The Stovebolt Site Forums The Shop Area Engine Shop just installed a mechanical oil pressure gauge, need help...

I just bought a mechanical oil pressure gauge, cause I dont like warning lights. Anyway, I got it hooked up all right, bolted it in the truck, and started her up. The gauge jumped to 60 PSI, which is the norm. oil pressure for the 305 V6. When at idle though, the needle jumped back and fourth with the rythem of the engine. My father told me it was just the oil pump doing what it does. I said okay, and all was well. A couple hours later, I started the truck up again, the needle had stopped wavering, and the pressure was 50 PSI. I shut her off, then started the engine again. The wavering stopped, and it was registering about 55 PSI. My question is, the nylon tube that goes from the engine to the gauge: is oil supposed to be running INTO the gauge? Because, the tube is completly devoid of oil, except down by the engine, where the oil has crept up about 6 inches. Later when I checked the tube after the wavering had ceased and the pressure was getting wierd, a few drops of oil were present near the top of the tube. COuld I have a leak in the line? wouldnt the oil just spray out all over inside the cab? does the oil need to go into the gauge? And if it does, do I need to bleed the air out of the tube? I need help, I dont need the oil gauge getting wierd on me down the road somewhere and having hot oil blowing out all over my legs. :o :o :o

Usually the tube's full well sortta.You can bleed it at the gauge.Un hook the coil wire and run the starter crack the nut and fill the line.
Once you get this really sorted the pressure should be stable
Readings flux when the gauge isn't dampened

My 39 BMW fluxes all the time. Large lines and I'mm seeing the pump'stroke' but I think that's uncommon

Thanx J.H. I'm going to try that tomorrow. I will also get some rubber washers to put between the gauge and the cab. Thanks again!

do yourself a favor and trash the plastic line in favor of a copper tube. gets real messy when the plastic decides to go to pot and your running down the road unaware it has

I would suspect you have a very small leak somewhere in the line. To my way of thinking, you should have vey little to none in the way of oil in the line--there is nothing special about an oil pressure gauge as compared to a common air pressure gauge. If you allow oil to reach the gauge itself, it will likely ruin it over time. BTW--the line should be nylon--very tough as compared to common plastic.

I have a 1967 Camaro. I put in a Stewart Warner mach. Oil Guage 20 years ago It still works great and I have never had a problem with it.
It still has the original nylon / plastic line too.
There is always oil in the line, once in a while it gets a few bubbles but it never jumps around, just goes up and down smoothly with the RPM's [img]http://www.stovebolt.com/bboard/ubb/biggrin.gif[/img]

I agree with Jack. Trash the plastic line. I had one on an aftermarket gauge installed in a F*** used to own, it broke one day while I was driving. If I hadn't noticed it, I would have ruined the engine. Bleed the air out of the line, I cracked the line loose at the back of the gauge while the engine was running, watched the oil approach, then tightend the line. Electric gauges are more expensive, but worth the peace of mind

Yeah, you gotta bleed the air out of the line. Air acts as a cushion, since its much more compressible than a liquid, and will cause inaccurate readings. The guage is meant to work on actual oil pressure.

That really doesn't matter, in the static case, pressure into a line=pressure out, no matter what the fluid. Air will only make the guage respond a little bit slower, but it won't make the reading wrong.

Ahh, good ole physics.

Rember the ideal gas law?
PV\T=PV\T

Jay

Get rid of that nylon line immediatly!!!! I just about lost the engine in my car because the nylon line fell down onto the intake manifold and melted. A buddy and I were going home from college one weekend listening to a ball game. I thought I smelled oil and as I looked at the oil pressure gauge showing 20 psi instead of 45 like normal, I heard the lifters clattering. I immediatly shut it down and coasted to a stop. Four quarts of oil later I was back on the road again. A copper line was installed the next day and I had no more problems.

I bled the copper line to the gauge but I never noticed the needle twitching unless I was at a slow idle fully warmed up.

i used #4 areoquip push lock and it worked fine with 100 psi.
loss or rise of oil pressure will show a lot quicker
ya still have to bleed the line at the gauge

with the small tubes the oil pressure is gone in the engine long befor the gauge shows you
get stainless covers to make it tough on the outside