Unusual oil temperatures and oil behavior - 08 S65 142K miles / VAC / CSF Rad

[Helmsman]

Originally Posted by jeremyuhh

Cleaned and straightened out almost every fin. Took out countless pebbles and debris.

Amazingly, I could see a difference in oil temp behavior just from the gauge. On highway and street driving, the needle would drop down just before 210F while moving and would not go passed 210F. Straightening the fins and clearing the debris made a huge difference...

BUT

before i got on the freeway, i shut the car off just before it got to operating temp, the fan stayed on. (ambient temp was 65F) Which is really strange because it would only stay on, at its fastest setting, after shutting down at high temps before i cleaned and straightened it (~230F)

now, headed home after driving on the freeway and seeing the temps cool as they should... after i exited and was driving at low speed (20 MPH) in about a 1/4 mile, temps slowly creeped above 210F as i approached my complex and crept up even more as i entered my gated community at a speed of 10 MPH...

which leads me to believe something is up with the fan as CTMike mentioned. The fan operates but i think whatever sensor connected to it is acting up.

and another big finding: macdude357 i felt my oil cooler after coming home from about 20 miles of freeway driving and it was stone cold. Any idea where to start checking for blockages ?

How did you reach to touch the oil radiator mate? Out driving so thought I took a feel as well.

[Davisca455]

I would try from underneath, through the opening in the bottom of the tray?

[jeremyuhh]

Originally Posted by Helmsman

How did you reach to touch the oil radiator mate? Out driving so thought I took a feel as well.

Originally Posted by Davisca455

I would try from under through the opening in the bottom of the tray?

exactly like that.

[Helmsman]

Originally Posted by Davisca455

I would try from under through the opening in the bottom of the tray?

Is it actually the oil radiator you get from there, thought that was stacked on the outside of the coolant rad?
Ps. Wow that is a clean inside man!

[jeremyuhh]

Originally Posted by CTMike

I ran in to overheating issues when my radiator fan bit the dust. It was intermittent at first and of course traveling at speed it wasn’t really noticeable. Slow cruising or traffic it became a real problem. Ultimately the fan and fan relay were replaced and a wiring contact repaired... no issues since.

CTMike

PN for the fan relay and its location? I've searched and all i was able to gather that its in the passenger footwell with no exact location.

is this it ? https://www.fcpeuro.com/products/bmw...caAlu2EALw_wcB

Also tried RealOEM, and its leading me to a relay next to the battery?
https://www.realoem.com/bmw/enUS/sho...54#61366901819

[jeremyuhh]

Originally Posted by Helmsman

Is it actually the oil radiator you get from there, thought that was stacked on the outside of the coolant rad?
Ps. Wow that is a clean inside man!

looking from out to in: oil cooler in front of ac condenser in front of coolant/water/main (whatever you wanna call it) radiator

Were you able to feel if it was hot or cold?

[Davisca455]

Originally Posted by Helmsman

Is it actually the oil radiator you get from there, thought that was stacked on the outside of the coolant rad?
Ps. Wow that is a clean inside man!

That is indeed the back side of oil cooler.
One of the main reasons I'm on the FCP Euro "insurance program" with the BMW front under trays, is that some BMW engineer went to the trouble of creating this nice curved, separated and sealed "exhaust" channel for the oil cooler.
I mean, it looks like the engineers went to a lot of trouble to segregate the heat dump of the oil cooler.
My guess is that they didn't want it exhausting onto the other heat exchangers?

(Full transparency: It's so clean in there because I had just installed a do88 oil cooler when the picture was taken)

[Helmsman]

Originally Posted by jeremyuhh

looking from out to in: oil cooler in front of ac condenser in front of coolant/water/main (whatever you wanna call it) radiator

Were you able to feel if it was hot or cold?

Ah, got it. Can't say I did but was juat hitting 100C where I assume the Tstat only should start to open up. I'll try to remember to check again, will report back.

