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Old 05-11-2016, 12:26 PM   #1
jeepster
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Join Date: Apr 2016
Location: Denver, CO
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My Ride: E36 LS6, 01 wagon
overheating strangeness! (no smoke, no milky oil, no leaks, new parts)

2001 325i Manual Wagon
166k
factory electric puller fan (no mechanical fan and no front Aux pusher fan)


Issue:

Short story:
blew expansion tank (replaced it) Yes I bled correctly
fan not working (replaced it...still not working)
Still overheats on highway with RPM between 1500-3500 RPM (no overheat under 1500 or over 4k)
No steam, no water in oil, no codes
Stumped

Long Story:
Started last Friday when my expansion tank ruptured. Car got hot. Temp gauge got to the RED but did not light up. I let the car cool (since it would not hold any fluid) and drove it home 4 blocks at a time (start, accelerate 10-15 sec, shut off, coast as far as possible. Wait 10-15 minutes and repeat). Car did not smell, act, or feel hot to the touch when I got home (over 2 hours later!!!)

Car had NO codes. I replaced the expansion tank Sat. morning, filled and bled the system. Took it for a test drive, got it up to temp 210*, then drove home. Let it sit several hours and topped off the ET (expansion tank) with about a 1/4 gallon.

Drove to parts store (about 3 miles) to get some oil (in preparation for valve cover gasket change) and the temp gauge started creeping up again. Had my scanner with me so I hooked it up. It would read 230* unless I ran the heater and then it would drop to 210-220*. Electric fan never came on.

NO codes. Tested the fan multiple ways based on another thread. Eventually I "hardwired" a test fan and drove around for 20 minutes after idling to operating temp. Temps stayed between 210-215*. At home car stayed this temp at idle with fan on. With the fan unplugged it creeps to 230* and no higher. I ordered a new $400 fan as I assumed the final control of the factory fan had died. Also changed valve cover gasket and plugs while I was waiting.

NO codes. Installed new fan, turned on with ac. Coolant level has been fine since (although it pukes out the ET cap after 230*). I assume at this point all is well. Drive it to my office (4 miles) Monday and Tuesday. No issues, Temp is right around 215*. I still never hear the fan come on though.

NO codes. Tuesday night I drive 90 miles. About 30 minutes into the drive through stop and go, the temp stays around 220*. Ambient temp is in the 50s. Traffic opens up get up to 70 mph and temp starts creeping up to 240*. I drive to a safe spot and pull over. Fan is not running. at idle with heat on car cools to 230*. Get back on the highway and same thing 240-246* with heat on full blast. outside temps are now in the low 40s. I don't think it should overheat even without a fan at this point!!!

I figure out that if I keep the motor above 4k RPM the coolant temps stay in the 235* range and I drive it home (with the fan removed to allow more highway airflow (which made zero difference).

Next morning (today). NO codes, coolant is "normal" level. Still no steam, nothing in oil. Pulled water pump and it is perfectly functional. When I changed the valve cover gasket and plugs two days ago, there was no clean cylinders, all plugs looked normal, no water in the oil, no steam from the exhaust etc.

Before I throw more money at this, what could it be? lower radiator hose sensor (not showing any codes though), Thermostat (runs normal temp whenever I drive around town, only overheat with sustained 1500-3500 RPM), Head gasket (not the usual signs)

I have an LS1 swap ready to go, just a bit short on funds and time right now. I was planning the swap over the winter. I don't want to spend more than $300 fixing the car otherwise Ill just wait to do the swap.
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Old 05-11-2016, 12:41 PM   #2
mr ilia
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I have had similar experience minus the cracked expansion tank. Car has overheated without prior warning. Once cooled down and with fresh coolant everything was more less normal except temp was slow to get to normal and I could not get fan to come on (it was cold outside).
I changed the thermostat and bled the system, also changed the temp sensor and the fan (just in case). Now everything is good, including fan.

I think your issue is a thermostat acting up. Check if your lower rad hose. If it is cold and car overheats then this is a sign of a closed thermostat. could be blocked rad, but not too likely), with the cold lower hose the fan wont come on, as the temp sensor will read low coolant temps.
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2004 BMW 325ci - Sapphire Black
1991 BMW 318i sedan - Lazurblau
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Old 05-11-2016, 12:52 PM   #3
jeepster
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Quote:
Originally Posted by mr ilia View Post
I have had similar experience minus the cracked expansion tank. Car has overheated without prior warning. Once cooled down and with fresh coolant everything was more less normal except temp was slow to get to normal and I could not get fan to come on (it was cold outside).
I changed the thermostat and bled the system, also changed the temp sensor and the fan (just in case). Now everything is good, including fan.

I think your issue is a thermostat acting up. Check if your lower rad hose. If it is cold and car overheats then this is a sign of a closed thermostat. could be blocked rad, but not too likely), with the cold lower hose the fan wont come on, as the temp sensor will read low coolant temps.

