[jmnew911]

Anyone heard of this? I have searched it extensively with little luck. Ever since I have owned my 2007 328i, approximately a year and a half, I have had this issue. When it is below 35 degrees or so outside my heat is insufficient. I decided to change my thermostat and that did not help. I did find a post where someone had the same problem and a new radiator fixed the issue. So, I then put on a new radiator. Did not resolve the problem. I did follow all the proper procedures for removing air from the cooling system. I did this work over a month ago.
So, here is what happens to the operating temp of the car When I drive with the hidden menu on that shows the operating temp. The car seems to take longer than is should to get up to a decent operating temperature. But, if I leave the heat off and do get the car up to say 75 degrees celsius or more, when I turn on the heat the operating temp starts dropping and drops a total of 15 to 20 degrees celsius. So, it is no wonder I have no heat when it cold outside.
My water pump is only two years old.
I am thinking I must have a heater core problem or my water pump does not pump strong enough. About a year ago I ran water through my heater core to make sure it wasn’t clogged and it wasn’t. I also have never ad any fluid leaking in the floor of my car which I think normally happens when the heater core goes bad.
Any ideas?

[rt7085]

Could the coolant temp sensor be bad? The thermostat works on its own, e.g. it is not controlled. However, I think the thermal control in your does take input from the sensor. I am not sure if this makes sense given that low reading would mean the core would compensate for that in opposite direction. However, these temp sensors have been know to go bad sometimes. If you coolant temperature would be too low you would probably get all sorts of codes as well and a CEL as it is emissions related; you might want to read the DTC codes to be sure.

[jmnew911]

Originally Posted by rt7085

Could the coolant temp sensor be bad? The thermostat works on its own, e.g. it is not controlled. However, I think the thermal control in your does take input from the sensor. I am not sure if this makes sense given that low reading would mean the core would compensate for that in opposite direction. However, these temp sensors have been know to go bad sometimes. If you coolant temperature would be too low you would probably get all sorts of codes as well and a CEL as it is emissions related; you might want to read the DTC codes to be sure.

I changed the coolant temp sensor on the top up near the oil filter. Not sure if there is another one on my car. Unfortunately I just have a cheap generic code reader. It shows no codes. I have never had a CEL for anything related to this.

[PhaseP]

The hidden menu displays the temperature sensor output near the oil filter housing.

If you have an SULEV 328 (N51) engine you would have another temperature sensor which measures return line of the radiator, part number 19 here:

https://www.realoem.com/bmw/enUS/sho...04#13621433077

'06 N52's also have this sensor. But that is used for monitoring the thermostat.

You can check if the sensor at the top near oil filter housing by using an IR temperature gun. They are cheap these days. Get the IR gun very close to the big coolant hose that comes out there and goes to the radiator and read the temperature. Compare this to what is being reported with the hidden menu. They should be reporting close values. IR gun reading probably will be a few degrees lower. I used to have a pesky thermostat code, had done this on my car as part of troubleshooting.

For fully warmed up engine 75 degrees is low.

One interesting thing you are mentioning is that the engine coolant temperature goes down when you turn on the heat. It means heat is being taken out of the engine and is going somewhere, just not inside the car cabin. Is your cabin AC fan working good? There could also be something wrong with the duct flaps at the air vents, like being stuck closed, so heat can't get from the core to the cabin.

[jmnew911]

Originally Posted by PhaseP

The hidden menu displays the temperature sensor output near the oil filter housing.

If you have an SULEV 328 (N51) engine you would have another temperature sensor which measures return line of the radiator, part number 19 here:

https://www.realoem.com/bmw/enUS/sho...04#13621433077

'06 N52's also have this sensor. But that is used for monitoring the thermostat.

You can check if the sensor at the top near oil filter housing by using an IR temperature gun. They are cheap these days. Get the IR gun very close to the big coolant hose that comes out there and goes to the radiator and read the temperature. Compare this to what is being reported with the hidden menu. They should be reporting close values. IR gun reading probably will be a few degrees lower. I used to have a pesky thermostat code, had done this on my car as part of troubleshooting.

