Recently, my courier (please don't laugh) has been rebuilt, by myself and a friend.
Here's the problem, type of engine, and diagnosis...

1981 Courier 2.3 L (140 cubic inch) -non turbo carb engine.

There is low oilpressure.

we started the truck up properly after the installation of the rebuilt engine.

all fluids were put in at proper levels.
the carb was rebuilt as well.

a new oil sending unit (no tape on the threads to ensure proper contact with the block), new oil pump/screen/gasket new everything, all gaskets, all new by-pass hoses, new water hoses. New oil filter (for starters I used FRAM, now, I'll be using MotorCraft because of the study done on them.)

5w30 castroil (recommended for 4 cyl. engines.

cleaned out radiator.
new fuel filter between carb and tank line.
new starter
new muffler/catalytic converter
intake and exhaust manifolds shined up and cleaned well, no left over gasket grunge.

new freeze plugs.

and of course all the new goodies that belong inside the engine, new crank shaft, new pistons, rings, bearings, cam, lifters, rockers,
you name it, its all new.


hmm...

low oil pressure?

what did we do wrong?
I've barely put 50 miles on it.

we primed the oil pump.
(some horror stories they don't do that)

I ran the engine, the water temp is perfect.
there isn't any oil leakage, no loss of oil (internally), and the gaskets appear to be okay, becasue of non-catastrophic water/oil mixing.

the sending unit wire has been replaced as well.


when I start the truck, the oil pressure is fine. after the engine warms up a bit (2 miles of 35mph driving or less speed?) I hear a rumbling sound that I can not pinpoint. and the oil pressure drops.

If I could only sit on the engine while someone else drove it, so that I could have an external oil pressure gauge testing it in motion!

also, sitting in the drive way, letting it warm up at idle speed, the oil pressure drops after about 10 minutes of idle time (I realize idling isn't a good thing to do, neither is revving up an engine, but, how else do you listen and look ?)

I bought some engine flush, gunk I believe to flush out the engine, and replaced the oil filter.

no luck.

even though the engine is rebuilt, Is it tired?

I'm out of ideas.

a fella said "maybe its the cam bearings" they are replaced, and to spec.
if there is a pressure release valve to send the oil back to the sump, I am unaware of it. and I wouldn't know where to find it on the 2.3 litre.

everything has been changed to new on this lil engine that could for a long time, and now says "uh huh! I'm tired!"

I really like this little truck, its been with me for over 10 years, and its the first rebuild that I am aware of.
Its always passed emissions tests, until the last year that I drove it (originally the carb sucked a nut through it, thus "rebuild" because of nut making it through the intake manifold, through the head and smashing down onto a piston, and the piston smashing the nut at TDC (eww what a mess)

so, Is there an expert that can understand all this mayhem, and sort through the process of elimination with me, so that I can get this lil engine running again? Please? I'm jumping for joy that you are even contemplating the assistance to help me.

Its either I go bonkers trying to figure this out, or, I'll just have to get an unknown rebuilt engine from somewhere that I've never even heard of off the internet thinking that I'm getting a great deal.
I dont want a different engine. Unless...

 

Did you check the clearences on the new crank?
Was the crank re-ground? (10-10, or something like that)
The reason I'm asking is, if the crank was ground and standard bearings wear used, it can cause oil pressure problems. That is the only thing I can think of.

Roger

 

Or you have a redtriction in an oil gallery. After a block is cleaned at the shop, they don't always clean the galleys with brushes to remove the oil scum and cleaning solution. This may not be the case if you are tapping the oil pressure line very close to the pump. If you are trying to take a reading from somewhere else, this may be the case.

Krosati
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The Rod/Main bearings came with the new crank shaft.
So, I'm thinking thats not the problem, but, thanks for the good try.
On the other hand, the second fella inline, you've a good point.
I don't know if the machine shop cleaned out the journals, or oil galleys. Is there any way to "blow" that crap outta there?

The truck sounds great until like 15 minutes of idle time.

The oil is at a perfect level, and clean, and the oil filter is getting oil to it.

If taking off the valve cover to watch, is this a good idea?

 

Typically, there three major causes of a low oil pressure condition when the engine warms up -

1. The oil pump. The pressure relief valve you spoke of is located in the oil pump itself in this and virtually every other engine ever built. Lots of times guys with your problem in an older engine will assume that the trouble lies with the pump and replace it only to find that it still drops at temperature. The oil pump CAN fail, but it is usually a trouble free item with not much inside to go wrong. Good rule of thumb is that if you have no or very, very little oil pressure at all, it might warrant examination, but since you have good pressure at cold idle, look elsewhere.

2. The cam bearings. Depending on the engine, the cam bearings are usually the first or second thing to get oil. Consequently, badly worn cam bearings will allow your oil pressure to drop when it warms up and thins out. Since yours are new and it is almost unheard of to use anything but stock dimension bearings, I'd rule this out as well.

3. Main/rod bearings. I'm with lanero. Personally, I'd finger this as your culprit. The reciprocating assembly is oiled either first or second. (Opposite of the cam - varies engine to engine) You'll lose oil here for the same reasons as the cam bearings. I realize that your bearings came with the crank and I also realize that you REALLY don't want to drag the motor back out of the truck, but I've got a case of beer that says this is your problem. Even though the crank and bearings came together, they were put in the box together by people. People screw up. I do. You do. It's life. I'm betting that you got the wrong ones. The crank may have came with a spec sheet of the new dimensions. Did you mic it to double check? When you assembled the engine, did you use plastigage to check your clearances? This is an absolute must. I learned the hard way. And here is my last piece of evidence - your mysterious rumbling. A bad rod bearing will knock. It is unmistakable. Bad main bearings will rumble. If the truck is a stick, the rumbling may even be apparent in the clutch in the form of clutch chatter or a vibrating pedal.

I hate to rain on your parade, but you might as well plan on renting a cherry picker again this weekend. Even if I'm wrong, I guarantee that whatever is causing it will be difficult or impossible to fix in the truck. Take heart, though. Even if it does turn out to be a bad or wrong size crank/bearings, you can fix it without taking the entire engine back apart. Changing a crank in a 4 cyl. with the rods/pistons in place is a piece of cake. Should this prove to be the problem, whomever sold you the parts will probably be willing to replace them. Remember - PLASTIGAGE! Less than five bucks. Cheap insurance policy. Good luck and let us know what you find!


P.S. Incidentally, instead of riding around in the engine bay with an oil pressure guage while your buddy leans out the window to drive, go down to the parts house and buy a cheap mechanical oil pressure guage. The kind with the nylon tube. Pull your sender out and hook it up to the motor. Route the tube out the back of the hood and hook it up to the guage. Zip tie the guage to the grill on the cowl. Watch the tube when you shut the hood, but there should be plenty of gap for it to fit through the the hood shut. Viola! Quick, temporary real-time oil pressure readings! All from the comfort of the plush surroundings of a Ford Courier. :7

 

I think it may be the bypass pressure releif valve in oil pump thas bad.

Also the only 4-bangers that can be rebuilt are the model t and the vw pancake.

When you have a ride you like with a bad 4-cylinder engine....boneyard....take your chances

 

[] I think the valves weren't torqued down enough.

Some days, you just forget things... cell phones ring,
dogs barking... who knows.
I talked with my friend that helped me with the rebuild, and we
tried to remember everything we did. I think we didn't check the clearance close enough.

I'll find out though.

I'll keep ya'll posted of results.