Oil temp sensor before or after external oil cooler??

I decided to outfit the Gen 2 Coyote in my Miura with a remote oil filter and external oil cooler given the tight spaces around the engine and that one of the headers pretty much wraps around the oil pan. I also plan to install a oil temperature gauge/sensor so the oil temperature can be monitored. My question is whether it is best to place the oil temp sensor before the oil cooler radiator or after it?

My intuition is to place the sensor after the cooler as this will show the oil temperature for the oil that will be going to all those precious internal engine parts. But in thinking about it a little bit, it seems that it would also be nice to know the "maximum" oil temperature which would have the sensor before the cooler.

So can you engine gurus lend some insight as to the optimal place for an oil temperature sensor?
 

Ian Anderson

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Fit two sensors with a toggle switch so you can get an entry oil and sump oil termerature.

That would be the way I would go

Ian
 

Randy V

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Sump temps are difficult to judge because they are immediately influenced by blow-by gasses.
In my opinion, the only temperature that you should be concerned with is the temperature of the oil you are feeding those bearings.
 
To measure sump temperature in this situation, it would be rather involved (would need to remove oil pan and weld in a bung) and it looks like that would only be an approximation for the actual oil temp in the oil galleries. I did check the oil flow layout for the Coyote engine and verified that oil goes from the sump to oil pump, from oil pump to filter, and then from the filter to the various oil galleries that feed bearings, cams, etc. Given this, it appears that the most accurate oil temperature readings would be from somewhere in the oil lines for the remote oil filter and cooler.

My initial question was assuming this and was asking whether taking the reading after the cooler was better than before. My thought was similar to Randy's input that the most important thing was the oil temperature as it was heading towards the engine bearings/internals. So I'll ask the question again for clarity, is there a good reason to measure the oil temp at it's highest, thus before the cooler?

I also have a related question as to the placement of the oil temp sensor. One alternative is to put a tee in the port for the oil pressure sensor (port located in return side of adapter block bolted to engine) and put both sensors in this tee. The other alternative is to install an inline adapter in the -10 hoses going to/from remote filter and cooler and install the temp sensor there. The inline adaptor alternative sounds superior to me as the sensor is more likely to be more directly in oil flow, but the other alternative is likely easier/cheaper.

I have another semi-related question but I'll start another thread for it to minimize confusion.
 
Drill a hole in the sump plug, thread said hole and fit the sensor.
easier than welding something in the sump

Ian
Good idea. (That's how we do it on dyno engines, in our case a 3mm thermocouple which protrudes into the sump pan as near to the oil pick up pipe as possible)

Regards Steve
 

Howard Jones

Supporter
I did mine like this. That is the return port to the engine line leaving the cooler that the sensor housing is attached to. My thought was I really wanted to know how effective my oil temp management is working. Since it is a separate housing it could be placed anywhere in the system but I put it there.
 

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I would measure the temperature before the cooler. Oil temps there indicate the state of the bearings under load. The oil cooler may hide a problem until it's too late.
 

Neil

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Why not put a temp sensor in both positions? In addition to all that has been suggested, it will measure how effective your oil cooler actually is. "Delta T"
 

Bill Kearley

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I think I would like to know the oil temp as it leaves the engine or in the gallery, it would be more informative, the same reason we take the water temp as it exits the head and intake.
 

Randy V

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Bill, with all due respect, the primary goal of the cooling system is to remove heat from the engine with the only lubricating being done is the waterpump bearings. Measuring the temperature of the coolant as it is leaving the engine gives you a good idea as to the heat in the engine itself. Of course one of the primary goals (there are two) of the oiling system is to carry heat away from the bearings. The other goal is to actually keep a viable lubricating film on those bearing surfaces.
Certainly a case can be made for taking both temps to judge the efficiency of the cooling systems (oil and coolant) - but frankly as a builder / owner / driver, that’s adding two gauges that would clutter up an already busy dashboard. Less is more in my opinion. Sensors to be used in D-A are another story…
On one of my cars, we ran a mechanical oil temp gauge in the center of the wet sump. (About 2” below the surface of the oil) Watching the oil temp immediately spike from 240 to 300 under hard acceleration and then dropping back almost immediately to 240 told us that we were not getting an accurate reading. I installed another guage on the output side of the oil cooler and saw 210 while the sump still averaged 240. That’s all I needed to convince me that my bearings were safe with the oil temp they were receiving.
 
