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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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  #76  
Old 02-27-2013, 05:22 PM
Aussie528iT Aussie528iT is offline
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A bit more info.
The thermostat is in the cold water return from the radiator not the hot water out to the radiator. The thermostat has a heater which is controlled by the engine DME. The engine temp is kept hotter under light load and speed conditions. This is for emission reduction purposes. The M52TU and M54 engines have completely different cooling system flows compared to the earlier conventional cooling system M52 engines. They have minimal water flow through the block. Most of the water flow is through the head and is closely regulated by the engine DME controlling the heater in the thermostat. Under high load high speed conditions most of the water flow is through the radiator. This necessitates the need for an auxilliary water pump to ensure adequate water flow through the heater.
See these pdfs for more info:
http://www.ge39.com/files/m54x5.pdf
http://www.beisansystems.com/misc/SE...ROL_SYSTEM.pdf
edit: added this pdf see pages 16/17 for cooling system details http://www.bmwtech.ru/pdf/e46/ST034/9%20Engines.pdf

Hope this helps
RonR
99 528iT M52TU

Last edited by Aussie528iT; 02-28-2013 at 04:11 AM.
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  #77  
Old 03-10-2013, 07:39 AM
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bluebee bluebee is offline
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Gary, who sells the modified expansion cap, explained this today:
Quote:
Originally Posted by gary@germanautosolutions View Post
I don't get on here as often as I would like, so I just stumbled across this thread.

There is a lot of good information here as well as a lot of misinformation.

When developing our coolant cap we risked possibly damaging two engines, an M52 e39 and an m54 e46. We tapped a pressure sensor into the air space at the top of the expansion tank and data logged system pressures from cold start up to full overheat (temp gauge pegged). To cause an overheating situation we removed the clutch fan and slid a full size sheet of cardboard between the radiator and AC evaporator to block the flow from the electric fan. We ran tests at proper fill levels, low fill levels and high fill levels.

We found the following:
  1. The system runs below 1.0 bar at all normal operating temps.
  2. A lower fill level results in lower pressure and a higher fill level results in higher pressure.
  3. Overfilling the expansion tank beyond the proper cold fill level can result in system pressures over 2.0 bar, at which point the OEM cap will start to vent excess pressure.
  4. Since the cooling system pressure, with a proper amount of coolant in the system (not overfilled), does not exceed 1.0 bar at any normal operating temperature, or even moderate overheating, the use of a 1.2 bar cap will not effect cooling system efficiency in any way.
  5. 1.2 bar equates to a system temperature of approximately 126 deg C (260 deg F), which also equates to a fully pegged temp gauge.

For those that argue that the engine was engineered by BMW to use a 2.0 bar coolant cap and you shouldn't mess with it, consider this. BMW has used a 2.0 bar coolant cap on many models from 1982 to late 2000 something. These models have included iron block iron head engines, iron block aluminum head engines, and aluminum block aluminum head engines, in 4 cylinder, 6 cylinder, 8 cylinder and 10 cylinder configurations. Either they start from the coolant cap and design their engines from there, or the coolant cap is not an integral part of the engine design.

BMW has also moved away from the 2.0 bar system with most if not all current models using a 1.2 bar cap. I think the original thought process was to use a cap that was at the limit of the cooling system rated pressure to give the greatest amount of extreme overheat boil over protection. What they failed to take into account is that a 5 or 10 year old system has lost some of it's original strength, and that reaching a 2.0 bar pressure in these vehicles can cause things to go boom.

By the time my engine has overheated to the point that the bong and dash message have warned me, and my pegged temp gauge has warned me, I would rather pull over, shut off the engine, and let the 1.2 bar cap vent any excess pressure, rather than let the pressure rise until something expensive goes pop and I also need to call a tow truck. I also like the peace of mind that comes from knowing that if while in a hurry I overfill my expansion tank a little, that I don't run the risk of a catastrophic cooling system failure.

I would like to thank everyone again for all the support you have shown, and all the kind words you have expressed to German Auto Solutions. It's been a fun and busy first year with many good things in the works for the coming year.

Gary
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  #78  
Old 03-10-2013, 01:50 PM
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JimLev kindly provided real world data ...

