2002 Dakota Quad 4.7 Auto 2WD
Suddenly while driving oil pressure gauge went to zero, check gauge light came on. Took to shop and was told needs new engine..$10000. For $500 they removed oil pan to check pickup. All clean. Towed home, removed front of engine and replaced oil pump, timing chains and guides. Put together, engine runs fine, no knocks..still no oil pressure. Removed sender, oil pumps out sender.Still can figure out why no pressure.

 

If the sender is good, it’s either the wiring or the gauge. Put a mechanical gauge on it to verify. $10000 is an aweful lot of money for an engine.

 

That shop sounds very dishonest and you may have wasted quite a bit of money. Should have simply attached a pressure gauge while the sender was out. I agree that it sounds like a bad sender.

 

Yes the shop repair cost is twice what the trucks worth, I had it towed home and attempted to repair it myself. As for the manual pressure test I did that and it showed zero pressure on the gauge, but when I took the gauge off I directed the open hose into a drain tray. I had a nice steady flow. When the engine runs it sounds great, no lifter noise. I am trying to determine if there is something in the oil galleries that has broken or fallen out or a valve or something that is not allowing the engine to build pressure.

 

If there is truly zero oil pressure, your engine would be making a racket and not sound great at all. Test it again with a different gauge.

 

Yes I will try another gauge, but it seems odd that after trying a new sender and now trying a manual pressure gage...I still get zero oil pressure.....what else could be going wrong. I've looked at all the possibilities everyone suggests..... like sludge blocking the pickup tube, wrong types of oil, wrong oil filter, bad oil pump, leaking pressure relief valve. I've run this truck since new and put on 160,000 miles, and never had a problem. For the oil pressure to be normal then go to zero.....it must be something pretty obvious, but I can't see it. It's like the pump is pumping oil but can't develop any back pressure in the engine, like an oil gallery has suddenly opened up.

 

My thought exacty...pumping but with no pressure, means pressure is bleeding somewhere. I'm not sure how OHC engines oil...since there's no lifters, I would assume that the cam and crank would both receive oil at same time, no priority, and no lifter holes to get blocked or clogged or wide open...
It's as if there is a main or rod or cam bearing clearance that has gone stupid wide. But that wouldn't happen in a quick moment.

 

You hadn't said whether you changed the sender until now. I can't get over there being no noise. So maybe there is low oil pressure, but not enough to register. What is the history of the engine... was it abused? I'd run some motor flush through it.

 

Well I finally tried a good manual oil pressure gauge and yes it shows zero oil pressure, even after I installed a new oil pump. I was reading in the manual that the head gasket has oil restrictors and there are some restrictor plugs in the heads. No after running the engine for a while I see a very slight amount of milky white in the oil......My only conclusion is something blew , either the head gasket or something in the head popped out. Either way I'm done with this truck, on to a new one.