2n new build losing prime

TheCarDoc

Member
Hey guys, I've got a 2n headache. Here's the deal, new sleeves, pistons, seals, gaskets, oil pump body (3/4 gears), line bore and machine work, new pick up and relief valve and spring, new valves and everything. Checked crank, cam and all with mic, it's to spec 30/30. New .30 rod and main bearings. Packed oil pump for initial start up, got oil flow from block. Both oil gallery plugs are in. After initial break in I stopped the engine and let it cool. Started it up again, started hearing some noise, no oil pressure, primed through relief hole, low and behold, oil pressure........until I cut it off and let if sit around 15 mins. No oil pressure. I know everything is to spec. Torqued and all. The only thing I can think of is the paper gasket at the pick up isn't sealing and allowing the hot thin oil the seep out and lose its prime. Anyone have any thoughts? I'm running 10w40 for break in. I'm in alabama so thicker oil isn't out of the question either being that we dont know what winter is.
 
I don't think thicker oil will solve your problem. Drop the oil drain plug and check the pickup tube for looseness. Maybe tube was cracked
during assembly?
 
I'm going to drop the pan shortly. I put a vacuum pump on the new pickup when I got it and closed the other end to make sure there were no issues.
 
What is supposed to keep the oil from running out of the pump when it is shut down? I'm wondering if it is the pressure relief valve and your new one isn't seating. If oil could run out of the oil pick up gasket like you are thinking, then what's to keep oil from running out when ever anyone drains the oil for an oil change? Just some thoughts.
 
(quoted from post at 15:16:29 06/19/20) What is supposed to keep the oil from running out of the pump when it is shut down? I'm wondering if it is the pressure relief valve and your new one isn't seating. If oil could run out of the oil pick up gasket like you are thinking, then what's to keep oil from running out when ever anyone drains the oil for an oil change? Just some thoughts.

Gravity keeps enough oil in the pump to maintain prime. Despite protestations to the contrary something is not to specification. My first WAG would be face width of new oil pump gears.

TOH
 
(quoted from post at 18:36:01 06/19/20)
(quoted from post at 15:16:29 06/19/20) What is supposed to keep the oil from running out of the pump when it is shut down? I'm wondering if it is the pressure relief valve and your new one isn't seating. If oil could run out of the oil pick up gasket like you are thinking, then what's to keep oil from running out when ever anyone drains the oil for an oil change? Just some thoughts.

Gravity keeps enough oil in the pump to maintain prime. Despite protestations to the contrary something is not to specification. My first WAG would be face width of new oil pump gears.

TOH

PS> New oil pump body needs to be align honed to get proper bearing clearances on the front main. That is a different issue but needs to be addressed.

TOH
 
The pump gears are 3/4" in a new
housing. Bushing was pre center reemed
with pump housing from the store. Just
put it back together with the same
issue. New pick up, no
cracks,dents,dings nothing. It is to
spec. Put the old relief valve back in
and has the same issue. I can prime it,
crank it and have oil pressure. Stop it
and wait 5 minutes, no oil pressure.
 

Check how much clearance there is between the "sides" of the oil pump gears and the housing using Plastigauge.
 
(quoted from post at 19:08:06 06/19/20) The pump gears are 3/4" in a new
housing. Bushing was pre center reemed
with pump housing from the store. Just
put it back together with the same
issue. New pick up, no
cracks,dents,dings nothing. It is to
spec. Put the old relief valve back in
and has the same issue. I can prime it,
crank it and have oil pressure. Stop it
and wait 5 minutes, no oil pressure.

I heard you the first time and I gave you something to check. Dont assume anything. Use a micrometer and check the actual dimension of one of your "new 3/4" gears". It should measure .725.. There are lots of junk kits on the market with new gears that are roughly .010 undersize. Let me repeat, those kits are unusable JUNK and will not pump reliably.

Your new oil pump housing is also a main bearing cap. Caps and blocks are bored as a matched assembly by the factory. You cannot simply swap caps from one block to another. If you replace ANY cap on an engine block you have to rebore the block and other caps to match. If you dont the bearing bore of the new cap will be out of round and alignment with the other bearing bores. This is basic engine building 101.

TOH
 
In my initial post I said I had it
lined bored. Every part I purchased
came from YT. Except my engine kit.
There was no attitude in any of my
replies, calm down. Was in the middle
of putting everything back together
when I responded, I checked the gears
with my dial caliper.
 
(quoted from post at 22:30:17 06/19/20) In my initial post I said I had it
lined bored. Every part I purchased
came from YT. Except my engine kit.
There was no attitude in any of my
replies, calm down. Was in the middle
of putting everything back together
when I responded, I checked the gears
with my dial caliper.

Calm as cucumber and I simply missed the line bore comment. I am trying to help you but you are not giving specifics. What did the oil pump gears measure?

TOH
 
.724 +- (on the fly measurement with my
dial). Trying to be very specific so I
don't leave anything out. I think I may
have another kit from a previous build,
i may swap the gears out.
 
