white93 GT

i was driving down the road and saw full oil pressure then a moment later i see no oil pressure. i pull off and turn car off. no oil leaks, full oil, oil pressure sensor is pluged in.

i just got done rebuilding my 302, boring it, new heads, intake, cam ect.

when the motor reaches 1800 rpms the oil pressure shoots up to 3/4 way up the gauge but as soon as it drops below that rpm it goes down to zero oil pressure and sits there.

any ideas? need help fast

primetime5.0

stock oil pressure gauge or aftermarket?

white93 GT

stock. is there an oil pressure relief valve on the 5.0s? if so where is it located?

primetime5.0

i wouldnt trust the stock gauge i fixed mine like 3 times and it still broke, i now run an auto meter mechanical gauge and havent had a problem since

white93 GT

thanks. probably the first thing we will do is replace the sender since its cheap. We just rebuilt this engine so its possible that we may have screwed something up... maybe didn't tighten the oil pickup tube enough, or the pump or something like that. I don't ever remember an oil bypass valve (maybe its in the pump?). I am going out to change the oil to ensure that the level looks good and it is clean (no fuel or antifreeze).

white93 GT

changed the oil. The oil was still very green from assembly lube. This is the second oil change. First oil change after running the motor for 20 min. Cut the filter open. Very green. If the oil pressure sender is downstream of the filter (wish I was paying closer attention to the oil passages when I had the motor apart) then perhaps the filter was clogging up.

Also noticed a small coolant leak on the pass side of timing chain cover. bummer.... I will have to figure this out tomorrow.

88BlueGT

The first thing I would do is get an aftermarket gauge. The stock gauges are known for crapping out.

white93 GT

i changed the oil filter, oil, and oil pressure sender. the oil pressure if full any time the rpm's are any above 1200. but as soon as it drops below there it goes to no oil pressure. could that still be my gauge?

i am thinking its an oil gally plug that came out or bad oil pump

ptown87

I had the same exact problem. My cars pressure would drop dwon to 9 psi at hot idle. With the new crank and bearings it never drops below 50. Thats what i had to do. First make sure your gauge is acurate. Bad oil pressure is usually caused by one of two things.
1. Bad oil pump
2. Bearings are shot

I hate to bring you the bad news but bad oil pressure usually means your bearings are shot. You will probably need a new crank and bearings. Thats what i had to do last week. Over time your bearings on your crank wear. This causes extra clearence. When the oil heats up it thins out and ends up slipping through this extra clearence and falling back into the oil pan causing you to lose pressure. If you live where it won't be getting too cold you could try putting a thicker oil in (10-40 or even 20-50) This thicker oil will help your situation a little but won't fix it. You should be getting about 10 psi for every 1000 rpm.


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white93 GT

i just pup in a new oil pump and new bearings. the motor has 30 miles on it.

the oil pressure was completly fine up till last night when it took a dive and im running out of ideas before i take the motor out AGAIN and tear it apart AGAIN.[:@]