Oil Presure Gauge Installation
 

I have a 1986 Mazda RX-7 N/A Turbo and just recently my oil presure gauge went out once i got the volt battery meter to work. So I went out Autozone (I know its not "Rotary Friendly" but they have the oil presure gauges) and bought a mechcanical oil presure gauge. it comes with everything to install it. the problem is i dont know how? i know that you are to remove the oil presure in the engine and swap it with the adapters that come with and just work you way from there. the thing is that i dont know where its located and really if i have to drain the oil and install or can i just do it with oil in there? also if you can plz show me some pictures of what it looks like and maybe a guild on how to do it.

Thank you for reading this

Gauge Install Guide

Step One
-Immediately return the mechanical gauge.
You.Do.Not.Want.A.Mechanical.Gauge.

Step Two
-Determine what exactly has failed with the stock gauge.
In my experience, it is typically the sending unit or the wiring that is at fault, hardly ever the gauge itself.

You mention that the "oil presure gauge went out once i got the volt battery meter to work"...so what were you doing in the gauge cluster?

I've been through this a few times.. Nothing is wrong with a mechanical gauge .Its usually the sender it leaks internally and bypasses. I purchased the autometer mechanical oil pressure gauge. I dont trust the tubing that comes with it so I would got to your local hydraulic supply and pic up some hose and fittings and make some..thats what I did its call Aeroquip AQP socketless hose and fittings..all you do is cut it to size, put some oil on the fittings and slip it all together no special tools and its good for 250+ psi..cost me about 50$ and I had extra hose..I've had it abotu a year and no leaks no probs.. heres where I keep my gauges..I can take more pics but my car is in my buddies garage while im away on vacation..

http://i488.photobucket.com/albums/r...d/IMG_0128.jpg

Actually mine are similar to yours. so i should go and buy a different hose for it?

yea the volt meter was working when i was driving then all of a sudden the oil presure gauge just shot up then just fell back down and didnt work. i thought my car was fucked up so i took it to Rotary Racing & Reliablity and they told me that the oil presure is fine that the gauge wasnt working. so that same day i went and bought one

"The gauge isn't working" tells you practically nothing.

If the sending unit has failed, it's a 10 minute, $70 fix.
If it's the wiring, it's probably just come off at the connector.
If it the gauge- and as I said before, that's a big IF- you can probably get a replacement gauge cluster for @$50 (hell, I have a functional S4 cluster you can have for that).

All of the above options are preferable to installing a mechanical gauge, IMO.

So you would rather buy a $70 sending unit over a more accurate and reliable $20-$30 mechanical gauge?



Aftermarket oil pressure gauge > stock everytime

The stock oil pressure gauge is crap, the sender fails quite often on the FC model.
Mine read below 20 PSI while my mechanical read 20-30 at idle.
3k RPM's it read barely over 20 PSI while my mechanical read 70ish ( Not a stock 13B FYI )

The following is how me and another buddy of mine ran our mechanical oil pressure gauges. He's been running his like this for probably close to a year now without issue, and I myself have been for a few months without issue. If it can withstand harsh driving in 2 cars that are driven hard 90% of the time, I think it'll be fine in what sounds like a lightly driven car.


No need to drain the oil, just make sure the car has sat for a few hours before installing the mechanical gauge, otherwise you'll get some residual oil leaking from the oil still draining from the oil filter.

Find the location of the factory oil pressure sender, it's to the right of the rear trailing spark plug and just below the oil filter.
It's a good sized, round, goldish looking peice.

I can't remember the exact size of the wrench needed, I beleive it's a 12mm or 13mm.
Remove the stock oil pressure sending unit, your new mechanical pressure gauge should have come with a brass fitting that the tube goes into and is threaded.

Unfortunately it won't screw into the stock oil pressure sender location all the way as the brass fitting is NPT thread and not whatever the factory oil pressure sender is threaded.

It will still work though, just tighten is firmly. Not crazy tight or a little tight, hopefully you can tell the difference.

Run the tube through the rubber grommet on the far right driverside firewall, you may have to remove a few things to get to it.

Route it so that it wont get caught in the pedals or any linkage of course.

Run it to wherever your going to mount the gauge and the instructions will tell you how to put the tubing and fittings together with the gauge.

