I have a secret shame. But I'm among friends so I guess it is okay to tell.

I swapped my engine last week and have been getting low oil pressure at idle sometimes. Also, when I start it up, it sounds like there is no oil for a couple of seconds. I've had this engine awhile and it just sounds different. To me, it sounds like the oil isn't there at the first of startup. I think it is flowing back out of the pickup tube.

I've ordered a real oil pressure gauge and the sandwich, among other things, but it hasn't all arrived yet.

I use Rotella. The oil pump is 3 days old and spun as it should in my hand. The oil pressure sender is also new. I do have an oil cooler (stock). I took the hit and blew my own personal air through the oil lines to be sure they weren't obstructed before I attached them. It is hard to blow Rotella but it came out the other end. The only oil leak I see is a tiny bit from the front crank seal because I reused it (had less than an hour run time, but I guess they just can't be re used). I packed the oil pump with Vaseline. I've put my finger over the dipstick tube while it is running and do not feel any pressure. I have no idea how many miles are on this engine because I have swapped before but I'd say about 140000. I don't hear or feel any slop in the bearings and I'd say the bearings are suspect except that I was using this engine before a failed swap and it didn't have low pressure, ever. No leaks on the front cover or oil pan. Temperature is about 60 degrees at startup. It just sounds wrong. No ticking or other of sounds once the oil pressure hits the engine but at first it sounds like it doesn't have oil; like it wasn't ready for me to turn the key.

The oil is nice and thick and doesn't smell of gas. I don't have any misfires.

I suspect the pickup tube. When I pulled it to redo the front cover oil spilled all over me, meaning that it was holding a vacuum for oil purposes I guess. For some reason I wasn't expecting that. It tastes bad, by the way. But I did replace the o ring with one I had in a box from harbor freight. Not official, not OEM, but it looked identical. I did clean the screen with brake cleaner sprayed from the top of the tube and the brake cleaner flowed freely. The screen just had some tiny bits of rtv on it. Nothing that would block it. The oil light goes off after it should at startup, if maybe a second or two behind its old speed.

So, obviously I am going to drop the pan and check the pickup tube, and probably replace the bearings. Joy. But before I do that does anyone have a great tip for sealing the oil pickup?

OR, could the Vaseline have just gunked up my filter? I'm using a Wix filter and I haven't changed it since the first startup.

 

It could be other things but not the oil filter, because it has a safety bypass valve & even if paper element is totally clogged, bypass valve will immediately allow oil flow, unless it's stuck/broke which very unlikely,

 

I'm glad you mentioned that. I've never done anything at all with my bypass valve. I'm only vaguely aware of its location and that it is hard to get apart. If the bypass valve is gunked that releases oil pressure back to the sump, I think, because it thinks the system is over pressurized. I'm not sure. Maybe I should read about and check that. Why do you think it is unlikely?

 

Correct. The oil filter was manufactured with a "safety" bypass valve in the occurrence an obstruction restricts flow.

Check this out. Excellent read on the operation / function of bypass valves - also provides elementary anatomy lesson.

Exactly how does a bypass valve work? | Engine Oil Filters | Bob Is The Oil Guy

 

you "might" want to check the bypass in the front cover. but i would wait in the gauge and get a pressure first

 

That's an excellent thread explanation of the bypass in the filter. Thanks for that. I guess I

My imagination based on what I hear is that in the morning the oil has flowed back to the the sump instead of staying in the pickup tube, oil pump and passages up to the open portion of the crankcase. Recall that when I removed the pickup tube oil came out, and I wasn't expecting that use I'd drained the oil. I understood that to mean that things were tight enough between the pump and the bottom of the pickup tube to hold the oil in place for startup. To me, the current sound and wait for normal pressure is the same as when you prime the pump on the first startup, if alot shorter. I hear a louder engine noise and some clicking and ticking, then the oil hits and it goes to a relatively silent running engine mode.

The front cover bypass... and any low oil pressure indications really... is new to me. But I think something is open or not sealed that shouldn't be and I hate to replace seemingly good bearings without exhausting the other possibilities. But once I take the oil pan and front cover off I might as well do everything.

Could the slight drip from my front main seal (new one arrived yesterday) be letting enough air in through the pump gears to allow to oil back to the pan? Seems unlikely you me because I have gone a year with a front deal drop before and didn't have this issue.

I am all ears.

I have a spare front cover to mess with. Time to crack the RAVE! Ugh.

 

I am still armchair quarterbacking my issue but I had another thought that may be relevant. Some know that I had a 4.6 remanufactured and ended up pulling it out last week because it did not sound right during breakin. Also, the oil light came on. When I opened the valve covers it looked to me like there was very little oil on the rockers and valves because it did not go over the head bolts to the return oil passage.

The oil related parts that I used from that engine when I put this 4.0 back together are the front cover and oil pan, and the pickup tube. I changed the oil pump for another new one. I just remembered that my original 4.0 front cover is still in the garage because it uses a different oil pressure switch and the one on the 4.6 cover was brand new. Also, I'd used gasket adhesive in the front cover and it is really difficult to get off.

Oil was circulating in the 4.6 because the filter was full (I'd forgotten to file it when I installed it, so oil was pumped into it, and there was oil in the bottom half of the engine and on the cylinder walls, though not much.

