Let's talk engine coolant temperature

In reply to Tom_Spangler (Forum Supporter) :

I doubt it's the same in the modern era, but for a long time, Ford did dummy temp gauges.  Mine included 98 F150, 02 F250, 99 Powerstroke van, 95 Powerstroke F250, 94 Ranger, and 97 Lincoln Mk8.  All of them used a pre-programmed range.  Cold was cold.  Once it reached something like 150 degrees the gauge slowly rose to the middle.  It stayed there as long as you were between something like 180 and 230.  If it went over 230 it was programmed to kinda quickly sweep up to hot.  It basically showed you cold, ok, and yikes.

Not sure if yours still does that, but it would be interesting to plug in a scanner and see if it tracks.

Curtis73 (Forum Supporter) said:

Suggestion for you... if it's easy to do.  Pull the electric off and re-install the belt fan for a week or so.  If your temps still get to 220, you know that the system is doing it's job.  If it suddenly starts reading 185, then you know your electric fan isn't up to the task.

I have to answer Curtis, as its an easy one ... if only it were so simple and my dumbass did not machine the threaded water pump nipple off, lol. 

The electric fan is huge and draws 40a. It would not clear the water pump otherwise. 

Its the biggest one Bimmerworld sells, and I still think the clutch fan moves 10x more air. 

I know that belt fans have inherent (massive) parasitic losses and inefficiencies, but the 10 hp it might take to drive it is now being replaced with a 40A device.  If you do the math, that's 10hp = 7355W which is 613A at 12v.  Again, totally invalid comparison, but just for giggles.

There is an electric fan out there for you, just maybe not this one... and as has been mentioned... maybe this one is enough.  I suppose time and testing will tell.  Do you have datalogging potential?  Maybe chart the coolant temp trends against IAT and throttle position?  That might give you an idea of how much or how little overkill things are.  If you see temps rising quickly, it might mean you need a little more cooling, but hard to quantify without a baseline.

I think you might be fine.  My posts were mostly to put your mind at ease.  If it's staying at 220 and not boiling, you've done your job and done it well.  If you start seeing the cooling system get overwhelmed, I think the first place to look is the fan.

Another thing I noticed was that you mentioned it seems to do great in traffic, but gets up to higher temps on the highway.  That is an indicator that your fan may be blocking more than it flows.  Every car is different, but I remember (ages ago, like in an 80s Car Craft or Hot Rod magazine) that the free-flow CFM of a square body chevy truck grille/radiator is something ridiculous like 6800 cfm.  The 78 chevy that I used to use for towing 10k lbs I don't recall it EVER engaging the fan clutch except in stop and go traffic.  On the highway with my foot down climbing a mountain, it never engaged because the free flow was way more than the fan could provide and it never needed it.  That includes a trip from Phoenix to Flagstaff, which is 150 miles of "up" from 1000 ft to 7000 ft.  It's one of those stretches with water stops every few miles for cars to refill their radiators.

Here's the other little thing that most don't think about.  When you have a belt/clutch fan, it's still moving parasitically when the clutch isn't engaged from belt drag on the viscous liquid in the clutch.  Electric fans also spin parasitically because they are robbing energy from the airflow moving through the radiator.  That, alone, means that the electric is stealing a tiny bit of airflow while the belt fan is slightly assisting.  That's the reason so many folks suggest rubber flaps on the shroud with an electric fan.  They will allow free-flow on the highway, but partially seal at a stand-still while the fan is drawing a vacuum in the shroud.

Is there room to fit the fan on the outlet of the shroud?  If you were able to mount your current fan in the hole of the shroud, I think it would do wonders.  Just move back a couple inches so that the fan blade tips are within 3/4" of the round opening of the shroud?  Then maybe use something like foam rubber around the circumference to close the gap, then cut some windows in the shroud and cover them with flaps of rubber attached at the top like scuppers.

Tom_Spangler (Forum Supporter) said:

I once saw 230F on my Scangauge in the Expedition while towing on a 90 degree day. It sat there for at least an hour and the factory gauge never moved from the middle, the truck never missed a beat, and the AC kept blasting cold air. 

I saw 263F on a scan tool in my Volvo and the needle had only moved one width from normal, which it reaches at about 185.

Yeesh.  I'd hate to see what takes it to the red.

I had one of those fans on my E36 because I was afraid of the exploding fan rumors and power losses and all that. 
 

