Oil pressure questions for a GE

[phoenix6]

OK I know the stock pressures are supposed to be but heres what mine does and what I know...

It turns on in the morning and stays at 40psi, and after 5 mins idle is like 30 and diriving is 40, never over 40, EVER. After the car is at running temp, and the oil is heated up, pressure never goes over 30 or even 25 sometimes, while driving. I havent had problems yet but Im wondering why

I know that SOME oil leaks out of my drain plug bc i didnt put a gasket, but will that cause ANY pressure leaks to make it act like that? Also I used Syntheitc for the first time, I heard it was thinner at temp.

Is it also possible that my pressure sending unit is fucked?

 

[Nick M]

How high do you think it should be? Pressure, which is resistance to flow, will drop as the vehicle ages. The bearings open up, and the oil flows through the passages easier, showing a lower number on the gauge.

That would be typical.

 

[plaaya69]

My N/A Supra is around 25-40psi when I'm driving and if it idles for a long time it will drop to about 17-23psi sometimes and I dont think that your pressure sending unit is fucked because your oil psi seems ok.

 

[suprageezer]

Mines around 60 when Its on the freeway and maybe 20-30 at idle.

 

[Nick M]

My last 7MGE idled a little above the bottom mark when warm (4.3psi). When driving, it never went over the 40 mark.

There is only one part number for oil pumps now. It has been that way for a while. So the relief valve is set to the same pressure. Back in 1987 they were different. Dr Jonez even pulled the little gears out of the housing and they are different sizes. So they used to be different.

 

[SupraSabre]

My last 7MGE idled a little above the bottom mark when warm (4.3psi). When driving, it never went over the 40 mark.

......

I'm glad you mention the oil pressure being down at 4.3psi.

I bought the car from my #4 son when the engine died last May, so the car has sat for about 7 months. My #2 son installed the engine, but had to swap out the oil pan and oil pump so I was beginning to wonder if a low psi was correct.

Again, thanks! :icon_bigg

Bob

 

[suprageezer]

Looks like something is funky in my car, time to check it out.

 

[jdub]

Don't forget the impact oil viscosity has on oil pressure, especially cold

 

[phoenix6]

Ok So Im getting normal numbers then? It worried me a little bit, I know about viscosity with temp, but I just though driving at normal temp should be around 40 or so, always, its a new pump when I rebuilt the engine. Its only got 1500 miles on it.

 

[jdub]

Keep in mind the supra oil pump relief valve (unless you shimmed the spring) is going to start opening at 40 psi. This in combination with bearing clearances and oil viscosity are the primary determiners of oil pressure. Thicker oil will give you higher pressure, the opposite for thinner oils. What I shoot for is 10-15 psi at idle and 40-50 psi at 3000 rpm when the motor is at operating temp, but it's going to depend on the bearing clearances in your motor. As long as you have 4.3 psi (or above) at idle and 36-71 psi at 3000 rpm, the pressure is in spec when the engine is at operating temp.

You have to be more specific about what your oil pressure is doing...."driving around" means little in this case. You need to tell us idle psi cold, idle psi hot, psi at 3000 rpm cold, and psi at 3000 rpm hot. Viscosity does have a effect and the brand oil used as well....look at the data sheet for the oil used for viscosity at 40 deg C and at 100 deg C. This will give you an idea of the oil's ability to flow at start and at operating temp. The differences (or lack of) between brands and grades will surprise you.

Does your oil pressure fall in TRSM oil pressure parameters? High oil pressure at idle is not necessarily a good thing...excessive pressure at idle indicates resistance to flow and could very well be the oil's viscosity, especially if you are using a thick oil. If the oil is too thin (not likely), the pressures will be low.

Also keep in mind you can't determine an oils specific thickness at operating temp from the numbers on the bottle...the numbers only give you a general idea. The 1st number has nothing to do with viscosity at operating temp...it is the cold viscosity. The 2nd number is the viscosity of the oil at operating temp and the actual viscosity (as measured in centistrokes - cst) will vary depending on who made it and the actual grade of the oil (i.e. a 0W-30 vs a 10W-30). Using these two oils as an example, it is not uncommon for the 0W-30 to actually be a bit thicker at operating temp...it all depends on the viscosity modifiers used in the formulation of the oil. To make a statement that an "oil is thin" requires you to look at the specific oil's data sheet.

BTW - Did you get the Marvel Mystery Oil out of that motor?

 

[phoenix6]

Keep in mind the supra oil pump relief valve (unless you shimmed the spring) is going to start opening at 40 psi. This in combination with bearing clearances and oil viscosity are the primary determiners of oil pressure. Thicker oil will give you higher pressure, the opposite for thinner oils. What I shoot for is 10-15 psi at idle and 40-50 psi at 3000 rpm when the motor is at operating temp, but it's going to depend on the bearing clearances in your motor. As long as you have 4.3 psi (or above) at idle and 36-71 psi at 3000 rpm, the pressure is in spec when the engine is at operating temp.

