i have a 440 with a milodon oil pump with 2 lines and the thing will set for about 3 days and it will lose its prime. what is wrong and how do i fix it??thanks Ed

It's bleeding off because it's not sealed somewhere. You can either try to tighten the fittings more or ..
1.take it apart and clean all the oil off
2.put a sealer on the threads and reassemble(Gray Permatex )

I put JB weld on the pan bulkhead fittings because the O-ring seems to be a common problem.

I past post on this subject a cure to the problem is to raise the pick up line from the pan above the pump . this will hold oil some oil to prime the pump. On my system,I have the line from the pan going up almost to the header then down to the pump, never had a problem. Now have added a accumulator for pre-lube which would pre prime also .

yeah..this came up last year in a post.. a longer line with sort of an horizontal "S" will work.
Don't take this as an insult or anything but..to me that seems to be overlooking a bigger problem of not sealed somewhere.
I've been using Milodon's for decades and never had that problem as long as it was sealed up. Believe me, I've taken them apart and reassembled them many.. many times before getting it sealed so it would prime. But now I use better sealer and the oil pressure always comes up while the car is cranking over.
I did have have a problem one time where the car had sit 4 years and wouldn't prime.
But these are my views and don't amount to a hill of beans

thanks for your help i would think it was sealed up it does not leak any where. all the fitting are dry

This has been a known problem since the '70's and has nothing to do with sealing up. If sealing were the issue then you'd be drawing air into the pump with the oil - definately NOT GOOD!

On a stock pump the feed line comes up through the block and down into the pump. No matter what, it will hold some prime.

However, with the Milodon pump setup either the single or dual lines both feed up and into the pump. When the engine is off, the oil just runs back to the pan.

Of course in order to do this it needs to have air bleeding in from somewhere - like around lifters, cam bearings, rockers, etc.. And any oil below the pump will bleed off - like around the crank.

The bleeding off speed will depend on the thickness of oil and how much your clearances are.

The solution was mentioned ... run the lines so a section is above the pump. Another solution would be a -12 check valve in each line (Summit - not cheap!)

If that's the case, why do my Milodon pumps ALWAYS prime themselves? I don't do anything with the lines.
Please explain it to me because I really want to know?
Maybe it's karma

but really, I've been using Milodon oiling systems since the early 70s..almost 40years. If you can give me a reason why I went from having those problems..to not having any, please give me a reason that makes sense.

Quote:

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why do my Milodon pumps ALWAYS prime themselves?

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They'll prime themselves alright ... how LONG it takes to prime is the issue! The engine should have pressure almost instantly when it fires. If the pump takes a couple seconds to prime and build pressure then there's potential for wear in the motor.

So you solved "your" problem by sealing a leak. Great! But that's not the most common cause for loosing the prime.

A suggestion im thinking of doing if i encounter these problems is to install a T-ee fitting at the inlet of the pump with a -3 or -4 line and rout it to my accumalater with a ball valve for the -3 line, crack it open for a few seconds to put some oil in the pump,close it and fire the engine right away, i would still use the accumalator for engine priming and as needed.

That's fine if you plan to have the hood up every time you start the engine (assuming all is under the hood!)

This is absolutely a known problem with dual line kits and has nothing to do with sealing. I put a single line on my last build and that solved the problem. Single lines are adequate for most engines. You can also use check valves in the dual lines but if you do this use GOOD check valves. I got mine from Kinsler for my last dual line and they cost almost as much as the system.

Yep, Milodon pumps are well known for losing their prime. If everything is nice and tight and you loop the oil line properly it will help to stay primed. The sure fire solution is to plumb in an Accusump setup but that is extra money, weight and space.

Here is one of my favorite pictures. It shows a nice clean setup that maintains prime really well.

thanks for your help

It is also possibe that a small piece of debris got in the ppump and scarred the cover or gears. This will cause pump to lose it's prime. I had a needle bearing from a rocker pass through and cause