I did mine like this. That is the return port to the engine line leaving the cooler that the sensor housing is attached to. My thought was I really wanted to know how effective my oil temp management is working. Since it is a separate housing it could be placed anywhere in the system but I put it there.

Thanks Howard! That's the same type arrangement I've been calling an "inline adapter" but I guess a more descriptive name would be "inline sensor port". I also understand your reasoning for putting it on the return side of the oil cooler and that's the way I'm currently leaning. Putting in 2 sensors seems like overkill, especially for a street car.

Given the number of people that have suggested putting the sensor in the oil sump, I'm curious as to the specific reasoning for that location. Is there a specific advantage to measuring temperature in oil sump over in the remote oil cooler line? The disadvantage of oil temp reading oscillations during oil slosh that Randy provided seems fairly convincing to go the inline sensor port route.
 

Neil

Supporter
Bill, with all due respect, the primary goal of the cooling system is to remove heat from the engine with the only lubricating being done is the waterpump bearings. Measuring the temperature of the coolant as it is leaving the engine gives you a good idea as to the heat in the engine itself. Of course one of the primary goals (there are two) of the oiling system is to carry heat away from the bearings. The other goal is to actually keep a viable lubricating film on those bearing surfaces.
Certainly a case can be made for taking both temps to judge the efficiency of the cooling systems (oil and coolant) - but frankly as a builder / owner / driver, that’s adding two gauges that would clutter up an already busy dashboard. Less is more in my opinion. Sensors to be used in D-A are another story…
On one of my cars, we ran a mechanical oil temp gauge in the center of the wet sump. (About 2” below the surface of the oil) Watching the oil temp immediately spike from 240 to 300 under hard acceleration and then dropping back almost immediately to 240 told us that we were not getting an accurate reading. I installed another guage on the output side of the oil cooler and saw 210 while the sump still averaged 240. That’s all I needed to convince me that my bearings were safe with the oil temp they were receiving.
I would put in the two sensors and use the information from each for testing. After satisfying myself that things looked OK I'd use the one dash-mounted oil temperature gauge, connected to whichever port I chose, and capping off the connector to the other and leaving it in place.
 
I have a related question. What sequence is best when both the oil filter and oil cooler are remote. I'm thinking it would be best to put the oil filter before the cooler so that if any metal shavings come out the engine they are trapped in the filter and thus don't get lodged in the cooler. I've heard that once metal shavings get into an oil cooler, there's no real good way to completely clean them out so the only answer is to replace the oil cooler. When comparing the cost of these two items, oil filters are comparatively much cheaper than oil coolers.

Are there any other considerations to the best sequence?
 
I would be as concerned with what sort of rubbish the little Chinese boys that welded up the cooler left in it. My thought, for what it's worth, put the filter last.

If you shred a bearing and the debris get's in your cooler, the filter should catch it.

As for the sensor location. it must be submerged in oil if in the sump. Otherwise, you can add a fudge factor for where it is.

Old Chevys read the water temp in the head, and that gives a reading 20-30 degrees higher than at the thermostat. Due to lack of other places, I have my Cobra's in the back water passage of the head, and under a light load at high speeds in cold weather, it'll read 135 degrees. It's seeing water that has been through the block, but not through the head on the way back to the front where the 190 degree T stat is is holding 190 degrees (megasquirt data where it's sensor is) If I see 185 degrees, I know I'm full temp and the fan isn't on or I'm not moving.
 

Howard Jones

Supporter
I used one of these. Oil from the pump through the filter, then to the cooler, then to the oil temp sensor, then back to the engine. Makes sense to me.

 
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