case 1840 right side drive problems

Hi guy's,
Well with the help of that 2 year old thread I stripped the rear side of the tandem pump and found the brass disk to be heavily scored (0.001" deep), took over 3 hours to hone it all out and finished with a dead flat high polished finish. So this morning put everything back together and fired it up and with the wheels off ground it all works nicely. Put it on the ground and the right side tries to start but fails. There is no noise when going forward but when in full reverse there is a noise like fluid escaping internally.

Now when I first started it after putting it back together silly me didn't fully tighten one end cap on the direction servo and oil was leaking. Now if that piston has rings and seals shouldn't that stop oil from entering that void so could that mean the seal and rings are shot and thats where the leakage is.

When I did the original pressure test all I got from right front was 220 psi, now after that brass plate hone I got 350 psi but still not the 4000+psi thats supposed to be there.

So for my thinking it's either that direction spool seals or the drive pump, tomorrow I will route the hoses from the left side and see if the right side will drive to discount or prove the drive motor.

Any ideas or help with this will be appreciate as this proving one hard nut to crack.

Regards Bryan

Ok did a pressure test today with the wheels off the ground and it does look like the pump has had a tough life.

Charge pump pressure 310 psi after putting 0.020" of shims in
Left side front and rear 450psi ( missing a zero)
Right side 240 psi and leakage noise coming from drive pump ( was 200psi before honing the brass)

Anyway going to strip it down again and take out the right drive pump and find out the problem there.

Now with the pressure on the left side that works, should it be in the 4000psi range when off the ground and no load ?

Regards Bryan

G'day Guy's,
Well now I've stripped the rear side of the tandem pump and honed that brass disk flat as it was scored, put the pump back in and still no go. So ripped out the drive motor and found very light scoring on the faces of the rear pump components and on the front stationary face a deep score where sand had got behind the roller. After 8 hrs + of honing I got the scoring down to 3mm diameter and on checking the hole was still 0.15mm deep so decided to let it go at that.

Well put everything back together and like before off the ground it works nicely with the same rpm on both sides. On the deck it want to go then stops like theres a brick wall in the line. On the forward motion no noise from pump but on the rear got that restricting noise. Now on reading a thread on a 1845C I saw a pic where the servo could of been put in backwards, so went a turned it around and still got the same results. So that asks the question with that slot on the threaded part got to the front or back as off memory it went to the back but eh ?

It does look like the servo piston may be the problem so I reckon that would be the next port of call on this repair.

If any guy's can chime in with any suggestions it will be great as this repair has become a tad frustrating.

Regards Bryan

BUMP

come on guy's I am stuck with this problem so any advice can hopefully let me move forward on this repair.

Regards Bryan

Well considering the problem seems to appear when resistance is applied (setting it on the floor) I would suspect the relief valve in the pump. You didn't say if you had stripped the pump of all components and checked the replenishing valves and relief valves so that is where I would start. Also how is your servo pressure for the suspect side, compare it to the good side.

Hi Bill,
I have done a pressure check and found the charge pressure was only 260 psi, so made some shims and got the charge pressure to 320 psi. Now on the left side which works the pressure stays the same when operating the left lever. Now with the right it drops to 260 psi, with wheels off the ground it works and the rpm is the same as the left side. But on the ground when moving the lever it wants to start the fails. I have swapped over the relief valves from the good side to the bad side and no change was found.

Due to the scoring on the rear pump brass plate and the scoring on the drive motor which I have honed out I now suspect the piston servo may have scoring. I will machine up a new fitting so I can check the servo pressures on the side plates.

Regards Bryan

Don't have access to books on this machine but most hydrostatic pump have three hoses going to them two bigger ones, one forward and one reverse. The third one is the case drain, usually a much smaller hose whose purpose "drain" off any oil that leaks by the internal parts. Some place there may be a spec. for the amount that is normal, but if one side is working good and the other is having a problem easy thing would be to compare the two. I'd disconnect the two small lines and plug them off, then install two test hoses to the fittings on the motors. Start machine up and try driving both sides either together or one at a time. If there is a noticeable difference on the weak side that would indicate a problem in that motor.

Anyone else have comments on this test method? I would be glad for a better idea for the OP.

My engineer mate rang today and suggested swapping the hoses which ain't a simple job. So I will do that and then I can see if it is the motor or the pump.

Bryan1 said:

My engineer mate rang today and suggested swapping the hoses which ain't a simple job. So I will do that and then I can see if it is the motor or the pump.

Click to expand...

Or how much a job would it be to swap the motors from side to side. If problem follows the motor then at least you have it narrowed down to what component is the problem.

Ok another thought on this,
As I'm a mechanical guy not a hydrostatic guru there something I am missing in the tandam pump. All I have to on is a coleman parts diagram not a complete circuit diagram. I'm sure if this can be supplied I will nut out the problem but trying to find the info on the net has been hopeless.

Regards Bryan