New oil pump and sender. All was well for a while then a couple miles from home it drops to zero then starts knocking. Comes back up stops knocking then goes to zero again and starts knocking again. Made it home. New pump was a year ago but I hardly ever drive the truck. Maybe 100 miles in that year. What could cause the drop then come back up then drop again? Oil level is full.

 

1998 ram 1500 5.2

 

I would cut the oil filter open and look for bearing material if there is knocking. If no material I would use a mechancial gauge to get actual oil pressure reading. The gauges on the instrument cluster arent very accurate. If there is no debris and oil pressure loss is verified by mechanical gauge Id drop the pan and take a look at the oil pump itself and then pickup. Look for degris, any cracks on the pickup tube or pump itself. It is a positive displacement pump, however if air is getting into the pickup tube or there is debris on the screen it can cause the oil pressure drop. If everything looks good, the oil pump may be bad again. What brand of oil pump did you install previously?

 

I don't remember the brand of pump. Where would you hook up the mechanical gage? Take out the electrical sender and put in a fitting with a tube barb? That's back by the distributor and impossible to see, isn't it?

 

Why did you replace the original?

 

Pulling the sensor and putting the gauge there is the way I do it so that I can compare what is shown at the instrument cluster and on the gauge at the same port. I recommend the oil pressure tester from Harbor Freight, its $30 and Ive had good luck with it for the random times Ive needed it. For the pump, if you cant remember but do find you need to replace it, I would go with the Melling M72HV High Volume Oil Pump and the Melling 265S Oil Pickup. Upgrading those two will help to push alot more oil thru the engine even filling bearing clearances that have started to wear down some but still within spec.

 

Sounds like something in the pan is restricting the oil flow. Silly question but it DOES have plenty of oil doesn't it? Were the bolts holding the pump and pick up tube were torqued properly with thread locker?

 

Pickup strainer was completely clogged. I replaced the original because the previous owner had bought a new one and said the old one was bad. But when I changed it the strainer was clogged also. It has moisture in the exhaust so I guess the water is fouling the oil and clogging the strainer repeatedly. Plus there is some iron dust in the sludge. I guess it's head work or the junk yard. I hadn't put thread locker on the pump bolt threads but it was torqued and still up there tight. The pickup tube is threaded on, no o-ring. Its a shame. It's a pretty truck.

 

If truck is still in decent shape slap a used engine in there. I got mine for $500 from a junkyard and its still running great. Is all of the oil emulsified?

 

The iron particles are probably from the knocking. I'd find a wreck that was running good when it was hit and snag the engine out of it. I've done this many times over the years and a good engine with a little prep work does just fine.

Before I drop one in, I replace the timing chain, oil pump with a high volume, replace the expansion plugs with new ones after flushing the rust and sand out of the block and generally clean it up. The last time I did that, I got an engine with 90K on it. That engine lasted over 100K and was going strong when the truck it was in broke in half from age, wear and rust at about 395K miles.

If you like the truck, keep it and replace the engine. I don't want anything newer than the year 2000 anymore as they just seem to be too dainty and not very robust. Look at all the engine failures recently from ALL the car companies.