What did I do?! Oil pressure reads very low.

aclos3 · 11-02-09, 10:55 AM

Here's my situation. I was up working on Alaska for a month and the LX sat untouched. I started it the night I got home and all seemed well. The next day I drove about 100 highway miles and all seemed normal. By normal, I mean the oil gauge goes up to around half way under some load and settles down to about 1/4 during light load with a warm engine.

That evening I got to yacking cars with my buddy (a fellow car nut) and as we were talking I popped the hood and checked the oil. Yes, I know the engine should be warm when you do this, but it looked a tad low anyway so I added about half a quart of Mobile 1 10W-30.

The next morning I started the truck and notice that the oil pressure gauge won't come off low. I was worried to say the least and took it very easy during the five mile drive. Temps looked great, engine ran as smooth as ever and no engine or oil light.

Later that afternoon I drive the 100 miles home. All the while the guage has not budged off low. I don't see it move at all regardless of load or temperature, and it seems to just stay almost even with the lowest hash mark if not above ever so slightly.

CLIFF NOTES: My oil gauge needle stays at low under all conditions, but the truck runs/ran great. The guage did NOT do this before!

Any help would be greatly appreciated.

-Andrew

Michael Hanson · 11-02-09, 11:03 AM

Miles? Pull oil sender off and check for loose wire or obstruction. probably fine if not getting hot. mike

Ebag333 · 11-02-09, 11:05 AM

Hook up an oil pressure gauge and see if you are actually getting pressure that matches the FSM spec.

So let me get this straight, there are 4 marks, you are saying that it's hovering around the bottom hash mark for the "normal" operating range? Not sitting at the bottom mark, which is where it'd be if the engine was off?

It's possible your sender is going out. When was the last time you had your oil changed?

e9999 · 11-02-09, 11:08 AM

this is potentially serious enough that I would not drive it until I'd figure this out.
Likely could be just the gauge or sender, hopefully.
But don't take a chance on a wild guess as to what's happening.
You don't want to blow up your engine. Can you say $$$?
At the very least make sure it's still full of oil each time you drive it. And that does not tell you whether the oil is flowing or not.

aclos3 · 11-02-09, 11:16 AM

Thank you for the responses.

The truck has 168,000 miles. I have a FSM and will inspect the oil sender. It seems like I'd have broken something with all the driving if I actually had almost no oil pressure.

I am due for an oil change. I run Mobile 1 and it has been 1 year and about 7000 miles since my last change. I plan to change oil this week. I've never hooked up an oil pressure gauge -- where does it attach? To the same place the factory dash gauge does? Also, I understand your question about the location of the needle and I believe it is not in the "off" position, but up just a little very near the lowest hash mark. I will watch the needle on startup this afternoon and see exactly what it does.

aclos3 · 11-02-09, 11:37 AM

Ebag, your comment about the sender made think... Something having to do with a stupid guy climbing into his engine bay at night, with boots on... stepping on a wire. I forgot that I did that (and why it may matter!) until you made your comment about the sender unit. Do these wires run somewhere from around the washer fluid tank to under the exhaust header tubes? If so, I think I may know what's going on. I'll check the FSM after work tonight and inspect those wires for damage.

EDIT: Hmm, looks like they're talking about this in this post. I bet I stepped on exactly what john_eckels talks about in post number 6 of this thread. http://forum.ih8mud.com/80-series-te...use-guage.html

Ebag333 · 11-02-09, 11:44 AM

Quote:

Originally Posted by aclos3

I am due for an oil change. I run Mobile 1 and it has been 1 year and about 7000 miles since my last change. I plan to change oil this week.

My guess is that your oil is shot and needs to be changed.

I personally would not go past 5,000 miles in these between oil changes. If you do go longer periods of time, it's better to use a heavier oil.

I've found 10w-30 too light for both my rigs. I prefer 15w-40, and have swapped in 5w-40 for the winter. I may go back to 15w-40 and put in a block/coolant heater.

aclos3 · 11-02-09, 11:53 AM

Ok, I always thought you could go a bit longer on the synthetic. My rig sees pretty easy use when I am not climbing under the hood to sabotage it. For my oil change a year ago, I used 5W-30 Mobile 1. I know that is light, but the owners manual specified that oil, so I stuck to it. I am going to run 10w-30 next, since I've already bought the oil, but I'll see how that holds up and consider going heavier next time. Looks like I'll do that oil change today and hopefully find a broken wire under the hood that will mend the oil pressure gauge.

Thank you for all the great information.

Tools R Us · 11-02-09, 12:10 PM

Sounds like an electrical problem to me, if you really had zero pressure, there would have been big issues long before you got home. Were you messing around in the area of the A/C compressor, the sender is just behind it and the wire is pretty easy to knock off.

IMHO running Mobil 1 to 10K miles is zero issue. The 1FZ is very easy on oil and there have been many tests of Mobil 1 run past that with the oil still being in good condition.

Ebag333 · 11-02-09, 12:23 PM

Quote:

Originally Posted by aclos3

Ok, I always thought you could go a bit longer on the synthetic. My rig sees pretty easy use when I am not climbing under the hood to sabotage it. For my oil change a year ago, I used 5W-30 Mobile 1. I know that is light, but the owners manual specified that oil, so I stuck to it. I am going to run 10w-30 next, since I've already bought the oil, but I'll see how that holds up and consider going heavier next time. Looks like I'll do that oil change today and hopefully find a broken wire under the hood that will mend the oil pressure gauge.

Thank you for all the great information.

The manual recommends 10w-30 for milage reasons. IIRC, everyewhere else Mr. T recommends 15w-40.

Quote:

Originally Posted by Tools R Us

Sounds like an electrical problem to me, if you really had zero pressure, there would have been big issues long before you got home. Were you messing around in the area of the A/C compressor, the sender is just behind it and the wire is pretty easy to knock off.

If his gauge is reading 0, I agree that it's likely an electrical problem. If it's staying at the first tick mark (bottom of the normal range), then I would find it more difficult to attribute that to wiring. More likely the sender, the gauge, or the oil itself.

Quote:

Originally Posted by aclos3

Also, I understand your question about the location of the needle and I believe it is not in the "off" position, but up just a little very near the lowest hash mark. I will watch the needle on startup this afternoon and see exactly what it does.

The

truck had similar (though not as extreme) behaviour where the pressure would not get into the normal range. An oil change fixed the issue, which is why that's my first guess.

She was about 5k miles post oil change, and this is the first time it's done it (despite going up to about 5k miles several times before). I'm wondering if the change of weather could be a contributing factor, as it's been much more wet around here lately.

Brian894X4 · 11-02-09, 12:29 PM

I'd bet that this is a gauge issue. Long story short, the toyota oil pressure gauges are total garbage.

The most common way to destroy them is to short out the wire to the sender. Usually by the wire coming off the sending unit and touching ground or a cut in the wire grounding out. When grounded, the needle on the gauge goes all way over to the max level until it hits the stop. But the internal mechanism will want to keep going, which means it does, but the needle can't move any further.

In worst case the heating element that moves the needle will burn out and the gauge will read zero all the time. Or the guage will always read zero because the mechanism bent too far. Otherwise, the needle could always read low, because the mechanism inside the guage will read one position, but the needle will now read a lower position.

Clear as mud?

Bottom line, check the wiring to the sending for any obvious problems. If none found, have your pressure tested. If it's fine, consider replacing the gauge or sender. The guage is more likely to be the problem than the sender.

By the way, the oil idiot light in the Land Cruiser is not a pressure light. It only reads oil level. They generally come on when you are about 1 to 1.5 quarts low, so don't rely on it as a pressure indicator. Low oil level, especially only 1 or 2 quarts low, will not affect pressure. I also doubt your oil is "worn out" or that your visc is too low. A lot of guys, including me run 10w-30 with pressures well within spec. But there could be mechanical issues involved, while I lean towards gauge failure, don't overlook the possiblity of something that could cause engine damage.

Tools R Us · 11-02-09, 12:31 PM

Quote:

Originally Posted by aclos3

... Something having to do with a stupid guy climbing into his engine bay at night, with boots on... stepping on a wire. I forgot that I did that (and why it may matter!) until you made your comment about the sender unit. Do these wires run somewhere from around the washer fluid tank to under the exhaust header tubes? If so, I think I may know what's going on. I'll check the FSM after work tonight and inspect those wires for damage.

EDIT: Hmm, looks like they're talking about this in this post. I bet I stepped on exactly what john_eckels talks about in post number 6 of this thread. http://forum.ih8mud.com/80-series-te...use-guage.html

Yes, the wire is in the harness that runs between the exhaust down pipe and A/C compressor. Very easily knocked off by a fat foot shoved in there.

aclos3 · 11-02-09, 02:02 PM

A few minutes ago I visited my car and inspected the wire more closely. It looks like I have indeed broken one of the small wires that leads to a clip connected to a round, poker chip shaped wafer that attaches to the block under the forward exhaust bank. Only one wire is going into the clip now and a broken one is just hanging. I am assuming both are supposed to attach to that clip. I'll have to wait to get home where I can get dirty and read the FSM before I go any further.

Also, if I'd really had extremely low oil pressure, wouldn't I have had a flashing check engine light?

The oil brings up another good point. I am a low mileage driver who averages five to eight thousand miles per year. 75%-80% of that mileage comes from highway driving. I've always sort of gone with 10k/1 year, whichever comes first for my oil changes. How do you feel about that? Should I scrap the time aspect and replace the oil every 10,000 miles regardless of how long that takes to drive? Also, I use the small Toyota synthetic filters. How long would you run one of those?

Thanks,
Andrew

aclos3 · 11-02-09, 02:18 PM

Thanks Ebag for the oil info, I will continue to run heavier oil now that I've been set straight from the owner's manual information. I will change the oil tonight and fix the wire.

Brian, Hopefully I will not have shorted out the gauge. The broken wire appeared not to be touching anything, so maybe I'm safe. I also never noticed any of the erratic needle behavior you described. I could have missed it, but I do usually pay close attention to my oil pressure and temp gauges. Also, I know the oil light is just a level light, but thanks for the clarification. Many people confuse the issue and it is a very important distinction!

ToolsRUS, yep, that is the wire. A wire with a small clip branches off and attaches to something very near (on top) of the A/C compressor, while the rest of it heads under the exhaust and attches to something in there. One of these leads broke off of that device, accessible under the forward exhaust header.

-Andrew

Ebag333 · 11-02-09, 02:28 PM

Quote:

Originally Posted by aclos3

A few minutes ago I visited my car and inspected the wire more closely. It looks like I have indeed broken one of the small wires that leads to a clip connected to a round, poker chip shaped wafer that attaches to the block under the forward exhaust bank. Only one wire is going into the clip now and a broken one is just hanging. I am assuming both are supposed to attach to that clip. I'll have to wait to get home where I can get dirty and read the FSM before I go any further.

Glad you found the source of the problem!

Quote:

Originally Posted by aclos3

Also, if I'd really had extremely low oil pressure, wouldn't I have had a flashing check engine light?

Evidentially not as your gauge was reading low but no check engine light. There was also another recent thread where there was little to no oil pressure, and no CEL.

Quote:

Originally Posted by aclos3

Thanks Ebag for the oil info, I will continue to run heavier oil now that I've been set straight from the owner's manual information.

