E32 750i overheating after engine repairs...

[shogun]

Is 8mm fine?>>>should be ok,
-When you are pumping the upper hose, should i do that on idle or when engine is off?>>> with engine in idle, when coolant is hot= thermostat open + fluid runs the large coolant cycle, see here the coolant
diagram on page 25 http://bmwe32.masscom.net/moswald/docs/BMWv12manual.pdf
visco fan clutch explained on page 27, when it kicks in and out.
-Heater is set to full hot, and with fan speed at low. Should fan speed be high? >>>>>low speed relay (with aircon off) should kick in at 91 degree C, high speed relay should kick in at 99 DC
91/99CE Double temperature switch at right side of cooler p/n 61311378073
-Should i bleed with radiator cap on or off?>>> yes, as you have to fill in coolant when needed, just run the engine to operating temperature, heater full on and then let it run in idle and refill if necessary, massage the hose, check temperatures with no contact thermometer , to confirm that your temperature gauge is not showing something wrong or the temp sensor is wrong. https://www.bmw-rudel.de/index.php/b...toren&catid=12

-I tried to compare by coolant return with this picture http://www.nmia.com/~dgnrg/ret2.jpg. Its way more coolant in the return hos in this picture than on my car..>>> that pic is from an M30, on my M70 in idle it is also not that much, important is that there is always fluid flowing.

[bjorneoen]

Is 8mm fine?>>>should be ok,
-When you are pumping the upper hose, should i do that on idle or when engine is off?>>> with engine in idle, when coolant is hot= thermostat open + fluid runs the large coolant cycle, see here the coolant
diagram on page 25 http://bmwe32.masscom.net/moswald/docs/BMWv12manual.pdf
visco fan clutch explained on page 27, when it kicks in and out.
-Heater is set to full hot, and with fan speed at low. Should fan speed be high? >>>>>low speed relay (with aircon off) should kick in at 91 degree C, high speed relay should kick in at 99 DC
91/99CE Double temperature switch at right side of cooler p/n 61311378073
-Should i bleed with radiator cap on or off?>>> yes, as you have to fill in coolant when needed, just run the engine to operating temperature, heater full on and then let it run in idle and refill if necessary, massage the hose, check temperatures with no contact thermometer , to confirm that your temperature gauge is not showing something wrong or the temp sensor is wrong. https://www.bmw-rudel.de/index.php/b...toren&catid=12

-I tried to compare by coolant return with this picture http://www.nmia.com/~dgnrg/ret2.jpg. Its way more coolant in the return hos in this picture than on my car..>>> that pic is from an M30, on my M70 in idle it is also not that much, important is that there is always fluid flowing.

Thanks for answer

8mm is now installed and expansion tank return hole is drilled to 1/4 so allow more air/coolant to let out. Unfortunately it didn't work. Still overheats, but it looks like coolant is returning just fine.
Im starting to give up now.. I really can't understand what is going on.. Everything was fine until i changed fan clutch, thermostat and coolant color. Never had any issues with overheating earlier so i find it very strange that doing preservative maintance would fuck it up

I know that my auxilary fan is bad so it won't run, but i also know that the engine didn't overheat earlier when it was not installed either. So i don't believe the aux fan alone would make the engine overheat when ambient temperatur is -15 degrees..

Im starting to believe that the fan clutch i bought is bad.. but thats just cause its the only thing i haven't swapped twice...

Some things i have noticed to diagnose further:
-Fan ctluch spins up fast when i start the engine and the engine is cold.
-Fan clutch slows down when the engine gets hotter and hotter.
-When engine is too hot (3/4 of temperatur gauge), it goes in what looks like "idle"/low speed. Much slower than when i started the engine cold.
-It spins up if i rev the engine. I can hear the fan clutch when i rev the engine.

