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1986 E6 350 Low oil pressure after rebuild


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I recently rebuilt my E6 350 after a cam lobe/lifter failure. Truck has 750k. I decided to pull heads and pan to inspect, and I decided on an inframe.

PAI Kit; Reman heads, reman turbo, reman oil pump, new rods and mains, new lifter, new camshaft, original cam bearings, original piston head bearings.

Truck had 30psi idle and 60psi @1600 operating temp.

Truck now has 18psi idle and 35psi @1600 operating temp.

The mechanic who started the inframe (no longer employed) put the upper #4 main in #7,  (#4 upper was initially installed correctly. I ordered another main bearing kit after he said that we were missing the #4 upper main.) Psi was down to 10 with the incorrect bearing in #7.

I finished the inframe after the mechanic was fired; mains 1-4, rods, heads, liners, pistons, cam. Started the engine, resolved the main bearing issue, and now I am stuck with this low oil pressure.

Pulled all rods and mains to inspect. Plasti-gauged 2 mains and 2 rods (Both were in spec).

Initial thought was that #7 did not feed the corresponding cam journal with oil when it had the incorrect bearing. Is this the direction I need to go? I looked at the installed cam when the pan was off and could not see any problems.

Oil pressure will get up to 75 when cold. Pressure relief valve is clean. Put old oil pump in, same issue. Pulled filter by-pass apart, everything looked fine. Plumbed mechanical gauge before and after filters to verify correct readings and good filters. Jakes (not working now) still have all plugs in the rocker shaft.

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Crank journals #2+#5 are the oil feed to the heads.. the cam bearings have an oil gallery that basically goes half way around the bearing, making them easy to warp when installing. Did the cam go in smoothly?

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I guess my next thought is.... are the cam bushings installed correctly, allowing oil to flow properly... ?  im going to open my E-6 book.  be right back.. Jojo

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Dissregard my saying the cam bushings have a gallery about half way around..  I had a 2 valve in my head.. these cam bushings should have 3 oil holes.. was the top end dry of oil after you ran it and opened it up? Is the new oil pump gear correct?  (ratio) I know you said same issue with old pump, just curiuos..

Edited by Joey Mack
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  • 1 month later...

Plasti-gauged 2(.0015), 5 (.002), and 7(.0015). Oil Flow show to go first to pressure relief valve. We pulled it apart and inspected; everything looked fine. Oil flow then goes to oil cooler. We checked oil pressure at the intake of oil cooler, and it matched the other readings we get on gauge at oil filter. 

@Joey Mack 1. Top end had oil flow but still low pressure. (Rev it up to 35psi and the jakes will then work.)

2. New Oil Pump gear was the same as old. We reinstalled the old one at the moment to make sure it was not our problem.

@br549 I did not take the piston coolers out to do the liners. They do not look damaged when looking at them with the pan off.

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Posted (edited)

no gasket for oil pump mounting.. Piston cooling tubes dont look damaged by eye unless they are F'D up.. they are probably fine as far as oil pressure loss, if they were not un bolted..  there is a target to aim them if this was to be done in your case.. There is a spring and piston in the base of the oil pump. it's easy to inspect and if there is a lot of scratches on the piston it will leak out oil pressure. the spring also has a spec. on it as well. there is also a pressure valve in the filter pad mount to the bolck.. Do you see a hex headed bolt behind the oil filters near the bottom of the mount? I think it's 7/8" but forget. that is the piston cooling tube relief valve. I dont have a compression spec for this spring and I think the oil pump spring spec is 45 pounds at 1-1/2" compressed..

Edited by Joey Mack
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@Joey Mack

1. I have taken apart the spring and piston on both new and old oil pumps. Both are smooth, clean, no scratches, and spring tension is good IMO. I don't have a spring tester.

2. I have taken apart the oil pressure relief valve. Same verdict that it was good.

3. I have taken apart the piston cooling relief valve. Same verdict that it was good.

@theakerstwo

That plug has not been touched (engine and transmission stayed together) If it was, would there not be oil everywhere? Inspection plate on transmission is not installed.

 

I am thinking of hooking about 10 psi of shop air to the port before the inlet of the oil cooler (only thing before this point is oil pump), and laying under the engine to maybe hear the leak or spray with soapy water to find it. Thoughts on this? A service manager at Bruckner's Amarillo had said he did something similar with nitrogen a few decades ago...

