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It does sound silly...I know it sounds crazy, but there is an actual method of diagnosing something like this. You start with the basic things and confirm them and move on in steps...Waterpumps don't pump and then decide to not pump..At least belt driven ones...Jason
 

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It does sound silly...I know it sounds crazy, but there is an actual method of diagnosing something like this. You start with the basic things and confirm them and move on in steps...Waterpumps don't pump and then decide to not pump..At least belt driven ones...Jason
Low and or dirty oil would obviously increase friction between metals. Not saying the op has not checked the engine oil but wouldn't hurt to triple check. A clogged or dirty radiator could starve the waterpump and cause shaft and bearing issues leading to inadequate flow. Do coolant temp sensors kick the fans & water pump on simultaneously?

These are valid theories to ask or question.
 
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Honestly, those are great theories...Unfortunately, none of them make any sense at all...Dirty oil increases friction so a car overheats? Really? sorry...Jason
 

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In my limited experience, water pumps that stop pumping, such as plastic impeller types that disintegrate or spin on the shaft, go temperature critical very fast. This sounds more like a flow restriction in the thermostat, radiator, pinched or collapsed hose. Or the radiators air flow is blocked.
Thermostat seems like a good first check as they are a maintenance item. If you got to the point of wanting to flush the radiator, it would be nice to be able to do it in the car. Removing it seems to be a major operation. Just from looking at the repair manual.
 

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I have had overheating issues with other cars and there are two general rules of thumb. If the car overheats while idling but not at highway speeds, it may be fan related. If it overheats at highway speeds, it may be blocked radiator or pump issues.

The other item would be to check is if the system is able to hold pressure. Some cars use plastic radiator fluid expansion tanks and they can sometimes get small fatigue cracks. The cracks may not leak, but they do not allow the cooling system to maintain the pressure it needs. Or is your radiator showing signs of leaks? Best of luck as it sounds like you are on the right track.

Jeff
Dallas, Tx
 

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What is the history of this behavior in this car? Did it just start doing it out of the blue one fine day? Or did you buy it recently and it came to you with this issue?

I don't see how a thermostat could ever cause this problem, since if the thermostat was faulty it would not matter if the car was idling or on the freeway, it would still overheat from being stuck closed. The problem must be caused by inefficient heat transfer in the radiator. Possible reasons are:

(i) Radiator is mucked up inside because oil got into it at some point or it's scaled up from lack of maintenance and routine flushing.

(ii) Airflow through the engine bay is obstructed; check both in and outflow vents (the three decorative vents on the fender look neat but they also let tons of air out and are pretty important).

(iii) There is not enough coolant in the system.

(iv) The coolant mixture has too much antifreeze and not enough water. Pure antifreeze is a pretty bad coolant in comparison to water.
 

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This type of overheating behavior is often the first sign of a failed oil cooler, assuming that the M139 oil cooler can fail in such a way that lets oil into the coolant.
 

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Discussion Starter #29
Update After Install: the issue is now resolved. My uneducated guess would be one or both the temp sensors were bad. Or maybe not having a thermostat at all messes things up, can’t be good. Either way, could also tell there were air pockets in the engine. After bleeding both sides properly, and topping thing off, everything is stable now. Let it idle for about and hour. Drove it around for about 20 minutes and sat for about 10 minutes. Doesn’t go past 195 any longer. Can see the temp on OBDII is correct with the gauge, and the fans come on and off at the correct temps. Thanks to everyone for the help. Hope this can help point someone in the right direction in the future.
 
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If you look at the back of the thermostat there is that flat disc...That disc covers up that opening in the housing when the thermostat opens.. That opening is the bypass that just circulates coolant around the block when it is closed..So yes, you don't get full flow to radiator...Jason
 

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Why's that Jason? Is the coolant not efficiently routed to the radiator? Just curious!

Cheers

C
From the cars I've seen with a removed thermostat, it's actually that the coolant is moving too quickly all the way through the system. It doesn't have time to absorb heat from the hot parts and doesn't have time to dissipate heat in the radiator. So, it takes forever for the coolant to heat up in the first place, and it can't get rid of heat once it does. The hot bits in the engine still get hot, and with no way to transfer the heat.
 

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Really? I cant believe in this day in age someone would think that its ok to remove a thermostat on any modern engine, especially a Maserati/Ferrari engine. Probably some idiot at a used car lot.
 

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This is good lesson in the importance of knowing where your Maserati has been. It won't guarantee zero problems... mine has been fairly expensive.... but at least the problems are not of this variety where weird stuff has been done to the car that gets people scratching their heads.
 

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Glad to hear it is solved. Removing the thermostat is a quick fix if you have no replacement and yours is completely stuck, but it is NOT permanent. It may get you moving again but it Needs to be replaced ASAP.
 

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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!
I have the same car and it overheats on the highway, while on idling it stays cool, what could be the problem ? Is it the thermostat??
 

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If it stays cool under any circumstance, the thermostat is likely good. Overheating on the highway is unusual because the high airflow should keep the radiator cool, but there is high load on the engine. You need a shop to analyze the radiator, there could be a water pump issue, coolant flow issue, or a radiator issue. My internet guess today is a failing water pump, but you can take that for what it is worth.
 
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