Quote:
Originally Posted by JimLev View Post
Here ya go. This is on my 2000 540 (M62tu engine) with the 2 bar cap. I do have a 1.4 bar cap but didn't use it as the cap doesn't effect the pressure.

I did this last fall, so the outside air temps were not in the 90's, no AC either.
I'll do it again this summer and see if it changes much.
It was posted and graphed on the other message board.
I heated the engine up in my driveway with the electric fan off to allow the engine to heat up quicker.
When the KTMP reached 103C I took the car out for a spirited drive, the temp never rose above 105C.

KTMP Reading/PSI Reading
  • 40C/1.5 PSI = 0.10 bar
  • 45C/2 PSI = 0.14 bar
  • 50C/2.25 PSI = 0.16 bar
  • 55C/2.5 PSI = 0.17 bar
  • 60C/3.0 PSI = 0.21 bar
  • 65C/3.25 PSI = 0.22 bar
  • 70C/3.5 PSI = 0.24 bar
  • 75C/4.0 PSI = 0.28 bar
  • 80C/5 PSI = 0.35 bar
  • 85C/6 PSI = 0.41 bar
  • 90C/6.5 PSI = 0.45 bar
  • 95C/7.5 PSI = 0.52 bar
  • 100C/9.0 PSI = 0.62 bar
  • 105C/16.5 PSI = 1.14 bar
When I returned from my drive I released some pressure via the cap. It was then down around 5 PSI. I went out for another drive, when I returned it was still at 5 PSI.
I'm going to modify the t-stat heater circuit to drop the temp which will drop the pressure.
Quote:
Originally Posted by JimLev View Post
The cap does not control the pressure. That is a function of the system temp.
The cap only vents the system when it reaches the cap pressure.
For the 540 tu engines that run at ~108F the system pressure is around 17-18 PSI.
Note: 17 to 18 psi is about 1.2 bar (to one decimal place).
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Last edited by bluebee; 03-10-2013 at 02:26 PM.
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  #79  
Old 03-12-2013, 10:29 PM
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While researching the answer to this question:
Quote:
Originally Posted by L0F View Post
So there's a bit of discussion on what "normal" operating temp range is for our cars once warmed up. Most of the figures I've seen for my m52 have been ballparks ~88-95. We know when and at what temp they overheat at, but what I would like to know is the factory stated standard operating temperature. With out knowing this value it leaves a grey area between "running hot" and over heating. I don't like grey areas.
I revisited this M62 document which shows the characteristic "normal" temperatures for the V8:
- M62 Engine Details.pdf (585.3 KB, 514 views)

Quote:
Characteristic map thermostat
The thermostat is integrated in the housing of the water pump. As on the M60, a conventional thermostat with integrated vent valve is installed on the E31 with M62 engine. This thermostat opens at 85 o C.

A new characteristic map-controlled thermostat is used on the vehicle series E38 and E39 with M62 engine.

Function of a conventional thermostat
The control of the engine cooling system with a conventional thermostat is determined by the coolant temperature only. This control system can be subdivided into three operating ranges:

Thermostat closed:
The coolant only flows in the engine. The radiator circuit is closed.
Thermostat open:
The entire volume of coolant flows via the radiator. This ensures the maximum cooling capacity available is utilized.
Thermostat control range:
A part of the coolant volume flows via the radiator. The thermostat sets a constant engine inlet temperature within the control range.