For fully warmed up engine 75 degrees is low.

One interesting thing you are mentioning is that the engine coolant temperature goes down when you turn on the heat. It means heat is being taken out of the engine and is going somewhere, just not inside the car cabin. Is your cabin AC fan working good? There could also be something wrong with the duct flaps at the air vents, like being stuck closed, so heat can't get from the core to the cabin.

Is it normal then for the operating temperature to drop when the heat is run?

[gbalthrop]

Originally Posted by jmnew911

Is it normal then for the operating temperature to drop when the heat is run?

Yes, the heater core is just like a small radiator -- a heat exchanger -- where the air going through the coil is warmed, taking heat from the coolant passing through the core tubes. Check your Coolant Reservoir level, and top-up if necessary. Have you run the "Bleed Procedure" with battery charger attached? Is air temp from the vents with heat ON the same on BOTH Driver & Passenger side? If NOT, that would indicate a "Mixed Air Flap" or Blend Flap issue.

Check your hood labels to see if you have "SULEV" N51 or ULEV N52 engine, and visually inspect the lower radiator hose for a "Radiator Outlet Temp Sensor" (ROTS). As stated, IF your car has an ROTS, that is the primary input for Thermostat Control. Let us know if you have an ROTS (SULEV) and we can suggest some tests, including with ohmmeter, as the Hidden Menu 7.00 is displaying ECTS signal to DME & NOT ROTS. If you had INPA or ISTA, you could read BOTH sensor signals in Real Time, but basic P-code reader ONLY reads ECTS signal.

Also, check the fuse that supplies power to the Thermostat Control System, F02 if you have EARLY 2007 model, built BEFORE 3/1/2007, and F78 for > 3/1/2007 build date per these TIS circuit diagrams (F02 is in the E-box on Early 2007 model):
Build Date BEFORE 3/1/2007:
https://www.newtis.info/tisv2/a/en/e...mostat/i7SHdY5

Build Date AFTER 3/1/2007:
https://www.newtis.info/tisv2/a/en/e...mostat/lqgyKuz

George

[jmnew911]

Originally Posted by gbalthrop

Yes, the heater core is just like a small radiator -- a heat exchanger -- where the air going through the coil is warmed, taking heat from the coolant passing through the core tubes. Check your Coolant Reservoir level, and top-up if necessary. Have you run the "Bleed Procedure" with battery charger attached? Is air temp from the vents with heat ON the same on BOTH Driver & Passenger side? If NOT, that would indicate a "Mixed Air Flap" or Blend Flap issue.

Check your hood labels to see if you have "SULEV" N51 or ULEV N52 engine, and visually inspect the lower radiator hose for a "Radiator Outlet Temp Sensor" (ROTS). As stated, IF your car has an ROTS, that is the primary input for Thermostat Control. Let us know if you have an ROTS (SULEV) and we can suggest some tests, including with ohmmeter, as the Hidden Menu 7.00 is displaying ECTS signal to DME & NOT ROTS. If you had INPA or ISTA, you could read BOTH sensor signals in Real Time, but basic P-code reader ONLY reads ECTS signal.

Also, check the fuse that supplies power to the Thermostat Control System, F02 if you have EARLY 2007 model, built BEFORE 3/1/2007, and F78 for > 3/1/2007 build date per these TIS circuit diagrams (F02 is in the E-box on Early 2007 model):
Build Date BEFORE 3/1/2007:
https://www.newtis.info/tisv2/a/en/e...mostat/i7SHdY5

Build Date AFTER 3/1/2007:
https://www.newtis.info/tisv2/a/en/e...mostat/lqgyKuz

George

Thank you. I do not have the ROTS. Sounds like a bad venereal disease. Seriously though, I have N52. No lower temp sensor.
I will check the other things you mentioned. I did follow bleed procedure after radiator and thermostat install.
It is difficult for me to tell right now because temps are mid 50s. My operating temp seemed real good today. It took me 20 minutes for it to get up above 70s degrees celsius but after that it stayed in the low 90s and low 80s or high 70s with heat on.
I have not had cold temps here in a couple weeks. It is unseasonably warm. I will probably have to wait until I have another cold morning or cold day to see what the operating temp does.
Oh also checked labels. N52, build 12/06.
I will check the fuse you mentioned. Thank you for the great info.

