Interpreting Hydro pressure readings

[tommyg 152]

Paul loaned me his pressure gauge and I was able to get some readings from my hydro pump on my d-180. I'm not sure how to interpret the results, but I thought I throw them out here and see what you guys think. The problem I'm experiencing is power loss as the oil heats up, and high oil temps. Here's what I found out...

At start up, the pressure reading is about 400-450 psi cold. At 125 deg and full throttle, that number is about 380 psi in neutral and 200 psi with the hydro engaged. At 150 deg., I have about 340 psi in neutral and 180-200 psi with the hydro engaged. At 175 deg. I'm reading 280 psi in neutral. At idle, about 175 psi.

In all cases, if I push the hydro hard when the oil is hot, the pressure drops as low as 25 psi. The pump really whines, but only in forward. Strangely, it seems that reverse doesn't affect it as much. In all cases,if I'm climbing a grade, the tractor often stops and I have to give it a little more hydro to get it to keep climbing.

I'm up for suggestions and advice. Is this a normal scenerio? Is it the pump? motor? What do you think?! Is there a different way to test? I'm just throwing out my observations.

[coldone 35]

Here is the pressure testing exert from the manual. The way i read it is that you should not be seeing in excess of 150psi when in neutral. The only time you should see High psi in nuetral is when the implement system has reached its full travel and the cylinder has bottemed out. This is a SWAG but I wonder if you have leakage in the lift control valve and it is letting the valve bypass to the cylinder.

Before I would act on that SWAG I would let somebody with more knowledge chime in.

CHARGE PRESSURE TEST

Charge pressure is on indication of transmission

condition. Connect the pressure gauge as shown in

Fig. 13 to the ~" pipe plug located between the implement

hose ports. The alternate port (straight thread)

just above this port may be used if it is more convenient.

With the engine running at % throttle the charge

pressure should be 70 to 150 PSI. The pressure must

. never drop below 50 PSI under any condition. Always

take pressure tests when the transmission oil is cold

and again after the transmission has reached operating

temperature. An appreciable drop in charge pressure

as the temperature rises indicates internal leakage

caused by worn parts resulting in loss of power.

IMPLEMENT PRESSURE TEST

Use the same gauge hook up as Charge Pressure

Test.

If the tractor is equipped with a hydraulic lift, implement

pressure should be checked. Pressure should

be 550 to 700 PSI when the piston has reached the

end of its stroke.

[tommyg 152]

Here's an update. The first observations were made under normal operating conditions, not controlled as the Sunstrand manual outlines. So I decided to do a controlled test as above and I found that I still get the 400 psi in neutral at 3/4 throttle. With the hydro in full forward, that drops to about 280-300 psi. As the oil heats up, it levels out at about 200 psi. According to the manual, that's WAY outside normal operating parameters! Doing the implement test, the pressure drops about 50% when I raise or lower the lever. However, there is no change in pressure as it reaches the end of the travel. The manual says it should hit 550-700 psi. As it is, there is absolutely no difference. Anyone else out there care to interpret?

[coldone 35]

I hooked the guage up to mine today too. Mine moves but has no power when moving. My neutral pressure was between 50 and 100 PSI. I took alot of notes and will be posting them later. I have no idea whats up with your system but I think with some patiences and perserverance We both will get the figured out with some help from the Disfuctional D family here. Just hang in there i am sure help is coming!

[tommyg 152]

I sure hope so. Seems strange my pressures are that high! I'm wondering if a valve might be stuck somewhere. My neutral pressure is off the charts according to the manual. Looking forward to seeing your notes.

[coldone 35]

It will be a day or two before i have time to put them up. I just cant understand how you have that much pressure and no power. Sounds like a restriction somewhere.Pulling the panels off and checking the relief and check valves wasnt as hard as I thought it would be. I even had to make a tool to remove the check valves cap screws. I will write up everything and start another thread.

[pfrederi 17,887]

Sorry have company right now and haven't been able to think this through ... later this week . As i recall you are now using 10w-40, correct?

[wheeledhorseman 574]

Seems strange my pressures are that high! I'm wondering if a valve might be stuck somewhere.

Tommy, looking at the Sundstrand schematic that would seem a reasonable deduction to me in which case the likely culpret is the charge pressure relief valve which isn't opening. I'm not an 'expert' and I'm sure the others will chip in but I'm pretty sure that's the valve that limits the pressure to 150 psi.

I even had to make a tool to remove the check valves cap screws.

I'll be interested to see the tool you made coldone as I have been putting off making one myself to get those pesky check valve cap screws out.

Andy

[Callen 64]

The heat is coming from the high pressure. Wonder if some one put implement relief shims in the wrong place? Or maybe too many

[tommyg 152]

Some interesting preliminary deductions. Using 10w 30 now. High pressure, high heat makes perfect sense to me. Where is the charge pressure relief valve located, on the pump or on the motor? How would I inspect and/or test this valve?

[wheeledhorseman 574]

To save me posting twice take a look at what I've suggested here

Andy

[tommyg 152]

Andy, so take me through the process to investigate this. Where will I find the implement control valve? Callen was pointing to perhaps the same culprit. What are these shims you speak of?

"As far as I can make out..... the charge relief valve remains shut until the charge pressure reaches somewhere in the 70 -150 psi range. The pressure generated by the main pump is fed to the hydro drive pump only until the valve starts relieving at which point it alows oil to bypass through the implement control circuit. It passes through the implement control valve assembly and back into the system to return to the reservoir. It's a critical feature of the desgn that the implement control valves be the type that alows an open flow through them in the 'neutral' position. It this pathway is partially blocked for any reason the charge pressure will be higher than it should be for normal operation. A dysfunctional D high pressure problem could relate to this. I have come across a hydraulic hose in the past where the rubber had swolen internally reducing the bore down to a very fine hole which fluid would still pass through at high pressure."

When an implelent valve lever is operated this bypass flow is directed to a ram moving it until it reaches the end and there's nowhere for the oil to go. At this point pressure in the whole system rises rapidly to the 500 -700 psi range at which point the implement relief valve opens alowing oil to bypass the implement circuit and return to the reservoir.

[wheeledhorseman 574]

Send me a pm with your email and I'll send you one of the better Sundstrand manuals.

It gives a good description of how the system works and servicing them.

Andy

[otrelwood 32]

man you guys are getting me nervous to even run mine it worked pretty good before i changed the rear end now i'm half scared to see if it works . i changed the rearend because when i bought the beast the po said it leaked a little oil at the right seal; yeah a little all right jackedit up and the axle would move at least a 1/4 inch in the housing up and down play not endplay

[coldone 35]

The implement valve is the hydraulic controls. The two levers that make the deck and 3PTH go up and down.

[tommyg 152]

For those of you who might still be following this post, I stumbled upon something interesting. The implement valve has a spot for two handles, although only one serves any function since I do not have a 3PT. As I looked closer, I realized that the one "spool valve" that directs the flow of oil to the lift cylinder (the one without a purpose) is stuck in the depressed position. It's like you would be lowering the 3PT constantly. It will not return to the neutral position as the other one does. Also, the valve is rotated at 90 degrees to the functional one. No amount of coaxing will get it to budge either. It's sounding like this is the reason for my pressure problems and probably my whole issue. I'd post a pic, but I have no clue how to do that. Suffice it to say, I'm looking for a replacement implement valve for a d180 if anyone has one they care to part with. I will make sure to post the result once I get a replacement installed. Thanks to Andy and Paul for your consulting work!

[JamesBe1 82]

Tommy,

Did you try good old vise-grips to pull it out? Also, are there any hoses running to it or is it capped off?

I am having trouble visualising it, a pic would go along way.

[coldone 35]

That would explain alot. I had the same thing on another tractor, I used vice gripe and a hammer to unstick it.

[wheeledhorseman 574]

Here's the photo of the valve that Tommy sent me.

I thought it might be useful to include a little explanation here for future reference by others.

The charge pump in the unit coupled to the engine is very much like the oil pump in an automobile engine and has a pressure relief valve (charge valve) that limits the pressure to the range 75 - 150 PSI. Oil presure in the charge circuit is used to keep the hydrostatic pump and motor circuit primed.

The pressure is controlled by the charge valve allowing excess oil to spill past it. This oil is passed on to the implement lift control valves which are an 'open centre' type.

When the implement valve is in the neutral position (shown above) oil passes straight through the valve. Where there are two valves for the mid and rear hitches the oil pases on to the next valve before being returned to the main pump housing.

Moving the spindle valve either way from its center neutral position blocks this through passage way and directs the oil to one or other end of the hydraulic piston at the same time opening a path for oil to escape from the opposite end of the hydraulic cylinder.

When the piston reaches the end of its travel there is nowhere for the oil to go and pressure climbs rapidly if the implement lever isn't released.

To limit this to a safe level the implement relief valve in the pump housing unit opens to regulate it to somewhere in the region of 550 - 700 PSI by alowing oil to bypass the implement circuit completely.

If one of the implement control spindle valves is stuck either partially or fully either side of the neutral position it will result in higher than normal pressure readings all the time. Restricting the flow of oil will also cause temeratures to climb above the normal range.

For completeness, the oil returns to the transmission reservoir via the hydro pump casing, manifold pipe, hydro motor casing, and finally the oil filter.

All hydros generate heat, according to a Sundstrand manual I read this can be up to 25% of the engine power being fed in ! The heat is dissipated from the pump unit, manifold pipes, and transmission casing in a 'D' but under normal conditions it shouldn't go above 200 degrees F. Any restrictions in the system that shouldn't be there will create more heat than normal as the oil is forced past them.

Hope this makes sense to you all.

Andy

[coldone 35]

Great writeup Andy!

[JamesBe1 82]

Wow, that was a clear and intelligent explanation, I really appreciate that.

To Tommy's problem, It certainly seems that his broken plunger has to come back out. No way around that short of replacing the whole thing. I recommend vise-grips, hammers, PB-Blaster (or the like), heat, or whatever it takes to move it back to normal.

Something to consider:

How long has it been like that? Does it pre-date the recent pressure problems? If so, then it might not be the cause of the pressure problems, but a contributor. With the spool valve being stuck in, it only blocked off the return flow of the oil. But the first valve was there to provide that the whole time. One would have to hold the first valve open with the implement cylinder at the end of it's travel for a while to cause any damage.

But then again, that's just my theory. It's not necessarily worth the paper it's written on. I've often heard the whine a system makes when an implement cylinder reaches the end of it's travel (it gives me the shivers - kinda like fingernails on a chalk board). Theoretically, that shouldn't happen as the other spool valve would be providing the return path, so I guess that theory is shot down in flames! Happily so as I would really like to see this broken valve be the answer to all the problems in this system.

Sooner or later, we are all going to have to deal with bad spool valves. Probably some of us already have. Does anyone know if it is an off the shelf part or something made specifically for wheel horse by the manufacturer.

[wheeledhorseman 574]

Here's a photo of my implement lift valve assembly from my D-200 as I got it (left) and the replacement unit I used to replace it from a D-180 that was being parted out in the US (right).

One of the spindle shafts had sheared off at an obvious weak point i.e. where a hole has been drilled through it. Unlike Tommy's valve it was still mobile and sitting in the neutral position causing no issues other than you couldn't use it.

An enterprising PO had swapped the plumbing around so that the mid lift valve would operate the point hitch. I guess he didn't use the mid lift. Look carefully and you'll see that the adpators have been moved over - that's why they're on the other valve in the replacement.

Anyway, these valve units comprise four parts: two spindle valve units with outlets for the hydraulic cylinders and two end castings, each with a connector for the flow and return.

The four parts are held together by bolts so I'm guessing there's an O ring between each to make a seal. For other applications you could mount several of the valve units between the two end castings.

All of this leads to several possibilities. In theory if there's no use for a stuck valve unit (e.g. no 3-point hitch) then it should be possible to remove the faulty valve and bolt the two ends together with just the one working valve unit between them. The problem here would be the rigid pipework to one end would need a bit of coaxing over to the new position.

Another possibility is to remove a valve unit from another identical unit where one of the valves has failed or had the lever broken off. It's why I've kept the old valve unit from the tractor - there's one good valve and I might just need that one day!

Obviously, a complete swap out for one from a tractor being parted is the less adventurous option and the path I took as there was the opportunity to do so.

These valve units would not have been specific to WH only applications - they're standard 'open center' control valves but whether the manufacturer still makes them in this exact pattern is unknown but I doubt it. In theory a modern equivalent could be used and was another option I considered but mounting such a replacement, possibly needing to adapt the dash panel slots that the levers sit inside, and probably needing to replace the rigid pipes to and from the pump unit all made this a less desireable option. There might just be a modern direct physical replacement unit available but I didn't get round to investigating that.

Despite my curiosity I didn't dismantle the old unit from my 'D' as leaving it whole was probably the easiest way of storing it for the future without dirt getting into it. Oh well, I guess I'd better open it up to find out how the parts seal together and see what's what so I can post some photos. I'll see what I can do this week folks.

If it turns out to be pretty straight forward then if the worst comes to the worst re finding a replacement Tommy, then I'll send you the valve I won't ever use - yes it's broken but only in that it has no lever, it does sit in the neutral position properly.

Andy

[coldone 35]

The "caps" on the bottom can be removed to access the shaft. There should be a screw, spring, and retaining washer on the shaft end. Remove the those 3 pieces and using a brass rod drive the shaft out, if its stuck. If its not stuck the shaft should push out easily.

ETA: For some reason the board tells me that uploading isnt allowed. I have some pics of what the shaft looks like and the reapir I had to do to one of mine. i will try again later.

[wheeledhorseman 574]

It was hammering down with rain here all day so with limited number of things I could get on and do I made a start on investigating the implement control valves.

Firstly, found that Bob (Trouty56) has uploaded the service manual on to RS so to save you spending time searching for it here’s the link:

The manual lists the fact that different valves were used for the 18 & D-series with Sundstrand, the 16 and C series with Sundstrand, and later C-series with Eaton.

Two WH part numbers are given for the 18 / D valves but this doesn’t appear on the valve itself.

Although I’d cleaned the old valve assembly as best I could before removing it to prevent dirt getting into the ports when the pipes were disconnected it was far from perfectly clean so got the remainder of the typical dusty oily grime off and discovered the manufacturer was Ward Co. but I haven’t been able to find out anything about them so I guess they’re long gone out of business or been swallowed up by a bigger company. I did find references to control valves by Ward Co being fitted to other stuff of the same era like the Massey 1855, Ariens 5-16 H, and Sears loaders.

The thing is though that the castings may look the same but not all valves by the same manufacturer are the same inside and I came across a couple of photos to illustrate the point.

This is the valve unit from a Massey 1855 and just out of view is a WH valve unit. One of the Massey valves has a longer spool cap indicating that the casting contains a ‘float spool’ which creates an additional position on the control lever in which the hydraulic ram is free to move either way as forced to do so by whatever. The other valve unit looks pretty much identical to the WH D series type from the outside at least but this is not actually the case as the following photo shows.

These are the spools from the following from top to bottom: Massey without float, WH without float, Massey with float. It is likely that spool valves identical to those used in the WH D series appeared in other manufacturers’ applications but one would have to dismantle a lot of Ward Co valves to find out where else they were used.

So the options if you have a jammed valve seem to be:

A: As Colone has suggested - remove the spool cap, spring and retainer and try with a brass drift to tap the spool back up to the neutral position.

Photo of my old valve unit with the cap removed: the screw that holds the spring and retainer is visible.

B: Obtain a fully functional replacement unit from an 18, D-180, or D-200 being parted and swap out the whole unit.

C: Dismantle the valve unit and remove the valve that’s stuck and replace it with one from a used WH unit as in B above but that still has one good working valve in it.

What you can’t do is start swapping the spools about between valve casings. Like other parts in the hydro these are matched to pretty close tolerances. A bit of reading revealed that the gap between the two has to be a thou or less ! The same bit of reading also answered something that puzzled me when I removed the valve unit from mine i.e. why are there three mounting bolts rather than four that secure it to the panel, and curiously again just three long bolts that hold the four sections together.

The answer to that appears to be that it is to prevent warping of the valve assembly – I guess like a three leg stool it will sit firmly and evenly in place.

Have run out of time for today now so I’ll have a go at separating the valve unit into the four parts tomorrow.

Hope all of this is of some use / interest.

Andy

[coldone 35]

Andy, as usual a great write up. The one I had stuck was on a massey 1650, the same as you have pictured. mine was the nonfloat one and it had broken off at the pivot hole. i would like to add to your post

Option D: Soak the top portion of the spool (while in place) with penatrating oil. Then lighlty tap and and twist the spool to break it free. I found on my broken spool that the rust formed on the exposed part of the shaft is what had it stuck. If you can get it to break free with tapping, twisting, and oil it should pop back up. Its highly unlikely that the spool is warpped.