I have a CAT D3C Series III Serial Number 4KS00297. I recently broke a hydraulic line on the hydraulics that control the angle of the blade. In my wisdom, I decided to replace all the soft lines that control the angle of the blade since they were all showing some wear. After replacing the hydraulic lines, the angle hydraulics now drift when pushing and don't stay in position. This was not the case prior to the hose replacements. I've run the angle hydraulics to each side 10-15 times and deadheaded each cylinder as instructed to bleed the system (did not work). I've manually bleed the hydraulic lines at the cylinders and still no worky. I replaced all the o-rings in each connection and have no hydraulic leaks. Can anyone on here help me wrap my brain around what else may be causing this?
don't have a line in the wrong place we always used old telephone wire to mark the lines and fittings when we took them off makes life a lot easier
Probably introduced contaminants into the system from the shards of metal left in the hoses from the hose shop. The hoses didn’t get scrubbed out before installing them. Now, all that junk is jamming up a valve spool. Seen it happen, too many times to count. Shame on the mess. This thread makes me sad .
Since the blade angle was holding fine before the hose replacement, I would first focus on something related to the hose job rather than the cylinders. A few things to check: Double-check the hose routing and connections. It is possible for two lines to be swapped and still have the blade move normally, but the circuit may not hold pressure correctly. Check for internal leakage in the angle control valve. Since there are no external leaks and bleeding did not help, the valve spool/section may be allowing oil to bypass internally. Check the cylinders for internal bypass. With the blade positioned and the machine shut off, see if the blade still drifts. If it does, suspect cylinder leakage; if it only drifts while pushing, the control valve is more likely. Because the problem appeared immediately after replacing the hoses, I would verify the hose routing before replacing any major components.
I went back last evening and reviewed CAT's part diagram and it does appear the hoses have a different connect pattern on each side. I did the right side first and noted the connections "assuming" both sides would be the same. Thx for the response.
I’m glad you finally got this sorted out. For me to make a service call, would upset my timeline.
The drift started immediately after the hose replacement, so the most likely causes are related to that work. On the D3C Series III the blade angle circuit holds position primarily through the control valve spool (and any load-check valves in that section) when the lever is in neutral. Raise/tilt functions working normally while angle drifts under load points to something specific to the angle circuit. Most Probable Causes (in order) 1. Incorrect hose routing / crossed lines This is surprisingly common when several soft lines are replaced at once. A crossed pair can still let the blade angle left/right, but the circuit will not hold under load. A similar D5C case was resolved exactly this way after the owner obtained the schematic and swapped the lines. 2. Air still trapped in the angle circuit Cycling and dead-heading helps, but on these dual-cylinder angle systems air can be stubborn. Manual bleeding at the cylinders is good, but you may need to crack the highest fittings while the system is pressurized and the blade is fully angled one way, then the other. 3. Contamination or debris introduced into the control valve Dirt that entered while the lines were open can keep a check valve or the angle spool from seating properly. 4. Cylinder internal leakage Less likely to appear the moment the hoses were changed, but possible if a cylinder was already marginal or was damaged when the original hose failed. Recommended Diagnostic Steps 1. Verify hose routing Compare every hose against the hydraulic schematic for the angle cylinders (SENR1254 or the equivalent for your 4KS machine). Make sure each line goes to the correct port on both the valve and the cylinders. Swap any that look questionable and retest. 2. Isolate the cylinders vs. the valve • Fully angle the blade one direction. • Disconnect and plug/cap the hoses at the cylinders (or install test caps on the cylinder ports). • Push against a solid object. Blade still drifts → cylinder internal bypass is implicated. Blade holds solid → leakage is upstream in the valve/check circuit when connected. 3. Re-bleed more thoroughly With the engine running at low idle, angle fully one way, crack the highest fittings on that side until a solid stream of oil (no bubbles) appears, then tighten. Repeat on the opposite side. Cycle several more times and recheck for drift. 4. Check for external leakage again You already replaced O-rings and report no leaks, but double-check every fitting under pressure, especially the ones at the valve and cylinders. Because the problem did not exist before the hose job, start with routing and isolation testing — those two steps resolve the majority of “suddenly drifts after hose work” complaints on these machines. If the valve is confirmed as the source, the angle section of the control valve (or its load-check valves) will need attention. If you can post the exact serial number prefix confirmation (4KS) and whether it is a 6-way blade, more precise port call-outs can be given.
See the two post before you!
Bots sometimes have a problem with that. It zeroes in on the original post and does not attempt to comprehend anything after that. Same bot ignores the OP has solved most of it. LINK EDIT Does it again LINK2 We need these bots, NOT!
No bots here, I did read the posts prior to mine however they weren’t as complete and left some things out. Don’t hate because I’m trying to help a guy out.
Maybe bot, maybe not. At the very least every one of your previous posts on this site was written by AI and posted without a human thoroughly double checking them. Helping others is great. That's what this forum is all about and most of us here have benefited from the hard won experience others have shared. We welcome you to join in and share real answers based on real experience.
I’ve been playing with heavy equipment since I was 10 at my grandfather’s place, just because I’ve learned a lot and I articulate it well doesn’t make it any less meaningful. And if someone is having a similar problem they are told to look at the previous posts. So while this issue was resolved, the next guy has a clear concise plan of action. Helping is what we are all trying to do.
I don't usually engage the basement dwellers but I'm rained out and bored right now so I'll do one more... Would you care to respond to the following? You may very well be as experienced as you say you are. Your last two posts here have a human feel and are somewhat less articulate than your previous posts. This actually makes me feel better about you. As I said before feel free to help all you want. We all need help. Just vet your AI copy/paste and make sure it's relevant before posting. It'll increase your "cred" here.
It’s a pleasure to make your acquaintance Mike. Rest assured I’m here to help, I’m not hiding behind some screen name, that’s actually me, you can google me the 727 number you’ll find is my cellphone use that number, the 617 numbers are my office, you’ll get my receptionist she’ll confirm that when I’m in business mode, she says it’s a dr Jekyll/Mr hide change in personality. Just because I come off as polished doesn’t mean I’m not real, and I’m really here to help. Call me I’ll talk to you soon!
@ChrisMafera Many of the folks providing help here are less polished and articulate than those working in white collar occupations but the input they provide is based on real world experience. They may not be the best at AI prompts but they can generally spot an AI generated answer and are rightfully doubtful of the validity of those answers. Again, this is due to real world experiences, both with the actual machines in question, and with the accuracy , or lack thereof, of AI generated responses. I'm not trying to chase you away. This forum is open to all and benefits all. If some of the responses you have been receiving here have seemed less than welcoming, know that it is because we recognize the risks of your input leading those seeking assistance down the wrong path, not because of you as a person. You may have been playing with equipment since age 10. You may be good at repairing it. We don't know. The input you have provided so far leaves some of us, at least, doubting that you know what you are talking about when it comes to heavy equipment repair and operation. Looking you up online as you suggested has, in fact, changed my opinion of your input on HEF. I now value it less than I did previously. Note that this hasn't changed my opinion of you. This isn't personal. I hope you stay and enjoy the forum with the rest of us. I may be completely wrong on all of this. If so, I apologize. Thanks for your understanding. Also, @dgeorgi , I've derailed your thread. Please accept my apologies.
No worries Mike, I’m accustomed to being the underdog. Professionally It’s in my best interest to keep machinery running and I don’t expect to make anything from free advice I’m here to help guys who depend on keeping their equipment running and not spend 6 weeks checking everything under the sun first. I think once you get to know me you’ll appreciate some of the things we’ve talked about.