Author Topic: AX160 No Oil pressure  (Read 3736 times)


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Re: AX160 No Oil pressure
« Reply #15 on: August 09, 2017, 07:46:10 PM »
    I agree with Steve that some of your oil passages might be blocked because of what you described that the oil drains back so slowly from the filter housing. Until you can figure this out this is what I would do if I were you.

Henry - From my understanding the filter housing drains back to the pan by gravity. I took the oil filter housing off yesterday and there was a little grey sealant we had used to save the gasket partialy plugging the drain passage.  That problem solved, but still no pressure.

From what I can tell from my reading the cap nut on the filter housing has a relief valve in it and the pump has a relief valve in it. I went and got a NOS oil pump from Rod Shaver yesterday as he is kinda local to us.  The new pump puts 3-5 PSI on the gauge. 

Checked the gauge with air pressure and a reguator - spot on.

I tested the relief valve on the filter cap with a pressure guage and air hose setup and it opens between 30-40 psi  - not that.

My old man thinks it's blow by around the rod bearings, The clearance is .0055-.006  right at the high limit of the tolerance in the manual.  Trying to source some .003 over Rod bearings now to bring that tolerance down.  I think he's full o crap, I could see 5-10 psi loss but not ALL of it....

We did not remove any oil passage plugs when rebuilding it  - we did not do a 100% rebuild -  left the crank and mains alone.  as they miked in tolerance and had no corrosion.  Did hone cylinders and replace rings/rod bearings.  Valve job, head gasket, oil pump, water pump, front seal, gaskets.   

The only place we haven't gone back into is the lifter gallerys, any chance that kind of pressure loss could be caused by the lifters?  - Probably tomorrow's project...

Thanks again for the help guys.



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Re: AX160 No Oil pressure
« Reply #16 on: August 10, 2017, 04:21:46 PM »
Hi Chris.

 I think that if you put a nos pump on and you still do not have pressure it is unlikely you have two bad oil pumps. I did some checking in my tech manual. There is a relief valve in the pump and if the spring is in spec it should be the correct pressure to supply the engine. If you check the oil pump spring it should be 2-3/4 inches free length and 7.85 lbs at 1-inch. I do not know where the relief on the filter cap is. I don't have one because mine has been converted to a spin on filter. But the tech manual says there is one, I cant find it, not even in the parts book.

Your pump should put out way more than 3-5 psi. I am curious how you tested it to get those readings. The book says 30-35 psi at normal running temp, that's about 160 degrees.

I am getting my info from tech manual TM 9-1711  (1942)

As you said there was blockage/debris in one of the drain ports, there is a strong chance that is not the only opening that is blocked.

Since you have an extra pump and drive gear. I would suggest you remove the teeth from the old gear so it will not contact the cam gear, and make an adapter to drive it through the distributor port with a drill and see what you get for pressure and flow. you should get at least 40 to 50 psi with room temp oil and the engine not running. You will know when it is pumping because it will pull fairly hard in the drill.

Good luck. I am really interested to know what you find.  Henry       


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Re: AX160 No Oil pressure
« Reply #17 on: September 03, 2019, 09:46:56 AM »
Most definitely prime the oil pump. I've seen more than one horror story of someone cranking with the motor not primed, and crunch.

What IS the correct way to prime the oil pump?  I'm going to be testing my engine soon and would like to know how other folks have done this after a re-build.


1941 M2 Autocar (restoring)
MVPA# 36810E