Run it and make sure you don't have any leaks and that the tubing doesn't interfere with anything and your done.

lol thanks for the guild
I'll install it today, now that i know how

also why is there a big battle between mechanical and electrical?
is there a big difference

you can also get an oil filter pedestal that has two threaded holes in it, I believe one is for pressure one is for temp ?? never used one, just THINK thats what its for, something you can research, if the thread pitch or count is wrong on your aftermarket sender you are gonna either strip something or cause a leak.. NOT a good idea to use the wrong threads not like you can just take the piece out to re-tap it, you will end up with shaving IN your engine, not consistent with life there... (apex / engine life that is)

edit:
electric is preferred, you don't really want HOT oil squirting on your lap if there is a leak do you?

I think most mechanical gages say something about not putting them in the cabin, I mean boost is fine its just air, but anything else I would not do MYSELF what you all choose to do is on you...

ive been waiting on this too but iam going to find a fitting so both stock and aftermarket ones will work. and so it doesnt look stupid in my dash from a guage not working.:rolleyes:

also did you check the wire?? shooting up then zero out sounds like it may have came off,, if the wire touched ground you would have seen the PEAK then all the way off, well zero.. trace the wire like someone said its right in front of and below the filter, fatty gold thing with a ? white ? connector on it...

Yes, you can also get the oil filter pedastal spacer as well.
I have one myself when I was running an electircal gauge, and will be using it for my oil temp sensor when I finally get around to installing it.
The Racing Beat version's have 2 holes, 1 for temp and 1 for pressure.

For those who don't want to spend $50 on top of a guage, you can install it the way I have posted in my above post.

Yes, you can damage your engine if you use a part with a different thread pitch, hence why I said it " will not thread all the way in ". You get a few turns and it starts to bind up which is where you stop. This is enough threads for it to seal and not leak or fall out on you.

If your mechanical gauge leaks then it is most likely your fault becuase you put it together incorrectly, or it's that 1% that the gauge had an issue from the factory. Which is why you test if before you fully install everything.

Never seen one leak myself in my experience....FYI working on cars is not just a hobby, it's what I do 24/7 as well as other vehicles.

my luck I would have that 1% that failed at 6K RPMS and 60PSI and I would get freakin soaked... lol

+1 for that :D

I'll take mechanical over electrical gauge anyday IMO

Yes, I would.
I disagree that a cheap mechanical gauge is superior to the stock system and also disagree with the statement that the stock sending unit "fails quite often".

How many new sending units have you personally had fail?
On what do you base "aftermarket oil pressure gauge>stock everytime"?

I've run both (stock with new sending unit and VDO- electric with sending unit in RB pedestal adaptor) simultaneously, the only difference in the readings was that the stocker is more dampened and the needle doesn't jump as fast.

A side advantage of the stock gauge is it's location...nothing is as easily visible as the stock gauge cluster.

You can disagree all you like, but this guys thread is not the place for an argument.
He asked a question on how to install his mechanical oil pressure gauge, you did not help him so I did. His question was answered so there's no reason to fill up the rest of the thread with arguments of stock oil pressure gauge vs. aftermarket oil pressure gauge. So, I will answer your reply and add nothing else afterwards.

Yes, I bought a brand new one when I first got my FC and the piece of crap went out a few months later. As well as the wire that runs from the oil pressure sending unit is so corroded that it's got a shitload of resistance in it making the dash gauge read way lower than it actually is.
I'm sure alot of owners on here can give their story on how their oil pressure sending unit failed on them, my buddy is one of them.

I have multiple reasons why I don't like factory gauges...cheaply built, don't have to be very accurate as they know the customer just wants to see a needle move to make them happy etc... Ford is one company that does it all the time, the new oil pressure guage on some models is just for looks, people complained about low oil pressure so they re-calibrated it to read higher than it really is to make customers happy.

If the stock gauge is what you would rather have then go ahead and use it, doesn't make any difference to me.

I don't just daily drive my FC and would rather have a more reliable aftermarket gauge when under high loads than the factory gauge.
It's easier for me to see the gauges on my A-pillar pod and ontop of the dash than it is to look down at the gauge cluster and focus on which orange mark the needle is at...
If the far left guage in my 3 gauge holder on the dash is over half way than everything is good, if the middle and far right gauges are not over half then the temperature is good as well. My gauge cluster is only useful for knowing how much fuel I have and when I need to worry about how fast im going and see how to get good MPG's when driving long distances.

