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

V28VX37

By V28VX37,
in Engines & Forced Induction

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V28VX37 Veteran

V28VX37

Posted
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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):

24160402470_0ab647bd3b.jpg

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?

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V28VX37
V28VX37

Got the car back today, oil temp sensor is now in the AN10 fitting off the hot outlet of the Mocal sandwich plate and all the moving parts of the plate have been replaced with the service kit. Prick o

Ben C34
Ben C34

There are people who know that information without having to use Google I would consider the post relevant to this thread.

dan.1337
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 hole

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

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 Veteran

V28VX37

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  • Author
Posted

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 Mentor

GTRPSI

Posted
Posted

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 Grand Master

GTSBoy

Posted
Posted

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.

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V28VX37 Veteran

V28VX37

Posted
  • Author
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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?

V28VX37 Veteran

V28VX37

Posted
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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 Veteran

V28VX37

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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 Proficient

dan.1337

Posted
Posted

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!

  • Like 2
V28VX37 Veteran

V28VX37

Posted
  • Author
Posted

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?

V28VX37 Veteran

V28VX37

Posted
  • Author
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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 Grand Master

GTSBoy

Posted
Posted

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 Proficient

dan.1337

Posted
Posted

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.

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Franko07 Enthusiast

Franko07

Posted
Posted

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 Veteran

V28VX37

Posted
  • Author
Posted

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 Veteran

V28VX37

Posted
  • Author
Posted

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.

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