jan the man

My issue is different then most, my oil pressure gauge goes to zero when i push in the clutch to stop or am idling, when i am driving around 4000 rpm it does move up to 3-5 bar but back down to zero when i stop. Initially though it was cheap after market senders i tried but just put in OEM same thing happens.
It has been doing this for a long time and car idles and drives great, its just that red warning light has finally driven me crazy and i need to figure this out. This is my third sender that does the same thing so pretty sure it isn't the sender.
Could it be the gauge it self? If so how would i check that?
thanks

IainM

What oil weight are you using?

jan the man

Mobil 1 0-40

Sword_of_the_Spirit

I wonder what the resistance to the gauge is? You have pressure, probably at 1-1.5br (which is ok) at idle when temp is less than 8:30. If you didn’t, you’d have seized long ago. Have a friend who could swap out with you?

annoying for sure, not detrimental to the engine.

notabot

Oh this will be a fun thread

pp000830

Hi Jan,
Try a 5W-50 Mobil 1
In warmer climates, it ups the measured pressure a bit.
Note on the below page how your other gauges related to oil should be reading as a proxy for the oil pressure gauge as proof of adequate lubrication, and the oil viscosity comment near the bottom of the page:
https://993servicerepair.blogspot.co...-leveloil.html
Also, test your oil cooler low-speed fan:
Easy to do how-to near the bottom of this page:
https://993servicerepair.blogspot.co...ooler-and.html

Andy

prschmn

993 engines are not built with bearing clearances suitable for 0 weight stuff . If using Mobil 1 I'd only recommend 15/50 since it has a better Zinc level.

Quadcammer

Not really a bearing clearance issue. The 993 hot oil pressure (which appears to be the topic here) with 0w40 should still meet the spec. 40wt oil is ok. The reason most dont run a 0 or 5 cold weight is piston to wall clearance, not bearings.

prschmn

Except that skirt clearance won't affect pressure-------

Hilltopper

Only Mobil V-Twin 20w-50 for me and approved by many in past for 993.

Quadcammer

of course it won't.

Point is, that a 0w40 oil, at operating temperature, may contribute to lower pressure than 50wt, but it is not an inappropriate hot viscosity for a 993 engine. 50wt would be better, but given that the OP is telling us that the gauge reads nothing at idle, its much more likely an electrics issue, not a mechanical one.

OP, I had some funky oil pressure gauge readings and replaced the sender. When that didn't work, I sent the gauge to I think North Hollywood gauges and they replaced the mechanism, which fixed my issue.

jan the man

Thanks for the input guys, i have had this issue for 12 years and replaced the sender three times. I always used 15-50 oil until my last oil change (could not find it up here then).

Only put on 1k miles a year will put 15-50 in next time.

I am thinking problem is gauge,. Any way to test that or is there a fix?

pp000830

Hi Hilltopper,
The old saw is that at 1750ppm of zink in this oil, almost double the amount in Mobil 1s recommended fill, it contaminates the CAT's at an accelerated rate and potentially precipitates their failure and a Check Engine Light. I guess if your car has over 100k+ miles on it like mine with no problems the old saw may not be true. If you have 50K miles on your car I guess we need to stay tuned. I like you want my car to purr along however I don't want my CATs to become expensive dead pets!
Andy

red64chevelle

You could try swapping the gauge with a known good one to see if that works. It’s not too hard to get them in and out. I have a spare one I would let you borrow if you spring for shipping back and forth. If it turns out it is the gauge, you could keep mine installed for a bit and ship your original to North Hollywood for repair. Then just swap them back when you get yours back.

TDW993

Having the gauge reading low at idle and the warning light coming on, wouldn’t that indicate a genuinely low oil pressure condition. They are two entirely different sensors/switches. I would run a 20/50 or 20/60 and see where you are at firstly.