Oil Pressure Assumptions.....

I'm trying to increase the oil pressure in a 96 Nissan Sentra 1.6 Liter engine. The oil light comes on with engine hot, idling in Drive, goes out when put in neutral. I just changed the oil from 10w-30 to 20-w-50, and the light has not come on again :) But it's still making a lot of valve noise when hot, so pressure seems to still be aproblem. I had a mech put a gauge on it and was reading ZERO when hot and idling, and only 15 when revved to about 1500. I know, don't drive it.

I think there is still something else that can be done to improve the oil pressure. I have received conflicting predictions about whether the op wouild be affected by it.

There is supposed to be an "oil pressure regulator" valve on the engine block, which is covered by the oil filter. When changing the filter, I noticed, on the engine block, there is only a hole with a spring resting loosely inside. No cap, poppet, lid, etc covering the hole. Just a wide open bypass hole. Looks like the "op reg valve" broke off and went somehwere, I hope into the garbage after an oil change, and not up into the engine !! :( don't know.

I have orderd the part from Nissan and will get it tomorrow.

My question is whether the bypass being wide open constanly is affecting the op.

My ASSUMPTIONS (some redundant, admitted) are :

A. The oil flows from the pump directly up to the filter inlet (unless pump bypass is stuck open!)

B. Once the oil is entering the oil filter area, most, or all of it, is going right into the open bypass hole, and ignoring the filter, since it is getting resistance there. Maybe 10 percent of the oil is going thu the filter if rpms are high enough.

C. The oil pressure is its highest immediately after it leaves the pump, and DECREASES as it encounters bleedoff opportunities on its journey through the engine.

D. The oil pressure AFTER an obstruction, like an oil filter, will be lower than the oil press in front of the obstruction.

E. An obstruction acts to INCREASE the oil pressure in the oil in front of (before) the obstruction. (Same as D, I know)

F. The idiot light op sensor is located AFTER the oil filter and also AFTER the bypass hole.

G. The oil flowing thru the filter and thru the bypass hole end up in the same channel, the oil from both sources recombines somewhere, like two streams feeding into a river, then goes on its way up to the head.

H. Installing the "oil pressure regulator valve" will INCREASE the op BEFORE the oil filter, but may actually DECREASE the op after the filter, since now the oil will be forced into the filter (obstruction) intead of just flowing thru the wide open bypass hole as before. BTW this is a new, clean unplugged filter).

Thanks. Some folks have told me installing the new bypass valve will boost the oil pressure, even AFTER the filter, but I don't see how. I hope it does, but I don't see how.

Thanks for any replies !!

Reply to
Caprice85
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Sounds like it is time for a new engine. How many miles on it?

Reply to
jfrancis311

ABSOLUTELY! I don't have specific knowledge of Nissans, but on engines that I have worked on, the OPRV works like this; when oil pressure is above a specified value, usually around 50-80 PSI depending on specific engine, the valve opens and allows oil to bypass the normal galleries and dumps it straight back into the oil pan. (well, maybe not straight

- on a Studebaker, for instance, the OPRV also provides lubrication for the timing gears. But I digress, and you get the idea.) The whole purpose of this is to bleed off oil pressure when it could be too high, such as immediately after a cold start or excessively high RPM operation so that you don't blow apart oil filters, wash the babbitt off of your bearings, etc.

At hot idle, oil pressure is almost never above the opening pressure of the OPRV, and the OPRV should be fully closed. This is almost certainly the source of your problem. In fact I'd be surprised if you had any measurable oil pressure under the circumstances you describe!

As an aside, this is yet another reason why ALL cars should be fitted with oil pressure GAUGES not idiot lights... who knows how long this car was run with marginal oil pressure before anyone saw/heard a problem...

Once you get the new OPRV parts and have them installed, leave the gauge hooked up and let us know what you find. I'm guessing you will be pleasantly surprised by the results, and I hope that you don't have any issues with this engine caused by being run with such low oil pressure.

The only thing that concerns me is the location you specified for the OPRV. From your description it could either be as I described, or it could be a bypass valve which opens when the pressure *drop* across the oil filter element gets too high (i.e. it's clogged) in which case replacing same will restore proper operation of your oil filter but may not improve your oil pressure. I'm hoping it's the former, and the nomenclature that they used ("pressure regulator") makes me somewhat hopeful for you...

good luck,

nate

Reply to
N8N

After you replace that valve you should consider hooking up an oil pressure gauge to find out if the pressure is truly within spec.

I could start ranting about how useful the three basic gauges are for monitoring your car's performance. But as cars and their interiors have been downsized some features have given way. I would trade that oversized tach for an oil pressure and voltage meter (or ammeter) in a heartbeat.

The last car I had that was set up for full gauges was a 1988 Volvo

740. It had slots for gauges within the very readable instrument panel.
Reply to
John S.

Downsized? Not in the US.

