reasons for low oil pres.

[hornet7288]

Ok...I recently replaced my oil pressure sender unit. I thought that would solve my low oil pressure problem, but it still didn't change much. The gauge shows over 40 when I drive while the engine is cold. I bought a pressure tester kit and checked it while it is warm (after 10-15 mins. of running). The gauge in the car(which I do realize is not very accurate to begin with) reads a little over 0 at about 10-45 mph. At about 60 it's at or a little under the first tick mark. Can this be the gauge or the wire going to the gauge? I am sure the sender unit is probably fine. I am really not an electrical guy so is it worth to re-wire somehow if that's what people think the problem is? Thanks guys!

 

[suprarx7nut]

I have the same problem, though mine doesn't seem to read quite as low as yours. It stays around 40 when cold, drops to about 5 at warm idle and hovers around 10-30 while driving. Thats right about the very lowest of the owner manuals "Normal Driving" ratings.

I don't leak any oil and have added 1/4 quart in about 1500 miles.

 

[BlackDynamite]

Would loose valve covers lower oil pressure? It did on mine...didn't notice they were....:]

 

[AJ'S 88NA]

Ok...I recently replaced my oil pressure sender unit. I thought that would solve my low oil pressure problem, but it still didn't change much. The gauge shows over 40 when I drive while the engine is cold. I bought a pressure tester kit and checked it while it is warm (after 10-15 mins. of running). The gauge in the car(which I do realize is not very accurate to begin with) reads a little over 0 at about 10-45 mph. At about 60 it's at or a little under the first tick mark. Can this be the gauge or the wire going to the gauge? I am sure the sender unit is probably fine. I am really not an electrical guy so is it worth to re-wire somehow if that's what people think the problem is? Thanks guys!

What weight oil are you running, and how many miles you have on the motor?
That sounds a little low.

 

[suprarx7nut]

Ok...I recently replaced my oil pressure sender unit. I thought that would solve my low oil pressure problem, but it still didn't change much. The gauge shows over 40 when I drive while the engine is cold. I bought a pressure tester kit and checked it while it is warm (after 10-15 mins. of running). The gauge in the car(which I do realize is not very accurate to begin with) reads a little over 0 at about 10-45 mph. At about 60 it's at or a little under the first tick mark. Can this be the gauge or the wire going to the gauge? I am sure the sender unit is probably fine. I am really not an electrical guy so is it worth to re-wire somehow if that's what people think the problem is? Thanks guys!

Dumb question, but how is your oil level? Is it on the full line? just below? Half way?

 

[hornet7288]

What weight oil are you running, and how many miles you have on the motor?
That sounds a little low.

i'm running 10w-40 oil. The motor has 193,XXX miles on it. I replaced the HG and have been driving it since 190,XXX. Seems to be running fine and like I said the pressure tester gauge shows that the pressure is normal...

 

[hornet7288]

Dumb question, but how is your oil level? Is it on the full line? just below? Half way?

I always keep it between half way and full. I check it always before I drive it.

 

[AJ'S 88NA]

i'm running 10w-40 oil. The motor has 193,XXX miles on it. I replaced the HG and have been driving it since 190,XXX. Seems to be running fine and like I said the pressure tester gauge shows that the pressure is normal...

What pressure tester gauge?? If you've tested with a another gauge and it test normal, it's proablly the gauge it's self, not the wiring because you are getting a reading, may not be right but it's a reading. That many miles on the motor, I don't know, you might be looking at a rebuild, there isn't any quick fixes for low oil pressure:nono:

 

[thelonerider]

A good rule of thumb is 10psi for every 1000RPM once warmed up.... Judging by speed makes no sense as it all depends what RPM you are running... 40mph in 1st redlined or 40mph in 3rd at 1000rpm makes a big difference in oil pressure.

 

[hornet7288]

the pressure at 3k rpms agreed with the TSRM so im pretty sure my pressure was ok in the engine...that's the first thing I checked. I was worried about the engine not having enough pressure. What does it take to replace the gauge? I actually have another gauge set from my other supra. Could I just switch the gauge (motors?) and keep the needle the same because they're diff. shades of yellow...

 

[ValgeKotkas]

Oil pump is a POS?

 

[hornet7288]

Oil pump is a POS?

already checked it with a pressure checker...everything checked out.

