oil pressure dropping
 

my original gauge (with a new sending unit) shows that the oil pressure lately has dropped an average of about 5-10 lbs. all around. i used to hold 65-70 when cruising at 60, but not it's looking like 55-60. i used to idle at 30-35, and now it's 25-30. the oil level never went down. this has been somewhat gradual. it is not temperature related (happens when cold and hot). the pressure is still higher on start up, and doesn't get to these levels until it's been running for a little bit. the engine still sounds fine and i have changed oil regularly. i have not driven it hard lately, and never driven it very hard ever. i always use mobil 1 10w-30. this has only become a problem within the last month. the car has 164,XXX miles on it.

so, the questions: where do i hook up a mechanical gauge? where can i rent one of those?

are there any remedies less than a rebuild? if i go to a thicker oil, will this continue the life of the engine to the expected 300k? or just give me more pressure while the engine develops a death knock? suggestions please!

i'm not totally opposed to rebuilding it this summer. i could get away with buying new main bearings, new rings, new oil pump, honing the cylinders, and having the crank turned. then i'd just need gaskets and head bolts. not too bad, but i'd rather not.

You can probably connect a mechanical gauge at the send or return hoses to/from the oil cooler - that's basically the same place that the OEM sensor is.

The OEM sending unit is considered problematic. But as long as it's showing pressure, you're fine... don't worry about such a small difference, it's likely just the oil itself slowly breaking down (if anything at all).

does the N/A even have an oil cooler? i've never seen it.

My mistake... I keep forgetting you have an NA. I don't believe they do... so it's not going to be easy by any means to get an oil pressure reading from anything other than the OEM sender. You'd need a sandwich adapter (look it up on Jegs if you don't know what it is) or to tap the block somewhere (I don't necessarily recommend that).

yeah i know what you mean. maybe i'll just trust the guage for now. we'll see if it gets worse. it may get better when i change the oil. i'm not pushing the mileage on this change or anything though. thanks.

I agree with Zlover. That small of a difference is probably nothing. Are you approaching an oil change? It's probably just the oil. My personal preference is to use 15/50 oil. I think 10/30 is a little on the light side.

interesting thought. 20-50 was necessary for my midget, but i expected tolerances in the Z to be tight enough to accept 10-30 10-40. but yes, i'm approaching an oil change. i'll go ahead and put in the 10-30 that i already have for it, but next time i buy oil i'll probably move up then. i have heard quite a few people recommend the 15 or 20-50 now

the OPSU in the Z32 is rediculous. If you get a spec of dirt in it the size of a micro nano milometer (yes I made that up for Randy's sake, picture something extremely small) it goes crazy.

The best way to monitor your oil in the Z32 is to keep a constant check on it. I've got into the habbit of everytime I put gas in the Z, I check the oil while i'm filling up. If you get low, you know your leeking and / or burning it somewhere (I had a leak in one of the valve cover gaskets that would only happen after a fun run up twisties, and the oil would burn off and not actually leak to the ground, which is why you can't just watch for a leak). Keeping a constant check on not only your oil, but all of your fluids for that matter (brake fluid, ATF in the PS system, etc etc) can help find, and prevent costly problems before they start, and the fluids literally take less than a minute to check 3 i just mentioned.

I usually check tire pressure while i'm filling up to, and I also smoke a cigarette (jk, I did see someone doing that the other day though, I parked my DD work truck next to them in hopes they would blow it up so i could get a new one).

It is also normal for the oil pressure sending unit to get clogged up and show less of a pressure. if you look in the FSM normal operating pressure is anywhere from like 2-10psi up to 70-80psi (these are just rough numbers). What I am saying is as long as you have constant oil pressure and your oil level is up to spec you are fine. Mine dips pretty low, but my guess is on the factory pressure sending unit.

i do keep a good check on the level, as i have a leaky front seal. and actually a leaky new head gasket, but that one's staying there for a while lol.

all things considered, i have had a couple dips in the guage that were indicative of an unreliable sending unit (not the dips that this thread is about), but then it got steady again so i forgot about them. perhaps that is what it is. the pressure shown is consistently lower than it actually is.

well thanks for all the suggestions. i'm pretty calm about it now. i think i'll be going to a thicker oil and leaving it at that.

Leaking HG, pretty sure those came standard in the Z. lol

I've got a 93' N/A and my oil pressure is "normally" where you're describing it now. The only time I've seen it change at all was a few months back I needed an oil change and my OP would shoot up to what looked like 90 PSI while on the freeway, was scary to look at but after an oil change it was right back down to where it was normally.

I think I use 20W40 Mobile One as well. High Mileage Synthetic with paired filter. 150,000 + miles now.

i use a 60 weight to a 100 weight oil......













depending on what airplane im flying :D

lol are leaking head gaskets that common?

i'm pretty pissed that they are leaking. i just did the heads not too long ago, used new gaskets, all the surfaces were clean, torqued the heads correctly, and still i get a leak. i just don't know.

didnt you get your heads rebuilt? how the F do you have leaking HG? i hope you used OEM nissan or better HG's and then when you rebuilt the heads had the heads MILLED and then got NEW head bolts or head studs. and the block is cast iron so a quick pass with a scotch bright pad should have taken any gasket material off. that or even a razor blade but scraping with the blade away from the line of travel as to not gouge any surface though unlikely.

all of the above was done. block surface cleaned off, new head gaskets, heads milled, new head bolts. the only part that i'm not sure about was the brand of the head gaskets. they may or may not have bee OEM, but i'm guessing not. so i blame it on that.

did you torque the head down in the proper pattern and in 3 increments?