Hope someone can steer me in the right direction with what is causing my oil pressure gauge to show high pressure.

Short story: My 2007 350z 6 speed manual (VQ35HR) Touring with 70k is showing high oil pressure.

Readings: Cold start (ac on automatic): dash oil gauge shows 110psi

20 seconds after start: 100psi

30sec: 90 psi. Temp gauge starts to move.

1min: 57 psi. 1/2 of normal running warm temp.

2min: 50psi

5 min: 45psi. Full running temp.

Idle @ 700rpm.

8 min: at idle = 35ps. @ 600rpm. Normal running temp.

8 min: rev to 2000rpm = 65psi

Rev to 2500rpm = 90psi

10min. Idle at 600rpm @ 30 psi

20 min driving-2000rpm @ 58 psi

40 min: no air conditioning idle 550rpm @ 25psi

From what I understand this is excessively high oil pressure as other posts have stated Nissan manual specs show 14 psi @ idle

43psi at 2000rpm

Long story:

• I checked the oil level frequently and it has been at the top fill line of the dip stick. I had the oil (5-30 full synthetic) & filter (Mobile 1) changed. Same psi readings as the old oil.
• I removed the oil pressure sending unit and did an oil pressure test with the test kits gauge. The readings coincided identically with the dash board oil pressure vs Rpm figures I had written down previously.
• I replaced the oil pressure sending unit with a new oem ( listed as genuine Nissan oem part) unit that I purchased from Courtesy Parts. No change, pressure still high. Has anyone seen these symptoms before? What is the problem?
• Car background: I purchased the car about 2 months ago. It was a northern car at some point as indicated by some rust underneath. When I purchased the car, it had straight pipes, I switched them with a stock exhaust system from my old 2004 350Z.
• I have an appt with a Nissan dealership. They said they would put the car on the computer.... there is no check engine light displayed. Will this $125 diagnostic test help indicate where the problem is or is it unnecessary. Thanks for your thoughts.

 

The first thing that comes to mind is an issue with the oil filter, but you had already replaced that. Are you positive the oil isn't overfilled? I maintain 3 HR engines, and 5 qts usually hits right in the middle of the dip-stick on all of them, if not just slightly over. But if it's at the max fill line, I can't imagine that little bit 'overfull' would cause such a drastic change in pressure.

The only other thing I can think of is possibly an issue with the crank case ventilation system, maybe check/ replace the PCV valve, it's pretty easy/ cheap part. If not that, something could be wrong with the oil pump.

"20 min driving-2000rpm @ 58 psi" is definitely higher than normal, but shouldn't be an issue driving with that pressure. But I would be cautious with high rpm driving, especially when cold. If the oil pressure shoots up above 120psi, you could cause damage to gaskets/ seals, such as the oil gallery gaskets, or rear main seal, as an example.

 

Same thing is happening to me, but it came after installing a hks catch can z1 motorsports oilcooler! Anyone???

 

Thanks chihuahuamaster, I’ll replace the pcv & let you know if that fixes the problem or not.

 

sounds like symptoms of a failing sender..

mine did something similar for 2-3 days before it gave out and got stuck on max high pressure.


went to the JY. found a few more VG35 engines. pulled 2 oil senders pocketed.. installed one in mine and it was good to go.

 

The oil pressures specified in the service manual are the minimum allowed. I get similar oil pressures running m1 0W-40 after I fixed the gallery gaskets so while yours seem high they might not be completely out of line. The oil pressure will rise with a restriction in the system so the previous answers of oil filter or PCV system are possible. How clean do the engin internals look from the oil fill cap? Are there any modifications like optimus's oil cooler?

 

Thanks again for responses.
i had the oill and filter changed by my mechanic... i don’t know if they looked for obstructions but I specifically stated why I wanted to change the oil 5w30, & filter (Mobile 1) due to high oil pressure gauge reading. I’ll get an OEM pcv & replace the mobile 1 filter with an oem filter which have a pressure release valve built in, right?

 

Your pressures all literally seem on point with my 07 HR. You have no issue. The 14psi that is stated in the manual is the minimum oil pressure that you should have at idle. Ideally you want about 25-30psi at (warm) idle for a healthy oil pressure. After I replaced my oil gallery gaskets on my HR, my oil pressure at warm idle was about 31-32psi but after a month or so and another oil change, it stays pretty consistent at 28-30psi depending on temperature. Your cold start pressure, 2k rpm pressure, idle, etc. are all perfect and the same as mine. There is no problem with your car.

 

I also have a 07 with the gallery gaskets changed. Your pressures are identical to mine. Mine will get a little less when tracking after its super hot, but looks identical to my daily driving pressures.

 

Nayeon & greyz
are you not concerned with the oil pressure (even at warm running temp) upwards of 110 psi at 3500rpm?
I believe the service manual states:
idle 14psi
2000rpm @ 43psi
6000rpm @ 57 psi

 

That's the pressure relief. Typical relief pressure is between 95 and 120psi. For the Z to be at 115 is completely normal. Oil viscosity changes drastically as it warms up. Don't beat on it the first 5 minutes and you will be totally fine. *Or do beat on it and you will still likely be fine because the pressure relief valve is there for a reason.


Your car is functioning as normal.

 

Took the z to my local dealer today, I was shocked when the service rep said I needn’t bother with the $130 diagnostic... Huh... a dealer talking me out of spending money, that’s gotta be a first! Confirming what Nayeon & greyz said: the pressure vs. rpm’s are not abnormal.
I’m still going to replace the mobile 1 oil filter with an oem filter and replace the pcv as a precaution.
Thanks for all of your help.

 

The Oem filter is kind of **** and very tiny I wouldn't do that. keep the M1 filter. If you really want to change it one option is a Fram XG7317. It's a good for the price synthetic filter. Other good options also exist.