Diagnose this oil pressure problem...

5spd GT · Apr 28, 2005

Well I realize how the stock oil pressure guage (stock guages for that matter have their problems) but here the last couple months I have noticed a lower pressure than normal. It used to read above the half way line and now it reads below the halfway line. Another thing I have noticed is when I go WOT for a few seconds I'll take a peak at the oil pressure guage and it is up near the top (between middle-top). It will take another 30 seconds or more for the oil pressure guage to "drop" again back to normal (around the half way point). So basically what does it mean when you go WOT and your oil pressure will go up (visibly by the guage) and then drop back down after normal cruising? Anything?

I have 152k on the clock and drive it everyday...

I'm just curious and bored...

Thanks

oldman · Apr 28, 2005

The gauge on my 93 did the same thing. Changed the sending unit, and now it stays at 3/4 up all the time. Sending units get weak over time and will start to fluctuate.

Randy

DMAN302 · Apr 28, 2005

Hey buddy,
Well from my experience my old motor 200,000 miles on it..the pressure would (warm) sit about 1/4 from the bottom on the stock gauge. When at cruise it would come up to aprox 1/2+one line..at WOT would hit aprox 3/4(again stock gauge). When the fresh mill went in..the stocker pegged at 3/4 and never droped wether warm idle/cold idle/curise. I would consider a gauge installed to see the actual PSI situation at hand...cheap insurance (looks nifty too). Your going to have to accept that your pressure will be diminishing as time wears on..but again the aftermarket gauge will tell you the truth about the internal pressure. The ideal scenerio is 10lbs for every 1000RPM, and I wouldn't feel safe with anything under 15LBS at idle.

5spd GT · Apr 28, 2005

DMAN302 said:
Hey buddy,
Well from my experience my old motor 200,000 miles on it..the pressure would (warm) sit about 1/4 from the bottom on the stock gauge. When at cruise it would come up to aprox 1/2+one line..at WOT would hit aprox 3/4(again stock gauge). When the fresh mill went in..the stocker pegged at 3/4 and never droped wether warm idle/cold idle/curise. I would consider a gauge installed to see the actual PSI situation at hand...cheap insurance (looks nifty too). Your going to have to accept that your pressure will be diminishing as time wears on..but again the aftermarket gauge will tell you the truth about the internal pressure. The ideal scenerio is 10lbs for every 1000RPM, and I wouldn't feel safe with anything under 15LBS at idle.

Sounds pretty close to what mine is doing Derek...I know when I first did my h/c/i swap my pressure stayed up to the 3/4 mark pretty much all the time with little fluctuation. I just noticed over the last couple-few months the pressure has dropped and can differ and isn't as consistent as it used to be. I just noticed it like that one day and I always look at it everytime I drive (out of habit). The stock guage reads about 35-40psi at idle and will go up around the 3/4 mark (peak) which is around 70psi right? I think when I added the heads (58cc) it helped that pressure out like in your case (the mill).

oldman - Yeah I thought it might be the sending unit going out as a possibility...must be these 93's

Oh I do have a worsening oil leak at the lower intake (mainly the back) if that will do anything. It seems to be pretty parallel with each other...

Thanks guys

oldman · Apr 28, 2005

Yea 5spd, my 93 had 170,000 miles on her when mine took a dump. Shure scary when you look down and the gauge is real near the bottom.

Randy

DMAN302 · Apr 28, 2005

Doubt the leak is causing pressure issues, but the filter may be...you could try swaping the old filter see if anything good comes of it. I also found the "MAXLIFE" from valvoline cut back on my oil usage, raised my pressure a bit, and even did slow some of my leaks(they were quite plentiful near the end) as it is designed to do. I would still stand by my idea of an aftermaket gauge..they are the only true way of getting the right reading. Should also note*you may now be experiencing something I often suffer from, I call it...being over aware of something. By "over aware" I mean your now paying ALOT of attention to a gauge that never really caught your eye very often. I am famous for worrying about things I JUST noticed for the first time..wondering "is that normal??"..usually it is but I never noticed before.

5spd GT · Apr 28, 2005

I actually use the Havoline MaxLife 10w-30 and the oil is freshly changed. Come to think of it I think I noticed it after the oil change...hmmm... FL-1A Motorcraft oil filter. I have used that oil/filter combo for almost 2 years now...

I'm thinking it is the guage/sending unit as the problem or the car really is getting worn...

Yeah I would like to do a nice set of guages but I need money to do that I want some Autometers to do it right...

Zero_chance · Apr 28, 2005

My 88 used to have relatively low pressure and relatively high amounts of leakage. Since I tore it down and then regasketed and rebuilt, pressure stays about halfway during idle and 3/4 at higher RPMs. Unfortunately, I have other problems since the rebuild that are taking away from that good note...

SamSnyder · Apr 28, 2005

The stock electric gauge is pretty worthless. I have seen them go down when they chould go up and vice-versa. I think it's mostly the sender. Also, I believe that after '90, the sender was just an on/off switch rather than a progressive unit, giving a fixed reading. My gauge was just sitting there in the middle not doing much of anything. I'm not worried about my motor, but would like something a little meaningful, so I went to the junkyard and grabbed a handful, but have only tried 2 so far. Both give crappy readings. Maybe the third time will be a charm. But you really need a mechanical gauge to get an accurate reading.

ninty1gt · Apr 28, 2005

mine does the same thing, and when its about time for an oil change, my pressure goes low and the car shuts off, i got scared the first time it did that, but it always does it after the oil gets thin, i bought a oil sending unit today and will be installing it, hopfully it fixes the prob

HISSIN50 · Apr 28, 2005

David, i know you know about all the info posted so far. for 10 bucks you can get a new sender (like others said). it helped mine a little. those gauges just suck. if you are worried, parts stores sell 10 dollar mech gauges that you can hook up for a day or a minute (in the engine bay) so you can see what is going on. i can dig around and see if i have a spare and mail it to ya.

and for the 3 bucks it costs, i would swap filters. it might be funky/jacked but not quite bypassing at lower rpm and bypassing at higher revs, which increases pressure.

no real info for ya - just posting.
good luck and chat with ya later.

5spd GT · Apr 29, 2005

HISSIN50 said:
David, i know you know about all the info posted so far. for 10 bucks you can get a new sender (like others said). it helped mine a little. those gauges just suck. if you are worried, parts stores sell 10 dollar mech gauges that you can hook up for a day or a minute (in the engine bay) so you can see what is going on. i can dig around and see if i have a spare and mail it to ya.

and for the 3 bucks it costs, i would swap filters. it might be funky/jacked but not quite bypassing at lower rpm and bypassing at higher revs, which increases pressure.

no real info for ya - just posting.
good luck and chat with ya later.

Yeah the car runs just like it has always run but it was something I noticed in teh guage itself. I'm hoping just the sender is going south which is a pretty easy swap and cheap as you so wisely pointed out A friend of mine had it go bad on him in his 94 5.0L because it was reading low all the time and he replaced it and it was "up there" after that and gave him more of a peace of mind which you know I like He had around 150k to...boy my car is getting internally "old"...

onefasthatch89 · May 3, 2006

where is the sender located??

dragnazz5.0 · May 3, 2006

right above the filter. it will have a little bar coming out of the block with the sender on it. im gonna change mine today too now that i think about it.

Diagnose this oil pressure problem...

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