1990 Ford Mustang 5.0 Loss of Oil Pressure when accelerating
 

Hi there

I’ve recently rebuild my 90 mustang 5.0. Was a 302 and was bored 30 over. Primed the oil pump before start up and put about 30 miles on the engine and then noticed my oil pressure gauge kept dropping to zero when I accelerated and on decel and idle it came back up. Brought the vehicle home and noticed some noise from the valve train assuming the oils not getting there? I removed my distributor to look at the shaft and couldn’t tell much. Now I’m wondering if I should run the car again with a gauge hooked up or if I should look towards dropping the oil pan and inspecting the oil pump? I replaced the pump with a normal oe spec melling pump and pick up tube.

I'd try checking by hooking up an aftermarket gauge just to be sure.

Okay I will do that first. I do have a fuel pressure gauge that measures 0-100psi. Would that work to test oil pressure aswell?

I'm honestly not sure if it will work or not, I had issues with mine a few years ago and I just bought a cheap gauge to check it. I think it was only around 20 dollars or something.

yeah, for sure check it with a mechanical gauge. they are pretty cheap at the parts store.

i guess the thrust bearing is good? I have seen that cause a loss of pressure on different type engines. I assume that may apply to the 5.0

is the car an auto or manual?

All the bearings were replaced when the motor was out. Car is a 5 speed manual. I will perform a oil change tomorrow and place a gauge and measure oil pressure

make sure you didn't blow an oil galley plug out.....there behind the timing cover.....right around where the cam slides in. that will cause the issue you describe. Had it happen more than once, now I tap those holes vs the press in plugs

Should I pull the timing cover out and inspect first?

Any guidance please? On if I should start by draining the oil and cutting open the filter to inspect and filling new oil and check pressure with a gauge or should I remove timing cover and inspect the oil gallery plug?

Anyway I can confirm I have a blown oil gallery plug without having to remove the timing cover?

personally, i would take the valve cover off. then verify no oil pressure and where the noise is coming from.

if you didn't want to crank it, i guess you could pull the distributor and use a drill to spin the oil pump shaft. either way, i am pulling the valve cover off.

No one has mentioned the galley plugs in the rear of the block. Course, in front the oil leak would be contained, but in the rear, it would leak out under the clutch/converter housing. Have you looked under the car?

Bad news,
i ran the oil pump with a drill and found it is working and giving oil to my valve drain. I drained the engine oil and cut open the oil filter. I noticed my engine oil is goldish bronze colour. I installed the pressure gauge and fired up the car and found 0psi of oil pressure and lots of noise coming from the engine? Would I have spun a bearing? I was wondering how would it have spun? Something must of caused it to destroy? Please input.

sounds like you spun a bearing. I'd say pull the motor personally. do you know if the bearing clearance was checked for the main bearings when the motor was rebuilt? First thing that comes to mind is that maybe the wrong thickness bearings were used.

could also be that the oil pump isn't working correctly and there's just no oil getting pumped.

Zero oil pressure,bearing material in the oil & a knocking noise at idle are usually an indication of a bearing issue for sure.Many things could have went wrong to cause the bearing issue.If the spark plug wires are removed individually with the engine idling,the knock will lessen or disappear once you reach the affected cylinder if its a main or rod bearing.However since youve already got bearing material in the oil,I wouldn't run it any further because you risk more damage to the rest of the engine components with bearing materials running through every surface that gets lubed.


https://www.enginebuildermag.com/201...spun-bearings/