HOW-TO: install oil pressure sensor & gauge on EJ25

Detailed descriptions of how to do things to your Liberty.

HOW-TO: install oil pressure sensor & gauge on EJ25

Postby Yowie » Tue May 04, 2021 9:59 pm

INTRODUCTION

This is how I installed an AEM "X series" 150psi oil pressure sensor & gauge on my Forester (2.5L turbo).

It's not the only way to do it. While I suspect most Subaru engines have similar bits in similar places, your situation may vary. Use this writeup as an example, along with some common sense.


PARTS

I used:

- Prosport Remote Oil Pressure Sender Installation Kit ( https://www.carmodsaustralia.com.au/rem ... lation-kit ) relevantly consisting of a female-female 90 degree 1/8NPT connector, a male-male 1/8NPT braided steel hose and a brass fitting for the oil gallery* plugs

- sleeving for the braided steel hose to prevent abrasion

- Oil Pressure gauge kit (consisting of gauge face, wiring loom, **150PSI sender, crimps & an AEM sticker)

- Adel clamp sized to hold the pressure sender

- M6 bolt and nuts/washers

- liquid thread sealant

- Narva "add-a-circuit" ( https://www.narva.com.au/products/54415BL )

- 5 amp automotive fuse

- one straight crimp connector & one ring terminal crimp connector

- gauge mounting solution

- zip ties

[NOTES
*gallery, not "galley". We are not cooking food on a ship here.
** Subarus run high oil pressure. A 100psi gauge/sender will probably not have enough headroom to show you max oil pressure. ]

This guide assumes you have the usual collection of garage tools.


PARTS PREP

The Prosport oil gallery brass fitting had a sharp edge on the wet side:

Image

So I smoothed that down with the pictured deburring tool, plus some sand stones. Wouldn't you know it, the factory also smooths off that edge (stock gallery plug from later in the process shown):

Image


I have seen others run the braided steel hose up and off the the left or right with the sensor attached to the ABS unit or something. I planned to run the braided steel hose under the intake manifold. Braided steel hose will cut through anything it rubs against, so I covered the hose in convoluted plastic sleeve, then this silicone heat resistant sleeve:

Image

Image


The two reasons to run a hose rather than screwing the sensor directly into the engine are:

(a) clearance is an issue under the alternator; and

(b) pressure sensors are noted for having a short life if subject to engine vibrations - better to remote mount on the chassis via rubber. A rubber-lined adel clamp in my case.
Last edited by Yowie on Wed May 05, 2021 11:57 am, edited 1 time in total.
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby rexhunta » Tue May 04, 2021 10:31 pm

None of your pictures work mate, but looks like a good write up !
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby Yowie » Tue May 04, 2021 10:41 pm

REMOVING PARTS

I wanted to take oil pressure from the location of the factory oil pressure sender under the alternator.

Alternatively you could take oil pressure from:

(a) the un-used gallery plug at the top-back-driver/turbo side (a PITA to get to and taken up by a temperature sensor in my case); or
(b) an aftermarket machined plate that goes where your oil filter screws on.

I wanted to mount the sender somewhere on/near the firewall. Once again, your options are only limited by what the braided steel hose will reach and what NPT adapters you might have, but "off the engine, rubber mounted" is a good guide. I would probably stay clear of the ABS sender unit, which I assume vibrates with some violence when ABS or traction control kicks in.

Accordingly, the engine cover and intercooler needed to come off (not shown). I also removed the engine under-tray in anticipation of the cleaning in step 9.


Removing the alternator is quite simple.

1. Loosen the passenger side alternator bolt and take off the engine cover support bracket:

Image


2. As a reassembly reference, use a pen to mark where the vertical thread goes into the belt adjustment device on the driver's side of the alternator (shown in pink STI cherry blossom red in the image above). It's also handy to get a feel for the tension on the accessory belt before you loosen it and also mark the direction of the belt with an arrow.


3. Wind down the vertical adjuster bolt to take tension off the belt so you can remove the belt.


4. Take out the two horizontal bolts holding the alternator and save the threaded bracket at the back (passenger side).


5. If it's in the way, unbolt your boost controller and move it to the side.


6. Open the red cover on the positive electrical connection on the alternator and undo that bolt to remove the positive lead. Set the lead to one side.