With the aid of the characteristic map thermostat, the coolant temperature can now be influenced specifically within this operating range (thermostat control range). In this way it is possible to set a higher coolant temperature in the partial load range of the engine. Higher operating temperatures in the partial load range achieve improved combustion, reflected in lower fuel consumption and pollutant emission. However, higher operating temperatures in the full load range would involve specific disadvantages (ignition timing (angle) reduction due to knocking). For this reason, lower coolant temperatures are set specifically in the full load range with the aid of the characteristic map thermostat.
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Last edited by bluebee; 03-12-2013 at 10:37 PM.
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  #80  
Old 03-12-2013, 11:07 PM
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I opened a separate thread to ask what the coolant flow is in the respective M52, M54, and M62 expansion tanks:
- Does anyone have a BMW description of HOW the E39 expansion tank actually works?
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  #81  
Old 03-13-2013, 07:35 PM
mrpumpk1n mrpumpk1n is offline
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So did anyone ever actually answer at what temp range the m62 (not with electronically controlled thermostat) is supposed to run at? Also, any answer as where the needle stays, wether slightly to the left, slightly to the right, or dead center? The needle on my old 97 540i always sat a smidge to the left of dead center, and on my new (to me) 98 540i, the needle is a smidge to the right of dead center, with KTEMP readings of 105-107 C.
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  #82  
Old 03-13-2013, 09:25 PM
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dont know about M62 but my M54's keep it 93C - 95C
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Last edited by champaign777; 03-14-2013 at 10:57 AM.
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  #83  
Old 03-13-2013, 09:29 PM
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Quote:
Originally Posted by mrpumpk1n View Post
So did anyone ever actually answer at what temp range the m62 (not with electronically controlled thermostat) is supposed to run at?.
I'm confused, but I don't know any other engine but the M54 that I have.
But, isn't the M62 covered in post #79?
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  #84  
Old 03-13-2013, 11:54 PM
Aussie528iT Aussie528iT is offline
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My 92 E36 318iS Coupe had a 200kpa/2.0 bar pressure cap. My E39 M52TU has a 200kpa cap. It seems most BMWs from that time have a 200kpa radiator pressure cap irrespective of which engine. There are bound to be some exceptions that prove the rule though. M series engines perhaps???
From Realoem.com
http://www.realoem.com/bmw/showparts...61&hg=17&fg=05
The M54 and M52TU engines should have a 97degC thermostat according to the TIS. The M52 has a 92degC thermostat. The M62 and M62TU engines don't get a mention as far as thermostats go. MMMMM?

RonR
99 528iT M52TU
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  #85  
Old 03-14-2013, 09:31 PM
mrpumpk1n mrpumpk1n is offline
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Is the pressure cap rated at 29psi absolute or gauge, because that is a huge difference.
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  #86  
Old 03-14-2013, 11:01 PM
Aussie528iT Aussie528iT is offline
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Its gauge pressure. ie: pressure above atmospheric.

RonR
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  #87  
Old 03-19-2013, 04:55 PM
kapetajr kapetajr is offline
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unlocked OBC shows coolant temp at 92C, this is after about 20 minutes on the highway the highest i have seen is 94C. 528i M52tu

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  #88  
Old 03-19-2013, 05:14 PM
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Quote:
Originally Posted by kapetajr View Post
92C
Wow. That's one of the lowest. They must have run the older E39 I6 engines considerably cooler than the newer ones.
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  #89  
Old 03-20-2013, 10:20 AM
L0F L0F is offline
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97-98 m52b28's (Not TU's) use a 92 degree mechanical thermostat produced by wahler. Mine's typically been around 94 while on the highway this winter. It's also very cold in Chicago, 16 degrees f right now, so the heat blasting is a must.

In town the car seems to run hotter, highest temp I've seen was 101 and that was from idling for some time.
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  #90  
Old 04-11-2013, 10:20 PM
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My electric fan died on me so while I'm waiting for the new one to come in, I've been driving without a working fan for the past few days while closely watching test #7. During normal highway driving I get around 104C, local roads/light traffic 108C-110C. The highest I've seen was 116C and this is where the temp needle starts to move right. 114C is still right on 12 o'clock, 115C does not show up at all for some reason, the next one 116C is where I saw the needle move slightly to the right from the 12 o'clock position.
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  #91  
Old 06-06-2013, 05:29 AM
bananaman bananaman is offline
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'98 528i (UK model)

After another coolant catastrophe, I just took my car for a test drive and recorded the following temperatures:

Detail
528i UK model
Manual says its a M52 B28 engine (Not TU)
August 1998 production

Temperatures
Read from unlocked debug test on the dash (test 7)

Warming up, I got 75C just as the needle reached mid-point. the needle stayed rock steady in the middle throughout

Went to 98C - 100C while getting out of town in moderate traffic/lights etc

Reached 102C max while on dual carriageway, doing 50 - 70 mph. Most of the time it was 100C - 101C.

Wellied it and hit the big button several times. This didn't seem to affect the general temperature.

I conclude that right or wrong, my car is operating in the 98C to 102C range under normal warmed up driving conditions.

