4200xl old problems
 

So I got this excavator back in early 2015 or 2016. I had a servo go bad which was giving me a lot of crazy feedback causing tracks to move, carriage rotation, etc. So I replaced the servo with a hitec. I haven't been able to get it to work right since. The booms barely move at all. I shelved it when my kid was born back in 2017 and I am just now getting it back out to try and fix. Now I have replaced all of the servos with hitecs, and I reversed the 4th servo prior to installing since I read Hitec servos run reverse from the tower pro's that were in it from rc4wd.

Is there a good way to check the 4th valve alignment? I have been thinking that was the issue but I have taken the servo out completely and even tried manually adjusting the 4th valve and I still cannot get the booms to raise no matter the position of the 4th valve. I am wondering if it is a pump issue now or if I am just not getting this 4th valve set correctly. I do hear the motor strain a little when trying to work the boom functions but nothing happens. If I push or pull on the arms of the excavator while working the functions the booms will move with assistance, but have no power at all.

Any ideas on getting this beast back to digging?

Re: 4200xl old problems
 

When changing the servos, did you plug the servos into rx & power up before installing into valve block to make sure servos were centered?

Your pump turning the correct direction?

This particular model from eagle mach, the suction tube draws from the top of reservoir, ppl have had trouble with pump loosing prime after long periods of sitting. Throw the tank away & use a fuel cell for an airplane so you're sucking from the bottom of the oil tank.

Re: 4200xl old problems
 

Those original servoes are known to break donwn pretty quickly in this machine, so it's a quite common task to throw them out.
The 4'th valve have 2 positions, open and closed. It is supposed to be fully open when the 3 other valves are not moving, letting the oil circulate nearly without resistance through the valve block and to the tank. If manually putting the 4'th valve to closed position, and the 3 other valves in closed/center position on will hear the pump work harder as it now needs to circulate the oil to the tank via the pressure relief valve, which is set to a certain pressure in order to open. It can happen that the relief valve pressure setting is too low, and/or have a internal leakage. In this case the pump will not work any particular harder when pushing oil through it. The 4'th valve is set up with a mix on the radio towards the 3 other valves. When any of those 3 valves are moved, the 4'th valve will close.
I guess you most likely have an issue with center positioning of valves after replacement of the servoes, so would continue looking closer into that. I'm not so familiar with the Hitec vs Tower servoes, I clould not quite understand why it was needed to reverse the direction when changeing servo brand. It's new to me that some servoes runs in the oposite direction from others. But maybe that is correct. It should be easy to see when testing.

Re: 4200xl old problems
 

Thanks everyone for the help! You guys steered me in the right direction. This thing has been sitting on my shelf for 5 years now because I was too intimidated to tear into her. In the last few weeks I got brave(and actually had a minute to work on it). I tore it down and checked everything. Now I don't remember messing with the pressure relief valve before but obviously I had. I was able to determine that I was an idiot back then and put this thing back together incorrectly. I fixed that today and she is up and running again. I may even get brave enough to change out my tx since I know more about mixing now.


TLDR: I'm an idiot and had put the pressure relief valve back together incorrectly at some point. She is running again now!