[Nick Gibson]

I am posting this to help anyone who wants to fit a additional oil pressure sender to the 4m41 motor as I could not find any accurate info when doing research on the net. I really struggled!

The service manual states that the oil pressure switch uses a 1/8 PT ??
Now as far as I understood you get 3 different kinds of imperial pipe thread (PT) = NPT, BSP, and BSPT... As it turns out, Mitsubishi uses BSP on the 4m41 block, took me a while to figure it out, see below.

I was transferring my madman EMS2 from my old 6g74 Pajero to my newer Pajero's 4m41 motor and the coolant temp, Autobox oil temp was a straight swap but I ran into a snag with the oil pressure sender...

To say the space is restricted is an understatement, the oil pressure switch is situated behind the turbo under the oil cooler against the block, with no clear line of sight to see it, it is done mostly by feel! To get some semblance of access to it you have to remove the air filter housing, and turbo inlet and boost pipes. I also released the alternator tensioner, removed the fan belts off the pulley and pushed the alternator down to be able to get a hand in there behind the turbo. The oil pressure switch was removed with a 27mm socket, universal joint, and a 125mm extension- that was the easy bit. I broke the copper spade lug off the switch by bending it flat (to fit in the 27 socket) too many times during the 3 removals/fitments, I replaced it with a crimp connector ring terminal.

The fitment of the VDO oil pressure sender with OEM switch is another matter entirely, on the petrol block it was a simple matter of fitting a (1/8 NPT) 'T' piece and screw both the VDO pressure sender and OEM pressure into so that the red oil idiot light on the dash and the madman oil pressure measurements both work. On the 4m41 block, the oil pressure port is recessed in a niche below the oil cooler, so the 'T' piece doesn't work as there is not space to fit the switch on the side and the turbo is too close to extend the 'T' out more. So I put everything back together and left it for another day.

Thinking about the problem I spoke to Epic hydraulics and decided to make up a 400mm long male-male 1/8 NPT Teflon steel braid hydraulic hose in order to mount the sensors remotely. The Teflon hose can take extremely high temp (good for position right behind turbo) and up to 120BAR + pressure so it was perfect. I removed all the bits again and I tried to fit the hose to the port... 4.5 hours, some choice words, and plenty skinned knuckles later I was no further than last time, I simply could not get the 1/8 NPT tread to 'take'. The hose also does not line up perfectly with the port, the turbo pushes it off square. I put it all back together and I went back to the drawing board.

Some of the unused items, 1/8 NPT brass elbow, 1/8 NPT brass extenders, Teflon braid hose and a 7/16 JIC male female elbow.


I spoke to Epic hydraulics in stikland again, and I had a another similar hose made up, but with a 7/16 JIC female thread on the hose end going to the oil port. I also bought a male 7/16 JIC to male 1/8 BSP adaptor. The 1/8 BSP thread is slightly smaller (and parallel) than the 1/8 NPT (taper) thread, so I hoped this would go into the port more readily. The JIC thread is also quite a coarse thread so the female thread on the hose would catch more easily on the male thread of adaptor as well, as the hose alignment caused by the position of the turbo was a worry to me.

I fitted it all this morning, ran the braided hose under steering column and extended the OEM switch wire with lugs, no cutting the wiring harness. Am happier with the remotely located senders, not so much weight hanging off the soft brass 'T' vibrating with the engine. I cable tied the bras "T" piece and sender units to the steel vacuum pipes next to the air-filter housing. The BSP - JIC adapter turned into the port easily and the hydraulic hose caught the JIC thread with no hassle. Very chuffed with my saga sorted!

Teflon hose running under steering column to oil port on engine block


Male 7/16" JIC to male 1/8" BSP adaptor into engine block. Teflon hose with female 7/16" JIC coupling attached to adaptor.


Brass "T" piece with pressure switch (top) and VDO sender unit (side).


Brass "T" piece again, VDO sender left & OEM switch top.


EDIT: Tidied the document up on a PC.

[CATS]

Sounds like a fun time!

Thanks for sharing the effort. This will definately be of value to someone in the future.

CATS

[Ritteling]

Thanks for the info... Will keep it in mind for future aspirations. I also have a ems 2 but for now its only an egt sensor.

[Ritteling]

Thanks for the info... Will keep it in mind for future aspirations. I also have a ems 2 but for now its only an egt sensor.