O.K. here we go.I just bought this truck 1997 5.4 f150 and it had a bad bottom half. I rebuilt bottom half(new rods, pistons, rings, crank, rings, oil pump, new oil pressure sensor. I did not hot dip block but i did clean it good and blew out all oil passages. The problem is I will start it runs good then oil pressure gauge drops and light comes on. Sometimes I weill start it no pressure then it comes on and off. So basicly I have oil pressure when it wants to. It will run for a little bit and sound find then it start to sound like it wants to rattle apart inside so I turn it off. I can wait half hour and it will run fine for awhile. I did change oil and it seems clean no shavings or chunks.

 

With doing all that work, did you replace the oil pump?
Did you check pressure with a gage?
The rattlring tells me no pressure. Why would you keep running it and lose all the new parts?
Maybe the bottom half was lost to a bad oil pump to begin with.

 

As I stated I have changed the pump. Why I keep tring it is because I thought maybe there was something on the screen on the pick up tube. This still pump I dont believe it would do this. I think it would either have pressure or none at all. I dont think it would shut on and off like its doing. I dont know anymore. Its just making me upset thinking about it.

 

I am somewhat having the same oil pressure issue with mine.. I have a 01 supercrew. really bizzare as to what is going on with mine.. when I start it when the motor is cold ( hasnt been running at all during the day or for some hours).. I get no movement on the gauge and the light is on.. but the motor is making no noises once so ever. Once the truck warms up and get to opperating temp the gauges goes up to normal. weird huh?!?! sometime the guage will come up then fall then come up again.. the truck only has 42000 miles on it and just got an oil change with 5w20 oil.. have any ideas as to what is going on..

 

check the filter, did they put on a anti-drain back filter- stick with motocraft

 

what filter are you using? what oil weight? I would consider dropping the pan and changing the oil pump again. It is possible you got a faulty one.

 

I would drop the oil pan and look for debris of some sort. A piece of rag, RTV pieces that were scrapped off the front cover when it was removed. Anything that could block off oil supply to the pickup tube. Also make sure that the pickup tube to oil pump "0" ring was in place when reinstalled. If it wasn't the tube will lose prime and starve the engine for oil. Did you tighten the pickup tube at the pump and at the main cap stud? If it is loose at the main cap stud it will be pulled down against the pan bottom and starve the engine for oil. Was the oil pump tight against the block when you reinstalled it. Also did you place a jack under the oil pan when you removed the engine? I have seen oil pans collapsed because of this and the gap between the pan and pickup tube is to tight to allow enough oil into the pickup tube at higher RPM's. I don't think the oil pump would be defective. It is a pretty good design but you never know. When you cleaned the oil passages did you remove the cup plugs at either end of the main oil galley? If so they may have tilted or were omitted during reassembly. I once found a part identification tag stuck in a oil pickup screen. The engine went over 5000 miles before the tag finally worked its way into the screen and blocked off oil to the engine causing engine failure. These are a few things to check. Just remember if your gage shows no oil pressure and is followed by engine noise do not continue to run the engine. If a gage is showing no pressure and you have no engine noise then chances are it is just the oil sender acting up. Good luck,

 

yeah ,
I am going to drop the pan and see what I have. I believe it will be the pick up screen or tube. what I have found is theat these pumps are almost built proof. I have to let the weather here warm up. I am tired of workingin the cold. It won't fit in the garage. Thanks for all your suggestion. Hopefully its one of those I don't want to pull that pump it a pain.

 

This is a known fault. You can replace your sensor or have Ford do it. There was a TSB about cold soak failure of the pressure switch.
Mine did it too and I replaced it for less than 10 bucks.

 

my truck's been experiencing this lately as well. at startup no pressure and light's on...no noise or anything, all running fine or so it sounds....after a while it'll pop up and read normal.

Is there a place we can get a copy of the TSB for the sensor replacement?

thanx

 

The oil sensor is relatively easy to change. It is right next to the oil filter on the aluminum oil filter adapter ( if you have a block mounted oil filter). If you have a remote oil filter follow the remote filter hoses up to the engine block and the oil pressure sensor is screwed into that aluminum adapter. Just screw the old one out and screw a new on in. The wire is just a push on connection.

 

If the engine makes noise after the pressure drops then that is a sign of oil pressure loss. Often something is loose in the pan and when the engine starts the oil pump sucks it up against the pick up screen. When you turn off the engine the suction is removed and it falls back into the pan. Pull the pan and look for debris. Do not run the engine with no oil pressure.

JMC