[CTMike]

Originally Posted by jeremyuhh

CTMike

PN for the fan relay and its location? I've searched and all i was able to gather that its in the passenger footwell with no exact location.

is this it ? https://www.fcpeuro.com/products/bmw...caAlu2EALw_wcB

Also tried RealOEM, and its leading me to a relay next to the battery?
https://www.realoem.com/bmw/enUS/sho...54#61366901819

That looks like it - it’s used in multiple places - and for the radiator fan it is indeed in the passenger footwell. I’ll see if I can find exact PN, but I think you have it.

[macdude357]

Originally Posted by jeremyuhh

and another big finding: macdude357 i felt my oil cooler after coming home from about 20 miles of freeway driving and it was stone cold. Any idea where to start checking for blockages ?

If oil isn't flowing, then it's a very good chance your oil tstat is not opening. FYI, I used an IR heat gun to check the front of my cooler.

[roastbeef]

well there is your problem. relatively cheap fix.

[jeremyuhh]

Originally Posted by macdude357

If oil isn't flowing, then it's a very good chance your oil tstat is not opening. FYI, I used an IR heat gun to check the front of my cooler.

Originally Posted by roastbeef

well there is your problem. relatively cheap fix.

Right.

My question now is to get a New OFH since an oil thermostat cannot he purchased separately or epic diverter valve?

Summer in CA is approaching so it might be ideal plus I live in the valley where we've been getting hotter than average weather in the past years. My only concern is the longer than average warmup times, other than that, there really isn't anything else to worry about, right ? Until winter comes ?

[roastbeef]

edit- i was wrong.

[tdott]

Originally Posted by roastbeef

looks like it can be purchased separately unless i'm missing something.
https://www.fcpeuro.com/products/bmw...hoCB3EQAvD_BwE

and the gasket.
https://www.fcpeuro.com/products/bmw...al-11427525335

I don't see M3 listed under fitment.

That looks like a n54/5 part not S65.

[jeremyuhh]

Originally Posted by roastbeef

looks like it can be purchased separately unless i'm missing something.
https://www.fcpeuro.com/products/bmw...hoCB3EQAvD_BwE

and the gasket.
https://www.fcpeuro.com/products/bmw...al-11427525335

Originally Posted by tdott

I don't see M3 listed under fitment.

That looks like a n54/5 part not S65.

looks like an N55 part and the housing in the diagram doesnt look like the S65 housing either.

[roastbeef]

Originally Posted by tdott

I don't see M3 listed under fitment.

That looks like a n54/5 part not S65.

crap- you're right!

[TX]

normal warm up in 80* summer FL takes me almost a 10 minute city drive from overnight car off cold to reach the middle tick mark below 210. Often the car isn't warmed up before I park it again. If I make a trip out during the day I take advantage while the temps are still there.

A few years back people were installing higher opening thermostats to make the cars warm up faster, but I still cant explain the over temp you are seeing as that is too high.

perhaps this thread can be of some use, regarding the latest thoughts on the oil thermostat in the OFH.
https://www.m3post.com/forums/showthread.php?t=963243

[jeremyuhh]

Originally Posted by TX

normal warm up in 80* summer FL takes me almost a 10 minute city drive from overnight car off cold to reach the middle tick mark below 210. Often the car isn't warmed up before I park it again. If I make a trip out during the day I take advantage while the temps are still there.

A few years back people were installing higher opening thermostats to make the cars warm up faster, but I still cant explain the over temp you are seeing as that is too high.

perhaps this thread can be of some use, regarding the latest thoughts on the oil thermostat in the OFH.
https://www.m3post.com/forums/showthread.php?t=963243

Thanks, yes ive read that thread about 5 times, lol. unfortunate that it just ends.

Ive already read the thread about higher temp thermostats, but i think i will be sticking to the OEM thermostat.

I'm currently trying to confirm if my oil cooler and oil thermostat is whats causing all this. Ive only driven the car a long enough distance once to feel the cold oil cooler. Havent had a chance to drive my car for more than 2 miles to pick up food since we're working from home. Need to wait for my next trip out into the city.

