Okay, I have gone through the faq's, and did a search on the topic of oil pressure, but I just didn't see one that fit my predicament. I have recently purchased a 1996 Dodge Ram 1500 Sport 2wd, regular cab, and I have some concerns regarding the oil pressure. Unfortunately, when I purchased the truck, I was so enamored with the way that it drove, and the condition of the body, that I really didn't pay close attention to the oil pressure gauge. Since I purchased the truck, it has become the center of my attention. As background info, the truck has 245,000 miles, and was said to have been rebuilt 60,000 miles ago.

Here is my dilemma. I got it home, and the first thing that I did was change the oil. For what ever reason, the factory oil pressure gauge has been by-passed, and a mechanical gauge is mounted under the dash. On a cold start, the oil pressure reaches the "60-70 lbs" of pressure, but after reaching operation temperature, it settles into the "20-23 lbs" range at 1500-1800 rpms. On top of all of that, I hear a "rumbling" noise when I crank the engine. As it gains rpm's, the rumble abates.

Now, in my mind, this rumble is a main bearing problem, but I am very much uninformed. The truck drives really well. It doesn't over heat, it doesn't knock...it just has seemingly low oil pressure..normally 20-25 lbs at highway speeds...and less that 10 lbs at idle..

I went cheap on my initial oil change with Castrol oil (on sale at Wal-Mart), and a Fram filter (I know..save your breath..will never do it again).. I was going to drop the oil pan today, but the fellow that I bought it from said that he used Penzoil and some sort of Lucas treatment in the oil when he serviced the truck. So, in hopes that it was the oil and filter, I changed it again this afternoon, using Penzoil and a Purolator filter....and much to my chagrin, the oil pressure did not improve..

My thinking is this, on a cold start the oil pressure reaches some where between 60-70 lbs....which leads me to think that the oil pump is doing it's job, and the problem is most likely the main bearings?? But, on the other hand, the truck seems to handle the diminished oil pressure just fine...It doesn't knock or ping?

My question is, what do I do? Is 20-25 lbs of pressure at highway speeds ok? Is 5-8 lbs at idle ok? Should I replace the oil pump with a higher volume pump? Is it the main bearing wear? Should I do an "in-frame" replacement of the main bearings?

I know that I drug this out, but I would love to hear everyone's thoughts?
Thank you for your patience with a "newby"..

 

According to the 96 service manual this is what it should be:

(6 psi)
At 3000 rpm 207 - 552 kPa
(30 - 80 psi)


* CAUTION: If pressure is ZERO at curb idle, DO NOT
run engine at 3,000 rpm.

 

And that makes sense...Just kind of "thrown aback" by the rumbling noise when it first starts?

 

What weight oil did you use when the oil was changed? You can likely pick up a bit more oil PSI with a heavier oil. Regardless, might want to pull a valve cover to see what the condition of the engine looks like. If sludge is encountered when removing the valve cover, dropping the oil pan to check the oil pickup, oil pump and main bearings would be prudent

 

I used 30 weight for both changes. Removing the valve cover does sound like a good idea...Thanks to all.

 

If you take the pan off get plastigage and measure clearances

 

10-4 on the plastigage. Have not pulled the pan, as I had another thought regarding the oil pressure. I have owned this particular truck for less than one month, and I've spent most of my time trying to remove the 14 million dog hairs left by the previous owner, so I have not driven it much. But it dawned on me that the water temp stays in the 220-230 F range. There radiator is full, and I haven't noticed any leaks, so I am hoping that it is the thermostat. It is my understanding that increased operating temperatures will have an adverse affect on oil pressure? I am going to change the thermostat and flush the system..maybe that will bring it into a more acceptable range...

 

That oil pressure is too low for my taste, but I still use the factory gauge and mine sits around 30 on the highway. You might want to do a compression and leak down test as well but you didn't mention it using any oil, so that may not be an issue.

As for the temp being too high, if your truck is an auto, that is too damn high and will eventually toast your transmission as the trans cooler is integrated into the engine radiator. You may have a bad water pump, or clogged rad or even a malfunctioning clutch fan. Does it stay consistently above 200 or just in town?

 

Yes, it was consistently running 220 F. I changed the thermostat this morning and installed and 180 f degree unit, and believe it or not, the temp dropped down to the 200 F range, and my oil pressure increased from 20 to 30, after everything was warm, and had driven quite a few miles. It may not be exactly where I want it to be, but there sure was a big smile on my face. I'm doing the flush job now, as you could not imagine how much crap was in the radiator...UGH..It looked like he had filled his radiator with water directly out of a muddy "Georgia red clay" pond.....adding more clay than water.. My only issue is that I was not able to break that drain plugs loose on the drain ports on the sides of the block. Will probably have to take it to someone who has a lift.. If I can maintain 30 lbs of oil pressure cruising down the highway, I will be a very happy camper.. Thanks to all for your input. These forums are a definite God send..

 

Well, that's a start. Keep flushing, brother! Keep at it! These trucks can be great if you have the patience and will to keep them up!