7. Unclip the green electrical clip from the driver's side of the alternator.


8. wiggle/swing/pry the alternator out and put it out of the way. You'll probably be confronted with this mess:


Image


In that image the connections are (top to bottom)

(a) the coolant temp sensor;
(b) the factory oil pressure sender; and
(c) the crank angle sensor (I think)

9. Now is a good time to clean the place up a bit. I unclipped the three sensors to make room, then used degreaser to loosen the muck, then water from a squirt bottle to help the muck get going.

Image

Remember to clip your coolant temp sensor and crank angle sensor back in on reassembly or your ECU will probably throw a wobbly.


10. Remove the stock oil pressure switch with a suitably sized large deep socket and socket extension.

Image


11. With a rag stuffed in the hole in the stock gallery plug, now is an excellent time to mock-up exactly how far your braided steel hose will reach, what amount of bending is tolerable to get there etc. to see if your basic sensor mounting plan has merit. Don't forget to loosely test fit the alternator / intercooler/ etc. while you're doing this quick proof-of-concept test.


COMMENT ON THE STOCK OIL PRESSURE SWICH/SENDER

This is a switch that is in the "on" position when the pressure is below 15psi (I think?) and "off" above that pressure.

It is connected to a "dumb" electrical circuit which is simply the small oil pressure light in the dash cluster. When the circuit is complete, the light goes on. 16+ psi of pressure breaks the circuit and the dash light goes off. The ECU is not involved. It follows that unplugging and/or removing the stock sender means your dash oil warning light will never come on.

It is probably possible to keep using the factory oil pressure switch via some kind of T-shaped collection of fittings if all that will fit under the alternator. If that is what you want - go for it. Rexhunta comments on this as follows:

"I used the same place for the oil feed on the turbo, the tee piece you fit in is snug, but has enough room for the alternator."

Personally, I will not miss the world's smallest "catastrophic damage occurring" warning light when it is being replaced with a much more visible pressure gauge that has programmable warnings.
Last edited by Yowie on Wed May 05, 2021 12:02 pm, edited 4 times in total.
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby Yowie » Tue May 04, 2021 10:55 pm

Once you have the sender out be very careful to prevent dirt & bits entering the oil gallery. This is after the oil filter here and you are messing with a mainline direct to the critical bearing surfaces of the engine.

12. Remove the stock gallery plug. I used an electric impact wrench with a deep impact socket. Without that, you would probably need to find a way to impart a sharp blow to the stock gallery plug to break the factory thread sealant without rounding anything off.

Some pictures of inside the oil gallery here, just because I find it fascinating.

And if you gaze long enough into an abyss, the abyss will gaze back into you.

Image

Image

Image


There is a long, straight, vertical channel that comes up from (I assume) the oil filter and pump, then two channels that go left and right. I'm a bit disappointed at all the sharp edges inside the oil system (see also next time you remove a filter). I wonder if custom/racing block prep work sometimes involves rounding off as many sharp edges as they can get at for the sake of better oil flow?

EDIT - they do. This is a listed feature of the $30,000 Willall billet block "Radiused coolant and oil galleries for improved flow and less foaming/turbulence"
Last edited by Yowie on Thu May 20, 2021 10:26 pm, edited 2 times in total.
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby Yowie » Tue May 04, 2021 11:00 pm

13. Very carefully clean out the threads where the stock gallery plug used to be. I stuffed a piece of rag into the hole, then used brake cleaner spray, a small wire brush and a toothbush, then carefully removed the piece of rag.

14. Apply liquid thread sealant to the brass fitting, make sure the washer is on it and screw it in to the gallery. Tighten to 18-28lb-ft (according to the Prosport kit instructions)

Image


15. Apply liquid thread sealant to one end of the braided hose. Screw into the brass fitting. Tighten to a metric "not too tight" with a 10mm open-ended spanner. The loose end of the braided hose needs to be free for you to be able to do this.

Image


16. Route the other end of the braided hose to where you intend to mount the aftermarket pressure sender. I sent mine under the manifold, under the intercooler and to the firewall protrusion that mounts the transmission pitch mount.

Image

Image


17. Secure the electrical connection that was attached to the stock pressure switch. I covered mine in heat-shrink and zip-tied it to the nearby coolant temp sensor wiring.

