GTAman

iTrader: (2)

hey guys,

i drive an 88 GTA with a 305 and 700-r4. a buddy of mine (mechanic) helped me with my brakes the other day (both front, new calipers and pads) and we found out my brake booster wasn't working. after the job is done he takes it for a drive. i agreed because he knows what to look for since i've never done this thing before. he flogs on it, does 100 in it on rt 4 east (for all you jersey people) and does some high speed stopping. ok fine, that's all for diagnostic. now, eversince that day the oil pressure has been acting weird. ie, on start up it's fine and stabilizes at 45 psi; put it in gear, goes down one step but then goes up again; if you go for a long drive and then stop at a light, the arrow will drop to 30 or one step under 30. that's what i'm afraid of. i'm afraid because it's never gone under or even near 30 psi before and i have no clue what's going on.

i use (and has always had) mobil 1 5W-30, ac-delco oil filters, engine is original and has 123,350 miles on it.

whiteshadow87

iTrader: (1)

I have a '91 L98 and mine does the exact same thing. I think its normal. Less strain=less oil needed.

GTAman

iTrader: (2)

wow, really? i thought the 350 would need more press? anyways, not to dismiss your entry, but i still think it's odd considering that it's never happened to me before. things like this that suddenly go out of what i call the "norm" just make me paranoid. any other thoughts?

GTAman

iTrader: (2)

i changed my oil today with the usual mobil1 5w-30 but i used a K&N oil filter this time. i didn't like the new, shorter AC delco design but things are still the same. i'm going to check my pressure sender within 2 days (mechanically of course) to see if it ends there or if it might be in the pump (really hope not).

steves86TA

in my car LG4 i dont know if the tpi is different, but witht he car cold i keep about 45 psi of oil pressure, and once it gets hot it will drop down to about 25 or so

GTAman

iTrader: (2)

when i replaced the oil today, when i first started it it went to 30, then when the oil got into full flow, it rose above 60 (highest my gauge goes) then sat at 60 and then rose over here and there, that's at idle. tonight when i went out for a drive, it almost seems like when i first step on the gas it goes down a little then goes up. and it never exceeded 60 while driving at normal engine temp. but when cold at idle it was at a good level.

ok, that may or maynot have made much sense but i'm trying to describe it a bit more in detail. i just don't want my engine seizing up =(

steves86TA

it made sense, but as far as i know it seems fine, but id ask a few other people first

REALPOWER

Lol, my gauge reads 0 at idle and 25 while driving. Needless to say, it has to be a sender/gauge problem!! Never trust electric gauges. Go to wal-mart and buy a 6 dollar mechanical oil press. guage to be sure.

89IROCNICK

10psi for every 1000rpm is pretty good so your safe at idle with a little below 30psi. My motor has about 15,000 mi on it and at idle it's a little below 30 but at 2500rpm its @55psi but I wouldn't worry about it. Since bearings make pressure, as they wear you will loose pressure. Running the ball$ off it may have loosened it up a bit which is cool just don't make a habit out of it. I did hence I have a new motor.

DON 88T/A

Mine does the same thing...start it up,runs around 50psi or so cruising...then slowly drops untill at idel its around 22-24...I going to throw a new sender in it and see if it picks up any...i use good oil,and usually don't have to add any between oil changes...has over a 160,000 miles so its wearing a little I guess.

GTAman

iTrader: (2)

yeah i've been noticing a trend these days with it. when i start it up when the oil and engine are cold, the press is high. when the oil starts to heat up i guess that's when it starts to come down.

one other question: does the oil pump make a noise when it's on it's way out? just wondering...

GTAman

iTrader: (2)

ok, i bought a new sender today and now it's reading lower, but i think it's just the sender beings messed up. it's going below 30 to almost 15.

Btw: when i was handling the sender it sounded like something was loose inside. is that normal?

DON 88T/A

Never delt with a sender before so not sure....
How involved was it to put the new one in?....Like I said I'm thinking of changing mine but not sure how much work it takes to put one in..How many miles on your GTA?

GTAman

iTrader: (2)

Don,
the sender is a snap to take out and install! it's just a small little cylinder with a thread at one side and a electrical connecter on the other. all you'll need is a 3/8ths socket wrench and a 3/4 deep size socket (deep size = long size socket). you just take the rubber boot off (mine was connected to a tan wire), take your wrench and put it over where you took the connecter off (there's a hex shape base to enable you to use the wrench), and rachet it off! simple as that. btw, if your new sender doesn't have this red coating on the threads use teflon tape. other than that it's in and out and you're done.

My GTA has 123, 500 miles

screamingz28

my oil pressure does the same thing and i have a 305 with 18,000 miles on it ( '85 z28 Lb9 ). I usually use 10w-30 or
10w-40 but this time i tried 20w-50. has anyone ever tried this? what exactly is the difference in the oil? I do not know much about oil so i thought i would ask. i am a little worried because my oil temp guage read at about 350 degrees and higher today. i have never seen the engine run so hot. is my gauge screwing with me or is it right? need help fast!

GTAman

iTrader: (2)

got a new sender today and it's still doing the same thing. does the sender have to be torqued to a specific amount?

josh1988

Alot of people will argue with me, but I usually run 20w-50 in any v8 i own, why? because anytime I drive anything with a V-8, i beat the **** out of it, and I feel better with thicker viscocity(sp) oil in my engine, hard acceleration, fast stops, all that ****, I don't like the idea of running water (5w-30) in my motor. it's probably not a good idea to run 20-50 if it's below 40F out though, it takes a while for it to get to the top of your engine, so you get to hear your lifters for a bit.