If you ever want to learn more than you wanted to know about oil, this site is the place to go:
Welcome

aclos3 · 11-03-09, 12:53 AM

After work today I dug into the issue and repaired the broken wire. There are two clips (one wire each) that connect to what I believe the FSM calls the "oil pressure switch." One of these wires was broken off from the clip, so I removed that clip and took it apart. With the metal conductive piece removed from its plastic housing, I soldered the piece back to the broken wire. Problem fixed! I also changed the oil to Mobile1 10w-30 and replaced the filter.

Thanks for your help everyone.

-Andrew

Brian894X4 · 11-03-09, 01:35 AM

Glad it worked out.

1yr/10K miles is a bit long for my taste. The combination of synthetic and a very large sump with about 7 to 8 quarts of oil definately helps.

I personally do about half that. 5000/6 months and I also run synthetic and I also only put about 10K a year...mostly highway. But I think probably the biggest indicator is how does the oil look. The blacker it is, the dirtier it is, and time to change it.

I'm curious...how many quarts (if any) do you have to add during that 1 year period?

e9999 · 11-03-09, 08:06 AM

glad it was just a wire

the best way to tell for (almost) sure how long to run an oil is to do an oil analysis with TBN.
Consensus seems to be that it does not make any sense $$wise to run synthetic for the same number of miles as dino.
5000 seems to me to be very low for a full synth.
TBN on my Delo400 dino showed that I could go quite a bit more than 5000.

Tools R Us · 11-03-09, 12:22 PM

Quote:

Originally Posted by Brian894X4

Glad it worked out.

1yr/10K miles is a bit long for my taste. The combination of synthetic and a very large sump with about 7 to 8 quarts of oil definately helps.

I personally do about half that. 5000/6 months and I also run synthetic and I also only put about 10K a year...mostly highway. But I think probably the biggest indicator is how does the oil look. The blacker it is, the dirtier it is, and time to change it.

I'm curious...how many quarts (if any) do you have to add during that 1 year period?

IMHO 5000K+ mi is good for dyno oils, is a waste of good oil for syn. In most cases, the color of the oil has little to nothing to do with it's condition.

Some high mileage syn reports:

http://forum.ih8mud.com/80-series-te...ended-oil.html
http://forum.ih8mud.com/80-series-te...otella-9k.html
http://forum.ih8mud.com/80-series-te...mobil-1-a.html
http://forum.ih8mud.com/80-series-te...10k-miles.html

aclos3 · 11-03-09, 03:33 PM

Brian,

I bet I added about 1 quart during the nearly 13 months and 7500 miles on the last oil. This was 5W-30. I don't get any drips on the garage floor, but when I crawled under the truck during the oil change I've noticed a bit of oil pan and main seal seep. Hopefully this will stay slow enough to not start dripping!

aclos3 · 11-03-09, 03:34 PM

e9999 and Tools, thank you for the advice. I think I'll shoot for somewhere in between what I've been doing. I should also mention that the truck sat once for nine weeks and then recently for four weeks all with zero starts. I'm not sure how, if at all that might affect the oil.

HarleyHetz · 11-03-09, 06:52 PM

Quote:

Originally Posted by aclos3

e9999 and Tools, thank you for the advice. I think I'll shoot for somewhere in between what I've been doing. I should also mention that the truck sat once for nine weeks and then recently for four weeks all with zero starts. I'm not sure how, if at all that might affect the oil.

If the engine is not running, the oil is not being "used". There is not much difference between sitting in your oil pan and sitting in the bottle on the shelf...before you oil nuts flame me, I realize that there is "some" difference because of the condensation, but that is minimized by the lack of starting the engine.
The WORST thing you can do for is your oil is drive short distances without properly warming up your engine. You will get condensation when the engine cools down, unless you run the engine long enough to burn that all out, it will eventually mix with the oil and become sludge...always try to get your engine up to full operating temperature, and keep it there for at least 15 minutes!!

*Oh, and as has been mentioned, the best way to tell if you are changing your oil often enough is to get an analysis done. They aren't horribly expensive and will tell you all kinds of stuff you never wanted to know about your oil!!