What is normal operating coolant temperature?

[vfwjed]

What is the normal operating coolant temperature for a BMW e32 M62 4.4L engine sitting at idle/parked? (2000 X5)

I ran the GT1 INPA diagnostic (Analog 1) and it was showing 216F – 220F for coolant temp. This seemed higher than I expected. In the process of my investigation, I discovered that the pusher fan (aux fan) was shot. More on this later…

I measured ** the coolant temp indirectly with a (calibrated) fluke laser thermometer the following day, and it measured 215F. So the laser reading is close to the INPA reading so the fluid temp is assumed to be accurate.

**Measured the surface a couple points near the Coolant Outlet Port of the engine. The easiest spot with a good reading was the stainless steel hose clam closest to the engine.

Note: The temperature needle on the cluster head is showing 12 o’clock, BUT this needle is No Longer factory calibrated because the cluster was disassembled to repair the missing pixel problem. – i.e. the needle was calibrated by hand. So I cannot state with certainty it is accurate.

Aux Fan Questions:

The Bentley manual stated that the Aux Fan comes on 20% speed when the car is first started to determine if the fan is working. My car failed this test. Also, my car was registering an 8D (fan) fault code but no SES light.

Should the aux fan be on at engine idle? Maybe this would be the cause of my higher than expected temp reading. (if it is fact high???)

The OEM replacement fans are very expensive so my question is regarding the aftermarket brands.

Any opinions or recommendations?

For example:
00 2000 BMW X5 Radiator Fan Assembly - Cooling System - Behr - PartsGeek

Final notes:

I tested the fan by:

First checking inputs into the fan, the voltage on the connecter (fan plug disconnected) – All good, pulsed control signal showed about 5vdc. (assumed to be good)

Second jumped the fan directly to batt.

(+fan to +batt)
(–fan to –batt)
(fanCTL to +batt)

The fan did not start/move/spin.
Conclusion bad (dead) fan.

thanks in advance

[civdiv99]

108C or 225 is the operating temp.

I think it's nuts, but that's just me. There's a few fixes around to run coolant around 200, which is on my to-do list.

[SlickGT1]

Originally Posted by civdiv99

108C or 225 is the operating temp.

I think it's nuts, but that's just me. There's a few fixes around to run coolant around 200, which is on my to-do list.

Please describe, or link to said fixes. I also always figured 225 is a bit nuts.

[civdiv99]

I'd link to it in a nano-second if I thought I could find it again easily.

The currently installed mechanical thermostat supposed to keep 225 as a norm. The computer can override this by tossing 12v at the "heater" incorporated with/adjacent to the mechanical thermostat, thus artificially making that 225 thermostat open earlier due to that local heating. Under light throttle cruise it's supposed to run at at least 225. The most mine has hit is 110C on the OBC, but is usually right at 108C. Under whatever load conditions are predetermined in the system, the computer will activate the control and on mine has brought it down to about 104C. I dunno if it'll go lower or not - ran out of hill by then. However, I intend to run mine at 195, and there's a shitload of theory and practice out there about the effects of combustion chamber temperature with a gasoline fueled mixture. Too cool, and you risk gas falling out of suspension and cylinder wall washing. Bad juju on the street. Too hot and you raise the octane requirements - AND negatively impact how aggressive the timing can be (power to the people!).

The immediate predecessor to this engine ran at a more ideal 195 or so (for gasoline internal combustion efficiency vs. power; mileage = who cares, it's a V8 for a reason). In one of the E39 groups, there is/was a post describing (pics and all) retrofitting the 195 degree (ish) mechanical thermostat from this engine's predecessor (M60 or early M62 perhaps). The mod retained the electronic control, but that was for convenience and lack of fault code tossing since it never had to come into play. NOTE - this is NOT a "bolt-in," but was certainly not an engineering challenge either. Came down to a small aluminum spacer to provide clearance for the size difference in thermostats. The dude was quite happy.

The other approach is to monitor the engine temp yourself (2 pairs of wires on the "dual-temp" sensor, pick one set to monitor) and have your circuit control the active opening yourself. Probably somewhat less effective and possibly a bit harsh on the heating element, but much less invasive. And you have to have some hysteresis incorporated into your control circuit (thus isn't just switching on and off continuously over 1 or 2 degrees), and/or modulate the power delivered to the heater - with a PWM circuit, for example. This is probably going to be my approach - I already have the circuit scratched out, but if I'm not happy with the effectiveness, and the heater element cannot maintain what I desire (And I'm guessing it won't be able to once the thermostat begins to open and a fresh supply of water is allowed to flow past the heater element), then I will go with the approach above. Whether or not I use the actual BMW mechanical thermostat that was in this engine's predecessor or not is something I'll decide at the time.

Oh, and then there's the "who gives a crap, lemme see what happens here" approach. For $35 at Jegs you can buy a 12v thermostatic cooling fan controller. Instead of hooking that up to a fan, you just hook that relay to the heating element, and connect the original heater wires to a load resistor of correct resistance and load capacity to prevent a code, and see whatcha get. That's not what I would do, but I'm just sayin'.........

[SlickGT1]

Brotha. You are too much for me with the electrical stuff. Wow, you sure know your shit. Ok, you got me interested. Waiting patiently for you to have time to produce a setup, with pics. Thanks for explaining it.