1. Soo, when engine is ideling and the temperatur is too hot (above 95 degrees), shouldn't the fan clutch go at least as fast as it goes when i start engine cold? Should i replace the fan clutch maybe? I read this on your fan-clutch test procedure. Mine does not increase when temperatur increases..
"Leave the engine idle and watch the temperature indicator. When normal operating temperature has been reached, some increase in fan speed/noise should be noted, in particular when the RPM is increased. If temperature is fairly stable and the fan noise/speed increases or cycles, third good indication. If temperature indication continues to increase, with no increase in fan noise/speed, clutch is defective and should be replaced."

2. When i bleed i put interior heater settings to max heat with fan at low speed. When i try to run full hot with fan speed at max the temperatur does not drop.. I read about everyone else using the interior heater max heat to lower the heat of the engine but that doesn't work for me. What does that mean?

[shogun]

Give it a try with a new fan clutch, or make a test with the old fan clutch by welding it like this, does not cost anything, just a bit of welding http://bmwe32.masscom.net/johan/fan_...an_clutch.html
When you put interior fan to max speed the temperature drop is not that significant, that could be that the visco fan clutch is not runnning at full speed.

[bjorneoen]

Give it a try with a new fan clutch, or make a test with the old fan clutch by welding it like this, does not cost anything, just a bit of welding http://bmwe32.masscom.net/johan/fan_...an_clutch.html
When you put interior fan to max speed the temperature drop is not that significant, that could be that the visco fan clutch is not runnning at full speed.

Thank you! Will test that
One more thing. Probably a stupid question but how does the fan clutch actually get to 95 degrees? My front end of the car is fully open and i dont have any cowl around the radiator either so im just wondering if it could actually be a problem that the viscous fan clutch does not get to its locking temperatur even though coolant is going past 95 degrees. The temperature in the fan clutch is just from warm air between radiator/engine block and fan clutch?

[shogun]

The engine bay is basically more or less an enclosed system, hood has a sealing, from below are the undercovers under engine and transmission, http://bmwfans.info/parts-catalog/E3...rtm_screening/
radiator has a shroud, the visco fan pulls in the cool air and pushes it around the engine and then around the transmission and the now hot/warm air should leave at the end of the transmission. If that sealing is not good = not hood sealing, no under covers, no fan shroud, etc, that has an effect on the cooling efficiency.
How Does a Viscous Fan Clutch Work? https://www.youtube.com/watch?v=UwM4OqsLek4
The mechanism of this product is based on the bimetal sensor located at the front of the viscous fan. This sensor expands or contracts, depending on the temperature imparted through the radiator. At cold temperature:
The bimetal sensor contracts closing the valve, so the silicone fluid remains in the reservoir chamber. At this stage, the viscous fan coupling is disengaged and turns at around 20% of the rotation speed of the engine.
At operating temperature: The bimetal sensor expands, rotating the valve and allowing the silicone fluid to move through the entire chamber to the outer edges.This generates enough torque to drive the cooling fan blades at engine operating speeds and remain at a consistent temperature. At this stage, the viscous fan coupling is engaged and turns at around 80% of the rotation speed of the engine. https://www.partinfo.co.uk/articles/275
My M70 fan clutch 11527502804 is designed for 92CEL

also read abt misinfo in workshop manual M60 sensors + how to test, Which-coolant-temp-sensor-does-what-M60 https://www.bimmerforums.com/forum/s...hat-M60-engine

[bjorneoen]

Hi!
Finally summer is here and i can continue diagnosing the overheating issue.. problem still persists..

I changed to an original fan clutch and i fitted the cowl around the fan to center the air towards the engine. Still overheating.

Then i measured the upper radiator hose with my newly equipped IR thermometer. And when gauge is above middle, i have only have 64 degrees at the upper hose.. everything is circulating fine now in the coolant return also.

What should the reading of upper radiator hose be when gauge is in center?
Could all these problems really just be a bad temperatur sensor? I measured ambient air before christmas and the ohm was fine then. But maybe it actually sends the wrong reading to the cluster of the cluster gauge itself is reading the values wrong?

