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No base oil pressure after oil cooler repair? Re o ringed my 95 7.3 and now ain't got oil pressure? Oil level full? Put mechanical gauge on port by oil filter. No oil even filling the gauge hose??
 

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There is an oil filter bypass and an oil pressure regulator spring in that rear manifold where the filter attaches. My guess is you accidentally dislodged the pressure regulator. Assuming you got the gaskets back on correctly and don’t have a port blocked off.


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As mentioned by RT, the oil filter/cooler header has a bypass valve and a pressure regulator valve. Since yours is a 95, they simply had those valves simply staked in place and they like to fall out. They updated the header to have the valves retained by snaprings for the later trucks. The bypass valve can be seen when the filter is removed. The one you need to be concerned with (at the moment) is the regulator valve which is located on the block-side surface of the header. If it falls out while doing oil cooler o-rings, the engine will not build enough pressure to run the HP oil system. See the attached pictures.
Reg Valve1.JPG Reg Valve2.JPG

Just for info, the bypass valve under the oil filter, consists of a spring, washer and disk. If it falls out the engine will run but the oil will be bypassing the filter (which isn't good obviously). Usually you can restake the parts in (spring, then disk, thenif you can find them (usually in the drain pan when changing the oil.
Filter Bypass Valve.JPG

Cheers!
 

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Discussion Starter #4
As mentioned by RT, the oil filter/cooler header has a bypass valve and a pressure regulator valve. Since yours is a 95, they simply had those valves simply staked in place and they like to fall out. They updated the header to have the valves retained by snaprings for the later trucks. The bypass valve can be seen when the filter is removed. The one you need to be concerned with (at the moment) is the regulator valve which is located on the block-side surface of the header. If it falls out while doing oil cooler o-rings, the engine will not build enough pressure to run the HP oil system. See the attached pictures.
View attachment 159118 View attachment 159119

Just for info, the bypass valve under the oil filter, consists of a spring, washer and disk. If it falls out the engine will run but the oil will be bypassing the filter (which isn't good obviously). Usually you can restake the parts in (spring, then disk, thenif you can find them (usually in the drain pan when changing the oil.
View attachment 159120

Cheers!
Mr. Feeley my 95 had lost part of the by pass. My issue now is the system beads down pretty quick. It has 40# of oil pressure after alot of long cranking. It idles fine amd sounds good. But takes a lot of cranking for oil pressure to come up...as soon as digital gauge moves up..it starts. But bleads of.quick
As mentioned by RT, the oil filter/cooler header has a bypass valve and a pressure regulator valve. Since yours is a 95, they simply had those valves simply staked in place and they like to fall out. They updated the header to have the valves retained by snaprings for the later trucks. The bypass valve can be seen when the filter is removed. The one you need to be concerned with (at the moment) is the regulator valve which is located on the block-side surface of the header. If it falls out while doing oil cooler o-rings, the engine will not build enough pressure to run the HP oil system. See the attached pictures.
View attachment 159118 View attachment 159119

Just for info, the bypass valve under the oil filter, consists of a spring, washer and disk. If it falls out the engine will run but the oil will be bypassing the filter (which isn't good obviously). Usually you can restake the parts in (spring, then disk, thenif you can find them (usually in the drain pan when changing the oil.
View attachment 159120

Cheers!
Thanks for the reply. I found the pressure bypass missing a few parts. I put a later style with a good bypass housing. Have a hard time priming the system. After 5 long starts it builds pressure and starts. It Will idle and rev just nice. It drains off pretty quick. After a few mins... It looses its prime....and have to crank and crank till gauge registers pressure and it will start again.
 

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So this is the low pressure oil pressure bleeding off after starting and this is verified by an actual pressure gauge (not the factory idiot gauge) correct? I may have confused things with the mention of the bypass. It's the regulator valve parts that like to fall out and cause the problem like yours. Is the later header adapter you put on have snap-ring retained valves? Obviously, check you oil level. You may need to remove the valvecovers and see if oil is bleeding out around the base of the injectors. That would be on the high pressure oil system side of things, but it can cause the engine to stall out. Cheers!
 
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