Best location for oil temp sender on e30

[Uber E30]

So i ordered number 13 and it seems the bolt got changed. It doesnt have the large "cylinder" on top anymore... its just a flat bolt which wont work well for this application. It seems the sensor would almost stop all oil flow being that low in the bolt.

Is it necessary to run that pressure sensor? I dont even recall seeing it when i took my oil filter housing off yesterday but maybe i was just preoccupied.

[reelizmpro]

Because of the turbo manifold, I have a remote oil filter and aftermarket cooler on my M Technic. It works well, perhaps too well. There is no oil thermostat! I'm sure you guys know about optimum oil temperature. I have an oil temp sensor in the pan and it never reads more than 150 F on a Turbo M20. Either the cooler is overcooling the oil or the pan sensor isn't accurate, maybe both. I'm going to install another temp sensor in the oil filter housing on the block and a sandwich thermostat from Jegs. Starts opening at 160 degrees and fully opens at 180 degrees.


I originally planned to install the sandwich between the block and the filter housing, but it's a little on the thick side compared to other more expensive sandwiches. While I probably could get it to work, the hoses will be pretty close to the manifold tube.



The other way I could install it (and I'm leaning this way), is install the thermostat at the remote filter housing where the oil filter is. I have yet to try it but it shouldn't be a problem. I just have to remount the housing to accommodate the added length of the sandwich. The housing is only about a foot and a half away from the block so it should see the same oil temp.

Plan to get it all finished tomorrow.
Any thoughts?

Copied and pasted from another thread. Tomorrow I'm going to have my fabricator buddy install a 2nd temp sensor in the oil filter housing on the block. I'm interested in the oil going to the bearings so I'll be tapping in AFTER the cooler. Temp sensor 1 should be hotter than number 2. If not, can we conclude temp sensor 1 is inaccurate? This should be interesting. I will update tomorrow.

[nando]

fine, but if mechanical temperature sensors were superior, I think that nobody would use thermistors for temp readings - except they do, for everything. ;)

also the only way to do a remote oil temp reading would be from a pressure line off the engine, that would never work from the oil pan.

I was seeing oil temps of 250f on the track today. pretty hot. one good reason to stick with synthetic!

(coolant temps are sub 200 for reference)

[george graves]

but you can't really have a "mecanical" temperature reading, they're all going to use a thermistor.

Fluid in a tube, it expands, the pressure moves the gauge..

[reelizmpro]

Well what happens is the hot oil goes down into the pan where it's pooled and continuously being picked up by the oil pump into the oil filter or filter housing (and oil cooler if temps are high enough) and back to the engine bearings, etc.

[nando]

if you think "a while" is basically never, then okay. have fun reading a gauge that won't even show a reading.

a remote sender is probably a good idea though, I can see how the block could heat soak the sensor. but you can't really have a "mecanical" temperature reading, they're all going to use a thermistor.

[AlarmedBread]

Maybe I don't understand how an engine works, but I thought all the hot oil drains back into the pan, and then it is sucked up by the pump, spat at bearings and dumped back into the pan again. The reason I'd choose the pan as a reference point is because that is where I want to know the oil is warm. Yes it takes a while to warm up. Compare your pressure drop to when a sensor in the block says it is warm. As already stated, we want precision, not accuracy. All you need is some base to compare with so you know when something is off.

Obviously the ideal thing to do is have a remote sender unit which is not skewed by hot parts around it, puts no stress on the mounting threads and minimizes potential failure points. Mechanical gauges are great!

[fporro]

Can someone please illustrate how oil flow?
so we can argue where at is it more important to know temp and press off.

Our tranis run lot hotter than engines do, right ?

[nando]

i've seen the temp rising to 180+ on the track.

put it in the block and you'll see how much higher it really is

[kishg]

drain plug.. stock m20.

[reelizmpro]

i've seen the temp rising to 180+ on the track.

Where exactly on the oil pan is it? drain plug? tapped on side? on top?

I'd bet your temps are down about 20 degrees from the actual temp. We're talking about your 325i right? 180 isn't hot at all for a car driven hard on the track. I would expect to see closer to 200 degrees even on an M20.

Another thought: Anyone see a coolant temp sensor in the reservoir? instead, it is right in the thermostat housing right there in the flow path.

[reelizmpro]

We don't know much about VDO sensors except they are thermistor based so they are slow reacting. The sensor is supposed to be grounded to whatever it's mounted to but I don't know if that means the temp of the pan is also being measured. It probably is but then again the pan is being cooled by the airflow underneath, a potential cause of false readings. All I know is my turbo M20 never gets hotter than 150 degrees, which I do not buy. Especially since I saw temps of 175 in my old naturally aspirated M20 with sensor in the oil filter housing and now Nando has the same experience. He did nothing but move the sensor and saw a jump in temperatures. Hard to argue with that.

[kishg]

i've seen the temp rising to 180+ on the track.

[reelizmpro]

ahhh the great debate. I've been studying this the past 2 weeks. Many people say the oil pan is best and it makes sense. Plenty of oil there just coming out of the engine. However, a temp sensor mounted lets say on the side of the pan is going to sample cooler temps than the hotter oil in the middle of the pan that immediately gets sucked up by the oil pump. The pan is a large heatsink by design that is cooled by airflow. VDO sensors lag, so it makes sense to put them where this is more oil flow instead of stagnant oil for the gauge to be useful. BMW put the oil temp sender on the oil filter housing on the E30 M3, so I did the same on my old M20 tapping the hollow bolt for the housing and routinely saw temps of 170-175 degrees. I was satisfied with the readings as they made sense. On my convertible with the sensor in the pan, I (like Nando) have only encounted 150 degree MAX oil temps and this is with a fully warmed up Turbo engine. Doesn't matter how hard I get on it...it will never exceed 150 degrees and I put some duct tape over part of the cooler. I thought it was the gauge wiring but I wired it with it's own dedicated ground. I do have an aftermarket oil cooler that isn't thermostatically controlled so I'm putting a thermostat (opens at 160 and fully opened at 180) on it tomorrow. Shouldn't make a difference but at least I can rule out the cooler and have another way of measuring the actual temp.

[kishg]

not sure about hours. i have temp from the oil pan and it heats up pretty quick.. not sure if its more or less accurate than getting it off the filter assembly.