Oil pressure Gauge - low oil pressure at hot idle

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Guy
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Oil pressure Gauge - low oil pressure at hot idle

Post by Guy »

Just completed a U20 swap into my 1600.

Now having very low oil pressure reading at hot idle.

During the swap, I notices the oil sending line to the dash gauge leaked most it not all of the oil out.

Should I bleed the oil pressure gauge at the dash connection?

Running Valvoline 30W
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nismou20
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by nismou20 »

U20 oil pressure gauge are not that reliable at idle. But, you should address the leak to the line.
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Guy
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by Guy »

Oil leak was a result of disconnecting the oil line to the gauge during the swap.

Bled the oil line connection at gauge, under the dash...not that hard to do. 13 mm wrench and determination.

2 to 3 second delay on oil reaching the gauge. immediate 8 to 10 lb improvement in oil pressure reading.

Hot idle oil pressure reading improved from 0 to +/- 8LB at 900 RPM
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Linda
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by Linda »

Interesting. So because the oil line could have air, or is not "bled" that could be another reason for reading lower on oil pressure guage? Mine was leaking once, and I tightened it, but never thought to bleed the line. Thx for the tip.
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by mraitch »

Idle pressure is typically low.

I've recently swapped oil gauges in/out/in/out repeat etc. and nothing has changed.

Not sure if oil actually HAS to run in the lines, or merely the 'pressure' that it generates.

Would be good to know the EXACT funvtioning.

Anyone out there??
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keith0alan
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by keith0alan »

In a closed line the pressure is the same at both ends. Bleeding should not be necessary. To answer the obvious question, brakes are different because the master has a limited volume capacity.
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by bajaroadster »

In the interest of not starting an additional thread i'll post to this one since it is oil pressure gauge related but a bit of a different symptom. Recently purchased a 67 1/2 1600. Oil pressure gauge was inoperable and needle not visible. P.O. indicated that he believed the needle had broken off. After driving the car for awhile I have noticed that the needle will on rare occasion appear and climb for a few seconds and then disappear. Is this an indication of a bad sender perhaps? Bad ground? Suggestions are appreciated. I'm not very mechanically inclined but like to learn and resolve issues when I can.
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MattC
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by MattC »

Could the needle be bent or indexed on the gauge shaft incorrectly?
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by bajaroadster »

Needle seems to move freely on rare occasions that it appears with no indication of being bent but of course I cannot see the entire needle to its pivot point. The intermitant aspect is what has me wondering. No rhyme or reason and only appears occasionally.
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by SLOroadster »

The low windshield cars used an electric sender, so either the sender is bad, or there is a bad ground somewhere. The late cars used a direct line to the gauge and were fully mechanical.

The early gauges/senders are notorious for being temperamental.

Will
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by bajaroadster »

looks like sender is part # PS202 from Summit according to Wiki. I'm 800 miles south of the border in Baja Mexico. Amazingly enough, we do have an Autozone store. Hopefully they can cross reference it to an available part number. Ill start there and see what happens. Any words of wisdom on location of ground(s)?
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by bajaroadster »

Once again reviving this thread with a bit more info on a newly observed symptom in regards to my non functioning oil pressure gauge. Since purchasing the car (67 1/2 1600) the gauge has not worked, but the needle will occasionally appear for a few seconds and then fall back to "zero". This happens randomly and with no apparent rhyme or reason. But it at least reveals that the needle has not broken off and that the gauge is probably still viable. Recently, the car had a difficult cold start issue and I noticed something with the gauge that I had not observed in the past. When the ignition switch was in the start/cranking position and the engine was struggling to fire, the oil pressure needle climbed and stayed at about 40 lbs of pressure. As soon as the key was released to the "run" position, the needle would again disappear whether the engine had fired or not. Is this a normal occurence or perhaps an indication of the problem with the gauge?
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by Gregs672000 »

Can't answer your most recent question. However, I've had the same issue, and posted about it last year where my gauge read very low while the engine was at higher rpm. I researched and purchased a new sender (BTW, what's listed for working on our cars is often not correct from places like auto zone, but you've got nothing to lose at trying). I was able to find ONE correct sender at a reasonable price, but it sits in my tool box because it reported the same as the old one. A 240z sender does not WORK! I installed a mechanical gauge and confirmed good pressure under all conditions, then went back to the old sender which is more of a poorly operating idiot light. Most I ever see is 40lbs, and the mechanical read 60 as I recall, and 10-15 at idle when the sender says 0. Rallye Roadster wrote about this back in the 70's. As noted, it's an electrical sender and contacts get old. I would assume there's a way to test its output under different conditions, but I will leave the parameters and tool needed (likely a multimeter) to the experts on everything electrical, like Curtis...
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by C.Costine »

bajaroadster wrote: Sat May 01, 2021 11:50 am Once again reviving this thread with a bit more info on a newly observed symptom in regards to my non functioning oil pressure gauge. Since purchasing the car (67 1/2 1600) the gauge has not worked, but the needle will occasionally appear for a few seconds and then fall back to "zero". This happens randomly and with no apparent rhyme or reason. But it at least reveals that the needle has not broken off and that the gauge is probably still viable. Recently, the car had a difficult cold start issue and I noticed something with the gauge that I had not observed in the past. When the ignition switch was in the start/cranking position and the engine was struggling to fire, the oil pressure needle climbed and stayed at about 40 lbs of pressure. As soon as the key was released to the "run" position, the needle would again disappear whether the engine had fired or not. Is this a normal occurence or perhaps an indication of the problem with the gauge?
Have you checked the wring of the gauge against Curtis's wiring diagram?
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Re: Oil pressure Gauge - low oil pressure at hot idle

Post by dads311 »

Hey Baja, check the wire at the sending unit for 12v while it is running. If not there check the source going to the meter.

Mike
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