Lost oil pressure while going through a deep hole, WHY??

[Mud4me]

Here is what happened. The motor is an amc 360. I was out riding with some friends and i went through a mud/water pit that was way deeper than i expected. I was almost out of it and the engine died. The water/mud was in the floorboards, and all around the jeep but not above the hood and i dont think it was above the intake. I tried to restart a couple times to no avail and winched out. Once out and after it sat a few minutes it fired back up no problem, showing normal oil pressure. It ran a couple minutes and then the pressure went to nothing. I pulled a spark plug, cranked it and no water came out. I ended up taking the bypass spring and plunger out, almost lost the cap as it was under extreme pressure, it bounced off my oil pan and went several feet in front of the jeep. Cleaned and reinstalled, put a new oil filter on, put some oil in the distributor hole, and a little in the oil filler. Started it up and had pressure again. Started it the next day and had 50+ pounds cold as usual. Finally my question. What caused this to happen and what can i do to prevent it from happening again if i am in the same situation. thanks

[tufcj]

Electric or mechanical gauge? If electric, it could be just that everything was wet. Go to a good quality mechanical gauge.

If the oil level was low (as little as a quart), and the Jeep was extreme nose-up or nose-down, you may have uncovered the pickup in the oil pan and sucked air into the system. You can run up to a quart over full if you're not doing highway miles.

Bulltear is developing a swinging oil pickup to help with this, or you could go to an aftermarket pan with a different pickup and external lines ($$$).

Bob
tufcj

[Mud4me]

The gauge in the cab is an electrical, but i have a backup mechanical gauge mounted under the hood. It was showing the same pressure as the electrical one. No real extreme angles were involved, just droppiong in the hole and going pretty much level after that. I was on much worse angles before and after this happened and it was fine, so i dont think that was it. The extra quart of oil is a good idea, any downfall to this?

[jeepsr4ever]

It is possible you pulled off the wire going to the sender and killed the motor with water. Unless I missed something

[Mud4me]

No it wasnt the wire on the sender, like i said in the other post i have a backup mechanical gauge that was reading the exact same thing as the electrical gauge.

[ironman_gq]

your bypass plunger probably stuck open causing no oil pressure.

[Goose]

Well My guess is you simply scared the poor jeep so badly it's little sphincter tightend up causing an interuption in oil flow..once you crawled under it an stroked it with a wrench and spoke sootihng 4 letter words it knew it was safe..

[Mud4me]

I was talking to it, but i dont think it was in a soothing tone :shock: :shock: It did get spoken to a little better when the pressure came back up. ironman_gq---The plunger sticking open is a theory i had also, but what would have caused it to stick? I have had this exact same thing happen before, the exact same way in another jeep. The situation was identical, big hole of mud/water, engine dies midstream, starts back after getting out, no oil pressure.

[AMX69PHATTY]

A sudden cooling by the water of the Aluminum Oil Filter Adapter / Oil Pump Cover plate causes it to shrink and sieze the hot steel Oil Bypass Plug in an open position in the bore which the spring cannot overcome to push the Plug back onto its seat ?
:-|

[Mud4me]

Is that possible?? Just before i hit the deep hole, i went through another hole of mud/water that came up about 3/4 the way of my tires. Hit it pretty hard, should have splashed water on the oil bypass assembly. It was fine after that, do you think it would take totally submerging the assembly for it to happen. Another concern is my distributor, the gasket was kinda trashed when i checked it after i winched out. Could water have gotten in there and caused the pump to lose prime?

[AMX69PHATTY]

I'm not saying I know that's what happened, but thinks it's a possibility. Oil is as much a coolant as it is a lubricant afterall. Oil Temps are pretty much the same as the coolant temps, approx 200 degrees F. The cover plate is aluminum and the Plunger is steel and they have different expansion rates and aluminum cools a lot faster than steel. It could explain the high pressure that blew the plunger cap off when ya took it loose.

Maybe get one of those Oil Pump Cover Plates from BullTear that does not have the pressure bypass port in it, put it on the motor, and try goin' through that sippy hole again =D>

I'm puttin' together a motor, think I'm gonna get one of those oil pump covers myself. From what it says in other threads here somewhere, that bypass thing has been the cause of a number of problems with AMC's.

Like I say, I'm not sure if that's what caused it, or if that could happen, but it sounds possible to me, and getting rid of the bypass would eliminate the possibility anyway. Let us know if ya make it through that sippy hole next time. :-|

#-o My bad, the BullTear cover eliminates the FILTER Bypass, not the PRESSURE Bypass, guess it still could help though maybe.

[Mud4me]

The cover that i have installed already has the filter bypass hole eliminated. I guess what i need now is some waterproofing tips so i can make it through that hole. The next time i am riding that area i WILL make it through it.......I hope

[fullsize fun]

you guys are right on about the warm-hot aluminum and then geting sprashed with cold water causeing the plunger to stick ,there isn't a whole lot of clearance there in that bore so it wouldn't take bu a small amount of contraction to seize that bypass plunger.