My manual says that the thermostat opens at 92C.
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  #92  
Old 06-06-2013, 05:37 AM
Ed Cheung Ed Cheung is offline
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For my 97 540, without the ac, the coolant will be steady at 105C, no matter I am at the highway or stuck in traffic. After the car had been driven long enough, roughly 2 hours, the VC fan will start to kick in and lower it to 95C.
But with the ac on, the temp will stay between 87-95C, it is running at much lower temp with the AC on, as the AC fan will move the air. Plus the hot air from the ac condenser will get the VC fan kick in as well. Whenever the coolant temp is below 90C, I can hear the roar of the fan.
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  #93  
Old 08-05-2013, 01:40 PM
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For the record, QSilver7 today posted a good description of what makes the electrical aux fan kick in, based on the thermoswitch in the lower radiator hose:
Quote:
Originally Posted by QSilver7 View Post
If the DIY is for a 3/5/7 series built before 9/98...the confusion may be the results of reading a DIY that doesn't apply to your e39. The aux fan in the M52TU/M54/M62TU engines don't use a relay...it uses a PWM signal from the DME to an output final stage in the aux fan to turn it on/off.
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  #94  
Old 09-05-2013, 10:53 AM
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For the record, this post today by JimLev explains the difference between the ATMP and the KTMP on the cluster:
> E39 (1997 - 2003) > Arcane instrument cluster function
Quote:
Originally Posted by JimLev View Post
In test 7 there are two temp readings available. The first is coolant temp and the second one is the air temp taken from either the sensor in the air filter box or the sensor in the MAF. The sensor location depends on the car.
As you know the 86F is from the sensor under the right front corner of the bumper.
The 40.5C/105F should be the air temp going into the engine. For that high of a reading I would have to guess the car wasn't moving so the under hood temp was high or you just started the engine with the car sitting in the hot San Jose sun.
While you are driving the car the 2 temps should be pretty close.


For those who wish to print the unlocking instructions, see this thread:
- E39 summary glovebox Glovebox printouts: fluids (1) bulbs (2) cabin air filters (3) oil service interval reset (1) & high cluster unlocking (1)
Quote:
Originally Posted by bluebee View Post
here's the simplest I can make it:
  1. Hold down the right button (about 10 seconds) until test 01 shows
  2. Press the left button to get the results of test 1 (your VIN)
  3. Add up the last five VIN digits, e.g., GZ12345 = 1+2+3+4+5=15
  4. Press the right button to go to any LOCK=ON display
    • Note: This is different than the instructions which say to go to test #19, IIRC
  5. Press the left button until it displays that number (15 in this example)
  6. With that number displayed (e.g., 15), now press the right button (this should unlock the display)
  7. To see alternator output, press the right button to get to test #09
  8. Press the left button to view the results (e.g., 13.7 volts at idle)

The only two tests I find useful on the display are test #7 (KTMP) and #9 (UB).

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  #95  
Old 09-05-2013, 11:46 AM
rdl rdl is offline
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We've seen various temperatures reported depending on I6 vs V8 and earlier vs later engines. Generally, the V8s reporting ~105C and I6s ~96C. A couple of months ago a light bulb came on for me & I'm now fairly sure that I6s and V8s actually run pretty much the same coolant temperatures.

The difference in temperature reported by the unlocked cluster is a result of the V8 and I6 sensors being located in different locations in the coolant flow circuit. As an aid, see post #80 for the I6 M52TU flow path and temp sensor location. Per BMW tech docs, the M54 flow path is the same as M52TU and M52 is similar.

Rather than repeat the line of thought, see this link.
http://www.bimmerfest.com/forums/sho...9&postcount=10
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Last edited by rdl; 09-05-2013 at 11:49 AM.
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  #96  
Old 09-05-2013, 01:13 PM
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Quote:
Originally Posted by rdl View Post
The difference in temperature reported ... is a result of the V8 and I6 sensors being located in different locations
This is VERY IMPORTANT, as it has generally been "assumed" that the V8 runs muuuch hotter than the I6 ... so it behooves us to understand this better.

Quote:
Originally Posted by rdl View Post
To keep it together in this one thread, here's that post from this thread:
> E39 (1997 - 2003) > Coolant temps

Quote:
Originally Posted by rdl View Post
I've always been puzzled by the I6 thermostat being labelled 97C while most people, including me, find normal idle and cruising temperatures of 95 or 96C. Particularly since the norm for thermostat specs is to list the temperature at which the t-stat just starts to open, i.e. just a tiny dribble of coolant flow to the radiator, which isn't enough to keep the engine at a steady temperature.

