Hi all!

I was trying to help a friend of mine diagnose a 2000 expy with a 5.4l in it. It was sitting for just a few weeks and when we went to start it today and let it warm up it lost oil pressure after running for maybe 2 minutes or so.

I wasn't sure if it was the light or not but then it started to knock! ack! So it definitely lost pressure. We checked the level, it was at the 'add', added some oil to it, tried again, same thing.

So, I'm at a loss here.. what would cause it to lose oil pressure after a few minutes of running? In my experience the oil pump either works or it doesn't.. is there something that could be bleeding it off? Maybe timing chain tensioner or something?

Thanks!

 

1. There could be gunk in the oil pan that is clogging the pick-up screen.
2. The filter could be plugged.
3. There could be a spun rod bearing.

 

It could also be pieces of the cam chain guides clogging the pick up, but a spun bearing is very likely.
How many miles on the truck? Has it been run very low or out of oil? Has it been severely overheated?
These are all factors to consider in the diagnosis.

Need more input.

 

I never realized it was different, but it's actually a lincoln navigator with the dohc 5.4l.

It has 223000 miles on it and I'm quite sure it has always been well cared for. The last time it was driven was on a 1000mile trip and said it had no problems. The oil was at the 'add' level but that shouldn't have caused this.

After doing some reading I'm kinda thinking it might be the chain guides plugging up the pickup, but you're right, it could be a spun bearing.

How common is the chain guide thing? Do they just get brittle with age or something? I found it so odd that it would have pressure for a few minutes and then stop.. that's why I'm thinking the chain guides.

I think I'll drop the pan and see what it looks like. Can that be done on a 4x4 navigator without pulling the engine? Maybe you can jack it up a bit?

Thanks guys!

 

I should add those are pretty much all highway miles and it was never really used for towing.. so while the mileage is high they were fairly easy miles..

 

I just went through an engine change on my 2000 navigator. It was severely abused and looked like the oil was never changed. The engine was broke when I bought it, a broken driver side cam chain, and because the engine was so nasty inside I just replaced it. I haven't taken it apart yet so I don't know the inside condition as yet.
The cam chain guides do get brittle with age and heat cycling, especially overheating.
The oil pan can be removed for inspection on a 4X4 as I have done it on my Expedition. It does require removing the crossmember that supports the front diff. and some gymnastics to remove the oil pick up, but it's not all that difficult.
Regular and timely oil changes will keep the engine looking nearly new inside, my 1994 Mark VIII has nearly 200,000 miles on it with Mobil 1 synthetic and inside is very clean and it uses no oil between changes.
If the chain guide(s) disintegrated the bits could have clogged the oil pickup screen and caused oil starvation leading to a spun bearing.
Good luck with it and keep us informed of your findings.

 

If you pull the pan for an inspection and the problem is a clogged oil pick up by chain guides, you might as well check the last 2 rods on the crank and if the bearings are going bad but the crank is not scored badly you might get away with just replacing the bearings on those rods but you will still be faced with the chain guides. All of that can be done in frame.
The job of R&Ring the engine in my Navigator has taught me that lifting the body off the frame is the easiest way to go. It's either that or cutting the radiator support like the Excursions and F 250s for room to work in.

 

That's good news on the pan. So you're saying you can't pull the front clip on these trucks? Sorry I haven't worked on anything new really , but have lots of experience on older vehicles.

I don't mind cutting the rad support and could even weld it back up after.. I have a plasma cutter, welder etc. Does that let you get the front grill/rad out of the way so you can pull the accessories and timing cover?

Like I say I don't think it will be that bad inside. If it did spin a bearing it would be very recent as I do believe him when he says it wasn't making any noise on the resent trip. So in theory the only knocking it's done has been at idle and only for a few seconds. I will definitely check the bearings when I have the pan off though.

Hopefully I will find out more soon.

Thanks for the great info!

 

Take a look at a Expcursion radiator support, it unbolts and you have access to the entire front of the engine. Ford made the Expeditions and Navigators as uni-bodys bolted to a full frame, While I was doing my engine R&R on my Navigator a friend was doing the same on his Excursion and when I saw the radiator support was removable I got very jealous of the ease of getting to most everything and I came very close to getting the cut off wheels busy. If you do cut the support I suggest that you add a little material and make it a bolt in part as it really does nothing to strengthen the body. You may never have to remove it again but the next owner may appreciate the consideration.
If you've never done a late model Ford engine I suggest that you take lots of pictures with a good camera. There's a lot of stuff that has to be disassembled, unplugged and unbolted. Then it all has to go back together the way Ford built it or you will have lots of problems. Inspect all of the electronic controls like the IAC, etc. and be ready to replace some of them. one last thing, be sure you carefully clean the inside of the middle intake manifold EGR port as they get full of crud and if theres a problem there you will have to take the mabifold apart to cure it and replace the EGR valve while you're doing the job.

