I have a 2001 Ford F250 V10 with about 70,000 miles on it and now the gauge indicates low pressure when my warmed up truck idles around 1000 RPM.

I went off road the other day into some mud and since then I have had my oil pressure gauge reporting low at idle and normal when moving.

I was a quart and 1/2 low on oil which I filled and the next day I changed the oil. I then had taken it Ford shop who replaced the oil sensor and said all fixed. It wasn't and I took it back in ... now the mechanic indicated it is probably the crankshaft bearing based on his experience and I should replace the engine.

This seems drastic? Wouldnt' the next step to go check/replace the oil pump?

 

In my opinion a qt and a half is pretty low. But 70,000 miles seems awfully low to need an engine replacement. Have you tried hooking up a real oil pressure guage ( mechanical) and check that way. That's the first thing I would do Is make sure there's pressure. It's possible that being low on oil and high rpm off roading that something got starved for oil and got hot. Do you hear any knocks or other noises? Of course ford is going to say replace the whole engine because that's all a dealer does, they just like to throw parts at it hoping they fix the problem especially on the customers dime. I would take it to a shop that knows modular motors especially the v10. The V10 is a very strong motor I had one in my old 00 F350 with 175,000 very hard miles on it and I still see it driving around pulling a landscape trailer with over 200,000 miles on it. At most if the main bearings are going bad all you need is a set of bearings and an oil pump. Oh and stop driving it untill you verify with the mechanical guage if theres pressure or you might need a replacement motor! I'm sure someone will chime in with the correct pressure. In my v10 I had 45psi at a cold start in 39 deg weather so it will vary I'm sure. Keep us posted!

 

The guy at Ford dealership said he got the following pressure measurements:
Cold @ 1000 RPM: 55
Warm @ 1000 RPM: 35
Hot @600: 10
Hot @2000: 20

I've been just driving short trips for the moment; guage doesn't drop to low at idle until after about 10-15 minutes of driving at which time I just give it a little gas bringing up to 1000 RPM where the guage says OK. I'm thinking I'm OK with that until I can get it into the shop next week.

 

I have to go out of town for the week; but, when I get back ... my plan is to have someone drop the pan replacing oil pump and put in a 50w oil. I am guessing a $600-$700 job. You mentioned replacing the bearings ... I'm guessing thats pretty expensive; but, I'm sure not as much as the labor and cost to put in a rebuilt engine. Thoughts?

Thanks in advance for you input.

 

Do not run 50w oil! Im pretty sure the motor has to come out either way. once the motor is out and the oil pan is off the bearings are right there. so maybe 200.00 more if thats the case. The timing chain tensioners are actuated by oil pressure as well as the cam followers and you will do more damage with the incorrect oil weight

 

If it were me I would spend the $30 and get a UOA. If the oil has been run for a while and the bearings are in rough shape the shed bearing material should show up in the UOA.

As for oil the thickest I would go to is a 5w-40 motor oil but that is really just a band aid if their if the bearing clearance is out of spec.

 

I would not worry about oil pump. Its most likely a leaking timing chain tensioner. Had several 5.4l and 6.8l with this problem