Hi, I have a 1597cc mk1 Eunos Auto.
I bought it back from Cambridge to Southampton 18months ago. Oil pressure was around 2.5 kg/cm2 @ 70mph. Thing is that it was as responsive as it should be. I did an oil change etc. It has been through 2 MOT’s with no concerns.
I am wondering, could it be the pressure gauge on the dash board or another cause that I have not thought of.
So, any suggestions would be appreciated.
Many thanks
Alan.
It’s not really clear what you’re asking Alan.
Has the oil pressure suddenly changed or is it something that’s been on your mind for 18 months ?
Agreed with Rob that your question is unclear.
Also are you relying on a 25 year old guage and sendor unit to give a reliable oil pressure reading?
Around 1995 according to our friends on Miata.net, Mazda changed from a pressure sender in the engine and a proper oil pressure guage in the dashboard to a pressure switch at the engine and an indicator guage in the dashboard.
Info on the earlier system here.
http://crowz.narmir.com/vehicles/1990-miata/miata-repairs/miata-oil-pressure-gauge/
In the case of the later cars if there is no oil presure, the indicator guage reads zero and if there is an engine oil pressure of around 7psi according to posters on miata.net, the indicator guage needle moves to the mid point of the dial and stays there until the oil pressure goes below 7 psi.
That’s about 35 psi which should be sufficient if accurate (as others have said, it might not be accurate).
Likely the old sender unit. You can disconnect and clean up the contacts on the sender unit, which is right next to the oil filter. That might work, might not.
A 1.6 I once owned:
https://www.youtube.com/watch?v=MvqrRfeDer8
Oil pressure indicated at a constant 70mph (minus the roundabouts). Check what happens at 1:57, its like a switch is flipped.
One of these early sender units taken apart
Moving parts and some really thin wires. Not exactly solid state.
Replacements are quite expensive, and fitting a similar 30 year old used part might not be wise (worth bearing in mind, that for the 1991 track special edition, the M2-1001, Mazda ditched the gauge altogether, replacing it for a light. They obviously thought that this gauge wasn’t that important. And its true, you can dump 3 liters of oil, and that gauge will not help. I suspect that long before the gauge gives any useful information about genuinely low oil pressure, your ears will be telling you that your engine has a problem).
Apparently, with some drilling and soldering, it is possible to repair the sensor, wrt to
You wonder how this happened:
