Mechanical Oil Pressure Gauge conversion

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joe toto

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1997 5.7 Tahoe:
If anyone could point me to a how-to/ a thread on how to install a mechanical oil pressure gauge that would be much appreciated. My oil gauge reads fine when cold/ in motion, but when I break hard/ come to stoplights the pressure drops to 0. I took it to my mechanic and he says the oil pressure is fine, so I just want to install a mechanical gauge for piece of mind.

Forgive me if this is a simple process to most of you, but I am a 18 year old with minimal experience.
 

Schurkey

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First Guess: The oil pump pickup tube has fallen off the oil pump. Your "mechanic" tested the unit at rest, not with the oil sloshed forward, away from the oil pump.

You could verify this at your next oil change, by pulling the oil pan drain plug, allowing all the oil to flow out, then poke a borescope into the drain plug hole. Take a look around inside the pan--if the pickup tube is lying on the bottom, you've found the problem. This assumes that the pan has the proper amount of oil in it now--a very low oil level can cause this problem, too.

Another possibility is that the wiring or the connector on the end of the wire for the dash gauge is faulty. Heavy braking causes the wire to move forward, and the broken conductor opens the circuit. Some time spent inspecting the wire and repairing as needed may be all you need.

If you insist on installing a "mechanical" gauge, you'll need to figure out where you want to put the gauge; you'll need some sort of mounting bracket. The gauge comes with instructions for how you connect power from the dash light fuse, and ground so that the gauge lights up with the rest of the dash gauges and the brightness is controlled just like the rest of the dash--via the rheostat near the headlight switch.

At that point, it's just a matter of getting a brass "tee" to screw into the engine near the distributor. You'd remove the existing sensor for oil pressure, install the tee, put the original sensor into one branch of the tee, and the plumbing for the new gauge in the other branch of the tee. Route the tubing through some hole in the firewall, PROTECTED BY A RUBBER GROMMET so the sheetmetal can't abrade the tubing and cause an oil leak. The tubing--usually nylon, but some folks upgrade to copper or steel-braid-over-Teflon (PTFE) liner hose--MUST be secured so that the engine can shake without stressing the tube/hose, and yet the tube/hose doesn't rub or abrade whatever it's routed near.

I put a tee into my 5.7L engine. I don't have a photo of the sensor and hose connected, though.
The brass tee is behind the "Sch" of my name on the copyright notice.
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stutaeng

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I just realized my '00 K3500 5.7 started doing something somewhat similar. My oil pressure is normal driving and coming to a complete stop. When I take off the guage dips to 0 and then goes to normal.

The first time I saw it I had just glanced and only saw the needle at 0 and kinda freaked out... I haven't poked around to see what could be the problem.
 

alpinecrick

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If the oil pressure gauge is working normally at idle or driving down the road, then does something funky when turning, braking, or accelerating, I don't see how it could be the gauge.
I would be quick to check for a proper functioning pickup tube, and not wait for a oil change.
There is a slight possibility the windage try has broke lose from it's welds, moved somewhere in the pan, and momentarily slows the oil from flowing around it to the pickup.
 

stutaeng

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If the oil pressure gauge is working normally at idle or driving down the road, then does something funky when turning, braking, or accelerating, I don't see how it could be the gauge.
I would be quick to check for a proper functioning pickup tube, and not wait for a oil change.
There is a slight possibility the windage try has broke lose from it's welds, moved somewhere in the pan, and momentarily slows the oil from flowing around it to the pickup.
Thank you.

Dropping the oil pan? Does that mean dropping the differential?

I did recently buy a nice OTC pressure guage set for a transmissions diagnostics with quick connects. Has 2 guages, and I think the lower range one is good for engines. Maybe I should check with a mechanical guage to see if it does the same thing?
 

Schurkey

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Dropping the oil pan? Does that mean dropping the differential?
In MY driveway, "dropping" the oil pan means first pulling the engine. But as said...I'd pull the drain plug and have a looksie before ripping the engine out.

I did recently buy a nice OTC pressure guage set for a transmissions diagnostics with quick connects. Has 2 guages, and I think the lower range one is good for engines. Maybe I should check with a mechanical guage to see if it does the same thing?
I have that same set. Yes, connect it to an oil pressure port and see what happens. Shouldn't be too difficult, and it'll eliminate the potential of sensor/wire harness issues.
 

thinger2

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Geez
Get a cheap mechanical op gauge.
Pull the block plug right above the oil filter.
Tee it in and drill a hole through the firewall.
Slap the gauge in place and drive it around for a bit.
If you like the results, pull the gauge back out, put the plug back in the block and check it again next year.
Dont forget to plug the new hole in the firewall so rain doesnt get in
 

mematt

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Geez
Get a cheap mechanical op gauge.
Pull the block plug right above the oil filter.
Tee it in and drill a hole through the firewall.
Slap the gauge in place and drive it around for a bit.
If you like the results, pull the gauge back out, put the plug back in the block and check it again next year.
Dont forget to plug the new hole in the firewall so rain doesnt get in
Awesome advice, thanks.

Next time drop the Geez, most people here are seeking information, and thus admit they do not know.
 

thinger2

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Awesome advice, thanks.

Next time drop the Geez, most people here are seeking information, and thus admit they do not know.
I didnt mean the geez for you. I meant that for the mechanic who didnt bother telling you why or how he thought the oil pressure was good and how he determined that.
And why he didnt tell you about the always awfull factory gauges.
Did he tell you what the pressure was? Or did he decide that you were too young to afford his mortgage and alimony and boat payments and then just gave you the brush off.
Thats the "geez" bud.
It wasnt directed at you.
 
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