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New motor with no low oil pressure at idle

4K views 43 replies 10 participants last post by  G8orFord 
#1 ·
Well, I just did a big motor build and I am having issues. Low/No oil pressure on the low side at idle and Low psi while driving. (I am talking about LPO not HPO)

Truck runs and drives, just takes a long time to start (I am assuming its because it takes that long to get oil to the HPOP)

Checked with a snap on pressure gauge through the oil cooler housing sensor
Idle - 0 PSI
1000 rpms - 7psi
2000 rpms - 15-20 psi
3000 rpms - 20-25 psi

Will not go above 25psi


I have checked all the easy normal stuff...
HPOP check ball valve is good
Complete new front cover with oil pump
Replaced oil galley plugs (2 front, 3 in back)
All 8 piston squirters were installed with loctite


I opened up the oil filter housing and checked the filter drain back valve and its seems to be good, I swapped it with a known good one just in case. While cranking over the motor it fills up the oil filter housing really quick... no issues supplying volume, just no PSI.



Anybody have any ideas before I pull open this brand new motor and start tearing into it :please::please::please:


Motor build includes:
All new main/rod bearing STD size
Polished crank (not reground)
RCD billet stage 2 cam with new STD bearings
.040 mahle pistons
upgraded lifters
billet push rods
oring heads
etc...
etc...
 
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#4 ·
I'm assuming it came with a new spring as well? I know you made a hybrid system on the HPO side but that shouldn't keep you from building LPO pressure.....usually that regulator and spring is the culprit when it won't get up to 75psi on a healthy system
 
#6 ·
Yah Nick hit the only thing I can think of on the head....For chits and grins pull the LPO regulator valve. It should spring out. I have had them get stuck in the housing and cause low or no LPO. If it does spring out then I would start narrowing down the other possible causes. Did you plasti-gauge the main and rods before putting the motor together?
 
#9 ·
No plastigauge... I figured with STD bearing and stock crank that I would be fine... but now I am kicking myself.

I will double check the regulator. The old one did spring right out... but we replaced it anyway just in case.
 
#11 ·
HPO is werid... it does not really move and will hang out around 50-100psi and then BAM it hits 500psi and starts. It is not "slowly" going up. It will also hold PSI for a long time after shutoff. If you shut it off it will start right back up (and then sometimes dies immediately) and then start right back up and run fine. If you ever let the PSI drop in the oil rails then it takes 30seconds to start back up.

I am assuming all of those issues are because the HPO system works great... as long as it receives oil from the LPO system.

Also we have pressure tested HPO system MANY times with ZERO leaks. Also new stand pipes, new dummy plugs, new injectors, new HPOP, and new branch tubes.
 
#8 ·
I agree its more than likely LPO regulator issue. The regulator piston isn't in backwards by chance is it? I remember the way it's suppose to go was counter intuitive (to me anyways) the first time I looked at it.
 
#13 ·
Good luck!!! that's frustrating. hope you don't have to tare the motor back down. I have PTSD about this sometimes. lol Only have about 1000 miles on my build so far.
 
#15 ·
I was thinking the pickup tube is sucking air and/or the upper oil pan is cracked and sucking air... BUT>>> would that show aerated oil in the filter housing?

I was testing the drain back valve (which is working great). I had the oil filter cap off and it fills right up? Only a few small little bubbles and the filter housing fills up fairly fast. I compared it to two other trucks sitting here at the shop and they do the same thing... same amount of tiny bubbles and fill up about the same speed.

Does anyone know of a way to pressure test the LPO system to check for leaks?
 
#21 ·
We are gonna double check the valve in the front cover today.

Then I am going to overfill the oil by about 10qts... that should get the oil up past the oil pickup tube and upper oil pan. If the oil pressure problem goes away then I will know it is one of those.... Don't worry I wont let it run very long LOL


I am leaning towards oil galley plugs not being installed right


Thanks for all the help!!!
 
#26 ·
For Anyone else that is trying to figure out a similar problem... Here is the list I came up with of all the things to check. Hope it helps anyone else chasing a similar issue.

Anti Drain back valve in oil filter housing
2003-2004 HPOP check ball in side of pump
Regulator in front cover
LPOP gears
Crack in upper oil pan
issue with oil pickup tube (cracked oring)
Issue with oil galley plugs


Now the that only happens during full rebuild
Missing cam bearings
wrong size main/rod bearings
piston cooler/squirter missing
 
#28 ·
For Anyone else that is trying to figure out a similar problem... Here is the list I came up with of all the things to check. Hope it helps anyone else chasing a similar issue.

Anti Drain back valve in oil filter housing
2003-2004 HPOP check ball in side of pump
Regulator in front cover
LPOP gears
Crack in upper oil pan
issue with oil pickup tube (cracked oring)
Issue with oil galley plugs


Now the that only happens during full rebuild
Missing cam bearings
wrong size main/rod bearings
piston cooler/squirter missing
The piston squirter missing will NOT cause that big of a drop in pressure. You most likely wouldn't even notice it at all. The 7.3 trucks drop them ALL the time sometimes multiple and have no issues.
 
#29 ·
I'd also think that a mis-sized bearings would have to be significant to affect the oil pressure as much as you're seeing and I'd like to think you or whomever installed the rods and crank would have noticed that. I'd have to lean towards an open oil passage somewhere.
 
#30 · (Edited)
The more I think about the symptoms the more I start to think it might be an internal problem as well. If it was me I think I would make some sort of block off plate I could put in the oil filter housing to dead head the LPOP and put a test gauge on the test port to see if you get normal pressure. I don't think its a leak in the pickup tube or upper oil pan as the pump wouldn't prime very easy (if at all) and it sounds like the pump is moving a reasonable amount of volume.

Scrap that idea, I was thinking the test port was up stream of the oil filter.
 
#31 ·
Maybe not even a leak....possibly a blockage. I wonder if a main bearing on backwards could cause it.
 
#32 ·
If the main bearings somehow got swapped (upper in place of lower) you won't have a problem oil pressure wise until that bearing spun anyways. :)
 
#35 ·
Well... we found out the problem (at least we hope it is the only problem)

Back oil galley plug for the HPOP popped out. That is what I thought it was the whole time but they were just installed by the shop. I am glad we double checked before pulling the whole motor.

 
#36 ·
But where did it go !?!
 
#39 ·
I thought it was a galley plug as I was a couple of posts down on page 1. It's pretty common for some 1st timer 6.0 builds to simply leave one or two out. It also happens a lot on small block Ford builds. It's pretty small item that can be easy to overlook. Especially when you leave the plugs in and the machine shop removes them to boil and shot-peen the block. I alway's run a really light film of RTV around the plugs before banging them in. I don't see any leaks this way and that may possibly help secure them a little better.
 
#41 ·
Are they aluminum? .....let it eat it lol.
 
#43 ·
We replaced the oil galley plug and all seems good... just gotta get the truck put back together. Oil galley plug was just sitting at the bottom of the back cover, it did not get caught in the gears and did not seem to cause any issues.

We were not taking any chances of it popping out this time... so we used loctite and a torch.


Now lets hope the low oil pressure did not cause any issues while trying to diagnose
 
#44 ·
Next time have the machinist tap while doing the other work, then use pipe plugs and loctite at assembly time. Not exactly sure how the galley plugs are on the 6.0, I haven't had the pleasure (?) of going in that far yet, but that method works well on small block Ford's and Chevys.
 
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