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Old 11-16-2011, 11:20 PM   #1
whatchamacallit
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Engine Temperature Gauge acting up...

Hi all!

I have a 2000 323Ci. Recently, in the winter, I've started to use my car's heater. Its only after that have I sometimes noticed that the temperature gauge show's the engine to be lava hot (see attached pic "photo 1").

Obviously this is not the case as I have driven for a while and then notice it and there is nothing wrong with the engine. I found a simple fix was to simply pull the car to the side of the road. Shut it down. Start it back up, and that always fixes the error (see attached pic "photo 2").

Therefore I'm pretty sure its just something to do with the temperature sensor going crazy when the heating is on. Anyone here faced something similar and have an easy fix for it? My cooling system was completely replaced around a year ago as part of the car's major maintenance, so I'm hoping there isn't anything wrong there.

Thanks!
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Old 11-16-2011, 11:23 PM   #2
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could be an air bubble.
hows your coolant level?
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Old 11-16-2011, 11:25 PM   #3
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Coolant level is not MAX, but not MIN either. Basically that floating-stick sensor is just a little above the lip of the reservoir cap, so I'm thinking I should let it be and just add more come spring.
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Old 11-16-2011, 11:30 PM   #4
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Coolant level is not MAX, but not MIN either. Basically that floating-stick sensor is just a little above the lip of the reservoir cap, so I'm thinking I should let it be and just add more come spring.
bleed the system correctly I would say.
turn on ignition and set AC to highest temp and lowest fan.
open bleed screw, add coolant till it starts to come out the bleed hole.
put bleed screw back.
idk if this is correct but what I do next is start the engine and rev it at 2000rpm for several seconds with expansion tank cap off.
then turn engine off and suck the extra fluid out till level is just at max.
I then go drive it around and let it cool overnight.
check coolant and add accordingly next morning.

but your symptom looks like gauge problem cuz I remember a red light would come on if its really overheating.
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Last edited by jasonbimmer; 11-16-2011 at 11:32 PM.
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Old 11-17-2011, 08:04 AM   #5
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When you're doing the bleed.. Jack up/elevate the front of your vehicle, it will force any air pockets out of your heater core.

NOTE: Do not take the temperature gauge warning lightly by thinking it's just acting up. Even if you've already replaced the cooling system components, a year is a long time and anything could have happened.

Last edited by BimmersGarage; 11-17-2011 at 08:10 AM.
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Old 11-17-2011, 08:18 AM   #6
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Just to get this straight.... are you saying that when the needle is in the red zone all you have to do is shut the car off and then start it back up RIGHT AWAY and the needles is back in blue?
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Old 11-17-2011, 08:27 AM   #7
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Quote:
Originally Posted by jasonbimmer View Post
bleed the system correctly I would say.
turn on ignition and set AC to highest temp and lowest fan.
open bleed screw, add coolant till it starts to come out the bleed hole.
put bleed screw back.
idk if this is correct but what I do next is start the engine and rev it at 2000rpm for several seconds with expansion tank cap off.
then turn engine off and suck the extra fluid out till level is just at max.
I then go drive it around and let it cool overnight.
check coolant and add accordingly next morning.

but your symptom looks like gauge problem cuz I remember a red light would come on if its really overheating.
+1

This is what I would also do...good recommendation
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Old 11-17-2011, 08:36 AM   #8
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Probably bad temperature sensor. ECT sensor on back of engine block.
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Old 11-17-2011, 12:44 PM   #9
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Just to get this straight.... are you saying that when the needle is in the red zone all you have to do is shut the car off and then start it back up RIGHT AWAY and the needles is back in blue?
Yup. That is exactly what I am saying. A quick engine restart ALWAYS fixes the gauge needle.

The gauge is just in the red zone, the red zone's red light is not lit. Therefore I figured the gauge was just being silly. Am I wrong to think that?
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Old 11-17-2011, 12:51 PM   #10
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Either faulty wiring/grounding in the instrument cluster OR faulty coolant temp sensor.
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Old 11-17-2011, 02:21 PM   #11
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Either faulty wiring/grounding in the instrument cluster OR faulty coolant temp sensor.
+1 def a posibility. Can you verify that the red light in the gauge is actually working? (during initial key on sequence). If so and it does not come up when the needle is in that range then it might suggest that the wiring (sensor to DME) and the sensor itself are functioning properly but something is wrong with the cluster or DME to cluster connectivity.

The sensor signal can be easily checked but you will need to tap into the wire at the DME as the sensor is located under the intake manifold and is a major PITA to get to.
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Old 11-17-2011, 03:58 PM   #12
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I'm going with the air bubble theory. OP, just drive around for a bit with heater on max temp, fan on, and 3 red dots above in the vents.

If there are air bubbles, they seem to hit the temp sensor and spike it...maybe the gauge is rigged to stay in the red once it gets there, that or it might just take a second or two which the OP didn't want to wait for...understandably!

