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Post by wannabe on Feb 13, 2017 12:18:24 GMT
For some reason my oil pressure gauge is currently maxing out at 2bar (!) (even under load) and settling around 0.5bar on idle, sometimes a bit less.
It's always shown that sort of pressure at idle since I've had it but it has previously gone up to about 4bar when under load.
This morning it was wavering around 2bar on the motorway under a steady load, so I am a little concerned that something may be wrong.
Skuzzle have previously wondered if it might not be working properly, but I don't know what the symptoms of a broken oil pressure sensor thingy might be??
Or what the symptoms of a failing oil pump might be?
I am kind of of the mindset that, ultimately, it either has oil pressure or it doesn't, so when it doesn't, it will just go bang to let me know all is broken... but I'd rather not kill it given the money I've spent on it!
It's a SNC 1.6 so I hope it is ok, as I don't want to 'waste' the good, working bits from it or have to pay for a whole engine rebuild with a LNC bottom end 
Perhaps it's just because it's (over)due a service and the oil (5w40 Asda Fully Synth  ) is past its best and getting thin??
Any advice gratefully received!!
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Post by Horney on Feb 13, 2017 13:16:44 GMT
Buy a proper capillary gauge and test it.
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Post by wannabe on Feb 13, 2017 13:52:06 GMT
Buy a proper capillary gauge and test it.
I had thought about that but I don't know how I'd do it...  lol
Can Skuzzle do it??
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Post by myothercarsa2cv on Feb 13, 2017 22:05:00 GMT
If you ground the sender the gauge should go full range (I think!). If it doesn't... buy a new one  If it does... check the pressure relief valve. It could be jammed open. |
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Post by wannabe on Feb 13, 2017 22:58:56 GMT
Thanks for the advice - I'll see if I can do that! lol |
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Post by wannabe on Mar 15, 2018 21:21:52 GMT
If you ground the sender the gauge should go full range (I think!). If it doesn't... buy a new one If it does... check the pressure relief valve. It could be jammed open.
Soooo, a year later and I've still not got this sorted... 
Looking at the diagrams in the manuals on that mellens website, the pressure relief valve is in the sump? (figure 15 here: www.mellens.net/mazda/Mazda-Miata-1991-1993/1991_engine.pdf)
Can it be checked/removed/cleaned by simply removing the sump pan?
Is it a replaceable part?
Or would it have to be cleaned with petrol or similar, to de-gunk it and make it clean and shiny and (hopefully) working again??
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khare
Chats A Bit
Posts: 248 
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Post by khare on Mar 15, 2018 22:48:45 GMT
Have you replaced the oil filter and oil? And cleaned the terminal on the gauge pressure sender?
I had the same things, sitting at 1 bar and no more than 2 at high rpm and after doing an oil change, filter, and sender terminal clean, it all was good again.
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Post by wannabe on Mar 17, 2018 16:01:55 GMT
Have you replaced the oil filter and oil? And cleaned the terminal on the gauge pressure sender? I had the same things, sitting at 1 bar and no more than 2 at high rpm and after doing an oil change, filter, and sender terminal clean, it all was good again.
No, no and no lol
I should hopefully be getting it serviced in the next couple of weeks, though, so will see how things go then, but there was no real change after the last service so I'm not hopeful
I was doing some trawling of a certain other forum and there were a couple of posts that seem to infer the pressure relief valve on the oil pump could be at fault: www.mx5nutz.com/forum/index.php?showtopic=263561#entry3145994 www.mx5nutz.com/forum/index.php?showtopic=366761#entry4344202
and that it is accessible through the sump: www.mx5nutz.com/forum/index.php?showtopic=320513#entry3884882
It could be a perished O-ring that is meaning it's not holding pressure: www.mx5nutz.com/forum/index.php?showtopic=313682#entry3803298 www.detailingworld.co.uk/forum/showpost.php?s=58d670aca25ae0e92d2326f1c4293d20&p=5109280&postcount=33 (bloody photobucket eating the pictures, grrrrrr)
but perhaps I should just drive it and be done with, as the sender may not be perfect! www.mx5nutz.com/forum/index.php?showtopic=304890#entry3701890
I'll perhaps have to see if anyone's actually fixed the oil pressure relief valve without changing the oil pump, seeing as that won't be a possibility on a SNC engine... |
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Post by wannabe on Mar 26, 2018 11:22:08 GMT
Just to update this thread for future reference, seeing as I mentioned it on another thread - with some wiggling of the oil pressure sensor connector, the pressure is now reading as it should!
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Post by atlex on Apr 4, 2018 17:05:06 GMT
love it when something is solved by the wiggle method. you can expect any 20 year old cable to be a bit oxidized especially where it is seeing current.
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Post by atlex on Apr 4, 2018 22:00:29 GMT
My grandfather, who was an RAF engineer in WW2, swore by the "brass wire brush" method on any suspect contacts. On distributors especially. :-) Brass wire won't damage any typical aviation/automotive contact terminals but will scour any dirt or oxide off enough to get a good contact.
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Post by martiny on Apr 5, 2018 14:45:03 GMT
"Bootlace", AKA Tape, Bank Cleaning, is antiquated stuff we still use. Originally for electromechanical telephone exchanges, we kept on using it for brass "Post Office" and "bantam" plugs but it also works a treat on relay contacts. www.canford.co.uk/BANK-CLEANING-TAPEImagine a length of bootlace that's been soaked in Brasso then left to dry. When you need to clean up electrical contacts it's amazing stuff. For finer jobs, especially relays, you used to be able to get "Bristol board" which was like strips cut from a business card and again impregnated with metal polish. Don't think you can get that now. P.S. Jumpers for goalposts, etc. |
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Post by wannabe on Apr 5, 2018 16:38:47 GMT
"Bootlace", AKA Tape, Bank Cleaning, is antiquated stuff we still use. Originally for electromechanical telephone exchanges, we kept on using it for brass "Post Office" and "bantam" plugs but it also works a treat on relay contacts. www.canford.co.uk/BANK-CLEANING-TAPEImagine a length of bootlace that's been soaked in Brasso then left to dry. When you need to clean up electrical contacts it's amazing stuff. For finer jobs, especially relays, you used to be able to get "Bristol board" which was like strips cut from a business card and again impregnated with metal polish. Don't think you can get that now. P.S. Jumpers for goalposts, etc.
Good tips, thanks!
(Showing your age  lol)
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Post by myothercarsa2cv on Apr 5, 2018 22:08:06 GMT
Worry gauges eh?
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Post by jackyboy on Oct 5, 2018 19:28:40 GMT
I think my late uk mk1 oil gauge is fake. Although i have been told that it actually works but doesnt fluctuate. Just reads whether there is oil pressure or not 🤔
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) is past its best and getting thin??
lol
If it does... check the pressure relief valve. It could be jammed open.
lol)
