D200 Hydro testing

[coldone 35]

I purchased the parts to make a gauge from Surplus center. Total cost was about $27 including shipping. It arrived about two weeks ago and I finally got some time to use it this weekend. I installed it first in the top hole (11/16 cap screw) thats the wrong hole for the 1/4 MPT. I had to take out the temp gauge (9/16 wrench) to acess the correct size port. WIth the rear wheels jacked off the ground my intitial readins were:

At idle Nuetral=50PSI

Forward/rev= 25PSI

At full throttle Nuetral =75-100PSI

For/rev= 60-75psi

Implement travel= 200psi

Implement full stroke= 400-450psi

Checked the Charge pressure relief valve and found no problems with it. Retested and had same pressures as before.

Checked the Implement relief valve and found no problems. Retested and all pressures went to 0psi. Found I had dropped the two shims that were in there. Reinstalled the two shims and had same pressures as before. Each shim measured 0.25inch diameter and 0.075 thickness. I made a third shim from 1/4X20 bolt, 0.025 diameter and 0.066 thickness. Installed third shim and tested (here is where it get strange)

At full throttle implement full stroke raised to 600-650psi

Neutral= 125psi steady

When I cycled the direction lever forward initial pressure at full forward was 100psi but started dropping and settled at 40-50 psi. When I rechecked the impl full stroke, it dropped back to the 400-450psi range. I never saw the 600psi again in any of the folowing tests.

After that i had to start checking the check valves. I had to make a driver to fit the screws. I tried a few different things but had no luck. I ended up taking a 3/4inch paddle drill bit and grinding the end flat. 3/4 was too wide to fit in the hole so i cut it down to fit. (A 5/8 bit should work but I have several 3/4 in so 1 was sacrificed). Using an adjustable wrench as the leverage arm for the bit I placed it into the screw. I gave it a few good whapps with the hammer to make sure it was seated good. It did seat good because the adjustable was slipping on the hex shank of the bit. Back to the grinder and I made two big flats on the hex shank. Well after that it worked. Be warned that when the screws finally let go, you will think you broke something.

both check valves looked ok. Last pressure test reading were the same as the first.

I decided to take it for a test spin with the gauge still installed. At first things felt a little stronger. I went over to a fallen tree Thats bigger than the front tires. I put the front tire up to the tree that was on the ground. I gave the control lever a little nudge forward and my pressure dropped from 75psi to 20psi. At full throttle and full forward stick my pressure dropped to 0psi. The entire test run, from barn door to final push, was less than 3 minutes.

I guess my next step is to start inspecting the motor and accel valves.

Here are some pics of my redneck/bodged tool

ETA: Not sure my I cant put them all in one post.

[coldone 35]

[JackC 617]

Clever tool you made.

It took me awhile to find one that fit the hole but I did find a 3/8 drag link bit.

I have not used it yet and it this is not it but this is what it looks like:

[1maidenfan 202]

Ok I am at a loss here What are you using the homemade tool for Looks like an altered spade bit.

[wheeledhorseman 574]

A great bit of 'red neck tech' there coldone - for me it's answered where to get the hardened steel to make a tool in the style of the drag link bit used by Jack. Unfortunately I damaged the slot in an attempt to use an impact wrench so my thoughts were running along these lines. Paul sent me a spare end cap screw so now I should be able to make a tool and pray!

Re the hydro -

Unfortunately the various Sundstrand manuals contain different content but I have one that has a detailed description of how the relief circuits work which together with the diags showing states in neutral, forward and reverse found in all versions of the manual perhaps give a reasonable understanding.

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.

The motion drive circuit between hydro pump and hydro motor is effectively a sealed circuit but both do leak some high pressure oil by design hence the need for the charge pump that replaces these losses. If for some reason the loss has gone off the scale that the charge pump can cope with then along with the charge relief valve not seating correctly then this could also account for low pressure dysfunctionality.

That's about the best explanation I can give. I'm sure Paul will chip in if I've got anything wrong here. If anybody with a dysfuctional D wants a copy of the Manual that has a pretty detailed explanation in it send me a pm with your email and I'll forward the pdf file.

Andy

[coldone 35]

Yeah a drag link was what I needed but I was running out of time to work on it so i had to improvise a field expedient item.

Ok I am at a loss here What are you using the homemade tool for Looks like an altered spade bit.

Thats execatly what it is. It is for taking out the screw caps that hold in the check valves that are located in the pump block.

Andy, Check your PMs.

Britt