I think I have an explanation - the KTMP sensor is remote from the t-stat at a cooler location in the coolant flow circuit. The coolant temperature sensor on the M54 engine is at the rear of the cylinder head. The coolant flow path is fairly complicated but to generalize, coolant flows from the block up into the cylinder head and then toward the front of the head and finally across the t-stat which "decides" whether to open and allow coolant to flow through the radiator for cooling. So the coolant temperature reported (KTMP) is less than what the t-stat sees, since the coolant picks up heat and temperature as if flows forward.

I've checked temperature of the t-stat housing at the upper rad hose nipple on my M54 with an IR thermometer under a variety of ambient temperatures. With the dual temp sensor reporting ~96 C, the IR thermometer on the housing indicates 105-106C. Interestingly, the same as what the V8 engine people report as normal, and the V8 KTMP sensor is in the t-stat housing. I had believed that the I6 engines ran lower temps and cooling system pressures than the V8s, but apparently not.

Most automotive wax pellet t-stats are designed for 10 to 15 degrees C between initial opening point to maximum/full open so the steady state temperature will always be somewhat higher than the temperature marked on the t-stat. How much higher depends on engine load (heat generation), RPM (water pump speed => flow), ambient temperature & air flow over the radiator (more or less cooling across the rad), etc. In control theory the difference between the 97C and actual steady state temperature is termed the droop curve (even though in this case it would be better labeled "anti-droop" Actually it's termed -ve droop)

All the above assumes DME is not using the electric heater to manipulate the t-stat for lower temperature during higher load/HP output. The DME is able to trick the t-stat to open wider & "force" lower temperatures using the electric heater in the t-stat. The lowest KTMP I've seen was 79C under hard acceleration for several minutes on a winding road. Driving up a long hill, a single acceleration to pass on the highway or city driving between stop light/signs results in mid 80s to low 90s C. From a steady speed & 96 C temperature, stiff acceleration results in the temp drop starting within 3 - 5 seconds, reaching the 80s C in ~10 - 15 seconds. Recovery time to the normal ~96C is 1 to 2 minutes once back at cruisung speed or idle.
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  #97  
Old 09-20-2013, 07:23 PM
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For the record, another question came up today looking for how to test the ENGINE temperature (on the I6):
Quote:
Originally Posted by staysidewayz View Post
ok so now i understand how to unlock the obc nut what exact test am i trying to run, i dont see which one shows engine temp unless its the coolant temperature? (am i being stupid)
I've always been confused about temperature sensors on the E39.
It would be nice to list them all, in a single thread.

I think these are the E39 temperature sensors that I know of:
1. Dual Temperature Sensor (both temperatures can be read from an unlocked cluster)
2. Intake Air Temperature Sensor (can be read from an unlocked cluster)
3. Ambient Temperature Sensor (reads directly on the cluster)
4. Oil Temperature Sensor in the oil filter housing (not in all E39s)
5. Aux fan thermoswitch (this is a switch, not a sensor per se, though)
6. Any others?

Plus, there are a few HVAC temperature sensors, I'm sure.
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  #98  
Old 04-07-2014, 06:26 PM
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bluebee bluebee is offline
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An interesting idea popped up today over here:
> 5 Series > E39 (1997 - 2003) > Anyone tried to change the temperature buffer range?
Quote:
Originally Posted by doru View Post
To read the correct value?
We all know the temp gauge is buffered, so it sits at 12 o'clock between 75C and 110-ish C. Useless..
the Fanatics found a workaround to code the temp gauge with PA soft 1.4
Has anyone attempted this? I might look into it with INPA, if it's possible.
Fanatics thread.
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  #99  
Old 04-08-2014, 02:55 PM
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golferjohnm golferjohnm is offline
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just a codicil to my previous *normal* operating temp response toward the beginning of this thread...after a complete coolant overhaul, my new *normal* is a rock-solid 110*C...with @ 3*C variation depending upon load...ambient temperature only adjusts the frequency of either the fan-clutch or the aux fan kicking in
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