In their readings, no.
In terms of install and future servicing, yes.

Mechanical gauges abounded on my first automotive loves- British sports cars.
Most of them had both oil pressure and water temp mechanically activated.
Properly cared for they were fine.

But, there are significant differences between say a Healey 3000 or TR-3 and an RX-7. Look under the dash of either British car and there is almost nothing there...the capillary tubes for the mechanical gauges had a straight shot through the firewall to the gauge itself.
In our cars that is not the case, so the potential for kinking or inadvertently damaging the tubes during future work is greater.
Also note that as soon as the British (and also the Italians) developed better electrical systems, they ditched mechanical gauges in favor of electrical.

Look at GeTCrAzYKiD's gauge panel.
Now imagine having to remove the console surround to service the radio/pull the Logicon...whatever.
Can't just reach behind and undo an electrical connector...those gauges are hardwired to the car.
Presumably, he left enough slack in the capillary tube to get behind to undo it but upon reinstall he'll have to remake a mechanical connection- a connection that can potentially leak, BTW- and that can't be as simple as plugging in a Molex.

I didn't originally respond because I have an implacable hatred of mechanical gauges- although I admit I would never consider using one in my car- but rather because I think it's wrong to jump to conclusions, which is what you've done.

I'll bet there's at least a 50% chance that the only problem with your stock gauge is the wiring/connector to the sending unit (the experience you described- "all of a sudden the oil presure gauge just shot up then just fell back down and didnt work" is exactly what you'd expect from a wiring problem).
If so, you're going to a lot of trouble installing a whole new gauge to fix a relatively simple issue.

But, have at it.
If you think installing a mechanical gauge is the way to go, good luck.
It'll probably be fine.



I didn't think I was "arguing", rather, presenting an alternative approach to solve the OP's problem, which is a non-functioning pressure gauge.
For all we know the gauge worked fine and he was happy with it right up till it stopped working.
At least pinpointing why it stopped functioning gives us a basis for evaluating future options.
Saying "my gauge stopped working suddenly, so I'm going to install an aftermarket gauge" is akin to saying "my car won't start, so I'm going to replace the engine".

In either case, replacement might be the proper course of action but without some basic troubleshooting, no one knows.

Well as for me, I anticipated the removal of the radio, gauges, for any future servicing. There needs to be a little common sence, not just hey that looks cool. I would prefer to have the gauges on my pillar but as I have a 10 AE I wanted to modify my interior as little as possible. I also have yet to install a wide band..hence the extra space.. Its all for monitoring purposes for better accuracy at troubleshooting etc. But not to change the subject, we all have our own opinion and we're entitled to it..

No one seems to have mentioned that the thread for the stock oil pressure sender is 1/8" BSPT. That's a British pipe thread. Most gauges are 1/8" NPT so you need to visit the local hydraulic store for an adapter.

And yes, I agree that it is crazy to use a mechanical gauge due to the possibility of leaks and the general pain in the ass of routing the tubing as compared to a wire.

Actually, Apex did touch on that very thing.
The difference between the BSPT and standard pipe thread is one thread per inch...BSPT being 28 and regular being 27 tpi.
In practice, I've found the two to be interchangeable but an adaptor is obviously the correct way to go.

how do you install a a boost gauge?

wow, you woke the dead... you hook a vacum hose up from the gauge to the engine... pretty easy....

let me specify. you have to cut and put a T on specific vacuum line, right?
which one? and mine as a couple wires on the backside of it. light maybe?
i bought it used on ebay.

any one that is on the uper intake should work... yea the wires are prob for lights, if just 2 wires well then one hot one ground, if there are more you may have one with memory or something that needs a constant and a key and a ground

unfortunately i would say you are wrong. the connector on the stock oil pressure sender is a POS design and the stock pressure gauge is too slow to react and isn't very accurate at lower pressures.

those are enough to say ditch the POS if you really want to.

i however wouldn't use the cheap ass nylon hose they provide.

if you're going to spend the money to replace the sender i would probably see if an FD one would work( i haven't check the resistance values of both) and replace the slide on connector since it likes to get greasy and lose connection or fall off because you look at it funny.