Image
Last edited by Yowie on Thu May 06, 2021 10:23 am, edited 2 times in total.
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby Yowie » Tue May 04, 2021 11:19 pm

18. Assuming you have figured out exactly where the pressure sender will go (and at what orientation) by this point, apply thread sealant to the other end of your hose, attach the fitting/s you need and attach the pressure sender to the end (using thread sealant each time).

Image

Image

Image

As you can see, I mounted my sender by running an M6 bolt up through the factory hole in the top of the pitch stop mount assembly, securing it into a "fixed stud" arrangement with a nut then attaching the sender with an adel clamp.


19. Route your wiring through the firewall, applying whatever additional wiring protection you deem appropriate.

Image

Image
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby Yowie » Wed May 05, 2021 8:19 pm

20. Figure out your gauge mounting inside the car, at least so you get a sense of how long the wires need to be. I used this figure-8 shape to piggyback on the existing temperature gauge.

Image

Image


21. Pick a spot on your fuse panel for the "add a circuit". Something on the "ignition" circuit (rather than "accessory") is probably best for an oil pressure gauge. Some clues about ignition/accessory circuit are on the sticker on the door to the fuse panel. If in doubt, use a multimeter or tester probe to work out when selected fuse spots are powered. My selected spot has the black label-maker sticker in the picture below.

Image

Image


Wiring for individual aftermarket gages will vary, but the AEM unit runs one connector from the back of the gauge to two looms. One loom to the sender (loom through firewall) and one loom for power and ground. I ran the red "power" wire to the "add a circuit" and the "ground" wire to a ring terminal that I placed under a factory bolt head somewhere above the footwell. excess wire can either be cut off or stowed with zipties in the under dash area.


22. If you haven't already, make sure everything is reassembled in your engine bay.

23. Fire it up to test. Check for oil leaks around the threaded joins.

Image

Image


Shown above are the oil pressures on:

(a) cold-start fast idle (100psi!); and

(b) oil-up-to-temp idle (16-18psi)

This is with very fresh Penrite "Ten Tenths" 10W40 oil and a May Brisbane "cold start" which is nothing by Mexican standards. Your readings may vary.

As is common knowledge, go easy on a stone cold engine until the oil gets a chance to warm up. There are very small holes that thick/cold oil has to get through.

---

Thanks for reading.
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby Yowie » Wed May 05, 2021 9:59 pm

Rexhunta's T-piece solution to fit the stock pressure switch and a braided hose under the alternator:

Image
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby rexhunta » Sat May 08, 2021 11:27 am

DonnBR wrote:Incredible write-up guide, Yowie! A close friend of mine is looking to get this EJ25 project after we finished installing the suspension from 4Wheelonline onto the Jeep. We'll definitely try that sensor installation.



I just went from a TJ to a 2.5 :lol:

P.S. if anyone ever need any oil fittings, hit up your local bearing or pirtek/ hydraulic fitting shop instead of repco or auto one. They're about 1/4 of the price and they have a heap more range of bends, and smaller tee pieces etc.
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby nvmylh » Wed Jun 02, 2021 10:01 am

Nice write up Yowie!

I have been playing around with installing an arduino nano and 150PSI sensor on my ez30. So far its working great, just need to make a faceplate of some sort to suit the gauge cup.

I bench tested it against a speco mechanical 100psi gauge and couldn't pick any differences. The sensor is installed on a filter sandwich plate, I'll look at moving it to somewhere further down the line in future.

20210602_075127.jpg
20210602_075127.jpg (207.26 KiB) Viewed 8722 times
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby Yowie » Wed Jun 02, 2021 9:23 pm

That's pretty awesome. For the faceplate, have you considered designing the shape then getting some 2mm thick aluminium CNC waterjet cut (then powdercoated or painted)?

That's how I got that figure-8 gauge holder made.

EDIT - or the problem might not even be that complex. Eg fabricating the faceplate might something manageable at home with a hacksaw, file and drill.
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Re: HOW-TO: install oil pressure sensor & gauge on EJ25

Postby nvmylh » Wed Jun 02, 2021 9:43 pm

Yea I drew up a part in cad, was thinking of getting it 3d printed or turn it up on a lathe out of black acetal plastic. Lockdown is screwing up those plans!
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