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There’s been quite a few threads recently about XE/LET oil pressure and oil temp senders, where to put them, thread sizes etc etc. so here goes for a mini guide/gen session.
On a standard 20XE there is a pressure sender/low pressure combo switch (astra gte, some calibra/cally turbos, also fitted to 1.6 nova gte) the bare copper pin drives the variable pressure gauge on the digi dash or cav/cally analog gauge. the single pin sure seal type connection drives the low pressure warning light on the dash/check control.
in all other cases you just have a low-pressure switch that drives the low pressure warning light on the dash/check control. as pictured, either type live in the rear of the oil pump. and both have a thread size of M14x1.5. i.e metric 14mm thread, and pitch of 1.5.
The normal route to add an aftermarket sender is to fit a T piece into the rear of the oil pump then fit the standard sensor/switch and the new sender to the T piece. This is what i set out to do originally, I had a 1/8 npt oil pressure sender from demon tweaks, the T piece reflected this, M14x1.5 to M14x1.5 + 1/8 npt. In reality space is tight, and sods law said that when the T piece was screwed in and tightened, the hole for the aftermarket sender would be facing the block and be useless, and this is exactly what happened.
So, what now? Well, as has been mentioned a few times there are 2 blanking plugs in the main oil gallery to the rear of the oil pump. the first of the holes is used for the turbo oil feed on LET engines, and once the stud is removed its M14x1.5 thread (again!)
On XE’s that hole just has an allen head plug wound in it, which is also M14x1.5 thread like the oil pump and turbo oil feed.
For me, personally, I found the standard gte pressure sender was a more comfortable fit in this “tubo oil feed” hole, so that’s where I moved it to.
Then i acquired a 1/8 to M14 adapter and the aftermarket pressure sender was fitted to the rear of the oil pump, in place of the stock sender.
An alternative for LET owners struggling for another tap (obviously the turbo feed is being used) is the large outermost nut on the oil pump, this is also on the high pressure side of the pump, its thread is M22x1.5 and adapters are available from rally design, lemans motorsport, demon tweaks etc. care should be taken though as it points the sender in the direction of the drivers side drive-shaft.
The 2nd of the blanking plugs, mentioned earlier, are redundant on both XE and LET, its also fitted with an identical M14x1.5 allen head blanking plug.
I purchased an M14x1.5 fluid temp sender from rally design (very cheap and a popular size) and bolted it home. I had a slight problem in that the tips of the hex section on the sender, which you do it up by, caught on the block face the closer the sender got to its seat. In the end I just whizzed a very shallow groove below the port with an angle grinder, and it was perfect.
and heres all 3 senders in action, on the back of my XE. temp sender - far left, aftermarket pressure sender driving racetech gauge - bottom right, standard gte pressure sender driving digi dash pressure gauge and digi dash low pressure warning light - top middle
for the aftermarket senders only 1 wire is required for each, the signal wire to the respective gauges. i just used some automotive twin core and spade connectors.
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Originally Posted by Miles 
