Oil Pressure, Rear Main Seal Leak Troubleshooting Help Needed

[DasFrem]

So I've been beating myself up about this problem for a couple of weeks and have finally decided to ask for help...(97 4.0 V6 ohv)

A few weeks back, I was about 100 miles from home and the oil gauge is dropping to nothing, then back up, and sometimes just flicking back and forth. I know its a dummy gauge and think that I might just be a little low on oil. I check the dipstick and it looks fine. Back on the road and it's fluctuating even more now and the dip stick still looks fine, so I add half a quart just for the hell of it. Seems fine for a couple of miles until the truck starts running really rough...I pull over and its smoking like hell from the oil leaking out of the back of the motor on to my clutch. So I know I'm leaking oil out of the rear main seal, but I'm suspecting an issue with the oil pump because when I start it up, it won't have oil pressure at all until I really get on the gas. But it still ran like s#it for the last 40 miles of the trip (I was on an early workday duck hunt and had to get back in time for work, otherwise I would had it towed). Now when I dropped the pan, there was very little oil left, maybe 1.5-2 quarts.

OK, here are my main questions....

-What does a bad oil pump behave like?

-Should I just replace the rear main seal and hope for the best with the oil pump?

-Am I missing anything?

So far the trans is out along with the clutch and pressure plate so I know for sure it's leaking from the rear seal...I've also got the oil pan off and there's some fine metal shavings at the bottom of the pan, but nothing blocking the screen on the oil pump.

Thanks in advance to anybody who can shed some light on this issue.

 

[JDraper]

Hey Matt..long time no see.

If you've already got the thing partially torn apart, I'd go ahead and put a new oil pump in. Better safe than sorry. The pump isn't that expensive and it's better than putting it all back together just to find that the pump is shot.

A bad oil pump can behave in many different ways, however what you are describing can be one of those ways. You could have the pressure spring in the pump going bad. Although, with only 1.5-2 qts in there, the pump could be cavitating which would produce the same symptoms.

Hopefully those metal shavings you're seeing aren't the bearings starting to wear from lack of lubrication.

 

[DasFrem]

Jeff, good to hear from you, especially your respected advice. You have a good point, I might as well swap it out, especially when you consider what a PITA it is to get to it. The metal shavings do concern me...there was enough to make a film of grimy silvery mess at the bottom of the pan....

....hold on....brain processing....it hurts....

Whoa, now you got me thinking....what if it was the oil pump failing (hence oil gauge going wacky while the dipstick showed enough oil), and then due to a lack of lubrication, the bearings began to fail, causing the roughness of the engine, then because the bearings are out of wack that causes a leak in the rear main seal?

Any thoughts O' wise one?

 

[JDraper]

That's possible...unfortunately...It might pay to pull a couple main caps (and maybe even a rod cap or two), check the bearings and plastigage them to make sure they're ok.

 

[DasFrem]

So I should have listened to Jeff, instead I got in a hurry and replaced the oil pump and gaskets and rear seal and once I put it all back together sure enough the oils comes spewing out the rear main seal again. So I guess I need to replace the main bearings because once I started it back up, I realized that the vibration is coming from the crank shaft and that play in the bearings must be making the gap in the rear main seal allowing the oil to spew out. So now I'm debating buying a junked motor for 500 bucks or pulling the motor and replacing the bearings and maybe the rings myself. I still haven't been able to determine what may have caused the bearings to go in the first place, but I'm sure it had something to do with the oil gauge fluctuating like it did.

 

[JDraper]

That sucks Matt...sorry to hear about the motor. I'd be tempted to re-build the one you have. If you buy a motor from a boneyard, you have no idea what you're really getting as far as condition. If you re-build yours, you know what you have.

 

[454burb87]

If you re-build yours, you know what you have.

X2 I avoid junk engines if at all possible...rebuilding is easy if your tedious and careful. Make sure to get torque specs!!!

 

[IAmTodd]

Hope you don't mind me poking into this thread, Matt.

What kind of damage can this cause. I imagine anything is possible but I'm trying to get a feel for what I'm in for.

 

[Currency]

My oil gauge sometimes jumps back and forth, sometimes just once or twice a day from what I've seen. When I get on the gas I hear a knocking sound which gets louder the more gas I give it. A buddy of mine said its my main bearings

My front main seal is leaking also but really slowly leaking.


If so he will be rebuilding it for who knows how much. Maybe just parts and enough beer to keep him drunk until its done. But he does at least know what he is doing and could save me over $800 if I paid a shop to do it.

More details on my problem here >>>>

http://www.explorerforum.com/forums/showthread.php?t=254517

We both may be wrong but I never thought the oil gauge may have something to do with it.