Sudden Loss of Oil Pressure

[Djthom]

HI All

 

I have a 74 that I've been using for months as a daily driver.  The other day I started it and the oil light was on.  I know it wasn't on the night before because I was watching the fuel gauge on my way home.  I put my oil pressure gauge on and confirmed no oil pressure.   No oil leaks or oil in the coolant.  

 

Since then I've pulled the pan, taken off the oil pump.  Everything seems fine including the relief valve.  The only thing I noticed was the o ring in the bypass tube was unseated.  But that might have happened as I took it down.  

 

Has anyone had a similar issue?  With no smoking gun I'm reluctant to just put it back together and repeat.

[Hans]

Check the upper O ring on the feed pipe. Hard to see how that could blow out. I'd look inside the pump and measure clearances. But odd that it worked, and then it didn't. Is there some way the filter can block flow?

[Djthom]

Thanks Hans.  I will look at that o ring also.  I took the front covers off to see if there was any type of internal oil leak inside the timing chest.  The car had sat for awhile. I bought a new filter thinking some sludge might have worked loose and blocked the old one.  

 

Are those o rings standard sizes that I can pick up at a local hose and hydraulic shop or do i have to order from part supplier?

[PaulTWinterton]

Quick test.

 

If you cover the output hole on the top of the pump with your thumb do you feel suction/pressure when you rotate the sprocket?  You should also be able to hear it sucking.

No suction.  No pressure. No good.  IMHO.

 

They can be shimmed.

[AustrianVespaGuy]

I like Paul's idea of freewheel testing the pump, but if that all seems in order and you have the pan off anyway, I would think at the very least a quick visual inspection of the crank bearings would be a good idea. I highly doubt you'll find a problem, but just-in-case/for-peace-of-mind, you know?

Edited July 1, 2019 by AustrianVespaGuy

[tech71]

Maybe no oil pressure at the sender because the oil passage is blocked/gunked up? Seen it before on other types of engines. Poke a pipe cleaner or something down there.

Edited July 1, 2019 by tech71

[Djthom]

Yes for sure.  Got to love the "while its apart... ." trail.  But that's part of the fun of having vintage machines 

[Mike Self]

Didja install your oil pressure gauge (presumably a temporary install) at the warning light sender location?  If so, did you confirm that there was no pressure at  the sender unit location by cranking the engine with the sender unit at least loosened?  It's just possible that the feed to the sender unit itself is plugged up with a piece of crud...

 

As folks have found out the hard way, when the sender unit goes, the engine will pump out all its oil via that spot in a couple of minutes at highway speeds...so there should be a healthy spurt of oil as you crank the engine; if not, run a soft copper wire down the hole and try cleaning it out--or pull the dizzy housing and clean it thoroughly.

 

mike

[Djthom]

Hi Mike, I did crack the fitting to see if any oil was there but nothing.

 

I think I know what happened.  The bent oil pan baffle and missing bolt on the pickup hanger of the oil pump suggests the PO had it apart before.  I didnt have to raise the engine to get the sump off.  

 

The o ring on the little pipe had some telltale indentations that look like it was pinched.  I think they may have put the o ring in the body of the pump rather than on the pipe when last installed.  

 

I opened and cleaned the  pump.  Resealed it.  Made an adapter to spin the rotor with my drill and its pumping oil.

 

So I'm going to assume it was the oring incorrectly installed which gave way and put back together when I get my gasket set.  

[Hans]

I'd be looki g inside the pump while its out. The o rings have to be suitable for that environment. 

[Dudeland]

Maybe make sure that the top end is tight. Someone on the forum found they did all that and it was a leaky oiler bar.


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[Djthom]

All fixed with 65psi at idle.  I believe the incorrectly installed oring was the root cause in the end.  I lost a few weeks of driving but I'm glad it happened when it did and now I have new gaskets on the front of the engine and the pan. 

 

If you're reading this please use it as a reminder to make sure your check oil light bulb is working and not burnt out

[Djthom]

Bumping an older thread.  If you're at home and looking for a project to do on your car, I implore you to fix a faulty or burnt out oil pressure light if you have that issue.  A working light saved me from catastrophe.