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Hello all,

I recently acquired a 79 and was kind of amazed there is no oil pressure warning system in the car. Where is the best/easiest way to hook up a pressure gauge? I'm sure it will be an electric gauge, just not that familiar with the rotary yet.

Thanks,
Howie

You should have one in the rear plate behind the spark plugs.

Yeah like Tool says, its towards the rear of the keg on the spark plug side. Follow the water temp cable and the sender sits just to the right of that. It's about 1.5" diameter and threads into the block.

There is no gauge or light on the 79. The Haynes manual shows a Mazda adapter that replaces the oil cooler banjo bolt.

My 12A looks like this
http://smg.photobucket.com/user/Gruntho ... 6.jpg.html

There are the two holes that the arrow is pointing to but they do not go anywhere. I am thinking about tapping the banjo bolt or getting an adapter for under the oil filter. I was just wondering what was the most popular way to install a gauge.

Howie

Hi Howie,

for some reason, some rear plates don't come tapped for an oil sensor and are blank, R5 plates I think..... is this a replacement engine / or rear plate?

The sensor should site here....



and looks like this...



On this R5 plate, the owner drilled and tapped it himself so that he could screw a sensor into it...



although you can do as you say and drill and tap a banjo bolt.

Are you sure there isn't an oil pressure telltale light in the gauge cluster among the row of warning lights, even if it isn't working? My 79 definitely had one... I think it's just the oil pressure gauge they are missing on early RX7's.


.
Ian

VolvoDad wrote:There is no gauge or light on the 79. The Haynes manual shows a Mazda adapter that replaces the oil cooler banjo bolt.

My 12A looks like this
http://smg.photobucket.com/user/Gruntho ... 6.jpg.html

There are the two holes that the arrow is pointing to but they do not go anywhere. I am thinking about tapping the banjo bolt or getting an adapter for under the oil filter. I was just wondering what was the most popular way to install a gauge.

Howie

That's a weird looking plate you've got there. I've not seen it before.

Be careful when you drill and tap. You can crack the plate. A user on here did it on a front plate.

Standard thread size is 1/8 npt.

This a S2 style plate

As far as I know the engine is the original engine, it has all the signs of an older 12A. Cream colored pulleys, no lip around the spark plug holes. That picture is just one I found that looks like the rear plate on my motor. My engine is in the car and covered with 30 years of oil. All the lights function in the cluster. The only light that is not on in the picture is the fasten seat belt light, as it does not always work.



The manual describes (N) as an indication that oil level is low and to check oil or take it to the nearest gas station or Mazda dealer to add oil.



When I first started the engine after resealing the oil pan and reinstalling the engine with a new oil filter no light was on on the dash at all. All the lights went out as soon as I hit the starter. The engine had been sitting with no oil for 6 months or so prior to me getting the car. There are no electrical connectors except the Coolant temp sender and the sensors in the oil pan.

The Haynes manual I have warns that the early engines do not have a oil pressure warning system and emphases after a rebuild to hook up a gauge to check the pressure. It showed the Mazda gauge adapter.

Howie

I have a pair of 1971 RX2s. Both have oil pressure senders and warning lights. These are twin dizzy motors.

I can believe you don't have one.

I've owned rx3's and rx4's in both single and twin dizzy, 1973 and 1974. All had oil pressure lights.

I also have the Haynes manual which is S1 specific, '79 thru '80. I've studied all the wiring diagrams and there is not an oil pressure sender to be seen

I can kinda understand that Mazda really needed to ram home the importance of having sufficient oil in the engine and that an oil level warning light would be more clearly understood by the motoring masses ... I just don't see the logic in omitting an visual oil pressure indication.

It can't be a cost cutting excercise like,say, rear drum brakes or a leaf sprung rear end. Baffling to say the least