[TX]

Originally Posted by jeremyuhh

Thanks, yes ive read that thread about 5 times, lol. unfortunate that it just ends.

Ive already read the thread about higher temp thermostats, but i think i will be sticking to the OEM thermostat.

I'm currently trying to confirm if my oil cooler and oil thermostat is whats causing all this. Ive only driven the car a long enough distance once to feel the cold oil cooler. Havent had a chance to drive my car for more than 2 miles to pick up food since we're working from home. Need to wait for my next trip out into the city.

Yes, I am sorry to have included repetitive information. I was sort of asking a quick one off question to see if someone might have installed the higher temp thermostat in your car previously which would cause the over-temp before it opens, but if not, then disregard my error.
My other thought was your fan wasn't operating properly, but that wouldn't be an issue at highway speeds. You would see a huge spike in temps once you pulled off and the fan wasn't operating causing the spikes. So this takes us back to a cooling issue regarding oil/water exchange of heat.

[jeremyuhh]

Originally Posted by TX

Yes, I am sorry to have included repetitive information. I was sort of asking a quick one off question to see if someone might have installed the higher temp thermostat in your car previously which would cause the over-temp before it opens, but if not, then disregard my error.
My other thought was your fan wasn't operating properly, but that wouldn't be an issue at highway speeds. You would see a huge spike in temps once you pulled off and the fan wasn't operating causing the spikes. So this takes us back to a cooling issue regarding oil/water exchange of heat.

no worries, appreciate your help. The invoice showed OEM part number thermostat, so nope, not a higher temp one installed. I thought that coulda been it too, but luckily i have all the invoices and documents for this car that the previous owner gave me.

My fan might be a factor. After cleaning and straightening the fins from my oil cooler and ac condenser, after about a 10 minute drive, car wasnt at temp yet, or maybe barley reaching temp, in about 65F windy weather, the fan stayed on at its lowest setting when i shut the car off, which makes me think its the relay or some faulty sensor.

going to replace thermostat anyway and see if that helps. was replaced back in 2018 along with the CSF radiator.

The only other thing that makes sense it that if my oil cooler is supposed to be hot, which it isnt, then oil is not reaching the cooler. Hence either a blockage somewhere or the oil thermostat is not opening, even after miles of driving at temp. Most likely the latter, im hoping.

[Helmsman]

Originally Posted by jeremyuhh

no worries, appreciate your help. The invoice showed OEM part number thermostat, so nope, not a higher temp one installed. I thought that coulda been it too, but luckily i have all the invoices and documents for this car that the previous owner gave me.

My fan might be a factor. After cleaning and straightening the fins from my oil cooler and ac condenser, after about a 10 minute drive, car wasnt at temp yet, or maybe barley reaching temp, in about 65F windy weather, the fan stayed on at its lowest setting when i shut the car off, which makes me think its the relay or some faulty sensor.

going to replace thermostat anyway and see if that helps. was replaced back in 2018 along with the CSF radiator.

The only other thing that makes sense it that if my oil cooler is supposed to be hot, which it isnt, then oil is not reaching the cooler. Hence either a blockage somewhere or the oil thermostat is not opening, even after miles of driving at temp. Most likely the latter, im hoping.

I don't have facts but would assume the fan only operate when there isn't enough air flow, i.e. stand still stop/go traffic. If you have over temp also at fair speed it shouldn't matter whether the fan is good or not?

I will check the temp of my oil cooler soon as I get a chance, doesn't come up to full temp on work commute and would assume the Tstat start opening around 100C. By any chance managed to confirm open/close temp spec?

[amrazM]

It seems too unlikely, the oil thermostat is a mechanically controlled part. Depending how mechanically inclined you are it may be possible to remove the housing and test the thermostat as the whole housing is nearly $400

https://www.getbmwparts.com/oem-part...ly-11427841525