I think the gauges went away because they revealed any misperformance of the engine and caused more warranty claims. Also some users didnt understand them and would bring the vehicles in for stuff that was not an issue.

Im sure the OEMs have no issue with you installing one after the warranty period is up.

Reply to
dnoyeB

I hope you will post what you find out when you get the OPR. I would really like to know where the ball, or whatever, went (that was a part of this pressure loaded device.)

IIFC, the old Fords (390 type blocks )had a pressure regulator built into the oil pump. Sometimes the springs would relax, and the oil pressure would drop too low. A new spring, or just stretching the old one, would often revive the oil pressure.

Reply to
<HLS

Sure it is, look at the instrument panel. It's smaller and filled up with outsized and useless tachometer, and a travel information screen. With most cars using front wheel drive one would expect to have more legroom, but that's saken up by a console filled with all manner of cupholders, cd racks switches and the like. The interior of most american cars is smaller than it once was although car makers do make more efficient use of the remaining space.

Naw, cars as a group are far far more reliable than 25 or more years ago. It is nothing to have a car go 300,000 miles and at least one car maker gives a 100k mile warranty. Gauges disappeared because not enough people really used them, cars were shrinking in size and car makers could use the space for other more useful things like oversized tachs, full entertainment centers and automotive compasses.

Try to find the room to fit an oil and amp gauge in or alongside a modern instrument panel. Sure you can tack a plastic or metal bezel to the bottom of the dash, but that looks like a typical backyard modification.

Reply to
John S.

You just said "It's smaller and filled up with outsized and useless tachometer" and now you say more useful things like a oversized tach?

Tell me how useful a tach is on a automatic transmission car? Give me a oil pressure gauge and a volt meter any day. Then give me the tach.

full entertainment centers and automotive compasses.

Compass? Men never get lost.......... ;)

I remember back in the 60's seeing the 3 pack combo of round gauges for oil, water, volts hanging under the dash. It was either cool or ugly depending on your point of view. Of course that was in pre "pimp my ride" days. On some cars, there were optional dashes with real gauges. On some cars your can retro fit them in.

Bob

Reply to
Bob Urz

Reply to
sdlomi2

Sarcasm sometimes doesn't come across very well in writing, although the comment about entertainment centers in automobiles might give a hint about my feelings. Or more plainly, tachometers of any size are little more that visual entertainment for virtually all drivers. The needle goes up, the needle goes down but the useful information it might provide in a very few situations goes unnoticed.

Oh, yeah, the little chrome three gauge bezel looked kinda cool to more than one teenage guy in the 1960's. My college car, a 1959 Morris Minor had one gauge - fuel. Temperature and oil pressure were idiot lights on the speedo. OTOH most of the older cars I owned prior to that had a full complement of useful gauges. As did a 1972 Ford F-250.

I have got to ask...what does pimping a ride mean given that a pimp and the business he engages in are not exactly pleasant or savory.

Reply to
John S.

I guess some late model vehicles have a gauge that is no more than a idiot light....

Ah, for the good ole days of super fly and when you could tell a pimp mobile at 1/4 mile. Remember those round chrome headlight covers on the caddies?

Today's pimp my ride:

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have got a old barracuda in the garage if they needa project!

Bob

Reply to
Bob Urz

Man, you guys need a Firebird. :) Comes factory with full gauges. You can get an aftermarket a-pillar "pod" for more gauges. And the dash vents just happen to hold 2 5/8 gauges. (they're round...)

Ray

Reply to
news

177,000 miles. Has been clacking for about a year. No definitive answers from mechanics about the cause. Could be this, that, etc. Oil and filter were changed every 5 to 7 k miles.
Reply to
Caprice85

Serious..??? Real analog oil, temp and volt meters with real numbers that fit inside the instrument panel????

Reply to
John S.

Amen. Carmakers now seem to think that a huge tach is more important than any other gauge... even on automatic cars. Hell, anyone who can actually *drive* doesn't even use the tach most of the time on a stick-shift car. You shift by ear after the first half hour in the car, except when pushing it to redline on every shift. Don't get me wrong, a tach is very handy and does have uses even on automatics, but it doesn't need to dominate the cluster or push aside more important gauges.

Reply to
Steve

I disagree with that entirely, but we've been around that tree a hundred times before.

And all my 60's and 70s cars have gone that far, too. One's still chugging at close to 450,000.

Some people's backyard modifications look more professional than a Lexus dashboard.

Reply to
Steve

The tach has gradually morphed over the decades from an option for performance cars to a standard feature on sporty cars to a standard feature on all cars. The car makers packaged it as part of a brand image and was applied to more and more cars. Similar to spoilers where it was repeated so often that the image got watered down to nothingness. Heck the Taurus I rented last month had a tach!

Because so many cars have them it will be a difficult feature to get rid of. No car maker will take the first step and risk losing sales in a difficult market.

Reply to
John S.

I would really like to know where the ball, or whatever, went (that was a part of this pressure loaded device.)

Reply to
Caprice85

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