Looking for most possible explanation for this symptom. Background is a Model 44 pump serial # 25c14957 (valves 1) 66 GPM @ 1600 rpm Its on a 59' D69U and it has worked in the past. Thought the problem was with the cylinders and had their rods replaced and repacked, so pretty sure they aren't the problem. The blade however would not even raise before the cylinder refurbish. Now it will raise slowly, but immediately begins to fall back to the ground. It has fresh ISO 46 fluid, but the filter has not been replaced for some time. Could the filter cause this symptom? Guessing that the problem is 'deeper' than the filter though. If so, can anyone give me specific idea of what is involved in rebuilding the pump or replacing the specific seals that may be causing this problem? Additional thoughts appreciated before I get into the repair, really like to get in and have an idea of what to look for and repair/replace. thanks in advance! yellerc@
The D6-9U uses a #46 Hydraulic Control 25Cxxxx. Check the main pressure relief valve first. They have been known to break the relief valve spring resulting in near zero pressure. If it's a problem with the pump itself you are limited to used as parts are no longer available. Filter should have been the first thing to check.
Good to see you Mag, consider myself sufficiently scolded over the filter. Will get it replaced first. Double checked the serial as 25c14597 as above (5 digits). Any chance of a schematic pic, none of my books have the hardnose features. Not sure where that relief valve spring is located.
Relief valve is in the tank, mounted on the control valve. Spring #4F7115, still available from Cat. Several other candidate sources for problems but that's a start.
Do you know the filter number ole' Mag? Maybe an aftermarket one?
Wix #51165 or NAPA 1165.
Thank you very much, Mag! Should be able to switch it out today and will report back with results.
Have replaced the filter, and there is no change in the symptoms. Looks like I will drop the blade and go into the tank looking. Understand about the relief valve spring. Of the 'other candidates' for the causes; what would you be looking for inside and can you give me an idea about how you would proceed. Have a general idea, but your tips are sure a boost to my understanding. Is there anything outside of the tank I should check before opening it up? Thank you for your time in replying, Mag.
The only thing outside to check would be the end of travel relief valves built in to the lift cylinders. You mentioned rod/packing work but are the relief valves seating properly? Was failure abrupt or occur over a period of time? Going inside check linkage to the control valve, operation of the four make-up valves plus the relief valve as mentioned. If all that checks out then it's on to the pump.
The failure was over a period of time, gradually increasing symptoms. Remember hanging a large rake on the blade that slowly took longer and longer to lift, then removed it for other reasons. After that, raising the blade gradually slowed down. Then, after a period of non-use, with the cylinders weeping rather badly, the blade would not lift at all. That was just before I recently had new cylinder rods and 'v' seals installed. Like mentioned, that provided enough improvement to raise the blade slowly, but with immediately decending when lever released. No telling the use on the pump itself. Not sure any of that is pertinent, maybe so.
Was any work done to the pistons/rings and internal relief valves?
The seals on the Pistons were said to be in good shape and not replaced. I did not view them, and when questioned was assured they were in good shape, and would not affect warranty time period. I did not ask about the relief valves inside, didn't actually realize there were any there. I can call and see what they remember on them. This is a large and long established shop which does many jobs in a day FWIW. What kind of questioning would be appropriate? Feel like they would redo their work if I can make the case the cylinders are actually failing. This being somewhat subjective, will appreciate whatever thoughts and opinions you care to share on their method. They did mention that they were to test them with air, but did not discuss when I picked them up.
An easy test to see if the cylinders are bypassing is to secure the dozer blade with the cylinder pistons in about midstroke. I usually tie to the tracks. Hold the control to bypass for a minute or two. If a packing is leaking internally the cylinder will get hot at the piston location.
Not really questioning the work that was done but I wonder how far they went to check things out. Also getting harder to find people that know the workings of these 56 year old tractors. You can do the test that OIH mentions. If the relief valves are leaking with pistons in anything but the end stop positions you can note whether they get hot or put your ear to the cylinder or use a big screwdriver with your ear to the handle and you can hear them leaking.
Starting to think they ignored the internal relief valve. Would that account for the described symptoms? I'll do the test and inquire further. Looks like a spring failure here would allow bypassing...is that the idea? Thanks for the feedback guys.
Remove cylinder from circuit. Plug lines with gauges. Measure maximum pressure at low and high idle, COLD and WARM. Reconnect cylinders in to circuit. Install gauges inline with cylinders. Measure and compare the pressure. If the reading is the same, cylinders not the problem.
Failed spring, buggered up plunger or seat insert would be the failure modes. However the failure of one would not be a colossal leak to the 70 gpm pumping capacity. Just something to be checked.
Checked the notes at the shop and the PRV seals were renewed. Air test showed 'no bubbles'. They did offer to break them down again to re check. Wonder if if the piston seals that were not replaced could be the weak link? They were visually ok. What odds on weak/broken spring on the PRV? On the test above, raise blade 1/2 way and secure with chain (before it falls), and then ??
If I remove the cylinders again, and drop the blade, what's the best procedure to get them empty before unhooking. Took a bath last time!
What are you referring to as PRV seals. Those are hard seats (metal). If they actually replaced them and checked them out they are probably ok. Piston seals checked as visually ok by who? OIH is referring to restricting the blade, putting pressure to the system and checking for leakage by either the heat generated as oil passes through a restriction or by sound.
Any way you do it there's going to be some mess. The least mess would be by cycling the blade and draining at the tank. Would take a fork lift or another tractor/loader to do that effectively. Those cylinders are to big to cycle them manually but probably could be done with come alongs.
Sorry Mag, by PRV I actually was referring to the IRV or internal relief valve, should have just spelled it! When the shop told me they changed those seals makes me suspicious if they are hard, because I did not get that impression from my discussion with the employee. He is same guy that said the piston seals were 'visually' ok. Thinking that I will stay while they do the work if I take them back in. Guess I will block the blade up and drain the tank, same as I did to change the fluid from ISO 10 to ISO 48. There was some very slight improvement with that change. Thanks for the clarification on the test procedure, it's on my do list. Appreciate everyone's replies.
Nothing has been discovered so far. Original oil spec is a SAE 10W, ISO 46 is equivalent to a SAE 20. Some change in performance indicates there is leakage/wear in the system. The fact that you had the problem before the cylinders were worked on still indicates to me there is a pump issue, or relief valve as originally mentioned.