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Discussion Starter #1
I know there are already too many low oil pressure threads on this forum since it is such a common worry. Having said that, I wanted to start a thread specifically about the sending unit.

Here is my experience so far:

My pressure gauge was always low, but would stay in the middle (between the high and low sections of the gauge); however, after having an overheating/replace head gaskets session this summer, I noticed my gauge is now always in the lower section.

I worried that maybe I damaged the oil pump, so yesterday I borrowed an oil-pressure gauge from the local NAPA and checked things out. After warming up the engine, my gauge showed 20psi at idle, and 70psi at 3000rpm.
This jibes with what my Factory Service Manual tells me (and maybe even a little on the high side):

Oil pressure:
At idle
29 kPa (0.3 kgf/cm2, 4.3 psi) or more
At 3,000 rpm
245 - 490 kPa (2.5 - 5.0 kgf/cm2, 36 - 71 psi)


Ok. So my pressure is fine, but the dash-gauge is off. I am now wondering if those sending units get lazy after 15 years or so and start showing lower than what is there. Add an over-heating session to the mix, and the sending unit really loses its ability to display any picture of what is going on with pressure.

I am adding new sending unit to my list of things to buy for the truck. It looks like I need Toyota 83520-34010

Once I have my new sending unit, I will follow up on this post. I am curious if others also noticed a degradation in their oil pressure gauge reading over time and fixed it with a new sending unit.
 

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I know there are already too many low oil pressure threads on this forum since it is such a common worry. Having said that, I wanted to start a thread specifically about the sending unit.

Here is my experience so far:

My pressure gauge was always low, but would stay in the middle (between the high and low sections of the gauge); however, after having an overheating/replace head gaskets session this summer, I noticed my gauge is now always in the lower section.

I worried that maybe I damaged the oil pump, so yesterday I borrowed an oil-pressure gauge from the local NAPA and checked things out. After warming up the engine, my gauge showed 20psi at idle, and 70psi at 3000rpm.
This jibes with what my Factory Service Manual tells me (and maybe even a little on the high side):

Oil pressure:
At idle
29 kPa (0.3 kgf/cm2, 4.3 psi) or more
At 3,000 rpm
245 - 490 kPa (2.5 - 5.0 kgf/cm2, 36 - 71 psi)


Ok. So my pressure is fine, but the dash-gauge is off. I am now wondering if those sending units get lazy after 15 years or so and start showing lower than what is there. Add an over-heating session to the mix, and the sending unit really loses its ability to display any picture of what is going on with pressure.

I am adding new sending unit to my list of things to buy for the truck. It looks like I need Toyota 83520-34010

Once I have my new sending unit, I will follow up on this post. I am curious if others also noticed a degradation in their oil pressure gauge reading over time and fixed it with a new sending unit.
BAM has more mileage than anyone that I've seen here at almost 500k and I don't recall him mentioning anything.I have about half that on my 1995 and the guage has always been nearly smack dab in the middle.
 

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I have over 500,000 miles (maybe close to 530,000?) on my 1998 T-100 5vzfe auto trans 2WD. I haven't had any issues with the oil pressure sender so far. If it bothers you too much, you can pick up an aftermarket oil pressure gauge and hook it up on one of the available ports off of the oil pump. You'll need a 3/8" NPT male to 1/8" NPT female adapter which you can pick up fer under $5. I think the port plug is 8mm hex. No teflon tape required since it's an NPT threading.

Oh...don't think about trying to thread an aftermarket oil pressure sender to the engine's oil pressure sender port which is a different type of threading 1/8"-28 BSP and not the 1/8"-27 NPT threads that the aftermarket sender ones have. ;)
 

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Discussion Starter #4 (Edited)
My oil pressure sender looks like this:

283418




I will pull it again and get a part number off it, but I am wondering if it is the wrong sending unit for my truck. My FSM shows me something that looks more like:

283419



Can anyone tell me what part number they have for their sender unit?
 

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Discussion Starter #7
Interesting to see what you find out
I am on a budget, and have been chasing down a different issue (random misfire on cylinder 1) so the sending unit will have to wait, but I hope to get a new one within the next month.
 

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Understandable. I had a bit of a random misfire on cyl4. I went ahead and did plugs and boots and wires. I found on #4 the wire connecting on the boot was poor and that was my issue. for #1 I believe that is on the coil side and will have just the boot. If so pull it out and look at it. Usually you will see evidence of carbon tracking. Check the plug too. But if you are in need of a tune up maybe its just time as well.

NGK only or OEM only for these parts. Go cheep and you will still chase issues.
 

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Discussion Starter #9
Understandable. I had a bit of a random misfire on cyl4. I went ahead and did plugs and boots and wires. I found on #4 the wire connecting on the boot was poor and that was my issue. for #1 I believe that is on the coil side and will have just the boot. If so pull it out and look at it. Usually you will see evidence of carbon tracking. Check the plug too. But if you are in need of a tune up maybe its just time as well.

NGK only or OEM only for these parts. Go cheep and you will still chase issues.
Here is my thread for the issue. I have already eliminated several possible culprits and am chasing wires now:
 

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I have about 151k on my 97 4x4 and at about 55 or so my gauge is in the middle of it's scale but at idle it is almost to the bottom of the gauge.

Steve........
 
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