It sucked (literally and figuratively) and wouldn't move enough air. I'm in SoCal so it gets warm here. I got rid of the car before changing it but if I had the car still I would have changed it back. 
 

Not saying it's your problem, just  agreeing with the above 

I recall my e36 m3 dummy gauge hit red when I got up to 240. I spent a lot of time with torque pulled up while driving due to a radiator crack(which blew my head gasket) and noted all it's strange behaviors. It's straight up from 160-220 then it goes slightly right between 220-240 then it pegs red. 

If it's getting hot on the highway, you either need more radiator or better airflow. 

I fought that for a while with the Jeep.  Eventually a combination of hacking up the drip trays for the hood vents and a thicker radiator did the trick.  It's still not as good as it could be, but that got it to good enough where I no longer worry about it. 

Historically, it cooled great up to ~50 mph, but then as you went faster, cooling got worse.  The models with clutch fans didn't show the issue, as the clutch fan could overcome the pressure buildup in the engine bay.  But with an electric fan, the problem was pretty apparent, as it couldn't push enough air against the pressure buildup (to the point where turning the fan on at highway speeds made very little difference). 

As far as BMW fans, when I deleted the clutch fan on my E38, I also removed the aux fan in front of the radiator for lower restriction.  For the new e-fan, I used a stock electric fan from a 5sp E90 328i (the version with the 400W fan motor).  It uses the same PWM control setup as the stock E38 aux fan, so I swapped the E38 aux fan connector onto the E90 fan motor and then cut down the E90 fan shroud to just the ring around the fan that supports the motor.  That got screwed into a stock E38 clutch fan shroud (it fit perfectly) and installed in the car (and plugged in to the aux fan connector). 

It has worked perfectly (and cooled great) for the last 5 years.  If I ever need more fan power, there are higher power fans out there (600W and 850W motors IIRC), but I'd need to upgrade the power supply to the fan for those, as the E38 aux fan circuit is a bit smaller (both wiring and fuse size) than the fan circuit used on the cars that came with those fans.  So far, the 400W fan has been plenty, probably due to the clutch fan shroud being more efficient than the factory E90 setup (the fan is further from the radiator than in the original application, which should help airflow). 

I'm not sure how hot the S52 will tolerate, but the M62tu in my E38 runs 215 - 230 as normal operating temp from the factory.  Personally with an all iron engine I've never worried up to 230-ish, but with the S52 being an iron/aluminum combo I'd probably be more cautious.  220 would probably be about the point where I'd start worrying.  And in general, if you're getting past 20* above thermostat temp then you're past the point where the stat is fully open and being limited by cooling system capacity which is never ideal. 

Have you tried turning the fan on at highway speed? Even just a temp switch will answer the airflow vs rad size question a bit. Maybe there is a loss of ducting with the bigger rad in the car. 

In reply to rslifkin :

My experience with BMW exploding fan syndrome is that the motor mounts are sloppy, which allows the fan to hit the shroud, which has the expected consequences.

Sloppy motor mounts are also why M3s of the E36 variety were known for 4-3 upshifts. Or was it 3-2?  Either way the drivetrain moved enough that you ended up depositing half of your rotating assembly onto the ground when you downshifted from 6500rpm

In reply to Pete. (l33t FS) :

3 - 2. The classic money shift

In reply to spandak :

Ah yes, now I recall.  A member of the RX-7 Mailing List borrowed a friend's new M3 for a track day and scattered the engine.  (Which tells you how long ago it was, by several metrics)  He wrote a nursery rhyme:

Around and around the Firebird track

The M3 was really revvin'

Shifted to second gear instead of fourth

Pop! Goes the engine

So I converted my E28 to a pair of electric fans to get rid of the clutched mechanical fan as I was sick of it not being that effective at idle when I needed it and then  staying engaged and ruining autocross runs because it was not effective at idle. I'm running my fans with a PWM controller from some Ford with an output from my standalone ecu so I get to do fun things with tables based on coolant temps vs car speed.

If I were you and the test with the fan running at highway speed drops temps to where you are more comfortable I would do two things.

1 - Get rid of the extra shrouding on the back of the rad that was directing air through the old mechanical fan, that is only hurting airflow through the rad at higher speeds now.