10-4 I found a new wahler thermostat locally for $40 that I plan to get tonight to check!
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Old 05-11-2016, 01:29 PM   #4
dmax
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You were running quite a bit above normal for a while. Working properly, it shouldn't get above, say, 98 C or below 212 F

I hope it is just the therm, but monitor your fluids--coolant for level and oil...and oil for coolant--because you could have easily blown the head gasket or cracked the head...hopefully nothing worse.

Good luck, buddy!
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Old 05-11-2016, 03:32 PM   #5
jeepster
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Im going to try a new thermostat and lower radiator hose sensor. If that does not fix the problem, the motor will be coming out so I can add two cylinders!!
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Old 05-12-2016, 06:28 AM   #6
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Quote:
Originally Posted by jeepster View Post
Im going to try a new thermostat and lower radiator hose sensor. If that does not fix the problem, the motor will be coming out so I can add two cylinders!!
Based upon what you've changed that would be my guess.
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Old 05-12-2016, 04:42 PM   #7
jeepster
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Replaced the thermostat and the lower radiator hose sensor last night. Filled it up, bled system, then heated it up to 200*. Shut if off and checked level this morning. Added a half qt of fluid and drove it to work. Water temps were 200-212* during the morning drive. Fan worked normally. Took it on a 30 minute city drive without temps going above 215* at lunch. Then went on highway for 25 minutes and temps were 195-208* @ 70* ambient temp. Drove back to my office an let it idle where the water temps rose to 230* again with both hoses are hot to touch (no codes and no Fan running!!!). Went on a short drive cooled it down to 210* and went into work.

Now what? Symptoms are different but still having and issue.
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Old 05-13-2016, 01:34 AM   #8
Commando
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Seems your thermostat was only part of the problem - now solved as the car is running normal temps when there is some air flow. The cooling fan is not operating when it gets hot at idle which we know it should.
Why not?
Something appears intermittent as the fan is working sometimes. Intermittent faults are the most irksome in my experience.
Is the DME reading the temperatures correctly. INPA will tell you that.
If it is then is the DME trying to operate the fan? In the wiring diagram I looked at (MS43) +12V is connected to the fan via a fuse. Ground is also connected to the fan. The DME supplies a ground on the control wire to operate the fan.

You may need to check your specific vehicles wiring.


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Old 05-13-2016, 10:02 PM   #9
jeepster
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Quote:
Originally Posted by Commando View Post
Seems your thermostat was only part of the problem - now solved as the car is running normal temps when there is some air flow. The cooling fan is not operating when it gets hot at idle which we know it should.
Why not?
Something appears intermittent as the fan is working sometimes. Intermittent faults are the most irksome in my experience.
Is the DME reading the temperatures correctly. INPA will tell you that.
If it is then is the DME trying to operate the fan? In the wiring diagram I looked at (MS43) +12V is connected to the fan via a fuse. Ground is also connected to the fan. The DME supplies a ground on the control wire to operate the fan.

You may need to check your specific vehicles wiring.


http://www.bmw-planet.net
That is correct. I can confirm that the DME varies the ground to control the fan. I had a friend use a digital reader to find out if the DME was sending a signal. It was sending a variable signal (although I have no idea if it is correct)




Where it sits now:

Replaced the NEW fan with another NEW fan and all seems to be well. Car runs between 195-212* at all times. Ran 30 minutes in town, 30+ minutes on the highway and several on/off cycles while running errands. Coolant level stays the same and the fan is clearly functioning "normally" at this point.

I guess time will tell but as of now I will call it fixed.

Appears that the lower sensor was bad (tested different ohms than the new one), the thermostat was stuck closed, and the fan (two of them actually) were bad. How the hell did that all happen at once? LOL
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Old 05-15-2016, 08:18 PM   #10
BMW-North
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Quote:
Originally Posted by jeepster View Post
That is correct. I can confirm that the DME varies the ground to control the fan. I had a friend use a digital reader to find out if the DME was sending a signal. It was sending a variable signal (although I have no idea if it is correct)




Where it sits now:

Replaced the NEW fan with another NEW fan and all seems to be well. Car runs between 195-212* at all times. Ran 30 minutes in town, 30+ minutes on the highway and several on/off cycles while running errands. Coolant level stays the same and the fan is clearly functioning "normally" at this point.

I guess time will tell but as of now I will call it fixed.

Appears that the lower sensor was bad (tested different ohms than the new one), the thermostat was stuck closed, and the fan (two of them actually) were bad. How the hell did that all happen at once? LOL

Ok when you said in the first post you had installed a new fan can you tell us the brand and source. Also where did you get the next fan and what brand is it? I've started noting brand new fans that are not working or not functioning fully right out of the box. Yours is number three that I've heard of.
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Single NRG file: Complete BMW Standard Tools Suite You will also need ISO Workshop (free edition - linked) to create the install directory (image) or disk. NRG file: 347,183 Kb

Last edited by BMW-North; 05-15-2016 at 08:19 PM.
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Old 05-16-2016, 05:59 AM   #11
Robbski
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Just went through this sort of overheat problem with one of our non-BMWs. The symptoms were nearly identical. T-stat was the logical culprit but no luck. Turns out it was a plugged radiator.
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