[font size="1" color="#FF0000"]LAST EDITED ON 06-Jan-01 AT 04:04 AM (EST)[/font][p]I have a 1990 F-150 w/ a 302. It has 150K miles on it. My father had it before me and drove the first 130K mainly on the highway. He had the oil changed regularly (I thought).

It suddenly developed a problem while driving the other day. The oil pressure dropped to nothing. Given that the gauge is not accurate, I only worried when the engine got noisy. I shut down and restarted about 10 minutes later. The pressure was fine. I had the oil changed.

Now, the pressure is fine at start up and fine at idle. If I start driving (raise the RPMs), the pressure suddenly drops to nothing and the engine clacks. It doesn't matter if the engine is hot or cold.

I had the oil pump and screen replaced. It was a mess with sludge and crap. The new parts raised the idle pressure slightly, but didn't help the real problem.

The mechanic (who called several others) and I think that oil is getting to the top end, but can't get back quickly enough. Maybe clogged oil returns.

Any ideas on how to get the engine clean without a rebuild? I know it probably needs one anyway, but I can't afford it right now.

 

you can try pouring kerosene or diesel fuel into engine and run it for a while. this will loosen some crap. but it can open a can of worms and cause as many problems as it solves, such as leaks where the gunk is caked up inside of valve covers near gaskets.
if you have to rebuild anyway, it might be worth a shot.

 

Thanks for the response Billy. I tried a flush and some diesel yesterday. It loosened enough junk to plug it up even faster.

Man, I sure hate to think about rebuilding, but then, the truck's still worth $4 or $5K and I can't afford to buy another one.

dand

 

scour the classifieds and i bet you can find a motor that runs for a few hundred bucks. throw this in until you can build the other one right. youmight even find a rebuilt or low mileage engine and not have to mess with old one!

 

Try dropping your oil pan. It sounds like your oil pump screen could be clogging. If that's the problem then a new pump would be a cheap investment while you're cleaning out the pan.

 

Sounds like the bearings are worn out. Was the truck used for towing or did it overheat?

 

Never overheated and rarely towed anything. I thought about the bearings, but I've been told that worn out bearings causes low oil pressure at low RPMs. This problem is just the opposite.

Thanks for the response.
dand

 

Try buying some STP Engine Flush. It's fairly cheap. (Around $10) It's basically a mild solvent that you run through your engine for about 20 minutes and than change the oil/filter. It does wonders for sticky lifters. Or if you have some ATF lying around throw a quart in the engine about a week before an oil change, ATF has a high detergent level and can to a good job of cleaning out an engine. My engine is prone to sticky lifters and I usualy add a pint of ATF at every oil change. Good luck!

 

 

I'd do what Laka says, I have experienced a similar problem on a 79 F-150 with the 400. I put a quart of ATF in ran it for about 2-3 days, changed the oil, and did it again (add ATF, change oil). It seemed to fix it as it doesn't drop pressure and clatter any more and it had around 200 k miles on it and never been cracked open (besides a valve cover gasket change). I know it needs a rebuild soon, but I will be swapping for a built 460 that's in the garage this summer. Hope this helps.

Karl