I am having problems with my oil pressure and could use some help to figure out what is going on. It started out as slow to get pressure on start up but once it got pressure it was fine. I have changed the oil quite a few times in the past two weeks trying to clean anything out that could be in there. I would get slightly different results with each oil I use, but basically I put castrol 10w40 in last night with slick 50 and a motorcraft oil filter and I get fine start up pressure, but after it runs for 15 minutes I start getting a drop in oil pressure if I press on the brake. It bounces some in park after that long, but keeps pressure for the most part and is always fine when going down the highway. I am going to try a sending unit but since I get different results with different oils what else could it be? Also if anyone knows the exact location of the sending unit on a 97 f150 with a 4.6 i would appreciate it.

 

pitch the slick 50 in the garbage where it belongs not to cut you down but to many people are suckered into thinking that the crap works spend yor money on good oil try a 20w50 if all else fails if changing the pressure relay dont work stay away from qawker state also every motor i have torn down that the owner used that stuff had a terrible sludge buildup i have even seen oilpump pickup screens plugged from it let us know how it goes

 

thanks for the quick response 7. I was told to use some stuff called auto-rx ever heard of it? the site is www.auto-rx.com and I was told that it is suppose to be real good. The guy scared me telling me that the slick50 was going to kill my bearing so I am going to dump that tonight. If the screen is plugged do I undo the motor mounts and trans mount, lift the front of the motor so I can unbolt the pan and just clean the screen. Sounds not to bad, but I have been told that it books out in 10 hrs. Has anyone heard of a pump working strange like this?

 

did you change the sending unit? if you cant locate it AUTOZONE has a locators section on their site also a good shop manual section to as far as the auto-rx ive never heard of it before the only add. that i have ever seen do any good is engine restore most of the junk on the market just gum up your motor making things worse

 

I haven't got out to take a look at it yet, I think it might be right above the filter on the driver side bumper. However I could not find it on the autozone site. I'll be out to take a look at it in a couple hrs.

 

Alright so I replace my oil pressure sensor tonight and got interesting results. The truck starts up and once I hit the gas once I get steady pressure on my gauge. And it is fine for about 20 minutes and the starts to drop quite a bit when braking. Once It is put in park and the idle is up all is fine again. This is much better than it was before but obviously not perfect and still scares me some. I still have the slick 50 and castrol 10w40 in the truck since it was making progress I wasn't sure what was giving me progress. My question is what to do next and what is my problem. I don't know if it is an oil pump (would it be getting better?) and is there and possibilty it is a bearing? It doesn't knock when it says there is no pressure but between fresh 10w40 and slick 50 the rockers and bearings would not be dry. If anyone could help me figure out what is going on I would really appreciate it because I am pulling my hair out.

 

need some more info. how many miles on motor, is there any engine noises before and after pressure loss? just how much pressure do you have after warm up and at low pressure? did you try 20w50? it could be worn mains, plugged pickup even a faulty gauge

 

Your gauge is an IDIOT LIGHT. It will change with voltage differences. Have your battery and charging system tested. The belt may even be slipping causing a voltage drop when you hit the brakes. NEVER rely on the stock gauge. The first thing to do when you see it start to move is get a REAL gauge and see what your pressure really is. It also runs in my mine that spec for the motor oil in these is 5w30..... The thicker 10w30 may be creating some problems of its own.

 

your right with the gauge subject but as far as oil concern 10w40 is not that heavy . with my high mile engine the only way i can keep any oil pressure is to run 20w50 the mains needed replaced a long time ago and lots of internal leaks dont want to put any more money into only work truck still running strong with fair oil pressure also my fiance has run 20w50 in her 4 banger since new now has almost 250000 miles on it it calls for 5w20 only time we run that in it is winter heavier oil will boost pressure if worn bearings look at the 351m-400s everyone knows about their problems with lack of oil pressure ive kept many of them alive with heavier oil

 

The truck odometer has 160k on it. I was told the motor and tranny were rebuilt 50k ago and looking at the tranny and the fluid it might have been, but as far as the motor who knows. The pressure is in the upper middle of the gauge when fine and low drops down to the bottom red line but generally bounces back up to the lower quarter of the gauge. Could be low voltage causing it. Any ideas were I can read up on putting an aftermarket gauge in?

 

im having the same problem your having in my 97 f-150.i start it up and the pressure is fine.but after about 30 seconds to a minute mine drops.Also noticed that when i give it gas it will start to flutter.i also changed my oil and filter.Im praying its not the oil pump.Oh yeah and if i keep it running after it drops it will start clicking.

 

im still leaning towards worn main bearings or oil pump problems hope its not so try a aftermarket oil pressur gauge first most include a replacement sending unit that replaces your factory one if after replacing the gauge you still have low pressure try the heavier oil all depends on how deep you want to get into the motor

 

10w40 really appears to be working. Every day I am getting better oil pressure now and it is just about normal again. Kind of makes me think that I might has some worn bearings, but it really could have been sludge on the oil pump pickup screen as well. I have changed the oil about 5 times in two weeks and now all appears to be well for the time being. I suppose I'll just keep frequent heavy oil changes and so how it goes. If it continues well I'll just run it as long as it isn't knocking. Thanks for the input. If you have any more ideas or this leads you in a direction of the overall problem let me know. Also to do an oil pump on one of these 4.6's do you really have to take the timing chains off? The chiltons says you have to take the timing chains off, but other people have told me you don't have to.
Thanks

 

Yes you have to remove the timing chains to replace an oil pump on one of these.
Like others have said, I would start by installing a good mechanical gauge and see how much oil pressure you really have.