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I went ahead and pulled the radiator coolant fan in my 2003 ML500 last night. Running out of daylight I waited until this morning to put the new fan in. Got the car reassembled. But, running into some issues.
I put about 2.75 gallons of coolant into the radiator little by little, to allow for escaping air to come out of the system. It's finally to a point where it's not burbling any more. I started the vehicle with heater and fan turned to pull in the cab.
Should the fan be moving at all when I start the engine? It's as still as a corpse right now. Additionally, I noticed the low coolant light is on, which doesn't surprise me. I expected that once I started cranking the motor that more air would escape from the system. At least seems to me I remember that happening last time. The temperature gauge on the dashboard started creeping up. But, never got about the first tic mark before I decided to potentially stop for the afternoon.
Right now, I buttoned the system up because I've got other things to do this afternoon. But, it really puts a cramp in things not having a vehicle this weekend.
Does all of this sound normal so far, or did I muck something up when I changed the fan out?
At this point, I'm guessing the replacement nut I scrounged from my brother-in-law wasn't tamping down one of the electrical wires on top of the fan because it was too big to use a socket on. I went over to the local hardware store to try and get a replacement today. But, they're closed on Sunday. Then I went to the O'Reilly, which is down the street. No luck there either.
Do you have any idea what size flange nut I need for the larger of the two posts on top of the fan? Somehow the original escaped the plastic bin I had it in, and it's nowhere to be seen.
Attached is a photo of what I"m talking about. The smaller one is a 10mm.
electrical posts on the coolant fan in a Mercedes ML500.
Originally Posted by Maj. Dundee
The cooling fan will only come on when the coolant reaches a certain degree and increase speed when the temp increases.
If the A/C is being used it will come on almost immediately.
When the eng. is cold, add 50/50 coolant to the mark.
I went to a local hardware store and they had only one M8 flange nut so went ahead and got one. The flange looks to be a tad bit too large so I'm going to contact another place to see if they have a anything different.
But, here's the kicker. When trying to put the new nut on I fumbled it and it slipped into that slot in the bottom of the photo, which gives access to a section behind the fan motor, and didn't fall out onto the ground, or into the shroud behind the fan blades
IIs there anything sitting behind the fan motor that it could do damage to by sitting in there If I were to drive around? I don't see any way of removing the fan motor without removing the whole fan assembly again; which I don't relish doing.
Someone on another Benz forum pointed out that the small one wasn't an M10. But, an M6. I ended up getting an M8 from a local shop for the larger post. Had to grind the flange down a bit though as it didn't easily go on the post of the new fan due to the plastic fin separating the two posts.
Also, something odd. Even though the VDO fan was listed as a direct fit, the existing plug that connects from my vehicle was not quite the same as the socket on the new fan. There was a small piece of plastic in the plug which didn't allow for a circuit to be made. Once that plastic was whittled out of the plug, it fit better, and created the circuit.
Haven't had a chance to take it for a protracted road test. But, will in a few minutes.
Thanks everyone for their help with this since I made the original post!
Originally Posted by Maj. Dundee
So find another hardware store and try an M12 nut.
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when should coolant fan start spinning?
