Help!!! 90 F150 5.8L At start up I have normal oil pressure. However after driving 3 miles or so the oil pressure suddenly drops to O and soon after the engine starts knocking. After shutting down and sitting 10 mins. the oil pressure returns to normal upon start up. However it quickly drops again after starting to drive. I regularly change the oil. I did an engine flush. Fluid seemed relatively clean. Replaced oil and filter. Same thing happened again.

 

The oil pump pickup screen is probally plugged with sludge (a common problem on these engines) To repair you'll have to remove the oil pan & clean it & the pickup screen out. I'd replace the oil pump as well. Hopefully the bearings have not been damaged---you might want to take a look at those also.

 

Thanks for the reply Tailgator. Thinking it probably was the oil pump, I attempted to remove the oil pan. Ran into the problem of not being able to remove the pan. I jacked the engine up until it made contact with the firewall but still could not get to the oil pick up bolts. I concluded that the engine has to be detached from the trans. or maybe between the trans. and the transfer box and lifted up and out. Is this a correct assumption? If so at which point would it be the best to seperate. Or should I be able to drop the pan without doing all this?

 

Kent-
You can remove the oil pan with out separating the trans. What I do is disconnect the motor & trans. mounts, raise the engine & trans. as high as they will raise, remove the exhaust crossover pipe(if it still has single exhaust), with the oil pan as far down as it will go, reach in & remove the oil pump & pickup tube bolts/nut, let the oil pump, pickup & oil pump drive shaft fall down into the oil pan. Then you can remove it from the rear. Hope this helps!

 

Souds like I was almost there. I had done everything you wrote but having such a small space to reach in up towards the front of the oil pan to disconnect the oil pickup tube bolts/nuts I was concerned about getting it back on when putting everything back together. Any tricks or just persistence?

 

Just takes a little patience, install the pickup tube & oil pump drive into the pump, then set them into the oil pan before installing. You can tilt the oil pan to the side a liitle to gain more access. just make sure the oil pump drive engages the distributor before you tighten the bolts. Good luck!