I sold my 98 a while back and missed it so much that I picked up an 03 with a spun rod bearing. I went through the engine replacing pretty much everything - New crank, rods, mains, pistons, rings, etc. The truck had a few electrical glitches from day one so when I started having oil pressure issues I sort of dismissed it. On a cold start, the oil pressure would drop to 0, light would come on and the 'ding' sound. I would shut it down and immeadiately restart and oil pressure would be back to normal. This would happen every cold start two or three times before it would stop. After that I could drive for hours and it wouldn't happen again until the next cold start. After reading on here about bad bad sending units I assumed it was electrical. Well last night I started it up to warm if for its first 1000 mile oil change since the rebuild. I left the truck, went to the garage and when I came back I noticed a little smoke in the headlights (night time). I shut it down, looked the engine over expecting an oil leak - due to the oil smell. Couldn't find anything so I restarted the truck - oil pressure normal, but more smoke. I revved it, it sounded fine but more smoke so I shut it down. Then I noticed the burnt oil smell was coming from the breather, pulled the oil cap and tons of smoke poured out. It was then I realized the oil pressure gauge wasn't kidding, I must have an air leak in the pick-up tube or something? Could be why it spun the rod bearing when I bought it. I should have pressure tested the pickup tube during the build. So, couple of questions, DID I SMOKE THE CRANK? oil pressure was good, and no knocking... #2 What would cause oil pressure to suddenly fall to 0 then be normal on restart? Cavitation? Due to ? Truck has 1000 miles on it since the rebuild about 4 weeks ago and has had the oil pressure issue since day 1. I should note that I checked the oil pump with feeler gauges and it was within spec. Block was honed and oil galleries checked for blockage.

 

You need to check the pressure with a different gauge. Pressure could be perfectly fine or the pressure switch could be acting up.

 

Time to pull the pan bud. When you drain the oil try to run it through a strainer and collect the bearing parts. Good luck!!!
Topper

 

My pressure would drop also, turned out
to be bad oil pump.

 

bummer... doesn't sound good...
anther vote for attaching an oil pressure gauge
use a known to be correct gauge, preferably a high quality one like Snap-on

at first sign of oil pressure troubles... I'd be attaching an external oil pressure gauge that runs into cab, immediately. penalties are too severe to take chances...

 

I'll try to get to the pan this evening. I don't think I'll have pieces in there, it ran no load for maybe 30 - 45 seconds and made no unusual noises. But does anyone have a theory on the oil pressure drops?

Blueboy, could you give me more info on your symptms?

 

Ok, I got the pan off... Good news is I found the culprit, a cracked oil pickup tube. I must have missed it when I rebuilt the engine - or it cracked after the fact? Bad news is the bearings are toast. I only pulled #3 and #4 rods and wow, #4 is mushroomed bad. Crank looks ok on those two and mic says 2.717, clean and round. Had to clean #4 with emory cloth, it had a lot of babbit stuck to it - maybe that is what saved the journal? I'm not counting my chicks until I inspect all the journals though. Has anyone ever reassembled an engine with a marginal condition crank? With scratches, worn down or out-of-round tolerances? Any regrets from not pulling the crank to machine it? So far I'm lucky, but who knows what I'm going to see when I get to the rest of the journals...

 

When you re-do this time, I highly recommend sending your main and rod bearings to swain and have them coated. Makes a big difference. About $180 to do this.

 

Coated? What does this do? Do they last longer?