(quoted from post at 23:14:13 06/19/20) .724 +- (on the fly measurement with my
dial). Trying to be very specific so I
don't leave anything out. I think I may
have another kit from a previous build,
i may swap the gears out.

Face width of .724 is right on. The bad ones are typically around .710. But apparently something in that pump is not right. Measure tip clearance to housing with a feeler gauge. Should be just a few rhousandths. Also measure end clearance with a good straight edge and feeler gauge. Remove all traces of gasket and sealer then set straight edge on face of housing and measure gap between gear and straight edge with the feeler gauges. Should also be just a few thousandths.

Which brings us to the unasked question. You replaced original oil pump and pickup tube. Why?

TOH
 
Housing had a crack from outside face
of fear shaft into center of pump
housing. This engine was not oiling
before. Pick up had been severely
abused in the past 70 years. I will
pull it and check all tomorrow and let
you know.
 
(quoted from post at 23:39:40 06/19/20)
Face width of .724 is right on. The bad ones are typically around .710. [b:736d9cbb3e]But apparently something in that pump is not right[/b:736d9cbb3e]. Measure tip clearance to housing with a feeler gauge. Should be just a few rhousandths. Also measure end clearance with a good straight edge and feeler gauge. Remove all traces of gasket and sealer then set straight edge on face of housing and measure gap between gear and straight edge with the feeler gauges. Should also be just a few thousandths.

[b:736d9cbb3e]Which brings us to the unasked question. You replaced original oil pump and pickup tube. Why?[/b:736d9cbb3e]

TOH


I could mention a lot of stuff here, but I'll keep it simple:

Listen to TOH

Oil pumps have been discussed here to great lengths.
 
Okay, just pulled it down again. The
edge of tooth to wall clearance is
tight on a .005 brass feeler. The face
of the driven gear to pick up back
plate (straight edge) is between .006
and .007. The drive gear is way more.
Low and behold, the drive gear face to
face is .710. The driven gear is .724.
When I had it line bored I got the
machine shop to go ahead and press the
gear on for me. Between me and dropping
of the kit(unopened package) and
getting it back, either a gear got
switched (most likely) or it was
packaged wrong (not like from yt). I'm
not happy, machine shop has some
questions to answer. I did knock it off
myself to check the measurements. It's
a mess.
 
(quoted from post at 13:37:38 06/20/20) Okay, just pulled it down again. The
edge of tooth to wall clearance is
tight on a .005 brass feeler. The face
of the driven gear to pick up back
plate (straight edge) is between .006
and .007. The drive gear is way more.
Low and behold, the drive gear face to
face is .710. The driven gear is .724.
When I had it line bored I got the
machine shop to go ahead and press the
gear on for me. Between me and dropping
of the kit(unopened package) and
getting it back, either a gear got
switched (most likely) or it was
packaged wrong (not like from yt). I'm
not happy, machine shop has some
questions to answer. I did knock it off
myself to check the measurements. It's
a mess.

Well I'd say you have found your problem and the good news is it is an easy and inexpensive fix. Hard to blame the machine shop if you provided the parts.

TOH
 
Yeah, I'm not blaming them, just gonna
fix it. The oil pressure wasn't good
when it was pumping so I'm pretty sure
that's it. I will keep you posted.
Appreciate it.
 
Got my new kit in today, used a dial
caliper and checked new gears, both are
.725 +/-. Packed and installed. The
face of gear tooth clearance to side of
housing was half of the other gears.
Filled with 30w. Started and had 65 to
80 psi on start up, went steady around
40 to 45+ cold. @Idle and normal
operating temp, it's around 20 to 24
psi and under mild throttle it's around
35 to 40. Darn pump kits. Thanks guys.
 
Also, I have an aftermarket oil pressure gauge from TS. Not sure how much I trust it. I'm now reading slightly under 20psi at idle and around 26-28 at mid throttle. It has oil pressure though and it's pretty hot today so I'm not too discouraged.
 


CarDoc, let me fill you in on a little background. I believe that it was early last year that an issue came up with the N oil pump kits. The Old Hokie was the one who bought some and measured them and found excessive clearances in some. He is the worlds foremost expert on Ns so you should acknowledge that and be thankful that he is willing to offer his advice, even if it is in a gruff manner.
 
(quoted from post at 18:42:13 06/27/20)

CarDoc, let me fill you in on a little background. I believe that it was early last year that an issue came up with the N oil pump kits. The Old Hokie was the one who bought some and measured them and found excessive clearances in some. He is the worlds foremost expert on Ns so you should acknowledge that and be thhe ouankful that he is willing to offer his advice, even if it is in a gruff manner.

Steve Dabrowski discovered the problem with the oil pump kits. I simply researched the gears and obtained full specifications from the Ford prints because I prefer facts over speculation. i know darn little about N series tractors and I am not gruff. I am in fact an arrogant a-hole who spends hours on the phone abusing silly N owners who call me looking for all manner of help. They apparently like the abuse because they call at all hours of the day, often talk at length, and frequently call again. Strange how that works.

TOH
 

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