Guy

I just recently swapped engines in my truck. My oil pressure seems to be dropping to about 15psi when my engine warms up. When I was tinkering with this motor, I opened up a bolt by the oil filter that a spring under it. Is that bolt and spring the Oil Pressure Bypass Valve??<br>Is it possible I may have tightened it too much allowing the oil to pass through at a low psi??<br>Does anyone have a schematic of the oil delivery system??

Jim Shulmister

OK, no problem,<br> the bolt you took out holds the spring that allows a oil bypass piston to relieve excess pressure thru a spill passage. There is an oil pressure piston, a pressure spring, and the bolt that holds it all in.I dont think you overtightened it because the more pressure on the spring, the harder it is for the piston on the other side to release the oil.(making more oil pressure before it bypasses). It is mainly used because the thicker cold oil causes Much higher pressures, it isnt used much when the oil is hotter and has lower pressure.You might try just changing your oil and see if the pressure comes back.<br> I had a railbuggy with high pressure springs in the oil bypass and it BLEW the oil filter apart.Good luck<br> -RATCHET-

Monty

[quote author=Guy link=board=9;threadid=12129;start=0#114684 date=1047434533]<br>I just recently swapped engines in my truck. My oil pressure seems to be dropping to about 15psi when my engine warms up. When I was tinkering with this motor, I opened up a bolt by the oil filter that a spring under it. Is that bolt and spring the Oil Pressure Bypass Valve??<br>Is it possible I may have tightened it too much allowing the oil to pass through at a low psi??<br>Does anyone have a schematic of the oil delivery system??<br>[/quote]<br><br>Did you check the oil psi with an external pressure gauge or go off of the one in the dash? If you went off of the dash, I would say your problem is the oil psi sending unit. Mine showed real low oil psi readings, turned out it was just a bad oil psi sending unit. It now reads right in the middle of the guage at highway speeds.

Sootblower

Be aware that early B engines had very low oil pressure at idle. My 91 was of concern when new and I measured with a guage as 18 psi idling brand new. Later years had increased flow volumes to give more like 35 psi idling. I think there were a lot of oil transmitters replaced needlessly on warranty because of customer concerns in those early years. Now they give you a guage that is driven by the computer reading mid scale even if pressure is anywhere above 10 psi, like the old &quot;dummy light&quot;. Treat the customers like dummys now.

Lil Dog

The oil pressure bypass valve in the engine opens at around 65 Psi. Normal operation at idle should be around 10-15 Psi and up to near 40 Psi at WOT.<br><br>J-eh