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I at one time had a oil tank that i could put pressure to and watch.I dont think you will find it with air.The flywheel housing is a wet housing and if the plug was leaking it would be inside but in front of the rear seal.I did not think you had the engine out so that will not be your problem.The main brg clearance of .001 dont sound right because it should have more.Also there is three different shape gaskets for different engines for the oil filter housing mounting pad on the side of the block.Have you had this off?

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glenn akers

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Posted (edited)
On 5/4/2021 at 3:52 PM, Mike Schilderink said:

@theakerstwo

Oil level stays the same after running 50 miles, and low oil pressure is occurring with fresh oil after 5 minutes of warmup.

 I have not taken any oil samples.

Being as we are grasping at straws here ! Just asking a dumb question You do have the correct amount of oil in the base ? If its over full the oil can get fluffed up and cause low oil pressure 32 litre is most common !  52 0n ESI engine (3 oil filters) If the engine was born ESI and the Pan changed to Standard is this a possibility ? Dip stick is calibrated correctly ?

Edited by fjh
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Posted (edited)

Hooking air into the oil system did not do much. I plugged into a port after the oil cooler and before the oil filters. Initially the air pushed out the oil inside the filters, but nothing out of the ordinary was occurring as far as I could tell. After the oil was pushed out, I tried to track down the leak using soapy water. Majority of the air just came out of #1 main, but it plasti-gauges to .025. Air did not come out of the piston coolers at all. Air did not come out of the small drain holes next to the cam.

Then I removed the oil pump to check the air flow through the oil cooler; It seemed fine to me.

Then I pulled the reman heads to check for a flipped head gasket. (It can almost be flipped, but the dowel pins will keep it from lining up 100%).

I pressurized the oil galley in the heads and they did not leak air.

I checked the tubes that come off of #2 & #5 cam bearings and go to the head. They did not looked cracked or broken.

@theakerstwo I have not had the oil filter housing off.

@fjh The truck does have 3 oil filters (2 paper, 1 centrifugal), but over the past 6 years I have always had about 9 gallons of 15w40 in it.

My next step is to build a pressurized oil tank to hook into the system and watch the oil flow with the heads removed.

Edited by Mike Schilderink
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Well that was my only straw I would really be interested to see what you find here! The psi drop is quite a big one! Back in the day if this were a V8 I would be looking for a cam bearing being pulled out! every once and awhile a v8 would loose 10 psi all of a sudden! The issue was the front cam bearing would work its way out and bearing would be  ripped out by the counter weight! this usually happened shortly after being put into service so under warranty we were instructed to install a new bearing and keep on keepin on! never seen it happen to a six thou! And you would have found the evidence in the pan! good luck with this bud!

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Posted (edited)

I pressurized the system using an air tank half filled with oil. 60 PSI with 1/2 inch hose.

I had the heads removed and plugged the oil passages to the head. I plugged the turbo oil feed line.

All of the mains leaked the same amount of oil. All coming at the same time

The return coming from the air compressor seemed normal.

The return from the centrifuge filter was the same as the air compressor. (I plugged this filter housing in my second test).

The oil pump leaked a small amount of oil.

The cam bearings did not seem to leak oil at all. Looking at the oil flow diagram, it shows that oil flow goes first to the mains, across the upper main bearing, and to the cam. See figure A (16&17).

How does the oil flow across the main bearing? I attached pictures of my upper main. Is there a passage in the block that allows oil to flow on the outside of the upper mains? Should there not be two holes, or what am I missing here?

IMG_0410.HEIC IMG_0409.HEIC

Edited by Mike Schilderink
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Posted (edited)

I have a full service manual for my engine.

I was trying to say that I do not get any oil flow out of the cam bearings. I do get good flow to the rods.

The oil flows from the oil rifle to the main bearings. Then according to the oil flow diagram (illustration A or #16&#17) the oil feed for the cam bearings comes from the main bearings.

I was wondering how that oil is transferred across the upper main. 
 

I almost think that the upper main needs to look like a rod bearing with two oil holes. One for the inlet from oil rifle, and one for the outlet to cam.

My original bearings are at the bottom of my scrap tote, but I’m pretty sure they matched the replacements. I think I better dig them up.

AB8DD264-214E-496A-BC7B-DD7D1D090748.jpeg

Edited by Mike Schilderink
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