Strange oil temp fluctuations 165F to 210F with start/stop

[quads]

Hey everyone,

I'm racking my brain and can't figure out why my e90 m3's oil temp is going nuts. Before I take it in to the dealership I'd like to try to figure out whats going on.

Ambient temp 45F
Car is fully warmed up. Have been driving for almost an hour.
I can repeat this phenomenon every singletime

1) oil temp hoovers around 210F, maybe a little more if I'm driving it hard. Usually with this ambient temp it's hard to get it higher but for some reason tonight I am able to get it around 220-225F just driving on on the street which is out of the ordinary

2) then I pull up to a stop light and let auto start/stop kick in. engine stops. when I let off the brakes engine first back up then the oil temps dive very quickly. Within a minute it's at 165F or even past that dot. It doesn't matter how long the start stop thing is doing it's thing - could be 5 minutes or it could be 5 seconds, this phenomenon is repeatable. The temps go for a straight dive.

3) Then I drive around for a bit - it takes a while for the temps to get back up to 210F even though the car is fully warmed up. If I drive it hard, high rpms, load the engine when I can then I can get the temps up in 5 minutes. Otherwise it takes a while for the temps to go back up. start/stop won't kick in until temps are 210F so I work the car hard trying to get the temps up so it would stop the engine again.

I was able to do this every single time consistently. I did the cycle 5 times consecutively. I can't figure out whats going on.

I have a theory but it's still strange because I've never seen this happen before - even when I was in germany driving around in sub zero temps.

My theory is that the oil cooler has a valve that only opens when the engine temps are high. But the start/stop mechanism will always open it up when the engine is started back up. thus each time it opens cold oil is circulated back into the engine and the temp sensor is right where the cooler flows the oil back in. But then a few things don't make sense - can the oil in the cooler cool off so quick while standing in the cooler - even with the car full warmed up? Secondly, why doesn't the oil cooler valve open when I'm driving it hard? I've pulled up to a stop light with the temps around 225F and it stayed there for a while from my hard driving and wouldn't go down until I make start/stop happen.

Now I don't even know if there is a valve that opens up the cooler or how the whole oil system is routed - so this is my theory.

Perhaps someone (bmw tech? or someone with manuals) chime in?

I took videos of this phenomenon. If you guys can't solve this I'll post it to show you.

thanks!

[Gearhead999s]

Dont use the stop/start switch and your problem is solved I have had mine for 7 months and have never used this feature!

[Singletrack]

My guess would be a bad oil temp sensor. I'm not sure what valving there is in the oil cooler though. But even if there is one, I severely doubt there is any oil that is that "cool" in the car. In reality, the total temp taken out of the oil is much less than the delta you are showing. Also, the lower sudden oil temps might make the ECU adjust the idle...don't know.

A lot of speculation there on my part; sorry I can't give you anything more concrete. Doubt you will figure it out without the dealer : (

Good luck!

[Richbot]

Remember that "oil temp" gauge is actually a composite oil/coolant temp gauge to some degree. As soon as fluids stop flowing through the various coolers everything inside the heat exchangers is going to cool off in a hurry. The sensors are probably located too close to the heat exchangers to smooth out the rapid cooling and heating that's happening when the engine does a stop/start cycle

Another good reason to just turn the damn thing off

[m33]

Scan your car I get this too , I get coolant temp sensor code so I ended changing the coolant sensor but it comes back 3 months later ... Pretty weird ...
Same symptoms as yOu explained , let me know what the dealer says ..

[quads]

Originally Posted by m33

Scan your car I get this too , I get coolant temp sensor code so I ended changing the coolant sensor but it comes back 3 months later ... Pretty weird ...
Same symptoms as yOu explained , let me know what the dealer says ..

Yesterday I was not able to reproduce this on a long trip.

Does this happen to you consistently from day to day or is it just when you drive it aggressively? What happen that night was I was driving it hard and it's was indeed fairly cold outside.

No I didn't get an error code on the dash but I will plug in a code reader to see if I get anything.

I'm not going to go to the dealer unless I can repeat it time after to them - I don't trust them for small things. Last time I took it in they tried to charge me for all kinds of small things (which I refused) AND scratched my car!

[vm]

I don't know where the sensor is but it is also possible that when the engine stops the oil goes to a level below the location of the sensor so the sensor is in fact not in the oil and cools down. It then might take some time to heat the sensor to actual oil temperature when you restart the engine. Is your oil at the right level? This is only speculation on my part.

