diagnosing oil pressure?

[buckspa]

I took a 60 mile drive today and noticed that the oil pressure was reading 15-20 psi throughout the drive. I'm hoping to find out some good solutions for diagnosing any issues and resolving it by taking the least expensive path, of course.

There is no knocking from the engine, so i dont think its anything to do with the cams/valves. I could be wrong of course. I don't appear to have any leaks, so i dontthink its gaskets. It could br the screen in the oil pan. It could be the oilpump. it could be the oil pressure sending unit.

Where do i start? Or where would you start? Should i just replace the sending unit first?

[712edf]

Could be the pick-up clogged. Does it have normal pressure at startup, then fall upon warm up? or is it always low?

Bucky

[buckspa]

always low. most vehicles this old are prone to the sending units going bad, right?

[Gordon Maney]

I think you should check the oil pressure with a known, good, mechanical gauge, rather than replacing an electrical part as a diagnostic method.

[greg rider]

It might be the pressure relief spring in the pump.

[Gordon Maney]

The most likely cause is excessive clearance in main and rod bearings.

[Charles Talbert]

The cam bearings are most often where pressure is lost if no rattle is noticed. Main and rod bearings are certainly a consideration as mentioned, but many times you will hear some ticking or slight knocking in a hot engine if that is the source of loss. A good tell tail sign is also erratic valve action due to the cam being allowed to jump around a bit in loose bearings. This will usually be noticed in the form of an occassional skip, weak performance, or both. Seriously, checking with a good mechanical gauge is the next smart step; if that reveals the same psi reading, I would then perform a compression test. If that produces test results of 90 psi or less in any cylinders, you may as well be thinking about a rebuild. Actually compression readings of around 110 or above are what is desirable, lower than that is reaching the end of the road for a good performer. If you are fortunate with good compression readings, then I would check the relief valve spring, oil pump check, drop the pan for a crud buildup, pick up screen check, etc. What type and weight of oil are you running, that can also be a factor.

[buckspa]

Yeah I'll have to get my hands on a mechanical gauge to see what it reads. It makes sense to do a compression test. It'll probably fail knowing the luck i have :) If not, i'll do as mentioned and droip the pan, etc.

I've never been involved in a rebuild, but have all the time in the world with this toy, so I am willing to try. So far this is a very easy vehicle to work on. Parts for the 318 easy to find? Cams,bearings, etc.

[n1265]

Twice in 6 years, I have had my pressure drop to 0 in my 318. ( Once when I was 200 mi. from home ) I changed the oil and filter and both times it came up to around 15 lbs. It is my belief that these oil sending units are finicky. and I doubt if the oil gauge is any more accurate than the gas gauge. ( mine is off 1/8 tank )

If it ain't knocking, ticking or running rough I don't loose any sleep over it. Put a mechanical gauge on it ( even if temporary ) to see where you are really at.

[KRB64]

Wow, thats good oil pressure for my 318 :). Mine starts out high then once warm it settles way down. But then again it puffs a good gray cloud when it fires up too... I have no idea how many miles/hours are on it but its had a rough life too.

[712edf]

The least expensive thing to do to increase pressure is switch to 20W-50 oil. I use only Valvoline Conventional. A good synthetic would work too. I stay away from parafin based oils.

Granted your engine will still be just as wore out as before, but the thicker oil does move the needle up a tad & holds it there when warm, unless you have major issues inside.

Yes to the mechanical gauge check..... & I agree if no knocking/ticking then you are probably ok, until they start then time to tear into it.

If you get an accurate 35-40psi reading you're fine for daily driving.

My opinion.

Bucky

[Charles Talbert]

May not be the smartest choice

You may not be fine at all. Artificially raising pressure with heavier oil may make more psi show at the gauge, but think of what it is that accomplishes that higher reading. Thicker, "harder flowing" oil is the cause of the higher psi. Many times that is actually causing further engine damage than what created the problem to start with. If oil does not flow freely, the needed lubrication is not happening. Flow is greatly reduced in the areas of small passages, as the thicker oil just can't pass readily as it must to do the job correctly. Using a premium quality oil in the correct rating is a much better choice, bear in mind that none of the common off the shelf oils these days are really premium quality products. I understand that it's hard to pour the high $$ product into an engine that may simply blow some of it right out; so when it reaches that point, then it's time to rebuild or replace it. Doping will most likely cause issues that will actually cost you more at rebuild time.

[712edf]

I didnt claim it was the smartest option, just the least expensive (short term) which was what Buckspa asked for in the original post.

Bucky

[Charles Talbert]

I didnt claim it was the smartest option, just the least expensive (short term) which was what Buckspa asked for in the original post.

Bucky

That was exactly my point Bucky, it can't be the least expensive, short term or otherwise if one does further damage in some effort to get a reading on the gauge that only gives a false sense of security, not needed engine protection. It's easy to get the reading up; also easy to starve vital components of needed protection with too heavy an oil.

I'm not suggesting you, Buckspa, or anyone else should follow any guide line of mine, that is your call. I'm just putting out factual information I've learned through the years for anyone who may be interested in taking care of the situation before it gets worse and more costly to repair. I can't recall ever seeing a situation where a band-aid fix had saved money when the end of the road finally came.

[712edf]

Starting over,

Buckspa first get an accurate gauge reading while using a proper grade/viscosity of oil. If pressure is sufficient, personally I'd just enjoy the vehicle. If its still too low, then it's your call as too how much to invest in fixing it. Charles is correct in that short cuts ultimately cost more than doing something properly from the get-go..... But complete rebuilds, while they do fix everything, aren't cheap and maybe overkill for some situations. It all depends on how long you want to keep the engine, how much & how you use it, how much income you have to invest in a rebuild, etc.

Good luck,

Bucky