 

[supramacist]

Well I don't know if it matters but after I swapped HG's.
My oil pressure stopped reading.
I don't know how the heck the oil sending unit can just go out like that.
But with this ride of mine....., anything is possible.

 

[AJ'S 88NA]

Well I don't know if it matters but after I swapped HG's.
My oil pressure stopped reading.
I don't know how the heck the oil sending unit can just go out like that.
But with this ride of mine....., anything is possible.

Something maybe get flushed into the oil line to the sending unit plugging it up???
Possible if you're not tearing down the whole motor.

 

[suprarx7nut]

Tip for original poster:

I just put in another quart of oil after reading all the threads(esp by IJ) about how they always run a 7M with one extra quart.

Well my oil pressure is now about 10*** at idle and 30-45*** on the highway.

Can anyone explain why that would be? Why would pressure be so low with oil level 1mm below full on dipstick, then read normal with an extra quart? Could it have been because the pump couldn't reach enough oil for some reason? :dunno:

Paging the experts


***edit, just drove and I got the numbers wrong. Idle=15-25, highway driving = 40-50.

 

[hornet7288]

Tip for original poster:

I just put in another quart of oil after reading all the threads(esp by IJ) about how they always run a 7M with one extra quart.

Well my oil pressure is now about 10 at idle and 30-45 on the highway.

Can anyone explain why that would be? Why would pressure be so low with oil level 1mm below full on dipstick, then read normal with an extra quart? Could it have been because the pump couldn't reach enough oil for some reason? :dunno:

Paging the experts

interesting...

 

[AJ'S 88NA]

Tip for original poster:

I just put in another quart of oil after reading all the threads(esp by IJ) about how they always run a 7M with one extra quart.

Well my oil pressure is now about 10*** at idle and 30-45*** on the highway.

Can anyone explain why that would be? Why would pressure be so low with oil level 1mm below full on dipstick, then read normal with an extra quart? Could it have been because the pump couldn't reach enough oil for some reason? :dunno:

Paging the experts


***edit, just drove and I got the numbers wrong. Idle=15-25, highway driving = 40-50.

I think you would have to run fairly low on oil to not have the pump not pick up oil unless you were under hard braking or cornering. I know that from experience:nono: How long since your last oil change? Maybe if it's been a while, a fresh quart maybe brought up the viscosity?:dunno:

 

[suprarx7nut]

I think you would have to run fairly low on oil to not have the pump not pick up oil unless you were under hard braking or cornering. I know that from experience:nono: How long since your last oil change? Maybe if it's been a while, a fresh quart maybe brought up the viscosity?:dunno:

Oil change done exactly 1600 miles ago. Its always been low(the pressure) and I check the oil level religiously. I even check it on days I dont drive. Its always been between halfway and full on the dipstick. Now its about 2 mm above full. I have only had the car a month so I haven't done ANY hard cornering or braking, lol. Just not comfortable with it enough yet.

_Andy

 

[AJ'S 88NA]

Oil change done exactly 1600 miles ago. Its always been low(the pressure) and I check the oil level religiously. I even check it on days I dont drive. Its always been between halfway and full on the dipstick. Now its about 2 mm above full. I have only had the car a month so I haven't done ANY hard cornering or braking, lol. Just not comfortable with it enough yet.

_Andy

Maybe IJ would know. I'm going to try with the extra quart tomorrow and see if it changes my pressure. Mine's almost 40 at 3K with the motor warm.

 

[shaeff]

i always run an extra quart in my system.

keep in mind that the 7M has a high volume, low pressure system. as long as your readings are within the specs of the TSRM, you're fine.

another thing that's one of my favorite's to quote in these threads:

Pressure is resistance to flow

if your oil pickup wasn't reaching oil, you'd have spun bearings by now.

when i had my motor apart, i put about 3-4mm of shims in the oil pump relief, and lowered the sump deeper into the pan. then i removed the super-restrictive (and based on pressure) filter mount, and replaced it with an aftermarket relocation kit, full flow oil cooler, and 180* thermostat. pics can be seen here: http://www.supramania.com/forums/showpost.php?p=744136&postcount=11

there are others with WAY nicer oil systems than mine. but mine is certainly better than stock. at idle i see around 5-6psi when warm, and at a cruise i see 40-43psi when warm. i wouldn't want it any higher than that, either.

-shaeff