GTAman

iTrader: (2)

the new sender brought the same results. i'm beginning to see a trend here. as the (water) temperature increases, the oil pressure decreases. that's the only thing constant going on right now.

Morley

In the owner's manual it says that at 2k RPM oil pressure should be about 45-50 PSI, never says anything about idle, but from the time my car was new till I replaced the engine (140,000 miles), the oil pressure at idle was always just under 30 (25 or there about).
If you really are worried, get an el-cheapo mechanical guage (as suggested above) and hook it up temp. to see what it reads. If it reads low too you may have some trash on the oil pickup screen that is partially blocking it. At this point you may as well get a new pump and pickup and replace them because to clean the screen off you'd need to drop the oil pan anyway.

GTAman

iTrader: (2)

does the oil pump make a noise when it's going out? i've been noticing this kind of fluttering sound coming from the engine that i've never heard before.

today i'm going to order a mechanical press gauge, melling oil pump and pick up. any recommendations on the melling?

Stekman

Oil pumps dont "go out" for the most part. They pretty much either "work" or they "don't."

M-55 pump should do the trick. No need for the HV unless you run increased bearing clearances or an oil cooler.

GTAman

iTrader: (2)

i've got an oil cooler...stock =)

Stekman

My vote still goes to the M-55.

GTAman

iTrader: (2)

cool. does it come with a pick up too? pick up screen?

Stekman

M-55 pump
55-S screen
Mr. Gasket #26 pressure spring
ARP pump driveshaft

4 different parts. 1 dependable oiling system.

GTAman

iTrader: (2)

alright, there's my shopping list going in today. thanks guys.

Stekman

What oil pan do you have? Stocker?

GTAman

iTrader: (2)

yeah, original oil pan

Russ-So Cal

With 123,000 miles on the engine, you should be runing a higher viscosity oil than 5w-30. The clearances in your bearings have opened up, so you need the thicker oil to hold your pressure up.
If your running Mobile 1, switch to the high mileage blend. Also, don't get into the mind set that the more oil pressure you have the better. You can have too much oil pressure. Cummins ran 100# oil pressure for many years, and they had to drop the pan every 150,000 miles to replace bearings. They dropped the oil pressure to a max of 60#, and now get 400-500,000 miles to an engine. If you have excessive oil pressure, you can actually turn your oiling system into a "hydraulic saw" and cut your crankshaft.

GTAman

iTrader: (2)

sorry if this sounds dumb, but these bearings you are talking about. whate bearings are they? cam bearings?

Stekman

All the bearings will effect oil pressure. That's how they work and what oil pressure is. The crank-related bearings perhaps moreso than the cam for what you would be concerned about.

screamingz28

Has anyone ever ran 0-w30 in their engine? It would warm up faster and thereby increase fuel economy because of a shorter warm-up time. One more question: would it be ok to have only water in your radiator in the summer to decrease the warm-up time for the eingine?

Russ-So Cal

The bearings I was referring to are your main & rod bearings. The cam bearings would also lower oil pressure, but they typically don't wear. They don't absorb the the reciprocating stresses that the rods and mains have to deal with. I suspect that if cam bearings weren't changed, they would probably last through two or three overhauls. Of course most people who are rebuilding a motor change them because it is silly to do all that work and not replace the cam bearings.

Regarding taking out antifreeze and running just water in the summer, you can do that. I would just make a couple of reminders. Antifreeze does three things. It keeps your engine from freezing in winter, it helps keep t from overheating in summer, and it has corrosion inhibitors to protect against rust.
If you are going to run water without antifreeze in summer. If the weather in your area is hot (90*f+), I think you should run Water Wetter. Regardless, of what else you run you should run a low silicate corrosion inhibitor. Remember, your engine coolant is flowing around and through disimilar metals, without inhibitor you will get corrosion.

305IrocZ28

For those who dont know this, actually your readings are a bit off...could be gauge problems...but here are the specs DIRECTLY from Chevrolet about oil pressure:

305 TPI/350 TPI

6 psi @ 1000 rpm
18 psi @ 2000 rpm
24 psi @ 4000 rpm (hot)

and considering that our lovely gauges read PSI, I'm sure we all have a case of minor electrical inaccuracy.

gearhead0384

iTrader: (7)

That is not that bad!! My 159,000 mile Iroc ran at 13 PSI at idle after it warmed up, that is untill I took it out and put a 350 in.

Kevin

ploegi

Oil pressure will fluctuate for a variety of reasons.

Engine temp.

Age of the oil.

Engine RPM.

Type of oil used.

Age of filter.

When cold, the oil is "harder" to pump, thus, you get higher pressures. As the engine warms up, so does the oil, and it "thins". Thus, pressure will always read lower on a hot engine, as compared to a cold engine.

Also, I have noticed..... When my oil is getting on toward time for a change, pressure at idle on a hot motor will be under 30psi, change the oil, warm the engine, and it runs around 40psi. And this is on a 350 with over 180000 miles on it.....

You are fine.

formulaman

That's pretty much normal for my oil pressure too.