[JCL]

Originally Posted by civdiv99

108C or 225 is the operating temp.

I think it's nuts, but that's just me. There's a few fixes around to run coolant around 200, which is on my to-do list.

Interested in why you think it's nuts. Do you have other engine modifications that push you towards running it cooler? Or is it just a predisposition to run at the temperatures we used to run in older technology engines, on lower specification oils? The earlier generation engine you speak of with a 195 C thermostat was probably using a lube oil from the late 1980s or early 1990s, I'd guess.

I like it hotter. Keeps the oil cleaner, burns off the condensation, and so on. Means you have to use a correct antifreeze glycol mixture instead of straight water, and have a functioning radiator cap, but I take those as givens, for a variety of other reasons.

[civdiv99]

Would that I had time to discuss - and nevertheless this will probably ramble on.

Here's where I am on all this stuff.

It's a 20 plus year old design. 4.0 M60 heads from back in the day will bolt onto an M62. But that's not real relevant; I'm just sayin'.

Engines are designed to run at an optimal temperature based on a lot of factors. No argument with BMW engineering - I've cruised past 100K mi with nary an issue. Which leads to the obvious question: Then why mess with it?

Because in a gasoline engine, operating temperature and tendency to knock are closely linked. Very closely linked. BMW can manage it via engine management systems that're a far cry from "back in the day." The DME already optimizes spark, and since I'm not real interested in the part-throttle cruise economy reasons for running at the high end of the range (yeah, I know, you're gonna want a reference here), I see no downside to dropping the running temp 25 degrees.

Upside? Remains to be seen. But I think it's relevant to this discussion just to point out that I think about and ultimately try stuff out on this car because of it's design, not in spite of. This is stuff I find interesting, and when I read in this forum all about suspension fault this and something else that, my inclination is to go take it apart, decrypt it, figure it out, and publish the findings. I think in another post I already committed to taking apart my air suspension components to develop a "here's how you can check the following components" post. And I will (sigh, there's that commitment again). Remember, I'm the guy who pulled the front end off his X5 and ran an aftermarket trans cooler - just because it was Saturday and there was one on the shelf down the street. Really.

So this whole temp thing boils down partly to experimentation. That, and I just don't think it's necessary to run at the high end of range when the lower end is in reach, but yet is in reach ONLY via the methods I mentioned above. If I could wander down the street and just buy something, then it's not nearly as interesting. And, I don't look at this so much as a "hey, you guys need to try this," so much as "Ok, here's what I did/know/discovered/fell into that can add to collective information. However useful, or not.

On my list of want-to-do stuff is modulating the PWM signal to vary the transmission's main line pressure to see if if I can firm up the shifting under various load conditions, but not all the time so it doesn't ever adapt. That'll probably drive you nuts in the "how can you justify that" sense, but I think it's fascinating, which is all I need. I already have the applicable wires tapped, but I probably won't get back to playing with it for another couple of months.

Last thing just for perspective here. I really do like this car, but it's not "important." It's functionality has no bearing on my daily routine or quality of life. It was not expensive to buy 4 years ago (ish), it still looks and drives great, and I take very good care of it. But in the end, it's metal and plastic, that's all. I hope I get at least several more years out of it before I move on to something else. In the meantime, this is a rolling hobby that I can drive to work, too.

[vfwjed]

Wow, thanks for your response. The passion for automotive engineering is commendable, even if it is a only a hobby!

Maybe this should be a new thread, but here goes anyway, what is the normal operational temperature of the transmission?

I seem to recall on my X that INPA reported that the transmission temperature was about the same as the coolant temperature. About 200F and something. Again, I thought this was high; I need to check INPA again.

In the meantime, I did point the fluke laser thermometer on the surface of the tranny fluid pan and it measured about 165F.

BTW I would be interested in looking at, or understanding the how of your PWM circuit or test jig. Up to you. I have a 1994 740il e32 that is down with transmission problems at the moment. Long story, this is what drove me into INPA/DIS world.

The PWM circuit could be used to modulate (for testing) the aux fan speed too!

j

[civdiv99]

Do a search for my threads, and you'll find where I asked folks to check. A few responses indicated well into the 200+ range. Inpa has my externally cooled running 170 ish. Sensitive subject, like a lot of things automotive. I did not post a how to on that; that's up to you. Somebody asked once, so i think i replied with some pictures and which cooler fit nicely between the front fan and radiator, so I'm guessing that info is still out there somewhere.

[civdiv99]

Agreed on the varied possibilities for PWM. This mobile tablet I'm using is dying. I'll catch up with you.

Civdiv99

Originally Posted by vfwjed

Wow, thanks for your response. The passion for automotive engineering is commendable, even if it is a only a hobby!

Maybe this should be a new thread, but here goes anyway, what is the normal operational temperature of the transmission?

I seem to recall on my X that INPA reported that the transmission temperature was about the same as the coolant temperature. About 200F and something. Again, I thought this was high; I need to check INPA again.

In the meantime, I did point the fluke laser thermometer on the surface of the tranny fluid pan and it measured about 165F.

BTW I would be interested in looking at, or understanding the how of your PWM circuit or test jig. Up to you. I have a 1994 740il e32 that is down with transmission problems at the moment. Long story, this is what drove me into INPA/DIS world.

The PWM circuit could be used to modulate (for testing) the aux fan speed too!

j