Overheating on fwy with AC on during hot weather

[0-60motorsports]

When did you replace the temp sensor under the manifold? I had a genuine BMW one go bad after 20k miles and 5 years. No codes, but the temp gauge would randomly fall to the first dot or below.

I believe the only other item left in the coolant circuit is the heater core.

Replaced with a brand new one last year. And the sensor in the lower radiator hose too.

The heater core you mean the one under the dash? Brand new evaporator and heater core installed last year too. No difference whatsoever.

[Pklauser]

Number one is https://www.ecstuning.com/b-genuine-...p/51717893229/. Not the metal radiator support.

Yea see, what on earth is that? I'll have to go out and look at my car, but that piece is not looking familiar to me even after having had the whole front clip off.

[0-60motorsports]

Yea see, what on earth is that? I'll have to go out and look at my car, but that piece is not looking familiar to me even after having had the whole front clip off.

All I can tell you is I have my car and another M3 next to each other in the shop and mines missing lol

Also an update on the overheating, seems to be an electrical power issue. When the car is overheating at 3/4 water temps and we connect another running car to my M3 to boost electrical output temp drops in 2 mins! I'm thinking alternator is not working at a 100% under load etc. so I'm going to order an X5 140amp alternator or a 150 Amp Z4M alternator.

[AWE46M3]

All I can tell you is I have my car and another M3 next to each other in the shop and mines missing lol

Also an update on the overheating, seems to be an electrical power issue. When the car is overheating at 3/4 water temps and we connect another running car to my M3 to boost electrical output temp drops in 2 mins! I'm thinking alternator is not working at a 100% under load etc. so I'm going to order an X5 140amp alternator or a 150 Amp Z4M alternator.

My Alternator (specifically my voltage regulator) were going out and I noticed my water temps starting to move off of the center line! This could be it

[0-60motorsports]

My Alternator (specifically my voltage regulator) were going out and I noticed my water temps starting to move off of the center line! This could be it

I will keep everyone updated as soon as fcp fix an issue with shipping system so I can order the alternator

[Thrifty S50]

Has any one here opened their owners manual? Im just going to leave these here...



Im not saying that its isnt a good thing to be concerned about "rising" oil/water temps, but rising indication on the gauges are not necessarily abnormal. Some cars gauges creep up, some do not. I do wonder if the gauges had this characteristic when the cars were new off the lot, however I would wonder why BMW would include these provisions within the manual if they didnt.

[0-60motorsports]

Has any one here opened their owners manual? Im just going to leave these here...



Im not saying that its isnt a good thing to be concerned about "rising" oil/water temps, but rising indication on the gauges are not necessarily abnormal. Some cars gauges creep up, some do not. I do wonder if the gauges had this characteristic when the cars were new off the lot, however I would wonder why BMW would include these provisions within the manual if they didnt.

That was funny 🤣

[Thrifty S50]

I know I know, telling you to open your manual is as about as useful as telling you to turning it off and then back on again, but ive seen this sort of thread posted literally dozens of times, only for everyone to suggest to each other to replace every little thing in the car, only to have no improvable result afterwards. These cars do run hot, especially in hot weather, and nearly always when driven hard. I dont mind being the guy to tell you that perhaps what youre experiencing in 100+ degree weather might not be abnormal, just to save you from the wild-goose chase. But in the end you are just caring for your M, so I can respect that. Hope you resolve the issue, will be following.

[0-60motorsports]

I know I know, telling you to open your manual is as about as useful as telling you to turning it off and then back on again, but ive seen this sort of thread posted literally dozens of times, only for everyone to suggest to each other to replace every little thing in the car, only to have no improvable result afterwards. These cars do run hot, especially in hot weather, and nearly always when driven hard. I dont mind being the guy to tell you that perhaps what youre experiencing in 100+ degree weather might not be abnormal, just to save you from the wild-goose chase. But in the end you are just caring for your M, so I can respect that. Hope you resolve the issue, will be following.

Thanks I got it lol. And when I'm telling you it's not normal I don't understand why people aren't believing me. You want me to line up All the E46 M3s in a hot day and show you how stable the water temps are going to be in 125f temps and mine are going to jump to 98+ in under 5 mins of standing still amongst them? It's probably not possible to gather them all but I hope you get my point.

Any way hopefully we will resolve it this time. I'm done after four to five years of this issue. Time to show my car the love that I show my customers cars 👍🏼

[0-60motorsports]

Installed the 140amp X5 alternator and problem solved, before it used to go up to 98/99c and very quick. Nope it goes up to 94c and drops fast after.

Note the outside temp is an indicated 50c/122f! The angle of the pic is deceiving but the water temp gauge was right in the center. Ali this was done after a two hour test drive, mixed highway and traffic rush hour.


Basically the alternator was the culprit and not supplying ample current to the vehicle in order for it give full power and performance to the aux fan while AC was running (blower fan).


Sent from my iPhone using Tapatalk

[tlow98]

Well, didn’t see that one coming, but very happy you got it corrected.

[sapote]

Op, measures that batt voltage when the radiator fan running to cool down the hot coolant, AC on. Much lower than 14v will cause slow fan running.

[0-60motorsports]

Op, measures that batt voltage when the radiator fan running to cool down the hot coolant, AC on. Much lower than 14v will cause slow fan running.

That's what we saw but I really discovered it through my battery monitoring app and Bluetooth device.

[elrichmeister]

Nice work OP. I too have my water temp go high on hot days 95F+ with the AC on while on the highway. I will monitor my battery voltage. On my car seems like the previous owner has replaced it with remanufactured unit in the past.

[sapote]

That's what we saw but I really discovered it through my battery monitoring app and Bluetooth device.

Saw what? What was the measured battery voltage (whatever apps or blue tooth devices) with the stock alternator?