Check the pictures attached. Thats after idelig for 5-10 minutes.
PXL_20230518_105440644.jpg
Screenshot_20230518-145055.jpg

[shogun]

the thermostat opens at the temp it is designed for, that means 85 or 91 degree C, whatever you have installed and if you have at upper left side radiator hose 64 DC, that looks like water pump and t-stat are working and at bottom right outlet hose of radiator it should less as the radiator and fan are cooling it down . Maybe you have no problem at all, just the gauge shows a bit too much. I have given you all data for the sensors, their locations etc on page 1 of this thread. I guess maybe a wrong sensor installed in the wrong place , wrong sensor connection to cluster gauge, or the cluster gauge.

[bjorneoen]

the thermostat opens at the temp it is designed for, that means 85 or 91 degree C, whatever you have installed and if you have at upper left side radiator hose 64 DC, that looks like water pump and t-stat are working and at bottom right outlet hose of radiator it should less as the radiator and fan are cooling it down . Maybe you have no problem at all, just the gauge shows a bit too much. I have given you all data for the sensors, their locations etc on page 1 of this thread. I guess maybe a wrong sensor installed in the wrong place , wrong sensor connection to cluster gauge, or the cluster gauge.

I see!
I have 64 degrees on upper hose and lower hose is ambient temperature. Last time when i checked the sensor i just ohmed the actual sensor not the values going to the actual cluster gauge.
I will measure the sensor again and i will also ohm the actual instrument cluster gauge to verify that the wirings are correct. Maybe the sensor works for ambient readings, but fails when its hot?

So upper hose should be at about 85-91 degrees when the card is fully warmed up, correct?

[bjorneoen]

I see!
I have 64 degrees on upper hose and lower hose is ambient temperature. Last time when i checked the sensor i just ohmed the actual sensor not the values going to the actual cluster gauge.
I will measure the sensor again and i will also ohm the actual instrument cluster gauge to verify that the wirings are correct. Maybe the sensor works for ambient readings, but fails when its hot?

So upper hose should be at about 85-91 degrees when the card is fully warmed up, correct?

Update:
After 15-20 min ish of idling it looks like this. Normal?
PXL_20230519_131113816.jpgPXL_20230519_131119763.jpgPXL_20230519_131156584.jpg

[shogun]

temp measured in / out of radiator seems normal, cluster gauge shows wrong temperature. Just to compare try to take temp measurement with your contact free thermometer at the area where the sensors are bolted in behind the engine, I assume either wrong sensor, wrong wire connection gauge to gauge sensor connectors, or gauge defect. The conversion of the data from sensor to cluster gauge is done by the chip in the cluster.
on page 1 I mentioned;
mixing up temperature sensors is also possible, different ohms.
coolant sensors:
if the coolant and temperature sensors are not connected or bad, then the system will go to pre-set failsafe values, which means it always uses data for a cold engine. Here are the test data which you can test on the DME pins, remove the cap on top of the DME -156 M1.2 connector and use a multimeter, the pins are marked with numbers http://www.europeantransmission.com/...out1988_90.pdf
this is the older M1.2 DME, if your 750 has the newer M1.2 -352 DME, check the pinout in the wiring diagrams.

sensors from fender to middle of the M70 engine: http://bmwfans.info/parts-catalog/E3...g_system_pipe/
# 8 12621710535 2-POL M14x1,5 , black 5000 Ohm, for temperature gauge sender, spec by Hella: M14x1,5, NTC-Sensor; resistance Ohm: 5000, 544 ; color: schwarz, V: 12.
# 7 temperature sensor water 12621288158 M14X1,5 engine coolant temperature sensor for DME, (20 deg. C, 2500 Ohm.) (White Top)
# 5 temperature sensor water, 13621707366 3-POL-2500-OHM , EML coolant temperature sensor

https://www.bmw-rudel.de/index.php/b...toren&catid=12

[bjorneoen]

Thanks again for great information. I have now verified all connectors with multimeter so i know exactly which connector that should go to each of the sensors.

