Hello, Working on a small Cat 305.5D CR excavator. The complaint which I can verify is that the left track intermittently gets extremely weak. It will track straight when pushing both levers together but at a stand still pushing only the left track lever either forwards or reverse occasionally results in no tracking, it just goes over relief. Turtle or rabbit speed does not affect the condition. Swinging when the track isn't turning can get it to start to inch ahead but could be due to weight shifting. I did a few tests I read about on SIS including a timed track rotation test to verify travel motor health. It was 1 second slower than the time given (think it was about 13 seconds per 3 rotations). I checked the main relief valve setting and it is set as per the manual (think it was 3550psi). I put a pressure gauge on the pressure lines going to the motor and both forward and reverse line get to main system relief pressure. Am I correct in thinking this eliminates the possibility of leakage in the center swivel joint considering I can get full pressure down to the motors? The gauge wasn't teed in it was dead headed if that matters. The track tension is also set correctly. The suspect bad motor has a tag finaldrives.com where as the good motor has a cat tag on it...could be a reman on the bad side. Any guidance much appreciated, about to pull the trigger on a motor but don't know the history of the machine and could be making the same mistake the guy that put the reman on made.
Have you verified track and idle condition/ tension? Have you measured case drain while in operation. Have you opened up the case drain filter? Let us know what ya see
I meant to mention that... I didn't have a very scientific way of measuring the case drain oil during operation but it looked to be no different from side to side. With the right side giving no problems I figured that was a passing result. I haven't opened the case drain filter, excuse my ignorance but what would that point to if I found it to be dirty or full of debris? The undercarriage is entirely new as of this winter.
It's a 2 man job. Cap case drain hose at motor. Run another hose off motor into bucket. Run track very slowly. Watch for a surge. If you can move past a few pads with no surge, run at full throttle, low speed travel at full stroke. Ideally, you should only get a trickle. None of this should be done until you have equalized track tension and verified that your idlers aren't shot. (New parts can fail) BTW, how do you know the track is "going over relief " because it won't move, or are you gauging pressure? To check reliefs. Pin sprocket against track frame to stall track. This pressure will be your relief pressure. Dead heading hose into gauge gives you main relief pressure only. Case drain filter catches debris from rotating assemblies. If a pump or motor craps the bed, that's usually where it shows up first. I always suggest carefully cutting the filter to inspect the contents. A filter cutter is required, not a suggestion. Good luck and be safe
Thanks for the reply. I did the case drain test that you described- when first engaging the track it spits out a stream and then once the track is moving just a trickle. Both the problem and good side had the same results. The idlers are in good condition I’ve given the undercarriage a good look over and don’t see any problems there. I am confused on where you describe pinning the track as going over a different relief valve than the main relief. My understanding of this system is that the boom and travel functions are all protected by the main relief valve. Is there another relief in this circuit that I am missing? When I installed a gauge in the working line going to the travel motor I was getting max main system pressure down there. This is what I meant by it is going over relief when the track is stalled. Working on sourcing a filter cutter to inspect the case drain filter.
There are reliefs in both directions on the travel motors. Typically, you would jack your main pressures to check the port reliefs of the motors. Checking reliefs on tracks you would put an appropriately sized pin between the sprocket and the frame. That prevents the sprocket from rotating, therefore you would be over relief, whether you're on the travel relief or the main is all in set up.