the ecu can see what you did, but not a check eng light. So if you don't look for codes you'd never know.
The pump kicks on when you touch the door handle to unlock it, and like the other motor, and it'll run for maybe 30sec and turn off if you don't turn the ign on. Then after shutdown it also runs for ~30sec. It draws ~4amps so I may make a circuit so it only runs when the eng is on, maybe add a delay too.
The Ign On draws something like 20A if I remember correctly, no clue why because that's a lot! This is why they say to connect your batt to a charger when you're messing around, like diagnostics or programming. So now it's ~24A.

The point of it all: The intercooler pump normally only kicks on when the intake temps are already too high, I think 120F? Then it takes a bit for the much hotter water cooking in the lines to flush thru the cooler and actually start cooling. In my experience it' now too late, I'm done flooring it. It still works to some degree when off because the intercooler is more or less cool from the air flowing thru it, so when you floor it you have its static mass which seems to be good for several seconds of cooling. That is assuming the air was cool to begin with because the intake tubing can get really frikkin hot when airflow is low, like traffic, and worse when hot out. This in turn make the intercooler really hot. With the pump on all the time it lowers the avg temp of the intercooler and lines from the start and is slower to heat up under load since the heated water is being carried away.
The system is not good enough to cool the air under constant full load, so it'll still heat up, just takes longer to happen. A more powerful pump is what most people do but it's not a fix, just an improvement, and my guess is a very small one. Also, the heat exchanger, like the radiator, is less effective as ambient air temps rise but the effect is much more pronounced with the intercooler than the rad.
To make matters worse, the AC condenser is in front of the intercooler for reasons I can't explain. Apparently they decided comfort was more important but I wonder if the AC would really suffer much being second in line? So when it's hot out and summer sun has the air over the asphalt sky high, and the AC is dumping max heat, the intercooler apparently becomes an interheater. Even if still cooler than the air temp, it's still too hot to work right.
Not much you do about that but you can turn the AC off if it's anything above warm out and you plan on flooring it.

As for performance, yes, it matters. If I floor it in the early afternoon this time of year and I'm down a huge amt of power compared to morning, heat is why. I can verify it because I record data like my temps and power output and lots of other things so I can play it back later and see it. This is why I know more details about all the related temps and what they do to the eng.
I have my ecu set to run the eng cooler, especially at a stop, and ignore heat related power loss that is controlled by the ecu. I can't tune out the physical loss caused by air temps, which causes loss in more ways than one.
So the pump mod does help, and I'd say it's well worth it. The cooler it is out the bigger the bennie, the hotter the amb is the less effective it is until that point I mentioned it seems to become an interheater, but that would happen regardless of the pump mod.

Drawbacks: It's harder on the pump and battery. The pumps, according to what owners say, start failing at ~5 years or so. Not sure why since unmodified they apparently rarely come on, but it seems life isn't shortened much by running 100% of the time and users say it's well worth it either way. A new pump cost me $113 last year and pretty easy to swap. I swapped it not because the orig failed, but it was 5yrs old and more importantly I was worried it was the old style which is less effective. The new stye, aka "010", is in fact what I had. I originally bought a Johnson CM30 pump which I read was better than the 010 pump, but data I found after the fact shows that isn't the case at all. Free flow and restricted flow in our system can be drastically different and the 010 is designed to flow under restriction. So it seems the oem Bosch 0392022010 aka "010 pump" is the way to go, plus no hassle installing it. The next step up pump up is 2-3x the price and barely flows more, plus the hassle of making it fit. I suppose the real fix for more flow would be a second 010 at the half way mark in the plumbing.

So after all this learning and what not I have a list of cooling mods I want to do, one which is to add water misters just behind the grill to spray the intercooler. As a bonus it'll cool the eng and intake pipes to some degree. Set to actuate at any sign of boost, plus a manual override button in preparation for a stoplight blast. Easy mod if you wanted to do something...
I also want to add Meth injection, which, as one member here said; "it changed my life". I bought a water/meth kit last month but install is rather complicated on this eng so I have yet to do it, plus I need more parts and injectors because of the mentioned complications.
One of the other reasons for heat related power loss is turbo efficiency, so even if your eng sees lower air temps thanks to an intercooler and water/meth kit, the turbos do not and will make less boost. The fix for that, excluding bigger/better turbo$, is meth inj just after the air filters so the turbos get it too. Meth inj is typically a 50/50 water/meth mix but water and ultra high speed impellers don't get along. Not sure how long it takes to cause damage, and it may be a non-issue considering the time it's used, but you can make the inj more effective while causing much less to no damage by injecting 100% meth. It's also substantially easier to install than the normal setup but I lose out on the main advantage of the meth kit. So really it won't do what I wanted for the engine, it's just to make the turbos work better. So really I'd need to have that plus the more complicated water/meth inj. Then the grill water inj makes three three systems. Ugg....
Rather than three pumps I'm considering using an air tank to provide the pressure, which is better anyway because higher pressure means better spray atomization, distribution and cooling. Engines are such a pita it makes me want to buy a Tesla.... Hmmm, I wonder what it would cost to make my car all electric?

Neptune36

Chevota, that was way beyond an undergraduate study of MB intercooler knowledge. I'm still studying it. Thanks. I'll check the relay as the first step. Cheers

Chevota

Too much info is better than too little, imo
Not just for you btw, anyone who searches the mod will hopefully get all their questions answered. Plus a pix of our wiring: