Think i found The D200 problem (teaser pics)

[coldone 35]

Dont have time for a full write up yet. Pulled the hydro motor and started taking everything apart. Found a few possibly clogged passages and some "junk" floating around in the system. I was able to pull the cylinder and check the valve plate.

Worked it down with 150grit, 220, 400,600. Off to get some finer grits.

Pics are "as found", "after 150", "after 400", and "after 600"

Crazy stuff happening with pics

[wheeledhorseman 574]

Things are looking up! Looks to have been quite badly scored.

Andy

[meadowfield 2,570]

yeah, hope that gets the pressure back ! :)

[coldone 35]

More pics. Here are some macro shots of the scoring and sanding.

[coldone 35]

[JamesBe1 82]

I'm not sure if the plate is the source of you pressure problems. More than likely it was your clogged passages. What did the junk you found floating around the system look like? What color? It might be an indication of something else wearing in the system that needs tending to.

Anyhow, it's great to see you dig into one of these pumps. It looks really great after the sanding. I'd say you are going to be back in the saddle again in no time!

[coldone 35]

I havent been posting much because I havent had much luck getting things going and finding the time to do it. This weekend I finally got the nerve to tackle the D200 and its problems. After the last vid of it I tried using it, it would go but had no real power in the hydro (sundstrand), it wouldnt even pull itself up the hill. I have been trying work through some of the troubleshooting. I went through all the little stuff, check valves, relief valves, accel valves, etc..I finally purchased a pressure gauge and fittings and the real troubleshooting started. My pressures are about where they are supposed to be at idle, underload the pressure drops to 0psi. There is obviously a leak somewhere in the system. I pulled the hydro motor and the "buffer assy" yesterday and started disassembling them today.

I started with the buffer, it is used when going from forward to reverse suddenly. It will bypass the sudden pressure spike to keep from braking things. It has two valves in it, one was stuck and had to be pulled. It also had some trash in it so i gave it a good cleaning and reassembled. I am not sure what the trash was but the PO had used gasket shelac everywhere, i think it was some of that but the stuff was too small to ID.

Next was the motor itself. I pulled the accel valves and disassemble them, cleaned and checked. Made sure the bleed holes were open, they are so small my smallest torch cleaned wouldnt fit I had to use a single strand of wire from a stranded 18AWG wire. I could pass air through the holes after that, didnt try before.

Next the cylinder housing so I could access the pistons and cylinders. No real problem there except for the shelac. The slippers on the pistons looked good and all the lube holes could pass air. I then pressed off the cylinder assy with the pistons still in. (This type has matched pistons to cylinders that are not interchangeable) After pulling the cylinder assy I could see the valve plate. It had very deep scoring in the mating surface and the mating surface of the cylinder did also. The manual says that if you can feel the scoring with your fingernail to replace the valve plate. The scoring could be felt with your finger tips, it was Deep and wide.

Being the type of person i am I figured nothing ventured, nothing gained. I broke out the flate plate and sandpaper. I started with 150grit and went through 2500 grit on the valve plate. (final thickness was 0.147inch) I did the same on the cylinders mating surface. Thouroughly cleaned both with carb cleaner and paper towels to remove all residue. Using lots of oil, i reassembled the pistons, cylinder,and valve plate.

Thats about as far as i have gotten. It will be a few more days before i have time to put it all back together and get new test results.

[JamesBe1 82]

Very nice work so far.

I like your point about nothing ventured, nothing gained. Besides breaking stuff, that concept is one of my prime learning tools.

When will you start accepting hydro pumps and motors for repair? Just kidding.

[pfrederi 17,741]

Nice work on the motor valve plate. I hate to rain on any parades but if the motor valve plate was that badly gouged it would indicate there was dirt and or metal shavings in the system at some point. As it all circulates it is likely that your pump valve plate has suffered similar damage.

Other than getting access and removal the pump is actually easier to tear down and work on. You do not need a press and there is no retainer clip that can have an ear break off (as did one of mine).

As soon as i finish up a couple of projects needing the FEL it is coming off the D200 and she is going on deadline to replace both the motor and the pump with ones I have tried to fix up. (At least i do not have to work off all the 1st and 2nd echelon maintenance gigs before I turn her in to support. ;)

[coldone 35]

Nice work on the motor valve plate. I hate to rain on any parades but if the motor valve plate was that badly gouged it would indicate there was dirt and or metal shavings in the system at some point. As it all circulates it is likely that your pump valve plate has suffered similar damage.

I was assuming I would have to tear into the pump too. For now I would like to see what happens with the pressures and performance just from the motor redo. If its acceptable and the fluid temp stays normal I will wait on doing the pump. For now I just want the d200 to be a mower. Not alot of strain on the hydro for that.

The rear had blown a few pinion gears years ago. Thats the reason the PO stopped using it. I am assuming that some of the pieces made it through the pick up screen and into the system. Speaking of that, I cant remember how the plumbing works on filter side, but if the diagram in the manual is correct the filter should protect the pump.

[pfrederi 17,741]

The filter receives the fluid coming from the motor and dumps it to the reservoir (the transaxle case. The strainer is the protection for teh pump it self. (Charge pump sucks from the reservoir through the strainer.

