98 PA low oil pressure

[gaguirre]

I have a 98 PA and my oil light came on on the last start, I checked the gauge info. and it shows I have low oil pressure and also shows 0 psi. Any ideads on what I should check?

Thanks

GA

[HotZ28]

Originally Posted by gaguirre

I have low oil pressure and also shows 0 psi. Any ideads on what I should check?

Thanks

GA

Check the oil first!! Is it high or low? If it checks ok, you may have a bad sending unit, The sending unit is located above the oil filter__in the block.

[wafrederick]

Or the relieve valve is stuck,not free moving and it will blow up an oil filter.

[Blue Bowtie]

...Or an incorrect lubricant was used.

Disregard the marking on the oil fill cap and consult the owner's manual. It shows a table of allowable lubricants at various expected temperatures. 5W-whatever may not be your best choice for protection, even though the EPA says its best for fuel mileage.

What most people don't understand is that multigrade oils are really single viscosity. There is no way any chemist has ever been able to make one liquid pass the SSU or ISO tests with the same drip times at two different temperatures. That's true for ANY kind of lubricant, synthetic or mineral oil. What refineries and blenders have done with mineral oils is to use a base oil of a given viscosity, then add enhancers like esters, olefins, polymers, and paraffins, to make the oil perform like an oil of a different viscosity at a higher temperature. Essentially, 5W30 oil is SAE 5W oil (ISO 22/SSU 105) with added long-chain molecules and polymers so that it lubricates LIKE a SAE 30 (ISO 100/SSU465) at higher temperatures. While this is great for low temperature operation and higher fuel mileage, it is not as good at lubricating as true SAE30 at those temperatures. Worse yet, all the additives are the first things to react with high temperatures to form ash and deposits. The resultant sludge formations can restrict oil flow, disable lifters, pack around rings preventing cooling and lubrication, and cause abrasion on bearing surfaces. As the oil ages, the additives get burned away or sludge out, leaving nothing but straight 5W oil in your engine for all temperatures. Ouch.

Group 4 synthetic oils are organic compounds that are chemically combined to make more complex molecules. PAO's (polyalphaoelfin) are produced by chemically knitting together molecules of ethylene gas (C2H4) using a catalyst. Organic esters (diester and polyolester) are synthesized by chemically combining various types of organic acids with ethyl alcohol to form fluids that just do not exist in nature.

That is the true beauty of synthetics - the viscosity is more stable over a wider temperature range. The lubricant is fluid enough to flow at low temperatures, but maintains its viscosity at higher temperatures. It is more of a "true" multigrade when compared to mineral oils under the same conditions. This inherent tendency of synthesized molecules makes the addition of polymers unnecessary, thereby reducing the sludge-forming tendencies of the lubricant.

As an example, Amsoil and Mobil 1 10W30 have a pour point of at least -68ºF, whereas Casrtol, Pennzoil, Quaker State, and Shell 5W30 mineral oils have a pour point of only -35ºF. The pumping points are similar, with synthetic 10W30 being -52ºF, while 5W30 mineral oils are -22ºF. That means that starting an engine in -22ºF weather with 5W-anything mineral oil means that there is NO lubricant pumping until the oil warms up. 10W30 PAO synthetic will only do that at -52ºF, and you can get 5W and 0W synthetics all the way down to -86ºF. Try that with a mineral oil. And that's all comparing 10W synthetic to 5W mineral oil. In an "apples-to-apples" comparison, 10W-something mineral oil doesn't even appear on the same map. Even 0W-whatever mineral oils don't get close to the cold performance of 10W synthetics, and don't have a prayer of lubricating at higher temperatures.

The bigger problem in colder temperatures is the other end of the spectrum. Regardless of how cold it gets while the engine is sitting, the engine will eventually reach a normal operating temperature. That means that in -20ºF air temperatures, once the engine is running and warmed up, the oil is still going to be at 230ºF or more. If the viscosity index of the oil is insufficient (as most mineral oils are) there is almost no lubricant film strength at those temperatures, and negligible viscosity. That’s why your oil pressure is almost non-existent.

