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I have an 2007 Quattroporte that overheats when its idling, but is fine when driving down the road. The fans are pushing air and I have checked the relays, bench tested them (successfully) then made sure they actually kick on when in the vehicle. 1st and 2nd stage fan relays both "energize" at least. So I am thinking I can rule out the two water temp sensors, fuses and relays.

I am confident the fans are getting power and are both blowing air. I am not however certain they are running "full speed". I do not really know how to test for that. I assume the 2nd stage fan relay is supposed to "kick it up a notch" on speed, but again, not really certain on that.

Hope someone is familiar with how this fan system works and maybe, is it possible the fan itself can just be failing / running slow? Wasnt sure if fans could even slow down to that extent where they would just go slow. Figured it would be all or nothing.

Also, if anyone has any insight as to where the resistor would be that I had seen mentioned by others, it would be a huge help. I cannot locate one (them?). Thanks!
 

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The fans have 2 speeds...You have the 2 relays in the engine compartment ...Google how to jump 4 prong relay..Jump both relays.Check that both fans run and have 2 speeds...You could also have a faulty thermostat...Jason
 

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So exactly how hot is it getting at idle?
It will climb, eventually into the red. Had that happen once and shut it off in a parking lot for the night. That was the first time I noticed it. It will, when warming up, heat to the 195 spot and stay stable for about 5 minutes at idle. Then it will eventually start to creep up.
 

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When parked...engine idling....turn on the AC....do the fans kick on? Is there any debris blocking air flow through the radiator?
Yes the fans do come on with the AC going. Both do spin and pull the hot air into the engine bay. There is no visible debris or anything out of the ordinary.
 

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I've replaced the thermostat and both coolant sensors in under 2 hrs. I didn't have heating issues but a relevant check light. Parts are easily sourced & priced low. Give it a go, here's a pic of mine.
I ordered a thermostat and gasket earlier today. I had purchased the sensors a while back and have those on hand but will wait to do them with the thermostat. Looks like you got the whole housing as well. I wasn't sure if you could just pop out the thermostat and replace it or if the whole housing was the thermostat? If that makes sense.
 

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It will climb, eventually into the red. Had that happen once and shut it off in a parking lot for the night. That was the first time I noticed it. It will, when warming up, heat to the 195 spot and stay stable for about 5 minutes at idle. Then it will eventually start to creep up.

Don't let it do that again...Most the the engines we replace in all makes is a overheated engine...Most shops will not fix overheated engines anymore for liability reasons...I would change the thermostat if the fans work on low and high speed...Thermostats can stick and malfunction ....Jason
 

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The fans have 2 speeds...You have the 2 relays in the engine compartment ...Google how to jump 4 prong relay..Jump both relays.Check that both fans run and have 2 speeds...You could also have a faulty thermostat...Jason
Ill try that and see. For what it is worth, I took an multi-meter to them. They do kick over and have 12v running through both eventually in the process. Though I didnt notice any audible increase in the sound of the fan.

I have tested it without AC running, and the fan eventually comes on, and also with AC from the start. Either way the fan is running, but not sure if its kicking into 2nd gear, so to speak. I had seen people mention a resistor(s?) on the fan(s). I am not able to eyeball one. Some other thread mentioned it being where the fan power connectors come into the fan housing, but I dont see anything there but the connectors. Also wouldn't really know what to do with the resistor if I got a hold of it. I suppose test for continuity, but past that I am not really sure. I also cant locate any part for a resistor on the fan. Maybe the fan unit is just a whole package and cannot get it in parts?
 

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Jump the fan relays like I told you one at a time...You'll hear both low and high speed...On low speed you are running current through the resistor..check if you have 2 speeds from both fans..Jason
 

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Jump the fan relays like I told you one at a time...You'll hear both low and high speed...On low speed you are running current through the resistor..check if you have 2 speeds from both fans..Jason
Curious. Maybe I am just tired, but arent the relays supposed to have a constant 12v + coming in on one pin, even if the car is off? Because I can jump the stage 1 relay, when the car is off and the fan spins up. If I try the same on stage 2 relay, nothing. It also doesn't have any voltage going to it on any pin. Just want to clarify that before I keep fiddling with it, just in case my assumption is incorrect to start with. Mainly curious if I need to jump both relays at the same time, or when stage 2 comes in, stage 1 shuts off?
 

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Curious. Maybe I am just tired, but arent the relays supposed to have a constant 12v + coming in on one pin, even if the car is off? Because I can jump the stage 1 relay, when the car is off and the fan spins up. If I try the same on stage 2 relay, nothing. It also doesn't have any voltage going to it on any pin. Just want to clarify that before I keep fiddling with it, just in case my assumption is incorrect to start with. Mainly curious if I need to jump both relays at the same time, or when stage 2 comes in, stage 1 shuts off?
Ok the "MF4 Maxi 50A Red 2nd speed fans" fuse is blown. Wasn't earlier. Must have been due to my earlier efforts. Ill replace it and try again on that stage 2 fan.
 

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Once the fuse is replaced, try to spin the fans freely with the engine off. When the fan bushings get old, they start to drag and that heats up the entire system and blows fuses and melt wires, etc., while making the car run hot. The fans (L&R) should both spin freely without any friction noises. The passenger-side fan typically fails first. All the ones I've replaced had a bad passenger-side fan.
 

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Discussion Starter #16
One at a time...join 30 to 87 and don't use a thin jumper...Jason
Replaced the fuse. I am able to jump the relay and the stage 2 kicks in. Audibly different, much more air flow. I ran the car, with AC on. Fan was running. Got to 195, then the stage 2 kicked in. Ran for about 3- 5 minutes like that then started to creep up in temp. I am assuming 195 is the stable range. Should I let it run higher and see? I just cut it off once it starts creeping up past 195. But 195 seems to be the "normal" operating temp of the vehicle.
 

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The gauge really not go past center at all...If it starts creeping up then most it will continue...I would replace the thermostat at this point...Jason
 

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I've replaced the thermostat and both coolant sensors in under 2 hrs. I didn't have heating issues but a relevant check light. Parts are easily sourced & priced low. Give it a go, here's a pic of mine.
I ordered a thermostat and gasket earlier today. I had purchased the sensors a while back and have those on hand but will wait to do them with the thermostat. Looks like you got the whole housing as well. I wasn't sure if you could just pop out the thermostat and replace it or if the whole housing was the thermostat? If that makes sense.
Its the entire housing that easily pops in and out. Same with the temp sensors, however make sure you also replace the o-rings.
 

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After replacing the thermostat and the issue persists: Do you hear any liquid running or bubbling once you let the car cool down? If so, there could be air trapped in the system.
 

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After replacing the thermostat and the issue persists: Do you hear any liquid running or bubbling once you let the car cool down? If so, there could be air trapped in the system.
This might sound silly, but have you checked your engine oil level? Second, have you checked the water pump and are you able to see coolant cycle through the reservoir.
 
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