VERY low oil pressure at idle

[LegacyL22]

I am new to this forum, so i everyone...Also, I have searched endlessly on the net before resorting asking you...I know you have better things to do with your time than to answere questions that could be answered by the first google listing.
After noticing my oil pressure gauge moving erratically at idle, I found out that it is actually only a dummy light that puts the needle at 0 when the oil psi is lower than 5psi (kinda a cruel joke i think) so I installed a mechanical psi gauge to find out that at idle it is below 5 psi or very close to 0 while idle. This only happens when the engine is warm, and under load at idle (meaning below 1000rpm in drive while stopped) The second i start to drive again it goes back up to around 20 psi. Any ideas would be greatly appreciated...Oil level is fine.

 

[Jspafford]

Sounds like a worn out engine. How many miles are on it? The oil PSI should be around 15 at warm idle.

 

[94 splash]

yea it could be alot of things bad oil pump warren out engin.. spun bearing ... how long has it been doing this

 

[LegacyL22]

its got about 120k on it...just started doing it a few days ago, but im not sure how long its taken to get to that point, because the stock pressure gauge doesn't actually give you the pressure...any ideas to help troubleshoot? Also, it only does it while warm...could that narrow it down?

 

[94 splash]

try changing the oil and filter sometimes the oilfilter can get cloged and kill it... and see if u put a thicker oil in it helps it should bring it up a little ...

 

[LegacyL22]

thanks, im going to try that tomorrow...Any recommendations on oil? I just moved down to florida, so its going to be pretty hot for the next 3 months. Thanks...thats another thing...it just did the 1300 mile drive from NH less than a month ago, and i havent changed the oil yet. I don't know if that helps, just thought i throw it in.

 

[MAKG]

Putting "thicker" oil in it can finish it off.

Do the valves clatter at idle?

Change the oil to CORRECT viscosity, and hope it was just old oil.

If the valves don't clatter, I wouldn't worry about it too much, unless it was also accompanied by excessive blow-by or other problems.

It's a sign that your largest oil clearances are probably worn. More viscous oil will hog out the SMALLEST clearances (probably hydraulic lifters).

The spec is 40-60 PSI at 2000 RPM. If you don't meet that, technically you need a rebuild, but I'd leave it alone unless you see true performance problems. You do risk throwing a rod with sudden acceleration of the engine, but it may be a very long time before this happens, if it ever does.

 

[LegacyL22]

Just changed the oil...unfortunately before i saw makg's post...replaced with 20w50 valvoline premium concentional and purolator filter...pressure shot back up to what i assume is normal, but there is a new noise...kinda sounds like a piece of metal bouncing around in the oil pan...also, lots of metal shaving in old oil...this isn't looking too good...oh yeah, and less than a month ago after the long trip, the rear intake manifold gasket blew and was replaced.

 

[LegacyL22]

So i'm thinking that the engine is probably terminally ill...anyone know about how much it would cost to replace the engine with a used one? or if it would be worth it to replace the bearing if that turns out to be it? it makes a nosie at about 2k - 2500 rpm that sound like a woodpecker...

 

[MAKG]

You'll have to price locally. Answers you get here will be for different locales, which have different labor rates. And even neighboring junkyards can have wildly different prices on the same stuff.

120K is a short life for the engine, but it really does sound like you got a bad knock.

You may find it worth it to junk the truck and get something else, rather than repair it. Though it's a '99 and not THAT old.