Oil pressure issue

I have e a 02 Toyota tundra sr5 with 4.7 the oil pressure gauge reads really low when sitting in idle and when I put it in drive it drops even lower iv tried changing the oil sending unit and it hasn't helped a whole lot when I crank it in the morning it climbs up to about half way a d when the motor heats up it drops I'm wondering is this normal the pic that's higher is in park and the other is in drive it has 243,421 miles [=full]340144[/ATTACH]

 

Pretty sure that's normal. Mine is the same. It should climb to the middle of the range when accelerating.

 

Automotive oil pumps are gear-type, positive displacement pumps, and are highly dependent on the input shaft speed, i.e. engine rpm. When you put it in drive without moving, the rpm drops on an already slow rotational speed, and the oil pressure is less than before. When the oil warms up, the viscosity is less, causing less pressure to be produced by the same pump running the same speed. At idle, required oil pressure is only 4-5 psi. At higher speeds, the gauge should be near the mid-way mark. If it's less than half gauge at highway speeds, then that's not too unexpected for 243K miles. Eventually, like everything else, your 4.7L will die.

 

I did notice take off and driving short distances it climbs to the half way mark but going long distances on interstate or highway doing that speed or usually runs in between quarter and half way mark. I'm no mechanic when it comes to motors all the suspension and stuff I redone myself I'm just not a motor person and don't know much about motors or transmissions

 

Why we're here...to help Tundra guys learn about things they don't know about. I learn something here every day.

Reason your oil pressure is lower once you're up to cruising speeds for long distance: Engine is finally heat-soaked, and oil temp is as high as it's going to get (lowest viscosity). Your transmission has also now shifted into the highest overdrive gear available, dropping the engine speed as low as it can go at that vehicle speed.

 

Thanks that helps out a lot

 

What type of oil are you running? When I first got my tundra, it was low like yours. The previous owner said it had a recent oil change but I don't trust people so I did it again anyways. After changing it to 5w30 synthetic, it came up quite a bit. It still shows 'low' at idle but it is definitely more than when I first bought it. It's all normal though.

 

San Angelo huh?

 

I use 5 w- 30 synthetic

 

Yea I'm inSan angelo at the moment I'm from south Mississippi though

 

Thought I'd seen that truck around. Also helps since that location is extremely identifiable hah.

 

Yea... that was at my uncle's shop on knickerbocker in front of the auction

 

It's pretty normal.

 

314K.....they don't make like they used to but you gotta get that bulb replaced on the ole girl

 

I need to replace this one too.

 

If your big end and main bearings aren't knocking then you have enough oil flow.

If that gauge is bugging really bad you can try Mobil 0W-40. That will improve your hot idle pressure and still flow enough oil through your bearings.

 

I have another problem I tested 1 out of the 8 cylinders with a compression tester and I was only getting about 50 to 75 pounds what do u recomend I do

 

So I'm not misunderstanding....you picked 1 out of 8 to test and that one was low or you checked all 8 and 1 was low ?
Normally to check further, one check is to pour small amount of engine oil into the cylinder through the spark plug hole and re-check.

From my 2004 Service Manual....

 

@BubbaW has provided the next step in the process, which is to determine if the problem is with the compression rings.

If the compression test pressure comes up with oil in the cylinders, it says your compression rings are not sealing. If oil in the cylinder makes no difference in the test pressure, then you have bad valves. Either way, you are looking at engine work to eliminate that hard miss you've been experiencing.

I would probably try running SeaFoam? through it. I've never used it, but in this case, I would give it a try. I am not optimistic that will do anything to help your low compression, but you have nothing to lose.

 

I don't know much, but I think its time for an engine fresh up. The guage is telling you and the cylinder issue. Its a great engine but it does wear with that milage yses some get alut more miles on them but there is so many reason why some of us don't .

 

Yes I only tested 1 out of 8 when I went to test another one the screw on fitting at the end of the tester stayed in my block so I faught with that to get it out and didn't try the rest but the 1 that I did do was low

 

Did you pin the throttle open during the test?

 

I only took one plug out and my uncle cranked the truck up and I checked the compression as he cranked it and while it was idling I'm not even sure if we did it right but it only averaged between 50 to 75 pounds every time

 

How does the truck run? We have a saying in EMS...."Treat the patient, not the number" Is that number the only problem or is the truck actually running badly in some way?

 

A. Hardest path, but dependable information for an informed decision:

(1) Buy a good compression tester or fix the one you have.
(2) Check that battery is fully charged.
(3) Pull all the plug wires, label any that could get mixed up. You don't want it starting.
(4) Open throttle completely and fix it open.
(5) Do a compression test of #1 and record the pressure reading.
(6) Continue testing and recording each cylinder through #8.
(7) Compare readings to data in post #18 above, and to each other.
(8) Make decision


B. Easy path, assume previous test was accurate and all cylinders are similar:

(1) Engine worn out. If you can get it to run, sell the truck...OR,
(2) It's a 17 year old truck. If you can't afford to trade up right now, buy a used engine for it, BUT VERIFY THE ENGINE MILES. The trucks age is against you...plenty of worn out Toyota engines out there.

 

It was running during test?????

 

It cranks and runs... I will attempt to drive it from Midland back home to Mississippi in about a month then I'm just going to probably get it over hauled...

 

Which bulb?

 

In @bmf4069 first pic, I'll take a slight WAG and say the P bulb. In second pic he posted, I'll take WAG it's the L bulb !

 

I don't think it is supposed to be running during compression test.

Just supposed to turn it over.

Pull all the plug wires first