Hey guys,

What oil pressure should our engines run at? My understanding was a healthy engine should produce 10 psi of oil pressure per 1000 rpm.

I ask because I think my slant is developing an issue. Normally my slant runs between 25-50 psi of oil pressure at any given moment. However, today my slant started running at 20 psi at idle and 10-12 psi under load no matter the rpm. I actually feel that the higher the rpm, the lower the psi reading. This is the opposite of my understanding.

I checked my oil level and it was a little low so I put more in, no change. When I rev the car in park, the oil pressure stays at the static 10-12. My oil pump has less than 500 miles on it as well as my last oil change. Running 10W-30 if that matters. No oil leaks that I've been able to find.

Please let me know what you all think. I appreciate any and all help/suggestions.

Thanks,
Aspen76

_________________
76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide

Mechanical gauge or electric?... If the pressure is that low I would suspect alot of buildup in the pan blocking the pickup... How many miles on the engine itself? Excessivle worn bearing clearances will cause low oil pressure as well...

I have a consistant 50 psi, idle, high rpm, hot, cold, etc... Run 10/40 royal purp, wix filter, and a Melling high-volume pump on a new rebuild.

_________________
"if it aint broke, fix it till it is"
78 Plymouth Volare Super Six wagon
89 Volkswagen Golf GTI 16v
92 Chevrolet K1500 5.7
98 Ford Escort ZX2 zetech

Thoughts:
- Is this a complete rebuild 500 miles ago or just replacement of the pump?
- Consider changing the oil filter as part of the process of troubleshooting this in case it has gotten partially clogged up.
- Have you had the valve cover off to look at the sludging in the engine?
- Any chance you hit a rock or something and dented the bottom of the pan in and constricted the pickup?
-Pull out the pump's relief valve and see if it is dirty or for some reason not seating.
- Excess air in the line to the oil guage?

Electric gauges, auto meter with their sending unit. Engine is somewhere between 200k and 300k miles per the old speedometer that is now replaced with auto meter. Oil pump replacement was 500 miles ago, not rebuild. Oil filter is with 500 miles with the last oil change. Will replace those together. Valve cover hasn't been off in over a year. Been wanting check valve lash anyway. With regards to the rock, I don't think so.

What really gets me here is how all this came out of the blue. There is nothing I can think of that would facilitate the sudden change.

I've got an oil filter and oil sitting around. Looks like an oil change this weekend.

I appreciate all the help,
Thanks,
Aspen76

_________________
76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide

Electric senders can go bad in a blink. Get a manual gauge on there to sanity check, then go from there before you do anything else drastic.

Why did you change the oil pump? Was it just for the heck of it or were you having pressure issues before the change also?

Hey guys,

Just looked at my mechanic's receipt and the oil pump is not new. Got it mixed up in my head with the water pump, which is new.

I agree with you on not wanting to do anything drastic Pierre. I'll see if autozone sells a mechanical oil pressure tester for a reasonable price. Otherwise, I'll be waiting on a delivery.

Is it safe to drive with the pressure being this low (10-12 psi)? I can't do any investigating until Saturday as this is my daily driver.

Thanks for all the help,
Aspen76

_________________
76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide

If you have to drive it, I would first do all these tonight if possible to avoid damage:
- Get on the new guage and check. If good, then OK. If really low, then:
- Change oil and put in 5W30 Mobil1 full synthetic for now; it will cost in the $23 to $28 range at Walmart for 5 qts. The protection afforded will help your engine last for some time with low pressure, if that really is the case. This is dirt-cheap compared to an engine rebuild.
- Change filter.
- Take out the pressure relief valve and clean; that is easy and is right on the side of the pump.

We don't know how far and how fast you drive each day or what rear gear you have, but several miles with 10 psi at 2500-3000 rpm could be end up with damage with regular motor oils; with full synthetic, you likley can go for days with no issues. I raced 4 miles for 4 minutes at full throttle on a 2.6L turbo motor with falling and then ZERO oil pressure for the last 2 miles (250+ HP at that time) with Mobil 1, and there wasn't a single scrtach on any bearing or pistons or rings or cam surfaces! (I swear this is true, and I have a witness of this at the post-event teardown.)

I can agree on that mobil one... Havnt ran it in the slant, but in my old VW I ran it in there religiously and that engine got beat harder than most race engines get...

However, any good oil ( Valvoline VR1, Royal Purple HPS, Mobil 1, etc) you will be fine... Had my pump fail in mine on the hoghway, engine wound up tight @ 70+mph, had to go a good distance with no oil pressure at all and there is 0 damage done that is visible to the naked eye.... Now Im running the Royal Purple now...

