The Ford Barn

29 Tudor · 03-09-2014, 09:47 PM

Odd situation. I have a oil pressure gauge and the A-Ford-Able full flow oil filter kit. I run 15W-40 diesel oil. Today when I started the engine, the temperature was probably low 50's. The gauge normally goes past 10 PSI when the engine is cold and settles to around 4 PSI at road speed when hot. Here's the interesting thing... when cold, if I rev the engine just a bit, the pressure drops to zero... stays there for a few seconds ... like maybe 10 or so and then comes back up. All this happens slowly because the oil line to the gauge is so small.

Since it comes back up and since once warm, it stays perfectly normal, I'm trying to figure out what's happening. I wonder if it's possible that the pump is pumping enough of the cold oil into the valve chamber, and the drainback is slow enough, to starve the pump momentarily. I was thinking that the bypass valve in the filter was opening and since the gauge is really reading the restriction of the filter, with the bypass open, the restriction is lower but before I installed the filter kit, I never saw the pressure drop to zero but, the outside temperatures were higher as well.

Clearly the pump is working since the pressure comes back shortly. I WAS running with the oil level about half way between add and full. Might try filling to the full mark and see if it makes a difference.

Anyone else ever seen this and have a theory?

The engine is relatively new and very clean inside.

Thanks in advance for any ideas.

Steve

03-09-2014, 09:47 PM	#1
29 Tudor Senior Member Join Date: Apr 2011 Location: Magnolia, TX Posts: 161	Cold Oil Pressure Drops to Zero, Then Comes Back Odd situation. I have a oil pressure gauge and the A-Ford-Able full flow oil filter kit. I run 15W-40 diesel oil. Today when I started the engine, the temperature was probably low 50's. The gauge normally goes past 10 PSI when the engine is cold and settles to around 4 PSI at road speed when hot. Here's the interesting thing... when cold, if I rev the engine just a bit, the pressure drops to zero... stays there for a few seconds ... like maybe 10 or so and then comes back up. All this happens slowly because the oil line to the gauge is so small. Since it comes back up and since once warm, it stays perfectly normal, I'm trying to figure out what's happening. I wonder if it's possible that the pump is pumping enough of the cold oil into the valve chamber, and the drainback is slow enough, to starve the pump momentarily. I was thinking that the bypass valve in the filter was opening and since the gauge is really reading the restriction of the filter, with the bypass open, the restriction is lower but before I installed the filter kit, I never saw the pressure drop to zero but, the outside temperatures were higher as well. Clearly the pump is working since the pressure comes back shortly. I WAS running with the oil level about half way between add and full. Might try filling to the full mark and see if it makes a difference. Anyone else ever seen this and have a theory? The engine is relatively new and very clean inside. Thanks in advance for any ideas. Steve