Engine Oil Pressure

Hypnotic818

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Jul 1, 2016
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I know I know, I keep coming back for help with this dam car lol. So my 94 GT had some issues from previous posts and I got everything worked out. Well today I took the car out around town and the oil pressure is bugging me.

When the car is cold the oil pressure is around 50. When it warms up the oil pressure is around 20-26. The dash stock gauge shows oil a bit under L. I'm not sure if that's temp or what. But today after driving for 30-40 mins the oil pressure went to 10. Which scares me because before when it dropped it blew the head gasket lmao. I shut down the car when I got to my spot let it cool for about 15 mins than turned it back on to get home and the oil pressure was at 20. Got to the first stop light a block away and it was back at 10 again.

Anybody got any ideas what this could be? All help is wonderful :)
 
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Dan_Soprano

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May 7, 2003
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What are you running for a gauge? Electrical or mechanical? If it's an electrical gauge, try changing the sending unit as they are notorious for going bad. Mechanical oil pressure gauges are a good practice for more accurate readings. How many miles on the short block? If you are getting north of 125-130,000 then falling to 10psi at idle isn't uncommon, as the bearings are wearing down the clearances open up causing a drop in pressure. Whats the pressure at when driving around?
 

Hypnotic818

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I'm running a mechanical gauge. Its a crappy $20 one right now from autozone. The old one that came with the car stopped working. The miles are around 115-120k I'm pretty sure. The odometer stopped working at 109k lol. When driving around the pressure is at 40 even when oil pressure drops to 10. If the bearings are wearing down when should I look into changing them? And is there an estimate of how long they'll last? Apts aren't the best for that :(
 

Hypnotic818

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Noobz347

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http://www.autozone.com/gauges-and-...us-chrome-bezel-oil-pressure-gauge/255972_0_0

This is the gauge I got. And its connected below the AC and on the right of the water pump. It came in that spot so I left it there. It has a nylon tube wrapped in heat shroud. And the gauge light is just wired in to my instrument cluster. Came that way also lol.
Rog thanks. Making sure we're working from the same sheet of music.

At minimum, you're going to need to verify the accuracy of that gauge by installing another, even if temporarily so that you can compare the two. After that, I think it would be time to look at the oil pump and after that, maybe a leak-down test to help gauge the health of the engine.
 

Hypnotic818

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Rog thanks. Making sure we're working from the same sheet of music.

At minimum, you're going to need to verify the accuracy of that gauge by installing another, even if temporarily so that you can compare the two. After that, I think it would be time to look at the oil pump and after that, maybe a leak-down test to help gauge the health of the engine.
I'll tear through my garage tm and see if I can find the old gauge to compare the 2. I hope its not the oil pump but knowing the mechanics who did it might be. They never replaced the oil pump shaft or if they did they did a horrible install job bc it fell off after a second dizzy pull lmao. And for the leak down test I'm reading that a tube goes into a spark plug hole correct? If so I'll need to find an adapter because these GT40 holes are different. My compression tester can't even reach into it lol.
 

Dan_Soprano

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May 7, 2003
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If you're at 40+ when driving around I'd say you are probably ok. An old rule of thumb was 10psi for every 1000 rpm. Doing a compression / leakdown test is not going to show any problem with the oil system. My old 87 notch with a 351w used to idle at 15-20 PSI when heat soaked.
 
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Hypnotic818

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A tube? No, a compression gauge. You can cross that bridge when you get to it though.
Yes a compression gauge. It was right on the tip of my tongue typing but I couldn't find the word lol.

If you're at 40+ when driving around I'd say you are probably ok. An old rule of thumb was 10psi for every 1000 rpm. Doing a compression / leakdown test is not going to show any problem with the oil system. My old 87 notch with a 351w used to idle at 15-20 PSI when heat soaked.
Yeah it takes awhile for it to even get to 10psi. But as long as it doesn't go below 10 I'm happy lol.
 
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