Condition, my '92 SR started to act up on me this morning with a winking oil pressure light, then full on at times.Now I'm at work with a gauge attached to the engine, and the pressure light has been off all day except for the various times it was on this morning after only a few minutes after start-up when the engine was still warming up and I was driving at city speeds[slow <img src="/forums/images/graemlins/wink.gif" alt="" />] The switch appears to be OK, and oil pressure is now 28-40psi at idle, and goes to 90 psi while holding the RPMs up. Output reading is very erratic, wild flucuation of the gauge needle over a 10psi range easy while at idle. Gets better with higher RPMs. Nice and steady.
Looks like a possible sticking/stuck open relief valve this morning, and a "trying" to stick relief valve this evening or just worn spot on the pump <img src="/forums/images/graemlins/confused.gif" alt="" />. Factory manual doesn't have ANY info on the pump other than the bolt lengths and a picture of the pump. Does anyone have a spec for the pump output? thanks, Houston

Whoops, I'm my own worst enemy on this one. I've been using 20w-50 for the past few weeks, but only hit the highway with the Montero for a long trip this past weekend at 3000RPMs or so for hours at a time. With the CORRECT weight oil 10w-30 <img src="/forums/images/graemlins/blush.gif" alt="" /> <img src="/forums/images/graemlins/blush.gif" alt="" /> <img src="/forums/images/graemlins/blush.gif" alt="" />, the oil pump output is a much more steady 28-30psi at idle, and still 80psi at high revs. Lucky I didn't blow the pump gears or the relief piston out of the engine while screaming along at 3200 revs <img src="/forums/images/graemlins/grin.gif" alt="" />. Would have caught my mistake sooner with a real pressure gauge, maybe the altimeter is going soon at the center gauge cluster for a plain oil psi gauge <img src="/forums/images/graemlins/grin.gif" alt="" />. I'll keep eveyone posted, since I didn't REALLY want to R&R the oil pump just right now.
Now I only have to worry about doing the valve stem seals that are starting to go <img src="/forums/images/graemlins/blush.gif" alt="" />

PART 3 OF THE SAGA: 4 blocks after leaving from work and testing the oil pressure repeatedly, the oil light comes on again!. <img src="/forums/images/graemlins/confused.gif" alt="" /> I listened to the engine, no bad noises, no lifter/adjuster clatter, no bearing squeal <img src="/forums/images/graemlins/drunk.gif" alt="" />. Sooo, I wheeled back to the shop,going for broke that it was now a possible bad pressure switch and not a failing engine. Removed the switch, attached the gauge to the filter housing hole. Oil pressure was a steady 28-30psi, just like before. This meant I was also dealing with a intermittant bad oil pressure/light switch in addition to my wrong oil viscosity choice <img src="/forums/images/graemlins/notooth.gif" alt="" />.
I hooked up the switch to the trucks negative battery terminal and my test light to the positive cable & switch tab, and added shop air pressure with a rubber tipped blow-gun to simulate the oil pressure. After applying and removing air pressure a few times, the test light slowly started to glow with air applied constantly, then got fully on. Damn, bad 2 month old switch on top of it all, that's what started this mornings fun on the way to work. <img src="/forums/images/graemlins/mad.gif" alt="" />

Oh well, left the gauge/hose plugged in, drove home with no light and less stress than when I started. Final pressure check at home after 25 minutes of driving, gauge read 17-20psi at idle. Still shows a flucuation that shouldn't really be there, so I may yet have to R&R that darn pump due to age/wear, but at least I can drop the long block/spun bearing worries for now. <img src="/forums/images/graemlins/sleeping.gif" alt="" />

Houston,

I run 20W50 in both of my 3.0 V6 motors year 'round and haven't had any trouble. (Atlanta, GA) I don't think this is a bad thing... do you?

Thanks,

Powell

Well, the spec oil is either 5w-30 for cold weather to warm temps, or 10w-30 from 0F for up to a bit over 100F. I was seeing alomst 100psi out of my oil pump with engine RPMs at 3000 and 20w-50 in the engine. Seems a bit high if you do lots of highway driving AND, this is important, IF that number of 100psi is within spec limits using that heavy of an oil at that RPM. Since I don't have any specs or anyones input who has a regular oil pressure gauge or decent electical one mounted to their 3.0 liter V-6, I changed over to the stock oil per the manual.
If I still lived in West Texas like I used to, I might use 10w-40 and see how that went since it gets hot, all the time <img src="/forums/images/graemlins/cool.gif" alt="" />. I'm just a humble tech following some Mitsu' engineer's listing of what oil to use, until proven otherwise <img src="/forums/images/graemlins/wink.gif" alt="" /> The main problem of the bad pressure switch at least was proven and solved, and much cheaper than a rebuild that I don't have the time or money for right now. <img src="/forums/images/graemlins/grin.gif" alt="" />

That flutter really bothers me, especially it's downward direction. That indicates to me that you have a leak in the oil pickup path (crack in the pickup or a bad gasket) letting air in, or a bad bypass valve in the filter, or a bearing with excessive clearance. I use 20w-50 year round, and the only overpressure situation I ever had was when the pressure relief piston got stuck in the bore, and didn't "relieve", and on a cold start the pressure would blow up the oil filter (literally blow the can apart on a mitsu filter that's supposed to be good for 200psi), and sprung a 150psi Autometer oil pressure gauge. I'd consider dropping the pan and checking the pickup for a starter, and get a good mechanical gauge so you can see the fluctuations better - the larger the line size the better, as a small line will mask fluctuations. The pressure relief may ba accessible from the outside of the engine, and it would be worth pulling it if it is - hang on and I'll check the manual - looks like it's the big nut under the filter base, "maybe" accessible without removing the pan - lousy diagram.

All of the things you mentioned could be true, could also be one bad spot on the oil pump rotor. A friend has run into a bad oil pump once with a single tooth having a crack in it, so that the tooth acted like a vane in a steering pump, opening while not under heavy pressure, then closing up as the pressure increased during the rotation of the rotor.He saw the same type of gauge flucuations. With the lighter grade oil now in the engine, the flucuations weren't nearly as bad like when I had the 20w-50 oil in there, so I hope that means any bearing clearance issues aren't the cause. As for the gauge I'm using, its a Snap-On oil pressure testing kit, decent sized gauge with good graduations.
I see the relief valve on the parts blow-up page I got from my parts guy, so I'll take a look again when I replace the pressure switch tomorrow. If it's not to the side of the housing like you were thinking, then it's hiding under the very bottom of the oil pump, which means you drop the oil pan to even access the relief valve. As long as I have fairly steady pressure at all RPM levels, I'm not going to worry just yet about a 2-3 psi flucuation at idle speed on a engine with 159K on it <img src="/forums/images/graemlins/ignore.gif" alt="" /> Thank you very much for the concern and ideas, we'll see what develops. Houston