So that points to the pickup tube or something in the front cover. I also didn't mention that I used some black rtv on the pickup tube mating surface and it definitely had time to dry before I primed he pump (overnight). Maybe that will spark some ideas.

I'm not hesitant to drop the pan and front cover; I just want to make sure I have the right parts ready when I do. I am hesitant to replace the bearings only because it is such a PITA.

 

If you had good oil pressure on 4.0 engine before, then the suspect can only be things you replaced not the things you didn't touch, so as you said bearings can not be suspect.
Since Pickup tube was replaced it also can be suspect, but you will see an obvious crack or something,, unless when you put rtv for some reason (unknown) mating surfaces aren't airtight, which is unlikely unless rtv let go & now there is a very small gap that allows air to come in & drains oil from tube when left alone for long time ,, (but if you shut engine off & crank again after short time it still holds oil & you don't have issue),,,,
Other thing you replaced is front cover which can be more suspicious, since you say you took it from a 4.6 that had oil pressure issues & didn't send enough oil to top of engine & heads, that could have been the problem in 4.6 to begin with,!
Also you mention seal has small drip, well how much drip,? If you can see it dripping a little bit while engine running, I would say that's too much, because seals work like a one way valve,, and it holds pressure from working side (inside engine) much better than back side which you can see when cover is in place,, Because it can suck air in much easier than it will let oil out,,,
But the fact that you say 4.6 had very little oil pressure & didn't have much oil in heads after you removed valve covers, (& had not changed the seal yet & it wasn't leaking) points more to the front cover more than the seal itself,,
(I would suspect front cover most, because if something was wrong with pickup tube, you would have noticed it much easier than a problem with cover),
----
When you start an engine & it has oil starvation for 2-3seconds & you can actually hear it (as you mentioned yourself) you are doing far more damage in those startups than driving it with good oil pressure for thousands & thousands of miles, because with oil circulating adequately metal parts don't touch each other, they just ride on oil film, & I case of bearings oil pressure actually made a a wedge in between crank & bearings, so they never touch each other (in perfect world),

 

I appreciate you hashing this out for me; that's why the forums are so great and why I still have my rover.

The 4.6 was off of my parts rover. I forever regret doing anything to it other than the head gasket because the only issue it had was an exhaust leak from the head gasket. But it was also gunked worse than any engine I have ever seen so I had it done at an engine shop, done right, crank was turned and new cam installed with new cam bearings, done over an extended period of time with meetings, etc. But it was left to me to put new bolts, washers, bearings, gaskets, rings, etc. in it, and I think I did a good job at that (followed the RAVE to the letter, took weeks to get the right stuff, etc.). The engine shop never touched nor saw the front cover. I installed a new oil pump, cleaned it up, put a new front seal on it, and a new gasket and o rings (I have an oil cooler). The break in run was a trauma. A fuel injector stuck open, resulting in both thinned oil and a hydrolocked cylinder. A rod bent and the bottom of a cylinder came in contact with the bottom of a piston. Real bad. I have a thread on it. This was my first break in. So I took it out and ascertained the problem, got new parts, etc. This same front cover then went on my 4.0.

After replacing the parts (including a new rod and piston, and having the cylinders checked) I put the 4.6 back in it did not sound right. Rather than risk damage I just stopped it and took it out, after taking some steps to figure out what the problem is. It had a few misfires, too, but I prioritized the oil because the oil light was on. That's when I noticed the rockers appeared to just have the engine lube I originally put on them (the white stuff), and it appeared to have just melted a little or maybe been liquified by agitation. That engine is on a stand in my garage. I'll look at it soon.

The 4.0 goes back in. This all happens in the space of a week or two--I did alot of swapping!!! In my driveway.

A constant it the front cover, pick up tube, and oil pan. I did put a new oil pump in the front cover because I was afraid that the thinned oil had damaged it. It stayed together with the string, I packed it with vaseline... the whole 9 yards. I agree that I would have noticed a crack or crease on the pickup tube. I even held my hand under it when I was cleaning it with brake cleaner and let the cleaner slosh around inside for a bit--I think I would have noticed a leak. I used RTV on the mating surfaces (very thin tightened it up and siped off the excess) just because low oil pressure is such a huge deal. I also replaced the o ring. It went in tight.

So back to this front cover... I think I just need to take it off and examine every part of it. The oil pump gears are new and fine. I don't see an issue there. If there is some kind of relief valve on the front cover that allows oil to pour back into the sump rather than being circulated, I think that has to be the problem or the pickup tube has an issue. I really don't think it is the bearings, but it seems dumb not to replace them if I have the oil pan off and oil pressure issues, except for the fact that I likely need a new set of bearings for the cursed 4.6.

I noticed today I had the same issue... seems like it had no oil too long at th startup. I drove a bit, then went in a gas station, stood in line, and returned. I was gone maybe 3 minutes. Startup sounded NORMAL, like it used to. That strengthens my conviction that the oil is somehow draining back overnight, moreso than usual. That wouldn't be bearings because the oil pretty much stays in them because of viscosity. That's more like taking your finger off a straw and slurpee dripping out the bottom--it takes a few minutes to start, but eventually the straw is empty and you have to suck alot of air to get the slurpee going again.

 

I should have answered one other question. There is a drip from the front seal. It was alarming at first but that was engine lube. After that went away I have not actually seen it drip. There is about a silver dollar worth on the ground after it sits overnight.