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low oil pressure

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Old 10-01-2011, 05:44 AM   #1
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I have a 2000 F150 with a 4.6. I bought it about 4 months ago, about 125000 Mi. On the way home, I stopped at a light and oil pressure dropped put new sending unit in,ok. I got it home realized timing chain was shot, replaced it and all gears, oil pump, cleaned pan and pickup. Ran great for a couple of months, went on a trip last month, came to a light and oil pressure dropped to 0. Put in neutral, went back to normal, doesn't make any tapping sound, pressure fine when in gear or not driven for more than 30 miles. Put a manual gauge on it, drops to almost 0 when stopped in gear. I hooked manual gauge by filter, beside sending unit. Driving me nuts.
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Old 10-01-2011, 06:40 AM   #2
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Long and short of it............bad lower end of the 4.6 Triton. Your oil pump and crank bearings are the only items that are common in oil pressure loss. This motor has no OHV style camshaft, so all the oil pressure is created in the pump and bearings. (Modified and some Windsors would turn the cam bearings, causing the loss of oil pressure, but this motor doesn't have that possibility.

You could check the oil pump for grooves cut into the housing. Most likely you will find this to be your problem. Problem is that the bearings have run with low or no pressure, so they are most likely worn to the copper also. Any excessive wear and you will lose all you pressure when the motor comes up to full operating temperature or long run.

I hate to say it, but looks like you need a short block at the least. You may be able to cobb it together with another pump, but the wear on the bearings won't allow the pump to keep up over time.

One more thing, use a Motorcraft oil filter when you change the oil. These have a back flow check valve, so the oil pressure is immediate when started cold, and not looking for oil pressure, like with a Fram or Wix or Napa. There is a forum on filters on this site, that states that those brands are the worst for Ford motors. Purolator was rated good, as was Mann & Amsoil, but not the K & N's or the AC-Delco OIL filters. The air filters were not listed in the tests.

Hope that helps you.
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Old 10-01-2011, 06:48 AM   #3
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Sorry, I deleted one line of my post.

With the new oil pump (if you go that way again) you will need to roll in a new set of main bearings (at least) to bring up the pressure. Rod bearings need to be checked at the same time. It will be most likely mains and oil pump, to get it back to at least the 20# range in pressure. The OP light goes out at about 7#, and being the Ford cluster, will show in the mid-range of the dash, even though it is really quite a bit lower.

Good luck

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Old 10-04-2011, 09:13 PM   #4
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Thanks.
I will go the route with new mains. I found the trick to removing the oil pan when I replaced timing chain and oil pump. I cleaned the pan and oil pick up. I used to work on tractor trailers years ago and used to roll in mains without pulling the motor, just a little bit cramped on this. Just don't have the funds for a rebuild. Trying to keep the 250 & 350 on the road too.
Thanks again. Just got the recall on the 150 & 250 gas tank straps.
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Old 10-05-2011, 05:12 AM   #5
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Quote:
Originally Posted by jdhog View Post
Thanks.
I will go the route with new mains. I found the trick to removing the oil pan when I replaced timing chain and oil pump. I cleaned the pan and oil pick up. I used to work on tractor trailers years ago and used to roll in mains without pulling the motor, just a little bit cramped on this. Just don't have the funds for a rebuild. Trying to keep the 250 & 350 on the road too.
Thanks again. Just got the recall on the 150 & 250 gas tank straps.
Believe me, I know what you mean. It's tight in there. You wouldn't think so looking at the truck, but damn. No room.

Good idea to roll in the mains also. Let me know when you pull them if you are into the copper if you will. That and the pump are the only things that can cause your problem. I hope you fix it for a decent cost. Parts have gotten so high priced anymore. Glad I still have my old accounts still active, so the cost isn't so bad.
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