Oil pressure issue......
#12
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Joined: Jun 2009
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From: Chicago
My oil pressure has always dropped at WOT . Used to be worse with undersized oil cooler lines (40psi)
Again ran like that for years. As long as the volume is there it`s no ideal but does not cause any damage.
Now I run a Shumann pump and it still drops at WOT.
I`m open to ideas on why that is happening. Joes motors are rock solid at 75+ psi at wot.
I thought oil gets hot and thins out = lower pressure
Again ran like that for years. As long as the volume is there it`s no ideal but does not cause any damage.
Now I run a Shumann pump and it still drops at WOT.
I`m open to ideas on why that is happening. Joes motors are rock solid at 75+ psi at wot.
I thought oil gets hot and thins out = lower pressure
Last edited by ICDEDPPL; 04-03-2017 at 11:08 AM.
#13
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Joined: Nov 2004
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Likes: 54
From: Lago Vista TX
#14
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Joined: Nov 2004
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From: Lago Vista TX
without a oil temp gauge how do you know if the oil is HOT?90% of the oil will bypass the cooler until the oil t stat opens sending the oil through the cooler.35 lbs oil pressure at 5000 rpm usually indicates lack of oil present at the oil pump pickup that can be caused by many reasons.
http://www.mrcool.us/mrc-cph-775.html (flow diagram on this page.. Can't seem to link it as a picture)
.
My initial test run, my oil pressure would drop to 35 psi at 5000 RPM. No oil temp gauge on that run, but I leaned against my remote filter in the bilge and about lost the skin off my arm

I then plugged off the cooler bypass tube, got my oil temp gauge installed went out again with the same engine oil....
at 170 degrees I could hold my hand on the remote filter.. and came up with the pressure results shown in the first post...
Last edited by Boatally Insane; 04-03-2017 at 12:04 PM.
#15
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From: Lago Vista TX
#18
Pickup could be too close if you didn't measure, also what fittings are you using? Sharp 90 or sweep? I ran sharp 90's in past with no issues (stock brass Merc) but with new builds I went all long sweep or straight for flow.
Also did you run these coolers before? Maybe the stat in cooler is restricting it?
I run melling select pumps with mains at .0032-.0035 1-4, and rear is .0040 rods .0026-.0027 lifters .0020 I have 78 cold even at idle, 75 hot running And 40 idle hot..
Also did you run these coolers before? Maybe the stat in cooler is restricting it?
I run melling select pumps with mains at .0032-.0035 1-4, and rear is .0040 rods .0026-.0027 lifters .0020 I have 78 cold even at idle, 75 hot running And 40 idle hot..
#19
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Joined: Nov 2004
Posts: 922
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From: Lago Vista TX
They're full flow 90's... but there are 6 of them.. Don't know if it's worth going to straights ? Would have to use longer hoses...
I didn't put the oil stat back in..
I plugged the bypass tube by cutting a 1/4" carriage bolt to the right length held in by a plug so, no restriction there...
I didn't put the oil stat back in..
I plugged the bypass tube by cutting a 1/4" carriage bolt to the right length held in by a plug so, no restriction there...

Last edited by Boatally Insane; 04-03-2017 at 09:52 PM.
#20
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Joined: Oct 2007
Posts: 8,439
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From: yorkville,il
My oil pressure has always dropped at WOT . Used to be worse with undersized oil cooler lines (40psi)
Again ran like that for years. As long as the volume is there it`s no ideal but does not cause any damage.
Now I run a Shumann pump and it still drops at WOT.
I`m open to ideas on why that is happening. Joes motors are rock solid at 75+ psi at wot.
I thought oil gets hot and thins out = lower pressure
Again ran like that for years. As long as the volume is there it`s no ideal but does not cause any damage.
Now I run a Shumann pump and it still drops at WOT.
I`m open to ideas on why that is happening. Joes motors are rock solid at 75+ psi at wot.
I thought oil gets hot and thins out = lower pressure
Last edited by mike tkach; 04-03-2017 at 11:14 PM.