2. Add another fan switch into the head by your temp sensors wired in parallel with the switches located in the outlet side of the rad. You'd want the temp of this second switch around 210F (or wherever you think the thing should run at). The low temp switches in the outlet of the rad will take care of the slow speed stuff and the high temp switch in the head will help you with the problem you are having getting some extra air through the rad at high speeds. 

Pete. (l33t FS) said:

In reply to rslifkin :

My experience with BMW exploding fan syndrome is that the motor mounts are sloppy, which allows the fan to hit the shroud, which has the expected consequences.

 

Sloppy motor mounts are also why M3s of the E36 variety were known for 4-3 upshifts. Or was it 3-2?  Either way the drivetrain moved enough that you ended up depositing half of your rotating assembly onto the ground when you downshifted from 6500rpm

I always understood it to be something along those lines with some failures also being caused by failed fan clutches that were staying engaged all the time, causing the fan to over-speed and potentially come apart (especially if there are stress cracks from age and hitting the shroud).   Normally the fan clutch should slip at high RPM, so the fan never sees full engine RPM. 

In my case, I ditched the clutch fan mostly because I was tired of the noise from the clutch fan.  Plus the aux fan was very loud at idle with the A/C on once I replaced the non-working one the car came with.  The new setup is very quiet unless the car feels the need to crank it up to full speed (which is rare), and even then, it's nowhere near as loud as the original aux fan was. 

Curtis73 (Forum Supporter) said:

In reply to Tom_Spangler (Forum Supporter) :

I doubt it's the same in the modern era, but for a long time, Ford did dummy temp gauges.  Mine included 98 F150, 02 F250, 99 Powerstroke van, 95 Powerstroke F250, 94 Ranger, and 97 Lincoln Mk8.  All of them used a pre-programmed range.  Cold was cold.  Once it reached something like 150 degrees the gauge slowly rose to the middle.  It stayed there as long as you were between something like 180 and 230.  If it went over 230 it was programmed to kinda quickly sweep up to hot.  It basically showed you cold, ok, and yikes.

Not sure if yours still does that, but it would be interesting to plug in a scanner and see if it tracks.

Oh, they absolutely do. I was using an OBD2 Scangauge to get that number. But, like others have noted, the factory "gauge" (mine is part of the LCD screen) is still there as more or less an idiot light. As long as it's in the middle, nothing SHOULD be wrong.

Fake coolant and oil pressure gauges have a very good reason for them.  Customers who think they know what both should be, which is not what the engineers want it to be.  Nothing against the OP, but this thread is a good example of that, let alone the van example.  Customers complained that the water temp and oil pressure would move all over the place, and/or they would complain it's too high.

One funny thing- when I worked with Aston Martin, their oil pressure gauge didn't even read oil pressure- it would just make a guess.

Almost all modern engines run more efficiently when it's hot, especially at lower loads and speeds.  So when running the slow emissions test, we would run the temp up to 220F by letting the engine cool with the engine fan.  But when running the higher speed US06- where the air was driven hard into the car, it would run 195.

Anyway, fake gauges are there because enough people have no idea where it should be, and complain when it's not where they think it should be.

This is probably the best place to ask. What *should* a SBC run at temp wise?

On my e36 with the swap I have an OEM replacement rad (plastic end tanks) and a pusher fan. Puller is not an option due to space. 180* thermostat (as installed by the "builder"), Atomic EFI and the fan is set to come on at I *think* 190 (haven't checked it in awhile, been mostly trouble free since I sorted out the wiring).

In town traffic I'll see maybe 200*, but on the highway it struggles to even stay at 180*, some days I will average around closer to 160* (monitored by the Atomic EFI screen). Temp sensor is in the thermostat housing. This normal? too cold? Engine is a 350 Vortec style (Gm Performance Crate motor from 2010)

And when it gets colder out it struggles to hold temp at all. 

In reply to DjGreggieP :

Not a GM person, but that seems way too cold. Especially if it struggles to get warm in the winter. 

Toyman! said:

In reply to Pete. (l33t FS) :

The 6.0 in my Silverado ran steady on 220. The electric fan in my XJ came on at 217. 

 

Yep, came here to post something similar.  The 6.0 in y K3500 runs rock steady at 215 on the factory gauge.  And the heater is typical GM blast-furnace good.  

In reply to DjGreggieP :

Very odd it has a 180 'stat and a 190 fan switch and it won't get over 160.  Should be no issue running 190 on an old school SBC.  I'd check the 'stat and make sure that it is a 180 unit, and that it isn't stuck open.  Then I'd replace it with a 190 unit.

