Oil Cooler Too Eager, Faulty Thermostat Or Incorrect Temp Sensor Location?

[V28VX37]

Hi guys I'm reposting from here and here as this is going a bit beyond the scope of the original threads.

Anyway I've just had the Driftworks oil cooler kit install completed on my R34 GTT:

• Mocal/MIH 19 row Oil Cooler
• Mocal 92 degree thermostatic sandwich plate
• Braided oil cooler hoses
• Sandwich plate fittings

The cooler seems to work well - in fact too well - as I can't seem to get my oil temp up to the recommended range even after a long drive.

Test drives so far (all light cruising until I sort out the temps):

• Melbourne to Torquay, 1.5h freeway, Defi oil temp is reading 55-60 degrees, ambient temp just under 20
• Torquay to Melbourne, oil temp ~60 degrees, ambient temp 25
• Suburban driving, slower speed, oil temp 55-64 degrees, ambient temp 25

...

I can think of a couple of potential causes:

1. Maybe the thermostatic wax pellet in the sandwich plate is not working and the cooler circuit is stuck open or opens too early? Trying the core by hand it's hot but not unbearable. It's definitely flowing a lot of oil during each drive, and well below the expected 92 C opening mark. Also driving a couple of k's from cold start you can feel the oil cooler feed hose getting warm straight away whilst return stays cool.

2. I previously had the temp sensor in a separate sandwich plate with oil flowing through it. For this install the workshop removed the factory pressure sensor and teed off that point – I'm guessing this might be after the filter as opposed to before, which would explain the lower reading?

Here's how the Defi temp sensor is sitting at the OEM oil pressure sensor location (the other end of the T-piece is currently blank waiting for the Defi pressure sensor):

I did some quick temp measurements off the sump earlier tonight (externally using a laser thermometer) and found the following:

• Defi oil temp reading 53C – sump 68-70C
• Defi oil temp reading 61C – sump 76C
• Defi oil temp reading 64C – sump 75C

This might support the theory that the OEM oil pressure sensor point is not ideal for getting oil temps?

What do you guys think: a faulty thermostat, incorrect temp sensor location, or both?

[KiwiRS4T]

There will always be some oil circulating through the cooler.

What was your oil temp before you installed the cooler?

Use your laser thermometer to track flow through your sandwich plate and see if you have picked the wrong spot for your sensor.

The big difference between the sump temp and oil gauge temp suggests the cooler is not overcooling.

[V28VX37]

There will always be some oil circulating through the cooler.

What was your oil temp before you installed the cooler?

Use your laser thermometer to track flow through your sandwich plate and see if you have picked the wrong spot for your sensor.

The big difference between the sump temp and oil gauge temp suggests the cooler is not overcooling.

Yep I spoke with a Mocal distributor today and they explained the same thing that a certain % is always going through the cooler.

What I'm wondering though is if I have the right thermostatic pellet in the sandwich plate, since it seems like it's not just a trickle going through it? Assuming the temp sensor is currently post-cooler (as opposed to previously pre-cooler) it looks like I'm getting a pretty significant temperature drop at temps well below the previous standard operating temp.

Oil temps before the oil cooler installation were 80-90 degrees in normal driving. The same Defi sensor was sitting in a (different) sandwich plate so the oil was flowing through it, as opposed to sitting at the 'end of the line' like it is now.

[GTRPSI]

So your oil temps were perfect, before the cooler was fitted.

Put a sheet of cardboard over the cooler and see what your temps read.

If back to normal id say the unit is open allowing full cooling.

If the same low reading, wrong location.

[GTSBoy]

There is no flow over your Defi temperature sensor!!!!!!!!!!! It is not measuring the temperature of the oil flowing in the system. It is measuring the temperature of the oil in that dead leg, which being brass, will lose heat and be cooler than the rest of the circuit.

/basic physics.

[V28VX37]

So your oil temps were perfect, before the cooler was fitted.

Put a sheet of cardboard over the cooler and see what your temps read.

If back to normal id say the unit is open allowing full cooling.

If the same low reading, wrong location.

Correct, the oil temp was always spot on in street driving.

At the track the temps shot up to 120C after pretty much a single hot lap, though this was on a 37C day.

I'm yet to try blocking the cooler, good idea, I will aim to do that tomorrow.

There is no flow over your Defi temperature sensor!!!!!!!!!!! It is not measuring the temperature of the oil flowing in the system. It is measuring the temperature of the oil in that dead leg, which being brass, will lose heat and be cooler than the rest of the circuit.

/basic physics.

Ok so exactly as I thought, thanks mate!

Next question: Where do people place the temp sensor for an accurate reading with this type of sandwich plate? It doesn't have a sensor port.