Open it up on the highway a bit...with heater set this way. That will clear any residual air bubbles out. If the problem persists, it's an issue, as said, that needs to be addressed.
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Old 11-17-2011, 04:55 PM   #13
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Bleed your cooling system to be safe, check the wiring to the temp sensor for any damage, and wash off any road salt or dirt from the temperature sensor connectors with plenty of fresh water.
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Old 11-17-2011, 07:13 PM   #14
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Well the red light does come on during initiation sequence / start up. But it is not lit up when the gauge incorrectly reads the engine temperature as being lava hot.

I shall try the coolant air bubbles solution this weekend.

I would love to post results, but to be honest this seems to happen every 3 weeks and the only reason I notice it is if I'm stopped an intersection and I casually look down at the gauges. As I said, the red light doesnt light up and therefore it never catches my eye.

That being said, thanks for all the input and all the help. I will do a coolant bleed this weekend as recommended, and hopefully the gauge error is resolved. If not, I'll take it back to the dealership (the previous owner did a complete cooling system replacement at a dealership) and see if there is any warranty on the work done, and if yes I'll ask them to take a look at it!

Thanks everyone!
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Old 11-17-2011, 10:07 PM   #15
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I'm going through the same thing right now with the exact symptoms. I was waiting on tools to arrive to swap out my water pump and thermostat when it happened again today. I was about to leave work with outside temp at around 48 degrees and the car was only running for about 3 minutes when I noticed it pegged in the red again. I shut it off and turned it immediately back on and sure enough it was buried in the blue where it belonged. It has to be electrical. Now to try and find if its the sensor or something connected to it. I'm hoping its not the computer.
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Old 11-17-2011, 10:35 PM   #16
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FYI folks, here's the text directly from BMW's WDS. Please note that if everything is working correctly and you have a real overheating issue, the needle if moved to the center of the red mark and the light is switched on. Based on this information I can't imagine that you have a real overheating problem (your needle is all the way to the right and no red light). This is clearly an instrumentation issue. If I had to make a wild guess I would say it's the cluster.

==========================
Coolant temperature display

The instrument cluster receives the current coolant temperature from the engine control unit via the CAN bus. The "coolant temperature" information is then transferred to the body bus (K-bus ).

The "coolant temperature" information is evaluated by the instrument cluster and indicated by the coolant temperature gauge. The gauge is controlled in such a way as to provide approximately three indication ranges (cold, just right, too hot). If the pointer reaches the edge of the red warning segment, it is immediately moved to the centre of this red warning segment.

Since, after shut-down, the engine still heats the coolant for a certain period of time, an increase in the gauge temperature when the engine is stationary is prevented by a "post-heating filter" in the software of the instrument cluster. When the engine is restarted, this function detects a higher temperature than at "engine off" and indicates this "engine off" value. The current temperature is then indicated after 20 seconds with the engine running.

The warning lamp indicating excess coolant temperature is controlled by the engine control unit via the CAN bus dependent on the pointer position of the coolant temperature gauge. The "post-heating phase" for the coolant temperature warning lamp is also monitored by the engine control unit.
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Old 11-17-2011, 11:09 PM   #17
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Wow good find ZHP! I knew it was electrical but didn't figure it to be the cluster. Hoping that its just the massive PITA engine temp sensor Cant wait to price a cluster.
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Old 12-02-2012, 04:41 PM   #18
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Red gauge up red zone 2000 bmw 328i

Quote:
Originally Posted by whatchamacallit View Post
hi all!

I have a 2000 323ci. Recently, in the winter, i've started to use my car's heater. Its only after that have i sometimes noticed that the temperature gauge show's the engine to be lava hot (see attached pic "photo 1").

Obviously this is not the case as i have driven for a while and then notice it and there is nothing wrong with the engine. I found a simple fix was to simply pull the car to the side of the road. Shut it down. Start it back up, and that always fixes the error (see attached pic "photo 2").

Therefore i'm pretty sure its just something to do with the temperature sensor going crazy when the heating is on. Anyone here faced something similar and have an easy fix for it? My cooling system was completely replaced around a year ago as part of the car's major maintenance, so i'm hoping there isn't anything wrong there.

Thanks!



hi, whatchamacallit,

i am just having the same problem you had in 2011 red gauge going up red zone, but once i stop shut the car ..everything go normal.

As you i bought this car used, but is crazy when you see the gauge siting on the red zone.

Could you tell me how you fix this problem?

Any help will be well appreciated..

Thanks ...

Danny
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Old 12-02-2012, 06:20 PM   #19
North
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Hey guys, I have since fixed this problem and i was pretty surprised at what it turned out to be. It was indeed the thermostat. There is a sensor inside the thermostat and when the valve becomes inoperable or broken in my case, it will throw an intermittent high temp gauge . Like yours, mine would go to normal when I would do the engine off and restart maneuver. I just couldn't believe it was the thermostat because it was nothing like I had ever seen one do before but low and behold that's what it was. I bought two after market ones ( first failed out of the box) and neither one was the high quality that the factory one was. Compared to the aftermarket, the factory was a work of art.Very well built. I also changed the water pump etc while I was in there. So far a year later no problems. Good luck
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Old 12-02-2012, 07:28 PM   #20
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Thanks North, I ordered it, sound logical..

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