Good luck with it and keep us posted on your progress.

 

Sounds like a rod bearing to me. It will spin over OK when cool but start to knock as it warms up and the pressure drop shows because the passages get blocked as the engine warms and expands.

I seriously doubt you can just replace bearings. That is not how it works. There is a 99% chance the old bearing has welded itself to the crank or rod, or both.

The cheapest fix is a used engine.

Good Luck

 

Wow, thanks for all the info guys!

I finally got around to pulling the pan.. First I took the oil filter off and cut it open.. man was it plugged up. Then pulled the pan (I found it easier to just drop the front diff and it just came right out.. it's only 1 extra bolt).

The oil pickup is nearly completely plugged up with what I assume are bits of chain guides, although it kinda seems like it could be carbon too but it's really hard to tell. There was also some kind of white plastic clip sucked into it as well.

So that's why it has no oil pressure obviously.. now I haven't pulled the con rod bearings yet but I did try to wiggle them and while they had some side to side movement they all felt very solid in the direction of load. I presume the side to side slop is normal.

You were right about the space in front of the engine.. it looks like if I just pull the fan shroud and the fan and maybe the rad there would be lots of room to work on it.

So I guess I need a book or something to figure out how to get the front of the engine apart and I need to decide if I want a whole new timing chain/kit or just new guides..

How are the trannies on these vehicles? You think it's worth doing new bearings, timing chain etc while I'm in there? hrrm, the cams are in the heads which means I'm going to have to pull the valve covers? Might even be worth getting the heads done.. The oil is black so I'm guessing it has worn valve guides.. starting to sound like a rebuild now..

hehe, anyway, thanks for anyone who reads all that . Lemme know what you think.

Thanks!

 

I should mention I bought it off of him for $1000 since he didn't want to deal with it.. so I'm going to see about fixing it.

 

You must do the bearings now. Unplugging the oil pick up isn't going to fix what has ben damaged. If the engine was knocking and the oil presure gone, there IS a spun bearing.

I would do just what Mel did, buy a used engine and replace the bad one. If I had a plasma cutter, like you do, I would cut the rad support and yank the motor that way.

 

Not necessarily, the knocking only happened after they started it and let it idle, it wasn't driven with the knocking. I would remove the connecting rod caps and mic out the crankshaft journals. If they're within specs., replace the bearings and fix the chain guides. It'll be a whole lot cheaper than replacing the engine. Not to mention, a used engine could end up having the exact same issue in the near future.

 

Before making a decision on rebuilding v. replacing you should, by all means check those last two rod bearings. If they only show minimal wear and the crank looks good I would check for color codes on the sides of the rod journals, dabs of paint, and try to buy the correct bearings from Ford for that size and color code. Oops, I forgot, it's "colour" for you northern Americans. The color indicates the final size in ten thousandths. But it shouldn't matter too much in an engine with the miles that are on yours. Just match the size and replace the rod bolts. If the bearings show more than minimal wear, polishing, on the upper half but the crank looks and checks good, replace all of the rod bearings and bolts. If you have to replace the mains, I would pull the engine. The rods I would do in frame. The cam chain kit would be a definate replacement item and with the radiator support and condensor in the way it will be a lot of severe bending over the front of the truck. To me that would be time to cut, weld and paint to match.

I strongly suggest that you buy an original Ford service manual on CD as you will find nearly all of the info you need there. These 32 valve engines are interference engines and care must be tak3en that the cams do not move while the front is disassembled and the valve springs may apply enough pressure on the lobes to move 1 or more cams enough to create a timing problem. DO NOT DISASSEMBLE the front of the engine until you are ready to reassemble it the same day! That is a job that will require your full attention from start to finish! I would start fresh in the morning and stay with it until it's done.

Just one last thought, the noise you described could have been in the timing chain area or even a lifter not getting enough oil to pump up. If that is the case you might just find good bearings and in that case you will only have to replace the rod bolts (that you took off) when reassembling the bottom end.
Good luck with it and keep us informed.