The best analogy I can offer is comparing mineral oil to shortening, and synthetic to antifreeze. Put a cup of shortening/lard in a pan at 70º room temperature. It sits there like a soft lump. Warm that shortening up to 200º and it melts into a thin grease. Put that pan into your freezer, and it will turn into a rock.

Then pour a cup of antifreeze into a pan at room temperature. It's a mildly viscous liquid. Warm it up to 200º, and it's still the same liquid. Go crazy if you want and heat it up to 300º. Put that pan in your freezer, and it still remains a liquid.

Mineral oil and synthetics are just like that - Two completely different compounds. And no matter what you do to that lard in your freezer, it's still going to be lard.

I sit here and type all this out while it’s -14ºF outside, and I’ll have no problem going out and starting all three of the vehicles sitting outside and having immediate lubrication with the PAO synthetic in the sumps.

[BNaylor]

Originally Posted by Blue Bowtie

...Or an incorrect lubricant was used.

Disregard the marking on the oil fill cap and consult the owner's manual. It shows a table of allowable lubricants at various expected temperatures. 5W-whatever may not be your best choice for protection, even though the EPA says its best for fuel mileage.

Actually based on his geographical area per his profile (San Antonio, TX) the marking on the oil filler cap is most likely correct. Normally marked use 10W-30 and he should use 10W-30 in a SII 3800 engine and considering his climate.

I don't believe that is the reason why he is getting zero oil pressure.

[HotZ28]

Originally Posted by BNaylor

Actually based on his geographical area per his profile (San Antonio, TX) the marking on the oil filler cap is most likely correct. Normally marked use 10W-30 and he should use 10W-30 in a SII 3800 engine and considering his climate.

I don't believe that is the reason why he is getting zero oil pressure.

Yea, I remember the mild/warm winters & HOT summers in San Antonia! I lived there 10 yrs!


BTW, Current Conditions @ Randolph AFB, San Antonia, TX 78239
Sunny. Highs in the mid 50s. Southeast winds 10 to 15 mph. Low 19 ° F @ 6:00 a.m.

For this day Jan, 20
Average High Temperature 62 °F / 16 °C Record High Temperature 83 °F / 28 °C (1972)

Average Low Temperature 39 °F / 3 °C Record Low Temperature 19 °F / -7 °C (1943)

The record Low for this date (19 °F) was matched last night! It must be due to Global Warming! (Per; Al Gore)

[gaguirre]

Thanks to all the reply's, I did change the sender unit and now have normal psi. And yes I was in a short sleeve shirt and shorts while doing the repairs

Thanks again

[imidazol97]

Originally Posted by gaguirre

And yes I was in a short sleeve shirt and shorts while doing the repairs

Thanks again

Glad to hear you found the problem.

I'm going to complain to the moderators :grin about how you rubbd it in about your weather. I'm looking at my outdoor temp and it's 11.4 def. F. Last night's low was -2.5 deg. F. And you are working in short sleeves!

Maybe this summer we can post that it's 80 degrees when you're at 105.
Grin.

[HotZ28]

Congratulations on fixing the problem! Well, I noticed the official high in SA today was; 54° F @ 3:00 p. m.—a little cool for “shorts & T-Shirt”! I know, I've been there done that! You are on target with your prediction Imidazol97 for the summer in SA! I can remember one summer during the early 90’s in SA, we had 90 consecutive days of over 100 °F! Of course, 105 °F in SA, would be no worse than 95°F in Dayton!
(Humidity in Dayton sucks)!

[BNaylor]

Actually it gets hotter in EL Paso but San Antonio has the higher humidity. And yes I had a short sleeve shirt on yesterday afternoon but the morning lows a little too cold for short pants.

From the Packers/Giants game it sure looked super cold in Greenbay. Man I felt cold watching that game. BTW - Congrats to the Giants. Better luck next season Jeff.