[SousaKerry 501]

Hydraulicly speaking you almost never filter the suction side of the pump, every industrial system I have ever worked on filtered on the return to tank. IIRC it has something to do with the pumps not being able to pull prime with the restriction of a filter.

Nice hand lapping by the way, did you use a piece of plate glass or a surface plate??

[JamesBe1 82]

Hydraulicly speaking you almost never filter the suction side of the pump, every industrial system I have ever worked on filtered on the return to tank. IIRC it has something to do with the pumps not being able to pull prime with the restriction of a filter.

Nice hand lapping by the way, did you use a piece of plate glass or a surface plate??

I think he just used sandpaper. The only reason a am responding is that I would like to hear more about your technique. I've worked with lots of surface plates over the years and watched people lap them. I never thought of using a surface plate or a piece of plate glass to lap the plate in the pump. I am intrigued by the approach.

James

[coldone 35]

I have a 12 inch aluminum sanding disc for my Shopsmith that i use as a flat backer plate. I used one of the 3M rubber sanding blocks on top of the valve plate to help minimize the uneven pressure of my hand plus I rotated the valve plate every few strokes. My biggest fear is to get the plate out of parallel. For the cylinder assy I just rotated the assy every so often.

I wish i had a good granite surface block for times like this.

Nice hand lapping by the way, did you use a piece of plate glass or a surface plate??

[wheeledhorseman 574]

Inspirational work and photos coldone adding to the knowledge base of what can be done with these things. At first sight I'd have assumed from its appearance that it was a 'gonner' but you've brought it back. I too suspect that the pump's more than likely in the same poor shape but wait to see the results when you test it at this stage.

The underlying issue seems to be that the filtration system was designed with general wear and tear in mind rather than having to cope with a catastrophic failure and the shrapnel of various sizes that it likely produced.

Paul touched on the fact that the strainer protects the pump from larger particles that would damage it but unlike the moving parts in the hydro, the pump has hardened steel surfaces and is fairly robust. In an an automobile engine the oil pump is generally protected in the same way by a strainer. Ideally to my mind the fluid should then pass from the pump through the 20 micron filter before entering the rest of the system but I guess it is/was considered impractical/unecessary though it is what happens in an automobile engine by design.

Placed where it is in the return to reservoir flow the filter still performs 'full flow filtration' i.e. all of the fluid circulating in the pump circuit has to pass through it and is filtered keeping the fluid clean under normal circumstances. Interestingly though a generic Sundstrand manual for hydrostatic systems of the same era does show a main filter between reservoir and pump. The manual is not specific to any particular applications so I guess indicates the 'ideal' situation for designers to aspire to. Unless the pump was mounted below the reservoir priming would, as Sousakerry2 mentioned, be a problem and it would appear that filtration pretty much universally appears in the return circuit.

Anyway, great work coldone and good luck with the test. BTW did you take any photos of the 'buffer' valves by which I assume you were refering to the valves mounted under the rear fender? I haven't found any information on these and would be interested to see what they consist of.

Andy

[wheeledhorseman 574]

Sorry, forgot to say - does anyone have a cloesup photo of the 'strainer'. I'm curious about these but not to the extent of opening up the tranny just to see what they look like. I'm kind of guessing that it consists of a fine wire mesh cloth and pretty sure it will be not 20 micron as if it were it would need changing as often as the main filter, more often in fact due to its small size and surface area.

[coldone 35]

Andy, I did not take photos of the Buffer. It is simple to take apart, under each cap is a spring, flat washer and valve. The valve has a hole its etire lenght. I used needle nose pliers to pull the valve out. If you pulled out your pressure valves from your pump you can take this apart.

[Tap53 57]

Andy, heres a pic of the strainer, dont remember but I think I made this strainer of brass and used original end caps, you can also see this case was cracked, so brazed it up, did a little filing, friend still using it today after 3 years, Guess I can Do Something Right Occasionally,

Tim

[1maidenfan 202]

Here is what the strainer out of my 18 auto looks like, there is a magnet in the open end.

[coldone 35]

How does the oil get from the motor to the filter? I dont remember any hardlines being plumbed in.

[pfrederi 17,741]

How does the oil get from the motor to the filter? I dont remember any hardlines being plumbed in.

Had to think on that for a bit. If you look at the transaxle housing when it is split (page 57) you see there is an "extra hole" along the top edge. There are three holes for the case bolts but this one is slightly lower and is really a passage from the opening in the motor mounting surface over to the filter mounting surface, thats how the oil get from the motor back to the transaxle reservoir

[coldone 35]

Sucsess!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :happy-jumpeveryone:

I now have 100PSI at full throttle neutral and above 50psi in full forward and reverse! Implement full stroke gives me above 750 psi and It can pull the front tires off the ground!

Video later this evening.

[Sparky-(Admin) 21,350]

Thats great news! Its seldom we get to hear success stories with old hydro's that are giving someone problems actually getting fixed.

Mike............

[JamesBe1 82]

Way to go! I was starting to worry.

To what exactly to you attribute the problem?

Can't wait to see the vid.

[pfrederi 17,741]

Great News!!!!

Way to Go!!!