As far as I can figure the options are:

1. Run an inline AN10 male-female fitting with a sensor port – is there enough oil flow in the cooler circuit at <thermostat temp for this to work reliably?
2. Run a second sandwich plate for the sensor – not ideal
3. Drill a sensor bung in the sump – sounds like a big sump-off job
4. Get a Greddy/GREX sandwich plate that has both a thermostat and fittings for temp/pressure sensors – not ideal since I already have a sandwich plate

Would option 1 work? Any other suggestions?

[R_34]

I drilled and welded a bung on the oem oil filter bracket to install the sensor.

Edited January 19, 2016 by R_34

[tridentt150v]

My sandwich plate has a couple of blanked off tapped and ready positions, I used one of them.

[fatz]

Why no plug it into the stock location after the oil return ?

[V28VX37]

I drilled and welded a bung on the oem oil filter bracket to install the sensor.

Thanks mate, that seems like a good solution.

I've just ordered this AN10 inline sensor fitting, might try that first: http://m.ebay.com.au/itm/AN10-10AN-JIC-FEMALE-to-MALE-GAUGE-SENSOR-FITTING-ADAPTER-1-8-NPT-PORT-BLACK-/231353204035

Keen not to swap the sandwich plate again as I already have the previous one sitting on the shelf..

[V28VX37]

Why no plug it into the stock location after the oil return ?

I didn't realise there was a stock oil temp location on the RB25DET? Whereabouts is that?

[dan.1337]

I have a Greddy/GREX sandwich plate and have the oil temp and pressure sensors stuck in there.

It might be easiest (and best) to sell your sandwich plate and invest in one with pre-tapped sensor holes.

Do it once, do it right!

[V28VX37]

I have a Greddy/GREX sandwich plate and have the oil temp and pressure sensors stuck in there.

It might be easiest (and best) to sell your sandwich plate and invest in one with pre-tapped sensor holes.

Do it once, do it right!

I would tend to agree The one thing I like better about the Mocal one is the 92C thermostat (if it works?!) - I believe the Greddy plate comes with a 80C one.

What temps are you seeing in normal driving over summer?

[Ben C34]

Just block it off with cardboard or plastic. For daily driver you don't need it.

[V28VX37]

Just block it off with cardboard or plastic. For daily driver you don't need it.

I've considered that too, the issue being that it sits between the rad and intercooler so would block off airflow to other components as well...

[GTSBoy]

Put a fitting on the side of the sump and run the sensor in the sump. It will be the closest to correct oil temp without putting it into a new/doubled sandwich plate. it's currently reading at least 10°C low, which is only so useful.

[dan.1337]

I would tend to agree The one thing I like better about the Mocal one is the 92C thermostat (if it works?!) - I believe the Greddy plate comes with a 80C one.

What temps are you seeing in normal driving over summer?

Yup, it opens around 80C. I see temps around the 80-85C mark in summer with just normal suburban driving.

Temps go up to around 110-115C on track with mild (~20-25C) weather.

[Franko07]

This is what ive always used to get a sensor into the sump

http://www.ebay.com.au/itm/OIL-TEMP-GAUGE-SUMP-PLUG-ADAPTOR-FOR-NISSAN-S13-S14-SR20-SKYLINE-R32-R33-R34-ASQ-/121748884691?hash=item1c58cc8cd3:g:It8AAOSw3xJVbtGl

Just put a plug onto your sensor wiring so you can disconnect it for oil changes...

[V28VX37]

This is what ive always used to get a sensor into the sump

http://www.ebay.com.au/itm/OIL-TEMP-GAUGE-SUMP-PLUG-ADAPTOR-FOR-NISSAN-S13-S14-SR20-SKYLINE-R32-R33-R34-ASQ-/121748884691?hash=item1c58cc8cd3:g:It8AAOSw3xJVbtGl

Just put a plug onto your sensor wiring so you can disconnect it for oil changes...

That's pretty cool. So many options!

[V28VX37]

So your oil temps were perfect, before the cooler was fitted.

Put a sheet of cardboard over the cooler and see what your temps read.

If back to normal id say the unit is open allowing full cooling.

If the same low reading, wrong location.

Just block it off with cardboard or plastic. For daily driver you don't need it.

I did a run with the oil cooler blocked off, suburban speeds, ambient temp 20C:

• Defi oil temp reading 67C – sump 80C

So it's about 5C higher at both points than with the cooler unblocked. Note this is in slow speeds so the cooler wouldn't be very efficient anyway.

The temp sensor is definitely in the wrong spot, I'll get that sorted. The jury is still out on how well the sandwich plate thermostat is working.