True

Hey all...

Moved from Washington state to Nevada, stopping in California. The first day, everything was fine... car ran great. Next morning, about 50mi into the trip, I notice my oil pressure is ~30psi at cruise and down in the red at idle. No weird noises, nothing different... checked oil, seemed fine. I figured it was okay to drive.

Kept on driving it, and pressure slowly crept down. After a while it dropped to just above the first mark, then about 80mi from my destination it was in the middle red at cruise (~450mi later). At idle (hell, anything below 1800rpm or so) it's at dead zero right now. Still no power loss, knocking, anything as far as I can tell...

Any ideas? Does this slow decay sound like sender unit death? Or is it really the oil pump or something else?

I should have it looked at tomorrow, but I am curious as to what people may think here

Edit: Turns out it was oil level after all. My dipstick lied Runs fine now, though I suspect I am probably burning oil.

Edit 2: Actually, I developed a large oil leak during the trip. Sigh...

84 Z-28 350

that sounds like the typical oil pressure sending unit death, these things are notorious for dying, if you really were loosing pressure, first the lifters would start tapping as the pressure went further down you would start spinning bearings, neither of those have happend yet so my suggestion is to go to the nerest napa and get a mechanical gauge setup when you get a new sending unit, just take off one of the pipe plugs on the block just behind the water pump and use that to feed the mechanical gauge

Vader

Without any corresponding telltale noises, I'd suspect you have more idle oil pressure than the gauge indicates. Still, it would be good to verify that the gauge is right or wrong.

Or perhaps your engine is already acclimating to the laid-back, no-pressure Nevada lifestyle...

84 Z-28 350

yup...I've got that lifestyle going on...lol

Randy82WS7

yeah you would know it by now if it were that low

would be some top end rattling too from lack of oil

and so forth

True

Well that is very good news. I just thought it was weird that it took almost 500mi of driving for it to drop off that low... I figured if it's another problem, it'd have dropped a bit quicker than that

I'll probably have it looked at today with a mechanical gauge, and I'll let you know for certain what is up with it.

ZimGTA

Fram Oil Filter?

True

Never. Purolator.

I got a mechanical gauge today, but it didn't work too well... almost as flaky as the electric one But oil was pumping up slowly, so I figure there has to be pressure.

I was so certain I drove it around, was going to get another sending unit... store was closed though. But other than make believe noises (my car is loaded with all of my moving stuff and my front end makes some noise...need to have it worked on) it ran perfectly.

Vader

You aren't using any 5W-something oil, are you?

True

Syntec 10w-30

True

Just took it out for a drive... on the way back to the hotel, it died four times...and my steering is damaged too. But regarding oil pressure...

Put a new sensor on before I left. Started it up, still showed low pressure - figure it may just take a bit before it works. But after an hour of driving, it still doesn't show anything different - ~15psi ~2000rpm, goes down when turning, and almost 0 at idle. Don't know if it is the sensor, it is new... how long does it take for a new sensor to work?

LLLosingit

The new sensor should work as soon as you started the car.
Any idea why it's dying?
I would take a close look at your oil, Check and see if it's watery or contaminated with metal, antifreeze ect...
Are you 100% sure your not hearing any lifter noise or anything?
If the oil pressure is truly that low your gonna hear something.

True

Just got back driving it. Fired it up cold... slowly went to almost 30psi then dropped back down to red. The entire drive it went from ~0-10psi on the gauge.

I'm certain there is no noise. I have driven it up to 2500rpm (I am afraid enough to have it that far) and there isn't any clicking or anything else... I've been listening attentively but it sounds like it always has.

Any ideas? I really don't want to drive this thing around...

Also, the oil seems fine. Haven't been burning it, haven't lost coolant, looks and smells like oil. It's almost due for a change, though - but I'd like to know what the problem is before throwing $30 into that!

EvilCartman

iTrader: (1)

A friend's Blazer motor was doing the same thing, basicly it was just worn out. He drove it for about a year with the oil pressure at 15 while cruising and 0 at idle. It started knocking a tiny bit before we pulled it out. Dunno if it happened all of a sudden with his though. Maybe your oil pickup tube fell off or is getting clogged? Did you run over anything on the highway that may have dented the oil pan?

True

Nope, didn't run anything over... almost did though

And the engine only has 25k or so on it. :/

Damon

Try changing the oil filter. Probably not going to help and it SHOULDN'T help with the stock bypass valve in the filter adapter, BUT it's worth a shot.

91black5spd

What makes you say that? I run 5W30 in my '91 TBI and don't have any problems other than the oil pressure being pretty high(Oil pressure 30-60psi). It says that weight on the fill cap so I figured it was OK. Should I really be running 10w30?

killa_b

5w flows a little better on startup if you live in a colder climate but once its warm its the same viscosity anyways

True

Well, this is interesting...

Turns out it was oil level. I checked oil though throughout the trip... always between the marks on the dipstick. Maybe my dipstick lied.

Anyway, checked today and it was empty (??) with no leaks...so got some oil, put it in, and bam - pressure.

So now my engine slowly burns oil

Vader

Or, that's what they would have you believe. 5W-anything is just simply 5W oil with fortifiers added to keep if from thinning any more than a plain SAE 30 at higher temperatures. That takes a lot of polymerizing additive to pull off that feat, which leaves less room for molecules which actually lubricate, clean, and cool. 10W-something oil is 10W base stock with additives to keep it from thinning any more than SAE 30 at higher temperatures. It takes a lot less polymer to do that with a 10W than with a 5W base oil.

True synthetics don't play the game that way. They remain stable over a much wider temperature range and therefore require little if any fortification to do so. It's a different set of properties altogether. You know - it like how molasses is very thick while in the refrigerator, but heat it up in a saucepan only 150° and it's almost like water. That's 5W mineral oil. Synthetics are more like the metal with which the saucepan is made - heat it to almost the point of breakdown and it remains relatively stable.

I know your oil filler cap reads "5W-30" but what does the owner's manual say about that? How about above 40°F? And the cap doesn't read "synthetic" but you can't convince me NOT to use it. Just asking...

Huh. I can't believe I got wicked into another oil thread.

91black5spd

My owner's manual says to use 5w30 as the preferred oil viscosity and if the climate is over 0 deg F that I could use 10w30 but 5w30 is still preferred. For me it is easier to use 5w30, because I have an '03 Ford Ranger that I commute with and I use 5w30 in it so I don't ned to buy 2 types of oil.
btw, I don't use synthetic oil because the car is older and I'm a little worried that it'll make it more leak prone although it doesn't have any leaks so it prob wouldn't. Also, I had switched to synthetic ATF(same specs, meeting Dexron II) in my tranny and it made my fifth gear grind, switched back to regular and only occasional 5th gear grind. That's why I won't use synthetic in it.