[quads]

Originally Posted by vm

I don't know where the sensor is but it is also possible that when the engine stops the oil goes to a level below the location of the sensor so the sensor is in fact not in the oil and cools down. It then might take some time to heat the sensor to actual oil temperature when you restart the engine. Is your oil at the right level? This is only speculation on my part.

The oil level is rock solid - right at the max line since I took redelivery this march. I've got over 18k since and the oil line hasn't moved. The only time I saw it move was during break in and it moved just one step.

[m33]

What start stop switch are you guys referring to ?

[m33]

Originally Posted by 4sevens.com

Yesterday I was not able to reproduce this on a long trip.

Does this happen to you consistently from day to day or is it just when you drive it aggressively? What happen that night was I was driving it hard and it's was indeed fairly cold outside.

No I didn't get an error code on the dash but I will plug in a code reader to see if I get anything.

I'm not going to go to the dealer unless I can repeat it time after to them - I don't trust them for small things. Last time I took it in they tried to charge me for all kinds of small things (which I refused) AND scratched my car!

Right now only happenes when agressive driving

[quads]

Originally Posted by m33

What start stop switch are you guys referring to ?

The newer m3's have a start stop mechanism.

Originally Posted by m33

Right now only happenes when agressive driving

I see some consistency here. I'm not going to take this to the dealer. Between me and you we're getting more clinical data than a dealer would have - unless theres a service bulletin on this.

If it bothers me I'll just not turn on start stop

[m33]

where do i find this feature ?

[quads]

Originally Posted by m33

where do i find this feature ?

it's one of the buttons near the bottom of the center console just above your cigarette tray and lighter

[m33]

its funny cause when it hits 225 temp i pull to a stop let the car idle then all of a sudden it turns fans on and temps dive back down to 170ish and then slowly climb back up to the 210 mark ...

[m33]

Originally Posted by 4sevens.com

it's one of the buttons near the bottom of the center console just above your cigarette tray and lighter

hmmm where the ac controls are?
can you describe what it reads or looks like ( the button )

[quads]

Originally Posted by m33

hmmm where the ac controls are?
can you describe what it reads or looks like ( the button )

Bottom right. The A in a semicircle


What year is your car?

[m33]

Mine doesn't have that feature
[IMG][/IMG]

[m33]

what does that switch do?

[m33]

btw my car is a 2011 but 2010 build

[quads]

Originally Posted by m33

btw my car is a 2011 but 2010 build

Thats strange. It should have it. So at red lights the engine turns off right? You can get someone to go in there and turn it off by default.

Looks like you have a different lower panel. What are those switches? Is it something aftermarket?

[JCtx]

Originally Posted by Richbot

Remember that "oil temp" gauge is actually a composite oil/coolant temp gauge to some degree.

NO. It's an oil temperature sensor. Somebody spread that false rumor, and still circulates around.

OP, oil temperature is pretty much the same after 5 minutes with engine off, but I wouldn't worry about that man. These cars have many unexplainable electronic gremlins, and I assume yours is yet another one. Unless you get that fluctuation WHILE DRIVING, I wouldn't worry about it. Also keep in mind the M3 engine wasn't designed for a start/stop feature, so unless you're in a dire financial situation, I'd turn it off. Cars properly designed for that, don't use the starter (and battery) for that, like the M3... but you need direct injection for that. Extra wear and tear is a lot more than the fuel savings IMO, but to each his own.

[quads]

Originally Posted by elp_jc

These cars have many unexplainable electronic gremlins, and I assume yours is yet another one. Unless you get that fluctuation WHILE DRIVING, I wouldn't worry about it. Also keep in mind the M3 engine wasn't designed for a start/stop feature, so unless you're in a dire financial situation, I'd turn it off. Cars properly designed for that, don't use the starter (and battery) for that, like the M3... but you need direct injection for that. Extra wear and tear is a lot more than the fuel savings IMO, but to each his own.

Are you also spreading a rumor? I was told the on/off feature was added along with a bigger starter which was the biggest concern.

I seriously would doubt bmw engineers would just slap on the on/off feature on the M3 when - in your words "the M3 engine wasn't designed for..." Can you cite your sources? It's very unlike German character to do that.

Initially I was quite alarmed and thought perhaps I had busted an oil leak or something and the oil wasn't circulating - thus the low temps. I pulled over looked for oil and check the oil level indicator (yeah it could have been delayed). The fact that I could repeat it over and over that night and also that m33 has the same issue reassures me that it's probably ok. I'm not going to risk taking it to a dealer to check out. Now if the engine blew up of course I'd take it to the dealership. I just bought the car in january so everything should be covered