2001 Venture, oil pressure light goes on after engine is good and warm?

Got the car 2/14. Wasn't long before we determined it had a leaky manifold gasket. Time went on, I took it off the road because of lifer noise. Water/coolant was getting into the oil. Seam Foamed it, noise gone, then since I didn't have the money or time to replace manifold gasket (or head gasket too?), I poured Barr's Block Seal Head Gasket Fix (tall round bottle). Started overheating first 2 starts, then 3rd time thermostat opened up, strong heat from blower. THEN oild pressure low light came on. I shut it off. Started it up 3 times since then, still comes on. And this is after another oil change (didn't change filter or sender yet). This could be a leaky sender, or a leak somewhere else. I remember seeing oil leaking onto the starter a year ago, but I though that was because I had synthetic in it at the time. Oil pan was kind of oily, and after sitting months. Is it likely this is an oil leak somewhere, or a bad pump, or bad engine? Thanks in advance.

p.s. I also heard about a guy backwashing his pump screen by pouring B-12 in crankcase, letting it sit overnight, draining oil (and B-12), then repeatedly pouring diesel fuel in dipstick? (or strait in crankcase?), letting it run through opened oil pan, filtering through a screen, about 20 times. Said it worked like a charm. Chances are this isn't about a clog (I'm guessing). Either a bad switch or oil leak somewhere.

FWIW, there is no way to "backwash" the oil pump pickup screen without running the pump backward. Pouring anything into the dipstick simply drains it directly into the oil pan.

If coolant was contaminating the engine oil there is a chance that the main and rod bearings suffered damage, and the excessive clearance is causing a drop in oil pressure. It is possible to remove the oil pan and windage tray with the engine in the vehicle to inspect the bearings and crank (except the rear main bearing) and also to inspect the pump pickup screen. It is even possible to polish the crank journals to some extent and replace the bearing shells (again, all but the rear main) and this may help the problem. However, removing the oil pan requires supporting the engine from above and removing the subframe mounts since the front mount is connected to the oil pan. This is an eight-plus hour job for a properly equipped shop, and may take much longer for an average weekend warrior.

Coolant and water in the engine oil is NEVER a good thing. And they wonder why I frown so much on people advocating SeaFoam in the crankcase. The next problem is that the cam bearings could also be washed out, and all your effort could be in vain.

If the vehicle is otherwise in good condition and is worth the expense, it may be more effective to replace the engine with a remanufactured long block and solve all the potential problems caused by coolant contaminated oil. The labor and parts costs involved in replacing the bearings with the engine installed would likely come close to the cost of an engine R&R. A remanufactured engine can be had with a warranty for about $2K.

Quite frankly, if the vehicle is a typical 2001 Venture it also has other issues. If that's the situation it may be best to simply change oil to something with a higher viscosity what was originally specified for the engine. The oil clearances the engine was designed with are probably no longer valid, and it must be dealt with in another way. Older engine had greater clearances, just like yours probably does now, and those older engines used higher viscosity oils. Using a 10W40 or 20W50 synthetic (instead of 5W30) might help it maintain pressure better so that it doesn't continue to destroy itself from inadequate lubrication. I would heartily suggest a synthetic since they tend to be a lot more viscosity stable and tolerant of water. Additionally, synthetics tend to clean far better than mineral oils, and cleaning out sludge and deposits might actually and eventually help improve the situation. The engine probably needs all the help it can get now.

I would also suggest avoiding the use "designer" oil filters marked for synthetic use. A standard duty filter (such as Purolator) will flow better and restrict less than a high-purity synthetic filter, and you really don't need any more restriction if the oil pressure is already low.

all very good info. Thank you. (I actually had hoped I'd be able to come back and tell you your concerns were all in vain. But read below).

The "low oil pressure" light issue seems to have alleviated itself. But ... as when in late November when I first heard the lifers? making the racket, the "low oil level" light came on a bit. Still does intermittently, but clears up before long (either turning car off and restarting, or driving a few hundred feet). I dumped the intake manifold Barr's stuff, and it's holding. But after a 20 mile drive w/some stop and go, you hear a low thumping, not loud, coming from I presume the engine, though not sure. But the other day I was driving only about 4 - 5 miles, sitting in traffic for a while, and the heat started increasing, not that bad at that point, but the engine starting making noises similar to the original. If you're driving w/o stopping, the car does not heat up, quite the contrary. But if you sit in traffic, things go wonky, all kinds of racket, at least as bad, probably worse then the original lifter noise. Not sure what's causing the car to get heated up, and mind you the thermostat is out, and the heat will blow strong before very long!!! I thought you weren't supposed to get any heat w/the therm out???

After the drive the other day where the engine was making all sorts of noise, I parked it, started it up a few times throughout the day, and the noise/s seemed to diminish. By the next morning there was no noise. It's like something is restricting oil flow perhaps, and the engine starts to heat up I guess.

I hadn't mentioned prior to the Sea Foam treatment (the whole bottle), I changed the oil, but used a diverse mixture of 1 q. Rislone, 1 q. tranny fluid, and whatever oil I had laying around. After 10 minutes I poured a quart of Gunk engine flush I had laying around forever ran it for another 5. Then I changed it again w/whatever I had, and the Sea Foam. At some point I even had some 5w20, maybe Mobile 1 or whatever. During one of my mad mixtures.

Again the engine sounds fine when you start it up fresh. I even drove it a few miles today, no sounds or issues. I think after I BUY ANOTHER CAR to run around in, I'll eventually change the gaskets, maybe even the head gaskets, and deck the heads if necessary, throw 10w40 in there in place of 10w30 and see what happens. The engine may need an overhaul (or replacement). I guess I got to take it one step at a time.

Would love to hear your feedback. Thanks for what you've said thus far though. Good stuff.