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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 12-13-2012, 03:03 PM
Bmw94 Bmw94 is offline
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Engine suddenly overheating

So yesterday I was driving about 55mph on a flat and I looked down and noticed the temperature gauge was all the way to the max. I pulled over and shut the car off. Checked the coolant and oil levels (which were right were they should be), looked for leaks (none), and no smoke. I was puzzled. I called my dad to come get me. After I got done that, I turned the key to the 2nd position. The temp read right at the blue line, where it normally read when I am driving lately. So he picked me up and drove it home. He said it didn't even get to 1/4 up on the gauge. I took it out later (to the same place I was going earlier) and it made it fine. I went even further, put some gas in my car, and came home (total of about 45+ minutes of driving). During the whole trip, the car barely made it past the edge of the blue. Today, I left to go take a final. Not even 5 minutes from the house, the temperature gauge was on max. I pulled over and called my mom to come get me so I could get to school to take my test. As soon as I hung up the phone, I turned the key to the 2nd position. The gauge was right at the edge of the blue (not even 2 minutes after it was "overheated"). Does anyone have any clue what is going on here? I know that every cooling system part has less than 15k miles (most being less than 5k) except for the fan clutch, water pump, and thermostat. I don't think any of these could be my problem. Is there a sender that is reading the temperature wrong? Thanks in advanced for any help
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  #2  
Old 12-13-2012, 03:23 PM
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Nline6 Nline6 is offline
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I think it sounds like a bad Thermostat. It should sit at the 12o clock position. you have any lights on the dash?
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  #3  
Old 12-13-2012, 03:45 PM
Bmw94 Bmw94 is offline
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No lights on the dash. I have never had any lights on the dash since I bought it
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  #4  
Old 12-13-2012, 04:16 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by Bmw94 View Post
noticed the temperature gauge was all the way to the max
Yikes. The gauge is horribly slow to react, so that's not good news:
- What to look for in a perfectly normal E39 cooling system (1)

Do you have the high instrument cluster?
- High instrument cluster check of the cooling system temperature KTMP (1)

There are a zillion threads asking how to diagnose overheating.

I'd probably start here:
- What to look for when your KTMP (1) or coolant temperature gauge indicates overheating (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)

Here is a picture of my instrument cluster when I last checked the temperature:
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Each repair should invariably add to our knowledge base by the process of inexorable incrementalism.
Your job, in return, is to read the suggested threads, where the best people will always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #5  
Old 12-13-2012, 04:49 PM
AH673000 AH673000 is offline
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Agree with Thermostat diagnosis..... Sure sounds like it is intermittently sticking in the closed position . A quick check would be to take it out and put it in a pot of boiling water ....

Even if it opens, I would put a new one on the car.
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  #6  
Old 12-13-2012, 05:11 PM
rdl rdl is offline
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The symptoms do agree with a sticky thermostat except for the instance you found the gauge reading top of the blue segment only 2 minutes after an "overheat" with the engine off. This seems to me too fast for the temperature to fall so far.

The top of blue indicates an engine temp of ~60C. The gauge at 12 o'clock from 75C to ~115C. So according to the gauge you've been driving a cold engine for some time, if the gauge & sensor is accurate. Further, an engine temperature that sends the needle to max should result in a light illuminating the red segment in the gauge & I think an audible "ding" warning. Given your detailed listing of other events, I suspect that there was no "ding" or red light warning.

The engine temp sensor (dual temperature sensor) has two thermistors: one for the gauge, one for the DME. Trouble is that I don't know if the gauge side of the sensor controls the "ding" and red overtemp light or if the DME does that over the buss. Which would be a nice redundant warning system: needle + ding/light.

All this leads one to suspect the gauge thermistor, wiring/connector or the gauge itself may be faulty rather than the thermostat. A little support for this hypothesis is that the cooling system is fairly new.

I suggest doing the following.
A) belt and suspenders safe would be to replace both thermostat and the dual temperature sender. But you may wish to take a calculated risk, test for better data and repair only what is confirmed faulty. If so be very carefull not to overheat the engine.

Regardless of your decision in A)
B) search best links thread to find instructions unlock the instrument cluster and scroll to the engine temperature readout.
C) drive the car watching the gauge and digital temperature like a hawk. A warmed up I6 engine ranges between ~85C and ~96C with the cooling system operating properly.
D) if the gauge needle goes overtemp but the digital reading is in the OK range, change the sensor.
E) if both indicators go overtemp, change the thermostat.

Whichever part is "fingered" and changed, repeat B) through E) to confirm. If changing the sensor doesn't correct the gauge while the digital reading says temp is OK, you probably have a bad gauge & will need a new instrument cluster (unfortunately $$$)

PS: I took too long to compose this - interupted for supper. After my preview to check for obvious typos etc. I see that Bluebee has given you a list of alternatives. Her info is always useful.

On the bright side, you don't seem to have cooked the engine. Good luck on the diagnosis.
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  #7  
Old 12-14-2012, 09:24 AM
poolman poolman is offline
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To add to the above--what brand name water pump did you use int the car when it was replaced--do you know if it had a plastic or metal impellor--if it's plastic that might be the problem --there have been many here that have found that out the hard way--just thought too add
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  #8  
Old 12-14-2012, 09:36 AM
Dackelone Dackelone is offline
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I bet you have a plastic water pump impeller and it is spinning on the pump's shaft! Sometimes it spins and pumps coolant. Sometimes it does not.

