Failing oil pump?

[rikubot]

Hi guys, beginner mechanic here. Think I have a failing oil pump. After about 4 miles on the highway, I took my exit and immediately noticed a drop in oil pressure. When I stopped I check the oil level and it read full. No visible leaks that I could see, (this was at night, though). It's a 440 with 727 (69), power steering, power brakes, let me know if you need any more info. Thanks in advance!

-mike

[rikubot]

Not sure if this is related, but driving home from my girlfriends house, the car kept dying out so I had to keep the throttle a little revved up...and this isn't normal for my fuel system.

[RECHRGD]

What did the pressure drop to?  Did it come back up when back on the hwy?  Was it running fine when the pressure dropped.  Did the valve train get noisy?  Could be a lot of things.  First, get a mechanical pressure gauge to verify what your actual pressure is...

[rikubot]

Yes the valve train got pretty noisy. It dropped to below 10 psi and moved pretty erratically even at speed, but it did somewhat maintain decent pressure after a while. What caught my attention was the tapping of the valves just before I got off the highway. I'll see if I can get a mechanical gauge and sender to use for a while just to monitor it better. I understand that it will drop when you are sitting at lights and will move around a bit here and there but it was that sudden noisy drop that gave me all the anxiety. Then it would try dying out on me after I had parked it for a bit, which may or may not be related.

[RECHRGD]

If it dropped below 10lbs. And got noisy, don't drive it!  The noise indicates that is is indeed a oil problem and not the gauge or sending unit.  My first step would be to replace the pump and go from there...

[rikubot]

Ok, that's what I was thinking. I have a pessimistic friend who tried telling me it will be fine and his drops at stops too but the noise and the fact that the oil level was at full led me to the same conclusion. I usually go through eBay for stuff like this. I found a unit in eBay for about $70 shipped, and this is something I definitely want to buy new, right? I will do a full oil change too while I'm at it. Is this a difficult swap?

[RECHRGD]

Yes, buy new!  Difficult?  That depends on your tool chest and experience.  You will need to pull the power steering pump to gain access.  Some folks have had to jack up the drivers side of the engine also, but I didn't need to.  The pump must be "primed" before starting the car.  That intails pulling the distributor and gear, inserting a special tool (square rod) and spinning the pump counter clockwise with a drill until you feel the pressure.  Then put the whole mess back together the way it was.....  If that sounds intimidating to you, then hire some to do it that knows old mopars.

[rikubot]

I have a little bit more information: I didn't look under the hood last night after the drive because it was dark, but this morning I went out to scope out that oil pump location and noticed that one of my oil breathers was hanging off on the passenger side valve cover. Would with affect the oil pump functionality?

[RECHRGD]

Hmmm, I wouldn't think so.  You may just start it up for some seconds to see if there is any change.  How many miles on this engine since the last rebuild?

[birdsandbees]

It would explain it running rough though...

[rikubot]

That makes a lot of sense as far as it dying out. I'm not sure of the mileage since the rebuild as I've done some test driving without the cluster in but I'd say less than 5000

[RECHRGD]

Well, its almost new, so you shouldn't have had any clearance or bearing problems.  As said, I would get a new pump on there before going further.....

[John_Kunkel]

Either the valve train noise is caused by the drop in pressure or the drop in pressure was caused by the valve train. A bent pushrod can cause a lifter to pop out of its bore causing way low oil pressure and rough running.

[b5blue]

Either the valve train noise is caused by the drop in pressure or the drop in pressure was caused by the valve train. A bent pushrod can cause a lifter to pop out of its bore causing way low oil pressure and rough running.

John is spot on. Exactly how mine crapped out...bent push rod, only very tired engine at that point. Pull valve covers and inspect ASAP.

[rikubot]

The rods look good. Anything in particular I need to look for?

[flyinlow]

Push rods seated in the rocker pocket. If you push down on the intake side of the rocker there should by no appreciable play.  Crank the engine and watch the rockers , they should show a uniform movement  comparatively.

You said the rods looked good . Did you pull them and roll them across a sheet of glass? They should roll smoothly and not click. If you pulled the rods ,where all the lifters in their bores?

[rikubot]

I did not, but I will do that tomorrow for sure.

[rikubot]

The rods were straight and the lifters looked good 

[rikubot]

Also, now that I've got her opened up a little, what method/torque specs do I use to put the rocker bolts back on? I couldn't find anything I understood in the web. Might be I'm using the wrong terms

[rikubot]

I found a few oil pumps on eBay, does anyone know if this one a solid unit?

https://www.ebay.com/itm/390898403252

[b5blue]

Be certain the oiling holes are in the correct position, they should be about 15* offset to the exhaust side of the head. (Compared to rocker shaft bolts.) I tighten the bolts just a bit at a time to keep the rocker shaft level to avoid bending. When all are seated torque to 25LB. I would coat all contact areas with assembly lube if you have some.  Really good news all is well. 

[rikubot]

Thank you so much, I'm glad I asked because I didn't even notice any oiling holes. Is that 25 inch pounds or 25 foot pounds? I'm a bike mechanic so I'm used to using inch pounds.

[b5blue]

Foot pounds.

[rikubot]

Thank you sir. I'll grab a torque wrench on the way home from work. 

Any thoughts on the oil pump I linked in a couple posts back? If from the eBay Summit store I believe.

[b5blue]

I used a Melling H.V. with a new hardened pump shaft but not recommending you need one.