Piston Pump Suction Problems - Good Shaft Seal

Brad4321

New User
53 Jubilee with piston pump conversion completed many years and hours ago. This is my main utility tractor, typically used for mowing, hay, plowing, row cultivating, and pulling my big tractor out of the mud :lol:. I know we all love pictures, so here is this last weekend as I was loading it up with the 6' Ford 907 flail mower to do some trimming in the pasture. https://drive.google.com/file/d/173CNXyYx_lWoVo_QThdjZL4wxaS4BPRK/view?usp=sharing

Moving on to what is important....the hydraulics have been weak on this tractor ever since it was passed down to me. It started off as needing to prime the pump before using it every time, but would work after it was primed. I rebuilt the pump, found the front seal/shaft grooved and replaced both. The gear housing was cracked, replaced, and replaced both bearings.This did [i:87b6651523]not[/i:87b6651523] fix the problem and I still had to prime the pump every day. Within just a few hours after rebuilding the pump, the hydraulics died completely, no response from the 3pt.

I pulled the hydraulics cover and found the piston seal in the bottom of the case. I changed the cam pin which was grooved, replaced the piston with the new design and installed a new o-ring and leather backup washer. I adjusted the 3pt per the PDF that is floating around. I was not able to get both position and draft properly adjusted, so I split the error between them (I do use draft when plowing and cultivating). Both settings have a gap that is too large by approximately .015". I replaced the felt seal, draft control spring plate, and adjusted draft spring tension. Upon reinstalling the cover, the 3pt works again. Lifting counterweight for the loader tractor, around 800lbs, it held it in the air overnight only dropping about 6", and this is heavy enough to pull the front wheels on the jubilee without any front weight. I believe everything under the cover is good.

However, the pump will not hold a prime. Shutting the tractor off for 20 minutes, I have to reprime the pump. It will pick up anything, but the lift is very, very slow and jerky. Lifting the flail, which is fairly heavy for the jubilee, can take 30 seconds. The lift is slow and jerky without a load as well. This appears to be a flow problem as I have pressure (can lift anything). I have not put a pressure gauge on it.

I was thinking only half or so of the pump pistons were actually pumping, low flow and not smooth flow. Thinking I messed up the pump rebuild, I took it back apart. The front seal looks perfect, as does the wobbler shaft. I am not sure where the pump is sucking air from. However, I found damage to the ball seats on the pump head. This is the only thing I found wrong: https://drive.google.com/file/d/16uG5tkMCBvWm62fRnKi449izYTcxwbP8/view?usp=sharing. The seats are deformed enough to partially block the holes.

Here is a gallery of all the pump parts:
https://drive.google.com/drive/folders/1of03SwwaSnIY05-ybEqHTpKI1RNFGb45?usp=sharing

Can anyone identify where my problem lies? What is my best course of action here? The tractor has exactly 10 hours on it since I rebuilt the pump initially. I cleaned the pump body and head before these pictures, but did not clean or disassemble the gear housing as it is all new and still appears to be in perfect shape.

I run Travellers UTF in all 3 holes from TSC. It is "recommended" for 134D.

Thanks in advance for advice, this is becoming expensive and incredibly frustrating.

mvphoto79168.jpg



This post was edited by Brad4321 on 07/27/2021 at 08:05 am.
 

No, I did not. I have seats and the tools arriving tomorrow. Admittingly I don't fully understand how the pump works, however, I could see the leaky seats causing those pistons to bypass, but would it also cause a leakdown on suction?

Also, the seats are in the main pump/piston body. Are the seats in the head of the pump, the ones that are visibly damaged, replaceable?
 
Those are inlet valve seats, they
certainly wouldn't help maintaining prime
if not sealing. See picture below,
cutaway diagram, also shows where the
seats are. Also there are two versions of
the pump, are you sure you have the later
tapered roller bearing version? The
reason I ask is NAA is an older tractor,
could have older pump and some parts are
different. I also included parts list.

<IMG SRC =https://i.postimg.cc/SsYT8tyx/Ford-Hyd-Pump-Diagram.jpg>

<IMG SRC=https://i.postimg.cc/jsRY8HK7/nca905b.jpg>
 
I looked at your pictures and post again, you have the tapered roller bearing version which is good. The outlet valves seat to the valve plate, probably you should replace that.
 
Nothing jumps out in the pictures as being at fault but no check valves springs are shown. Hopefully they are in good shape, especially the 6 intake
ones in the pump body. The pump seal looks like it is in backwards although it looks like it has a spring on it. The wobble plate bearing plate looks
suspicious, but doubt that has any thing to do with ingression of air. But pictures may be deceiving!
 
The wobble bearing plate was new as well. It is shined where the bearing has been riding on it, but the surface is smooth.

I thought these seals were reversible? Both lips of the seal are positive with a spring.

Here is a picture of the springs: https://drive.google.com/file/d/17PemneJe-RmeHjrcl1Tx9OkDBHpyAuBU/view?usp=sharing . They all appear to be the same height with no physical damage. I think these were replaced when I rebuilt the pump the first time, but I don't remember for sure. New ones are in the kit arriving today.

Great diagrams Andy. It took me a bit, and some experimenting, to get a better grasp on this. The pins (number 2, p/n 354347S2) that are really deformed on my pump in the pressure/outlet housing are there to hold the outlet ball in place, correct? I initially thought those pins were the valve seat and the fluid flowed through them. Studying the diagram more, it appears they just hold the ball in the open position. I tried shooting brake cleaner through one of the pins and nothing came out. I was concerned over the deformation of those pins because I thought they were the sealing area. With that in mind, no reason to change them yet.

So, the outlet valves seal against the "valve plate" in the diagram and the inlet valves seal against the seats that are coming today. A new valve plate is coming in the kit as well, although I don't see anything wrong with the one I have. The chamfered area where the balls seat appears smooth, although a couple are a bit off-center of the hole.

In the end, I guess it all rides on my intake valve seats being bad/not sealing? I don't see anything wrong with them, no deformation or anything obvious, but I will be changing them out. I was hoping there was an obvious smoking gun here!

Well...I can't believe this. I was looking at the pictures in the gallery and thought I seen a crack in one of the inlet valve seats. Looked at the pump and it is cracked. I thought I inspected it close, but couldn't make it out until I looked at the enlarged pictures. My vision is really starting to go. Regardless of anything else, crack=bad. I'll replace those and post back on the results.

This post was edited by Brad4321 on 07/28/2021 at 05:36 am.
 
The pins are called stop pins in the
manual. I think they are there to let the
balls open the right amount without
overtravel. I'm not sure why yours are
beat up. In the manual it says:

Inspect the plate for damaged outlet valve
seats or damaged or worn valve stop pins.
Replace the plate if the seats are worn.
Replace worn or damaged pins.

Anyway I think you are well on the way to
getting a good rebuild if you install the
whole kit.
 
The Ford Master Parts book shows a drawn picture of the seal and bearing setup. The seal is shown as thicker towards the tapered bearing, hyd oil side
and the narrower side towards the Torrington bearing side.. That's the way the OEM seals were as I remember. Been a while since I have seen one!! I
think the damaged roll pins will have more effect on your problem that the crack seat! Maybe letting the balls getting to far from the seat and not
getting back in time. Just a thought!!!
 
I looked at the new, aftermarket seal that came in the kit and I don't see any real difference between the sides. This may be an issue of OEM vs aftermarket too.

The pins are backordered. I ordered a set and will change them out next time the pump is apart (with this tractor there is [i:7bde067dd7]always[/i:7bde067dd7] a next time). I don't like broken or known bad parts, never works out good long term. I put the pump together last night and had an interesting observation.

The intake seats were put in [u:7bde067dd7]upside down[/u:7bde067dd7]. The flatten side was towards the ball, the chamfered side was seated down. This tells me a few things. First, when looking at the picture you can see pounding marks on the seat. Without the chamfer, the intake balls were pounding it a bit randomly as besides a sealing surface, the chamfer guides the ball in straight. I'd guess this random pounding cracked the one seat, which was cracked clean through. The second thought is this was not a new pump when it was installed, but a reman unit that wasn't built correctly. I don't see Ford/NH making this mistake on an assembly line. It was many years ago my uncle had it converted when the original vane pump went bad, but he thought it was all new parts (or at least paid for all new parts). It is sad to think how many years my uncle fought the hydraulics on this tractor not working quite right, and I have too for the past 6 years or so, for something so simple.

Put the pump on, replacing only the intake seats, balls, all springs, plate/outlet ball seats, and gaskets. Did not touch the already assembled gear housing. After priming, it works. 3pt lifts rapidly with fast response. It responds fast enough to bounce the front end with the 602lb flail attached. Let it sit overnight, 3pt worked immediately this morning. I can't say it will hold prime for a long time yet, but overnight is a whole lot better than the 15 minutes before. The only noticeable issue is the 3pt is a bit jerky at low rpm still, but lifts smooth above 900rpm or so. I may still have air in the system as I haven't ran it much, or need a bit of seat wear-in to fully seal. I don't use the 3pt much at idle speed, so even if this issue persists, I consider this a victory.

Thanks for the guidance everyone, I consider this fixed at the moment. I knew something was fishy with the symptoms I was having, which is why I made this post. I've done tons of research on both of my Fords on this site and everyone points you towards the front seal when you have a prime issue. For anyone in the future researching this, got to make sure your intake valve seats are installed correctly as well :x
 
Remember how I said there is always a next time? Well, this isn't quite over yet.

Fired her up this morning, no hydraulics. Cracked the bleeder on the pump and got a burp of air and everything was fine. Air rises and it sat for a few days; I hopefully told myself it made sense.

Loaded on the trailer and headed to the farm. No hydraulics when I get there, got another little burp out of the pump and all was well. Ran her at pto speed for an hour, hydraulics working fine, then they just quit, with it still running. I had the bleeder cracked for a solid minute before anything came out. When fluid finally started coming out, it was extremely aerated. I let it bleed for another minute, but it didn't really get much better, however, the hydraulics worked again. Ran another 45 minutes or so at speed, implement broke, shut tractor off for 20 minutes or so while I fixed it. Had to bleed pump again when I restarted. Ran another hour and the hydraulics quit with it running again. Bled to get it working again, loaded on trailer came home. Of course I had to bleed them again on the trailer to get the tractor back in the garage. I shut it off, pulled the bleeder plug completely out and I don't see a drop in the pump outlet right after shutting it down. I pulled the dipstick on the hydraulics right after shutting it off and it was obvious the fluid in the sump is aerated. Pure foam on the stick.

As before, when it works, I can lift anything with the 3pt and it lifts fairly quick now. Losing prime while running is odd and so is the aerated sump, both new problems. Is something under the 3pt cover aerating the fluid by chance, causing the pump to suck foam? I haven't tried pulling the cover with it running to see if I see anything in there. My frustration level is too high this evening. I'm guessing this is the next step. Is there a particular culprit I should pay special attention too?
 
Pulled the dipstick cover and watched. The air is coming out of the backpressure valve tube. Sometimes big burps of air, sometimes ultra-fine aeration, but it is all coming out of the backpressure valve. I get a steady flow of drips out of the control valve assembly, as expected, but nothing odd there. Piston is completely dry. None of the pressure reliefs popped while I watched.

I ran a hose from the pump bleeder to the case and let it flow for about 5 minutes. With no pressure going to the hydraulics, no aeration was present and I got an excellent bleed on the pump. Flow looked good. Putting the plug back in, instant aeration out of the backpressure valve.

The valve seems to be working, I have control. I installed a new NH seal on the valve when I rebuild everything under the cover. Where is this air coming from? The only thing that makes sense to me is my new seal isn't working for whatever reason and I am sucking air there (possibly like a venturi). Running the tractor for 15 minutes or so, the entire sump turned to foam. I bet this is where the pump is getting air. After pumping so much air, it finally air-locks.

As anyone ran into this? With the backpressure valve tube under the oil level, I see no way for air to get into the system except through the seal between the valve and the piston body.
 
Are you aware of the warning that backpressure tube outlet should not be located near the pump intake? One thing to check:

<IMG SRC =https://i.postimg.cc/DZJk0L53/Backpressure-Loc-Warning.jpg>
 
Sadly yes, I was aware so no simple fix. My tube is positioned at the rear of the sump, farthest from the pickup. The flow through the sump, especially at PTO speeds, is pretty quick. I can watch the bubbles flow along the length of the sump right back into the inlet. I'm running a 134d fluid, however, there are just too many bubbles and too little time for them to dissipate before being recirculated. Its effectively foam/carbonation coming out of the tube. At 2.5gpm, it would effectively change the all the fluid in the sump in less than a minute. However, I see a direct flow from the backpressure outlet into the inlet, and based upon the sludge I cleaned out, the far corners of the sump don't circulate well. I'd guess the aerated oil from the backpressure tube hits the sump inlet in less than 30 seconds. That isn't much time for air to escape from oil.

I left the covers off last night. I'll try it again this afternoon and see if I can manage a video. I'll pull the acorn nut and make sure the backpressure valve is tight against the seal as a double check. I wish I had a better understanding of this hydraulic system. I have 2 different manuals on this tractor, but this system is so odd from any other hydraulics I have worked on and the books are not that clear on operation/troubleshooting. With pure fluid coming out of the pump bleeder when I have a hose connected, I am not sure where this air is coming from, but I don't believe it is the pump itself.
 
The recommended NAA piston pump upgrade
was 2.5 GPM, but the later piston pump was
4 GPM. The 4 GPM pump is far more common.
I wonder if you have a 4 GPM pump and the
increased flow causes problems with air
feeding back into the pump intake. The
problem may have become worse when you
rebuilt the pump to make it work to specs.
 
It is the 2.5gpm. I have the small pump pistons. Keep the ideas coming though, we are eventually bound to find the problem!

I have a 4cyl 4000 as well. It has the big pump and also bigger 3pt piston (3"). I'd guess, in theory, the smaller 3pt piston of the jubilee (2.5") matched with the smaller pump pistons means the 3pt is just as responsive as the 4000. However, it isn't. The 4000 lifts much quicker than the jub, twice as fast easily. I am not sure if this is a sign of something, just an assumption they should be comparable.

So, this makes me wonder. What if my backpressure valve is failing and isn't providing the proper backpressure? It obviously is supplying some, but if the pressure is low, the control would suffer. The unloader valve uses the pressure created by the backpressure valve to operate, so lower backpressure, loss in operating control (slow lift response). Not sure how this relates to air, but makes sense in theory. In turn, with all the air going through the backpressure valve, it may be having difficulty controlling pressure also causing my 3pt to lift slow. Throwing out speculation here.

If I get time and can find my gauge, I'll chain down the 3pt and see what pressure I am making. I do not believe pump flow is the problem, I got a powerful stream out of 1/2" hose through the vent last night. I also don't believe pressure is the problem either specifically as it lifts the 602lb flail without issue (on a tractor rated for an 800lb max lift).
 
What if you put your 4000 pump on the NAA
for troubleshooting purposes and see if
anything changes (isolate problem to pump
or the rest of the system).

If you get busy with a gauge backpressure
should be 40-45 PSI with control valve in
neutral or lowering position. I think you
would have other problems if that was too
far off though.
 
Not that long ago I decided to fix all the engine leaks, which was quite the task, and I cleaned up the oil mess. The tractor lives in my garage, but this garage is a 1 car shack with a busted up floor covered in oil. Needless to say, not the best conditions for noticing a leak.

While I believed my pump issues were solved, trying the 4000s pump would verify that. Well, when I went to disconnect the lines, I noticed they were wet. I had just cleaned the tractor. I cleaned this area again, came back a couple hours later, and had a small drip forming on the suction tube. Well, look at that.

Pulled the tubes off for a closer look. I replaced the original tubes when I got this tractor with the $295.00 dollar set from here at YT due to the tubes taking a hit and cracking the cast o-ring adapter piece. The welds on these tubes is absolute crap as an understatement. Welded by hand by someone who is not skilled leaving multiple visible pinholes in the welds, and undercutting that led to cracking in the weld toe. I was/am a welder and this is just flat out unacceptable for a $300 part (or any part). I didnt pay attention to the welds when I bought them, but I sure am now. So, I tigged these up. I burned out crazy amounts of contamination before I could get a solid bead. I dont think the tubes were cleaned before welding initially. Here is a picture after a quick wire wheel job on the original welds. The crack is on the left side. While there was an obvious crack, I also bet there were leaks through the pinholes as well. https://drive.google.com/file/d/1BDZTpOz16kdYv96FA0NLsKqfq4dbk7BQ/view?usp=sharing I put a solid bead on both ends of the suction tube as the pumps end didnt look any better with cracks and porosity. This was even more scary as this connection is above the fluid level and may never produce a noticeable leak. I didnt touch the pressure side, if it leaked it would be obvious.

Put it back together, filled the pump up through the vent, left it loose and fired it up. Had a burp of air, but the 3pt raised immediately. Backpressure valve had a burp, but cleaned up quickly. The 3pt raises just as fast as the 4000 now and is no longer jerky at idle speed. So, in conclusion, I was sucking air through cracks in the nearly brand new hydraulic tubes.

This was quite the adventure. Many issues at hand compounding the problems. With the 3pt raising very fast now and no longer jerky, as well as visibly seeing the crazy amount of bubbles in the reservoir gone, this may just be fixed. There will be a next time without a doubt. These tubes are a bad design. I may see about building a little skid plate for them.

This tractor has sat in the garage for years, rarely using it due to the 3pt issues. I decided this year to try to get this fixed, starting with everything under the hydraulic cover, in an attempt to save fuel. The 4000 is thirsty, twice the weight to haul around, and I rarely need that much power as our farm and implements are small. It may take a while to break even on fuel with all these repairs, but hopefully I have another 68 years before any more repairs are required ;).
Thanks for the help everyone.

This post was edited by Brad4321 on 08/07/2021 at 05:18 pm.
 
Very nice to hear you found and corrected
the problems. I compliment you on your
perseverance. It's a real bummer to
receive defective new expensive parts.
 

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