Could be your thermostat... but when a thermostat fails - it fails in the closed or open position. NOT intermittently!
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  #9  
Old 12-14-2012, 09:37 AM
Bmw94 Bmw94 is offline
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Thank you for all the replies. I will get a new thermostat, water pump with the composite impeller, and the temperature sender. I do not know when the water pump was last replaced or what type it is.
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  #10  
Old 12-14-2012, 01:44 PM
poolman poolman is offline
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You want a water pump with a METAL impellor---now reading you OP again--replace the stat and the fan and fan clutch---when you stated that you had replaced everything on the cooling system--I took it you ment what you said--on these cars--you replace everything --every 100 k miles
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  #11  
Old 12-14-2012, 01:48 PM
Dackelone Dackelone is offline
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Quote:
Originally Posted by poolman View Post
You want a water pump with a METAL impellor---now reading you OP again--replace the stat and the fan and fan clutch---when you stated that you had replaced everything on the cooling system--I took it you ment what you said--on these cars--you replace everything --every 100 k miles

AND,,, replace your radiator(and coolant hoses), Your due for a new radiator now!


I second the motion for a metal water pump. I bought a BMW unit from the dealer bc some of the aftermarket ones over here for my v8 looked cheasy(plastic). The BMW unit looked very nice(all metal).

Last edited by Dackelone; 12-14-2012 at 01:49 PM.
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  #12  
Old 12-14-2012, 04:43 PM
josemedeiros007 josemedeiros007 is offline
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A blown head gasket or cracked head leaking combustion gas into the cooling system, would pressurize the cooling system and cause a similar symptom. First thing to check is the thermostat, and possibly running it with out one to see if it still over heats. Also check the plastic impeller on the water pump.
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  #13  
Old 12-14-2012, 04:54 PM
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Flybot Flybot is offline
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Before you go dumping a bunch of money on parts, do a simple bleed of the cooling system. It only takes a screwdriver and a few minutes and its free. If you get air out of the bleeder screw I would just monitor the temp for a few more drives and forget about it. I like to start simple and work my way up.
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Old 12-14-2012, 05:38 PM
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Nline6 Nline6 is offline
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Since you have a 2002 I don't think you can do the boiling water trick as your t stat is electronic, not mechanical.
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Old 12-18-2012, 09:13 PM
Bmw94 Bmw94 is offline
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For Christmas I am going to be getting (and putting on) a Wahler thermostat, Saleri water pump (with composite impeller), and a new dual temperature switch for on the side of the cylinder head. I hope all goes well and I will test it out after I'm done. Hopefully these new parts will fix the problem. Thanks for all the help guys
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  #16  
Old 12-19-2012, 08:15 AM
Dackelone Dackelone is offline
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Quote:
Originally Posted by Bmw94 View Post
For Christmas I am going to be getting (and putting on) a Wahler thermostat, Saleri water pump (with composite impeller), and a new dual temperature switch for on the side of the cylinder head. I hope all goes well and I will test it out after I'm done. Hopefully these new parts will fix the problem. Thanks for all the help guys
You really want a METAL impeller water pump. Using another plastic one... it WILL fail sooner rather than later. The metal impeller pumps seem to last much longer.
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  #17  
Old 12-19-2012, 10:33 AM
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doru doru is online now
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Quote:
Originally Posted by Nline6 View Post
Since you have a 2002 I don't think you can do the boiling water trick as your t stat is electronic, not mechanical.
Statement not entirely true.
It's a normal T-stat, with an "electronic" module, that forces the T-stat to open when you floor the engine under certain circumstances. Otherwise, the "electronic" T-stat works like any other "regular" T-stat, meaning the element can be submerged in boiling water, and you can check if it opens.
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  #18  
Old 01-02-2013, 08:42 AM
Bmw94 Bmw94 is offline
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So I replaced the water pump and thermostat with my dad. However, we are having a difficult time finding out how to get to the temperature switch that is on the cylinder head. The Bentley manual only shows where it is in a parts diagram. It doesn't say how to get to it. Do you have to take the intake manifold off? Or is there an easy way to just reach around and change it somehow? And do you think the actual temperature switch that is wrong is the one on the cylinder head or is it the one on the radiator hose? That one is much easier to change and I could go ahead and order that part and change it if getting to the rear dual temperature sensor on the cylinder head is hard to get to. Thanks for all the help guys
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Old 01-02-2013, 08:54 AM
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i believe the dual temp sensor is on the driver's side at the rear end of the engine below the intake manifold. You might want to take off the big air boot and the DISA that's in the way, getting by removing the intake manifold. However when you take off the DISA and replace it, be careful how you re-seal it.
Also, I would check the wiring of the dual temp sensor first, because there was a post not long ago that showed a fried wiring of the CPS sensor due to heat cycling. Both are very close to the engine, so that is a possibility that fouled wiring mess up the sensors, which could be actually working fine.
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Old 01-02-2013, 09:12 AM
poolman poolman is offline
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Temp sensor is located at the rear of the engine over #6 cylinder under the intake--You may be able to remove the part by removing the Cabin duct work on each side--tah is removed by first removing the covers and then unsnapping the duck work from the covers and thn spinning the duct work upwards and then it will unhinge fron the firewall--then with a flashlight u can look from the back and see the sensor your after--Good Luck
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  #21  
Old 01-02-2013, 10:35 AM
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flyboyy flyboyy is offline
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Quote:
Originally Posted by Flybot View Post
Before you go dumping a bunch of money on parts, do a simple bleed of the cooling system. It only takes a screwdriver and a few minutes and its free. If you get air out of the bleeder screw I would just monitor the temp for a few more drives and forget about it. I like to start simple and work my way up.
I would agree with you sir...

bleed the cooling system first as it is free.. all it takes is a screw driver and some bmw coolant.. make sure its full and no bubbles coming from the bleeding points. there are 2 bleeding points on the car so check those two.
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  #22  
Old 01-02-2013, 07:30 PM
Bmw94 Bmw94 is offline
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I know how to bleed the coolant system and did so when I previously replaced the expansion tank not too long ago.
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