Either way, find a way to verify tyhe actual oil pressure... If it is truly that low, fix the problem and dont try to mask it....

_________________
"if it aint broke, fix it till it is"
78 Plymouth Volare Super Six wagon
89 Volkswagen Golf GTI 16v
92 Chevrolet K1500 5.7
98 Ford Escort ZX2 zetech

+1

On a highway trip once, I got progressively more anxious as I watched a newly-installed electric gauge start bouncing around in ways that didn't make sense. It really is unnerving, though, to imagine there might be an engine problem. Even when I knew it might be a gauge problem-- my mind wouldn't let me believe that theory first.

A cheap mechanical under-dash gauge from a parts store a few towns away showed that the engine was healthy as ever. That mechanical gauge later became a part of my toolbox, for pre-purchase testing of old jalopies. Have had to replace the plastic line and compression fittings a few times, but whaddaya expect in a couple decades of sporadic use?

- Erik

PS. That memory reminds me of a really cruel bumper sticker i saw once-- in little tiny letters it said, "Pssst, hey I think you left the stove on."

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Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

I have a true mechanical gauge on mine, but when the initial plastic failed I replaced it with copper. When that failed and started dripping oil on the carpet I replaced it with braided stainless. No problems since.

Sam

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Ive had 2 mechanical now, both read the same total pressure, but one was definately faster reacting... The new one doesnt register fast changes in pressure, kind of seems to show an "average" like most factory gauges do. The old one showed every little flicker in the pressure, but never ranged too far from 1-2+/- PSI at any time... Both were installed with copper line, not plastic...

_________________
"if it aint broke, fix it till it is"
78 Plymouth Volare Super Six wagon
89 Volkswagen Golf GTI 16v
92 Chevrolet K1500 5.7
98 Ford Escort ZX2 zetech

I am honestly glad I sat and read this thread.
I was just on Summit, and was going to order a set of electrical gauges for my Belvedere slant.
Maybe I will just got to advance with my coupon I just got in the mail, and get somemechanical gauges and new olil and filter.
I just got my car days ago, and really don't know when the oil was last changed, although it don't look bad and the engine is quiet.
I was warned by my father, 'years ago", I am no longer a young man...LOL To stay away from electrical gauges.
I guess there was an incident that made him tell me that quite a few times.
I was curious why the OP changed his oil pump in the first place? Was there an issue?

All gauges can fail..... Cheap mechanical gauges can be just as problematic. I've had a few VDO electric oil pressure gauges over time, one was factory fitted, never an issue. I've fitted on to my 1970 V8 Valiant , been there for years, perfect. Anything can. Fail, but in my book I'd prefer an electric gauge , if it fails it doesn't work, a mechanical gauge fails you can lose your oil and if your not watching your engine is toast. Then if the bouden tube inside the gauge leaks your not going to be concerned about floor rusting anytime soon. Sure, you can run copper line to help with line reliability, but it's still not a perfect setup.

I would run an electric IF there was more quality control in the manufacturing of parts... I do live everyday with the fear of screaming hot oil @ about 200*+ and @ 50psi covering me and the inside of my car... Unfortunately though the quality control on electronics are crap these days... Even replacement senders for factory gauges tend to be a little off and fail quickly...

So the choice really is up to the consumer, I personally like the clean install of an electric, but like the crude reliability of a mechanical... Fear the oil sling in the failure of a mechanical, but also fear the inaccuracy of electric due to faults in the sender, heat or bad connections giving a false reading...

_________________
"if it aint broke, fix it till it is"
78 Plymouth Volare Super Six wagon
89 Volkswagen Golf GTI 16v
92 Chevrolet K1500 5.7
98 Ford Escort ZX2 zetech

I'm going to see if Advanced/Auto Zone just can rent me a mechanical oil pressure tester. We'll see if it's the electrical sender by Sunday... If it is, I'm sure autometer will replace it. If the sender/gauge is accurate and the oil change doesn't fix the low pressure, where is the next step in diagnosing the problem?

My oil pressure has leveled out to about a static 25 psi, which makes me feel a little better but not fully confident. Still falls to about 20ish psi under throttle. Car almost never sees 2000 rpms on my short commute to work. Picking up some Mobile synthetic tonight either way.

Also, correction again, oil pump is new. When the mechanic was installing my new oil pressure sender he said that the whole oil pump housing cracked. He replaced it for free, which is why it is not on my receipt.

Thanks for the help/suggestions,
Aspen76

_________________
76 Dodge Aspen
225 Super Six w/ Dutra True Dual Exhaust

http://i1245.photobucket.com/albums/gg5 ... AG0095.jpg
http://www.youtube.com/user/BZuko1?feature=guide