As I've gotten older and wiser, I've come around to the school of thought that engines need to run warm to be happy.  When I was young and less wise, I tossed a 160 'stat at everything, because cooler seemed "better".  Even the old pushrod iron block sand cast lumps from the 60's can stand to run at 190.  Modern engines, well over 200.  

BMWs of this generation did not like elevated coolant temps, so you are wise to be concerned as it goes over 220. I am in agreement you have an airflow issue, as that radiator is highly capable of cooling an s54 as proven by the mcoupe of its day. Fans at highway speeds are more of a hindrance than a help, so you need to make sure ducting is adequate, and remove the shroud if your mechanical fan has been deleted. 

If it's not airflow due to shrouding probpems that's the problem, it has to be faulty equipment (water pump, thermostat, or radiator faulty) IMO.

Mine always ran hottest at idle when airflow was a problem, and if you are getting more flow out of a fan than you are with no fan at speed, then there is something blocking the path or letting it go around your radiator instead of through it. Some track guys run no fans at all, just shut their car off on grid or whenever they are not moving.

Thank you all for the help with this. 
To answer some of the questions:

- Running the fan all the time while on the highway with an ambient temperature of around 85 degrees F, yields a coolant temperature of ~188 F, just shy of 190 F. This is somewhat perplexing as I always thought the fan being on would hinder airflow.

- Water pump along with every piece of the cooling system is new with less than 3k miles. All BMW factory parts, except the water pump which is an all metal higher flow Stewart/EMP unit.

- All factory shrouds are in place. The only difference is that I have an aftermarket under tray, it does have a deflector to route air towards the radiator.

- The fan is about 5/8-3/4" away from the radiator and the fan motor is 1/8" away from the engine, so there is no way it can move further away from the radiator. You can see the fan motor to the right and the water pump pulley nuts on the left. This is the reason I machined off the water pump clutch fan snout, the aftermarket one would not fit otherwise as I went with a bigger unit than is usually used on these cars. 

Yesterday in the afternoon is was quite warm, 85 F and I did some data-loging. Of course the car makes me look like an idiot and work as it should.
The temperature data is being pulled from the factory sensor at the head and not the aftermarket one, but I never saw the aftermarket gauge go to 220 either. I have a ton of engine parameters, anything else you would like to see on the chart, please ask.

I will not be able to drive the car for a couple of weeks, but I will do some more dataloging once I can put some miles in it.

adam525i said:

1 - Get rid of the extra shrouding on the back of the rad that was directing air through the old mechanical fan, that is only hurting airflow through the rad at higher speeds now.

2. Add another fan switch into the head by your temp sensors wired in parallel with the switches located in the outlet side of the rad. You'd want the temp of this second switch around 210F (or wherever you think the thing should run at). The low temp switches in the outlet of the rad will take care of the slow speed stuff and the high temp switch in the head will help you with the problem you are having getting some extra air through the rad at high speeds. 

Number 2, I guess, was my original question. I can trigger the fan with the aftermarket switch. My gauge has an option to ground the relay and I can set the temperature to whatever I want.

I agree with everyone that the way to go is the factory clutched fan, but I really think that this set-up has been used countless of times on this platform and has to work. I am doing something wrong.

What I want to do now is experiment with a different trigger setting on the fan for high speed and play with the factory shroud. I thought the factory shroud was needed, but many of you have suggested removing it.

188 is a bit low in my opinion, but I think you found your answer.

If that's what I discovered, I would wire the relay hot and give your relay two grounds; one through an oil pressure switch that is NC, and one through your temp switch.  That way it is always on when the engine is running, and turns off when the engine is off.... unless it's over temp, then it will continue to run the fan a bit to cool it off.

But looking at your datalog, I see absolutely nothing of concern.  The temperature doesn't have any "oh my god" trends in it, and even at it's highest temperature you still have about 15 degrees before you're in danger of boiling.  Where I would start being concerned is if you saw fast deltas, or trending up under certain conditions like load or IAT or vehicle speed.  I don't see any of that in your log.

In reply to Slippery :

A spinning fan moves the air, a non spinning fan blocks the air flow.  That's why it cools at speed on vs. off.  And it's worse when the fan is in front shrouding the fins from the air flow.