You have to be more specific about what your oil pressure is doing...."driving around" means little in this case. You need to tell us idle psi cold, idle psi hot, psi at 3000 rpm cold, and psi at 3000 rpm hot. Viscosity does have a effect and the brand oil used as well....look at the data sheet for the oil used for viscosity at 40 deg C and at 100 deg C. This will give you an idea of the oil's ability to flow at start and at operating temp. The differences (or lack of) between brands and grades will surprise you.

Does your oil pressure fall in TRSM oil pressure parameters? High oil pressure at idle is not necessarily a good thing...excessive pressure at idle indicates resistance to flow and could very well be the oil's viscosity, especially if you are using a thick oil. If the oil is too thin (not likely), the pressures will be low.

Also keep in mind you can't determine an oils specific thickness at operating temp from the numbers on the bottle...the numbers only give you a general idea. The 1st number has nothing to do with viscosity at operating temp...it is the cold viscosity. The 2nd number is the viscosity of the oil at operating temp and the actual viscosity (as measured in centistrokes - cst) will vary depending on who made it and the actual grade of the oil (i.e. a 0W-30 vs a 10W-30). Using these two oils as an example, it is not uncommon for the 0W-30 to actually be a bit thicker at operating temp...it all depends on the viscosity modifiers used in the formulation of the oil. To make a statement that an "oil is thin" requires you to look at the specific oil's data sheet.

BTW - Did you get the Marvel Mystery Oil out of that motor?

Ok, at idle cold, its 38 - 40psi. At Idle temp, its about 15 - 19psi. At 3000 (which usually Im at 2000 - 25000) its about 40 or a tad over cold, and at temp its 21 - 30.

No I stupidly didnt change my oil yet(doing that TODAY I swear) although, the drain plugs been leaking oil, like I said. Ive been puttin in a qt a week. Chances are its drained out haha. I know it was STUPID but Im fixing it today. With everythings thats going on lately, I know this sounds cliche but I really havent had a choice or time to do ANTHING about it.

 

[jdub]

Ok...what brand and grade of oil are you using?

Your pressure is good at idle...low at 3000 rpm at operating temp. Did you rebuild the bottom end on this motor? If so, where were the bearing clearances in the TRSM spec range?

 

[phoenix6]

Ok...what brand and grade of oil are you using?

Your pressure is good at idle...low at operating temp. Did you rebuild the bottom end on this motor? If so, where were the bearing clearances in the TRSM spec range?

I did. The clearances were on par is all I remember, well within range on everything. Checked twice. Like I said I think its bc theres no gasket on the drain plug which drips oil out when the cars sitting there.

Penzoil 10W-40... After my change today and its all fresh, well see whats up/

 

[jdub]

Is that Pennzoil Platinum?

Use a good filter...not a Fram! Wix, PureOne, NAPA Gold are all good choices.

 

[phoenix6]

Is that Pennzoil Platinum?

Use a good filter...not a Fram! Wix, PureOne, NAPA Gold are all good choices.

MobilOne filter for me, Ive heard good things... haha fuck FRAM!

Not platinum, I might try something else, well see.

 

[jdub]

Pennzoil Platinum is very good, but not a true synthetic...try the 5W-30

Castrol European Formula (German Castrol) is a true PAO based synthetic...it's at AutoZone and only comes in 0W-30. It's also pretty close to a 40W at operating temp.

I'm concerned about your oil pressure at 3000 psi hot...it's low.

 

[phoenix6]

Pennzoil Platinum is very good, but not a true synthetic...try the 5W-30

Castrol European Formula (German Castrol) is a true PAO based synthetic...it's at AutoZone and only comes in 0W-30. It's also pretty close to a 40W at operating temp.

I'm concerned about your oil pressure at 3000 psi hot...it's low.

I really think its bc of that plug having no gasket, its like a vaccumm leak.

Ill try that stuff but Im kinda worried about such a low weight oil, 5w-30, I wanted something heavier

 

[jdub]

The plug will have no effect on your oil pressure
Not too sure where you came up with that one, but it's the bearings that determine pressure.

Concerning the weight oil to use...read this:
http://www.supramania.com/forums/showthread.php?t=35437
(ignore the 1J motor)

and this:

http://www.supramania.com/forums/showthread.php?t=36026

 

[phoenix6]

The plug will have no effect on your oil pressure
Not too sure where you came up with that one, but it's the bearings that determine pressure.

Concerning the weight oil to use...read this:
http://www.supramania.com/forums/showthread.php?t=35437
(ignore the 1J motor)

and this:

http://www.supramania.com/forums/showthread.php?t=36026

Well, when I did overfill my system by 1/2qt, the pressure got way better.. but still wouldnt push OVER 40

 

[jdub]

That could be because your oil pump pick-up is too high in the pan
You might want to run a quart over full.

Also, read post #10 again...I thought I explained it pretty well.
But...what do I know :icon_conf