Install Oil Pressure Gauge

Started by Carolyn, November 15, 2016, 18:36

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Carolyn

Back in the days of yore, a racing car had three instruments:  RPM, Oil Pressure and Temperature, they were (and still are) the essentials.  I've always thought that an oil pressure gauge is an important instrument. I'm a bit surprised that the Roadster doesn't have one as standard. So I've finally installed one on my MR S.  If you drive with real enthusiasm, or are a track-day nutter, then it's an essential tool to have.  A quick reacting oil pressure gauge lets you know when you're pushing your luck and about to damage the bottom end. A sudden dip when the revs are on and your oil pick-up is sucking air instead of oil!

It also tells you a lot more, like when your oil is up to temperature (when the idle pressure settles to it's normal warm running). And it lets you know how different oils behave. I recently changed to a different oil and the idle pressure when cold went way up (both oils 5W) and the high rev pressure when warm stayed the same.  As it's less than wise to spank an engine when the oil is cold, this all helps you to look after your motor.

It only helps if the gauge is pretty much in your line of sight and it needs to be an analogue type as the eye picks up movement much quicker than it picks up a change in a digital display.  When you're about to blow your engine, 'quick' is useful.

What follows is a 'How-To'.  Rank beginners shouldn't attempt this.  This is a job for the reasonably competent.  I won't be answering tons of questions on this. 

So the first step is to install and 'sandwich plate' between the oil filter and the engine.
Here is a pic of one:


They're available on Ebay for about £20. 

Remove the oil filter and, using the only non-metric adaptor that comes with it (these come with the kit) and double checking that the filter will screw to it, bolt the plate, lubricated 'O' rings towards the engine, where the oil filter used to go.  Make sure it's good and tight.  Screw the oil filter back on to the thread that's left sticking out.

Next you have to add the sender unit that comes with the oil-pressure gauge.  I chose an un-damped gauge so that the needle would move quickly.
This one:  m http://www.ebay.co.uk/itm/290947927681? ... EBIDX%3AIT m

It comes as a kit with gauge, sender,  and  the sandwich plate comes with a couple of blanking plugs to seal up the holes in the sandwich plate that you don't use.

The sender and blanking plugs all use tapered threads.  Wrap some PTFE tape around the threads and spanner then all into the sandwich plate and make sure they're good and tight, or they WILL leak.

That's the easy bit. Now you've got to get it wired it up.

You need to run one wire from the sender to the dash.  Leave plenty of excess length.  Crimp a round connector to the wire and attach it to the sender. Then remove the plastic cover from the driver's side sill, the covers to the front and rear of it and the cover in the corner of the luggage compartment.

I taped some welding wire to the sender wire, poked it through the big grommet that carries the wiring to the drive's side of the car (down on the driver's side of the bulkhead). And then pulled the wire through.  Run it along side the other wires that run along the sill and up under the dash.  Then you can replace the plastics.


I wanted the gauge to be on top of the dash, just to the right of the instrument panel. I bought a mounting pod to put on there and hold the gauge where I could see it.


More wires are now needed: Power to the gauge, switched by the ignition. Power to the light, switched by the light-switch. And an earth wire.

So it's time to remove the plastics from under the dash and under the steering wheel. 

The connections were made using 'Piggy-backs', which allow you to tap off a wire without cutting it.


Take your time to see how they work. The wire you're connecting to passes though the piggy-back, the wire you're adding goes into the side that only has one opening. Use a pair of pliers to push the piggy-back blade in and clip the cover closed.

Use a meter to find the wires for the ignition and sidelights (you can identify these by switching the ignition and sidelights on and seeing which one goes live. These are the ones you want to connect to. Using a meter, identify a good earth wire.


All these wires, including the one from the sender, need to be fed up into the gap between the pillar-cover and the dash.


Feed the wires though some shrink-wrap (to keep it all tidy) and through the hole in the pod.  Trim them to length and crimp on round connectors (except for the live to the light).  Crimp the wire from the light switch to the red wire on the gauge using a straight crimp connector.  Crimp a round connector to the black wire on the gauge.  Some people don't care for crimp connectors and prefer to make all soldered connections.  Your choice.

Now, using the nuts and washers that come with the kit, connect the wires to the gauge. Power from ignition to '+'.  Earth to '-'  and the black wire also to '-'.  Sensor to 'S'. All the terminals are marked on the gauge.



Push the gauge into the pod.  I needed to put an O ring on the gauge to make it snug in the pod. You could also use electrical tape for this. 
Now you need to stick the pod to the top of the dash.  Clean surfaces thoroughly.  Don't bother with the glue-pad that comes with the pod to stick it down on top of the dash.  A couple of well trimmed layers of number-plate sticky tape (from your local parts shop) will help it to stick to the textured surface.  I had some extra thick sticky rubber tape which worked very well.


Shrink the shrink-wrap with a heat gun.  Put all the plastics back.

Pressure gauge is now installed.

PHEW!

Now for a word about accuracy and the readings you're likely to see.

You may see readings some 10 to 15 psi above those specified in the workshop manual.  That's because the method in the manual takes the reading from further along the oil system.  The sandwich plate taps off right after the oil pump, so the readings will be higher.  Also the quality of the earth affects the readings.  If you're picky, the gauge should be earthed all the way back to the engine and not through the chassis.  I'm not that picky.
Readings will be silly high (100 psi at idle) when the oil is cold.  They will come down to around 20 psi at idle, when it's all good and warm.

For me, the purpose of the gauge is to show rapid variations when the engine is revving so I can back off, to let me know the oil pump is doing its job and to show when the oil is up to temperature.  You will find that the oil takes a lot longer to get there than does the coolant  Once you know what is 'normal' with your installation, then it's easy to spot variations that should cause concern.
Perry Byrnes Memorial Award 2016, 2018.  Love this club. 
https://www.mr2roc.org/forum/index.php?topic=63866.0

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