According to the wiring diagram the 2 pin #7 goes to the EML and the 3 pin #5 goes to both dme1 and dme2. I have checked all the pins and they are connected correctly to the EML and the DME's. The #8 is also connected correctly to the instrument gauge.

Earlier i posted a picture of an error "engine temperatur sensor bank 2". I believe that must be the sensor #5 since it is connected to both dme1 and dme2 and also because the scanner told be to check connection to pin 78 which is correct for dme1 and dme2.

A couple of questions:
You say it will go to preset failsafe values if something is wrong with the sensors, but the actual temperature gauge will always just show the values that is read from sensor #8 right? Since that is directly connected to the cluster itself? If i disconnect #8 i will probably not get any readings at the gauge at all?

Do sensor #5 and #7 have any impact on the temperature gauge at all? I understand they will affect how the engine operates but does it affect the actual needle or is that only controlled by sensor #8?

And if i need to remove 3 pin sensor, how do i do so? The access is very limited.. and the 3 pin connector head of bigger than the socket itself so i need some kind of wrench but thats impossible to fit. Any tricks?

[shogun]

Gauge I have explained before, there in the past a lot of discussions what is right or wrong when the temperature gauge on the cluster temp indicator is right or left of the 12 o' clock mark. The fact is:
Temperature indication on the BMW is not linear, they call it 'tableau', basically the indicator at 12 o'clock can mean everything between roughly 75-110 degree Celsius (depending on the temp support values programmed). Everything in between 75-110 is just 12 o'clock. Plus/ minus 1-2 mm to the right or left (deviation cased by the parts installed). The analog signal is processed in the instrument cluster and compared with data in the coding plug. A corresponding signal is sent to the instrument. Five temperature support values are stored in the coding plug. Exceeding the temperature limit stored in the coding plug will additionally send corresponding warning information to the check control and display it there.

That is written and shown here on page 4 of the instrument cluster check control training reference book http://www.e38.org/e32/BMW_pdfs/INST_info.pdf
What is NOT shown in the English version I found in the German version, that page showing the temperature diagram curve, and there one can see the so-called 'tableau' between 75-110 degree Celsius.That depends on the engine type and the five temperature support values in the cluster chip.

...but the actual temperature gauge will always just show the values that is read from sensor #8 right? Since that is directly connected to the cluster itself? If i disconnect #8 i will probably not get any readings at the gauge at all?>>>>>see explanation abv, just disconnect and see.

Do sensor #5 and #7 have any impact on the temperature gauge at all? I understand they will affect how the engine operates but does it affect the actual needle or is that only controlled by sensor #8?....>>>5+7: no impact on cluster gauge

And if i need to remove 3 pin sensor, how do i do so? The access is very limited.. and the 3 pin connector head of bigger than the socket itself so i need some kind of wrench but thats impossible to fit. Any tricks?>>>>>>crawfoot wrench with extension?

if you have a spare instrument cluster, test that one for the gauge, clusters can also break, capacitors, resistors etc http://bimmerboard.com/forums/posts/467642/

[bjorneoen]

Finally everything works again! Thanks for really good help and all the information

I checked connectivity on all wires and marked each connector so they would connect to the correct sensors! That helped

Its a little bit embarrassing though... Problem was that I must have mixed the sensors.. i was 100% that i tried all the combinations possible both in the autumn and now but somehow i connected to the same sensors each time.. so much effort and diagnostics for a stupid mistake.. ANYWAY.. it now all works fine and temperature is stable 90 degrees!! :O

I also got rid of the "engine coolant temperature sensor" error after cleaning the corroted/greenish pins in 3-pin connector.

Thank you again and sorry for misleading information.. its a tight spot behind the engine and i was 100% sure i tested everything.. i fooled my self! Good news is that the cars temperature is now fine! Now i can go ahead with the other problems!

Screenshot_20230521-141333.jpgScreenshot_20230521-141340.jpgScreenshot_20230521-141342.jpgScreenshot_20230521-141344.jpgScreenshot_20230521-141346.jpg