[gbalthrop]

Originally Posted by jmnew911

Thank you. I do not have the ROTS. [NOT YOU -- your car ] Sounds like a bad venereal disease. [Not unless you have a convertible named "Monica" and you let her run around with her top down] Seriously though, I have N52. No lower temp sensor.
I will check the other things you mentioned. I did follow bleed procedure after radiator and thermostat install...Oh also checked labels. N52, build 12/06.
I will check the fuse you mentioned. [That's F02 in the E-box on right firewall under hood, per "Installation Location" linked below] Thank you for the great info.

The "great info" is available 24/7 in TIS:
https://www.newtis.info/tisv2/a/en/

Here's the TIS "Installation Location for Fuse F02:
https://www.newtis.info/tisv2/a/en/e...2-fuse/SNEe0ZE

If it takes that long to warm up, and temperature drops that much when heater is used, you MUST have something wrong with the Thermostat Activation circuit, or possibly the Coolant Pump running more/faster than it should, or the E-Fan (Radiator Fan) running too fast. INPA can quickly test each of those for proper operation, and monitor Pump & Fan Speed, as well as Coolant Temp per ECTS (NO disease ;-) You DID check proper coolant level in reservoir?

If F02 is OK, I would suggest testing for voltage and proper connection at Connector X6279 at the Thermostat, as shown in this previously-linked TIS circuit for your 12/2006 build 2007 328i:
https://www.newtis.info/tisv2/a/en/e...mostat/i7SHdY5

Please let us know what you find,
George

[jmnew911]

Originally Posted by gbalthrop

The "great info" is available 24/7 in TIS:
https://www.newtis.info/tisv2/a/en/

Here's the TIS "Installation Location for Fuse F02:
https://www.newtis.info/tisv2/a/en/e...2-fuse/SNEe0ZE

If it takes that long to warm up, and temperature drops that much when heater is used, you MUST have something wrong with the Thermostat Activation circuit, or possibly the Coolant Pump running more/faster than it should, or the E-Fan (Radiator Fan) running too fast. INP mi A can quickly test each of those for proper operation, and monitor Pump & Fan Speed, as well as Coolant Temp per ECTS (NO disease ;-) You DID check proper coolant level in reservoir?

If F02 is OK, I would suggest testing for voltage and proper connection at Connector X6279 at the Thermostat, as shown in this previously-linked TIS circuit for your 12/2006 build 2007 328i:
https://www.newtis.info/tisv2/a/en/e...mostat/i7SHdY5

Please let us know what you find,
George

Yes! Great stuff. I certainly need all this. It definitely does not get to operating temp like it should. This morning ambient temp was mid 40s F. Car only got up to upper 70s C without heat on and dropped to mid 50s C with heat. It has been that way since I owned it past year and a half. As I said I just put new thermostat and radiator on it a month ago and did not help. I will be checking the fuse today and then the other stuff if fuse is good.
I do not have diagnostics but have seen all the INPA and the other one (can’t think of name) mentioned a lot. Would you be so kind as to tell me the best source for this software for a laptop and a good source for laptop cord?
Oh, it is not radiator fan. That is not running. And yes did check proper coolant level.

[jmnew911]

Not the fuse. I pulled it tonight and it looked to be fine. I was kinda hoping that was it but not the case.

[marvinstockman]

A thermostat, at least in most cars is like a valve, which opens and closes. My guess is that your thermostat is always open.

[jmnew911]

Originally Posted by marvinstockman

A thermostat, at least in most cars is like a valve, which opens and closes. My guess is that your thermostat is always open.

That is my guess too. But my car was doing this so I replaced my thermostat a month ago and it did not fix the issue. It is still doing it.
But yes, seems to me like open thermostat.

[RiffE90]

Did you ever find out what the issue was? Think I am having a similar problem. Thanks!