I have a cat 312 excavator. The steering on it has never worked properly since we got it. Wasn't bad at first, could run it for a few hours, then notice a loss in the steering. going forward and back is good, boom works good, just seem to lose steering once machine warms up. It now loses the steering quicker. Will run for 20 to 30 min now then lose steering. I don't use it very often, farm machine, so havnt looked into it . Would like to get fixed before it gets worse or does more damage. Any ideas or tips on where to start looking. Thanks
Serial Number..? The most usual culprit is the centre swivel joint leaking internally. Your symptoms (Ok-ish when cold, **** when warm) are almost classic of leaking seals in the swivel.
Steering? Are you referring to rotation of the upper house? When was the last time the case drain filter was changed? The case drain filter will affect (and eventually damage) both the swing and travel motors if restricted. Unfortunately, I cannot find out if that vintage even has a case drain filter. Serial number? 6GK?
I'm wondering how long people need to get educated before asking a question? People used to call me and ask what their machine was worth and give no information at all. I would come back with I have a car with four tires, four doors and painted black, how much is it worth. Put it another way, no serial number and there is no way to help you.
Center swivel
Thanks guys. Serial # is 6LK06640. I was talking about the travel motors. The boom, and rotation seems to work fine. 8000 hrs on machine. Dont really have any history on the machine. Thanks for your input too Johnny. It was most helpful.
The seals in the hydraulic center pivot need checked they would only affect the travel motors
Right - now the dog can see the rabbit......... I would advise caution on the sarcasm. There are a large number of members on here who are experts in their field but despite our best efforts we are not psychics (yet). Psychotics maybe, but not psychic. Trying to give informed guidance without information is like someone walking into a Ford dealer and saying they want parts for an F150. To get information, suggestions, and direction one has to first give at least some basic information. In the world of heavy equipment the Serial Number is the first starting point. First up the Serial Number you gave is the Engine not the machine, but no big deal. From the engine number comes the machine Serial Number which is 6GK01066. As Tyler states above the centre swivel is what takes the hydraulic oil from the machine upper frame down to the travel motors. There are a number of seals in it to keep the oil in the various separate circuits apart from one another. Those seals harden with age and oil starts to track from one circuit to another, which produces a loss of track motor performance, especially when you try to turn the machine. This is more pronounced when the oil is hot - back to my comment in post #2. So a Swivel remove and reseal is the first thing on the list of things to do. If you search the word "swivel" in the excavator forum on HEF you will likely find some threads with photos people have posted showing how they did the job. That may also give you some ideas. Attached is the Parts List and the R&I procedure. When it is disassembled you might be unlucky and discover that the centre rotor (4I-7605) is scored. If that's the case post back for further guidance. DO NOT attempt to reassemble with a scored centre rotor. So what you have is pretty much all the info needed to do the job. If anything is unclear please ask. If you want to contract it out, I'm available. US$1500/day plus travel time from home base and business class flights (about US$3000 give or take) to your location and back.
Yeah, but do you bring your own tools?
If the customer pays the excess baaggage on the plane, yes.
Wow. Thanks for all the info Nige. I wish I could get that kind of service from dealers I have to deal with. Feel like I owe you at least a cold beverage or 2. Maybe I could take you out for some ice fishing in exchange for your services. First time using a forum for a mechanical problem. Really impressed and appreciated the quick responses. Hopefully there wont be any scoring. If there is I may be back for more advice. Thanks again,
Remember that there no such thing as a stupid question if you are not familiar with the machinery in question, but to get sensible answers you always have to give as much info as you can first.
8000 hrs my bet is swivel seals
Is there only me on here who doesn't like fixing things by guesswork? Yes, the swivel could be leaking but there are also four crossover relief valves in the system, any one of which could also be causing trouble.
You better be careful with them last words or you may end up overly busy
Chris, How would you suggest testing them in order to eliminate the possibility..?
What I did when we had trouble with ours was plug the lines at the drive motor and dead head it and check pump pressure then cap it at the control valve and if on the second test it is way higher it's the seals. Or I guess you could shoot the center with a heat gun if it gets way hot way to fast you have leakage.
Pretty much what Tyler just wrote. Pressure gauge on main pressure test point. Block the sprockets. Note maximum pressure in all four directions. If one or two of the four pressures is low, exchange the position of the crossover relief cartridges to see if the fault follows. If still inconclusive or all pressures low then; Disconnect and cap the drive lines at the motors. Repeat the test. Similar readings indicate possible swivel leakage. To confirm; Disconnect and cap the lines between the MCV and swivel. Test again. If any pressures are still low then the fault is in the MCV or pump control system.
I suspect the OP will have no access to pressure gauges, test gear, etc. With the excavator being 25+ years old (built 1994) my first thought was that the seals in the swivels had got to the end of their rope.
Look, there's every chance that you're right but rather than encourage someone to spend $250 on parts and spend a day frigging about resealing the swivel, which, let's face it isn't a walk in the park, my own personal preference would be to encourage him to spend $150 on a pressure gauge and adapter and troubleshoot it properly. Teach a man to fish and all that. And before we get into a pile-on, Nige knows me well enough to know that I'm not trying to start an argument, just put forward an alternative point of view. Rational comments are welcome......
Oh BOY!! DOG PILE!!!! I much prefer to diagnose correctly, but... most people don't. You are both right, in other words. Most machine owners would rather spend the day resealing the swivel and feeling like they were getting somewhere, rather than testing pressures and then fixing the problem. Most would feel like that was a big waste, particularly if it is the swivel. If you reseal the swivel and it doesn't fix it, they seem to feel that is is ok, that's just how you fix stuff.
I used to pin one track( sprocket ) and lift the opposite side and apply pressure to the pinned side.If the track in the air moves then it is the manifold. I would also test the propel motors by pinning both tracks and remove the case drain going back to the tank from the rotary manifold.Apply pressure to each side and check for leakage at the case drain,. If oil comes out of there like a fire hose then one or both motors is pooched.
No offence intended or taken. I was simply thinking of the OP's situation & possible lack of resources but in the strict sense of the word CMark is right in his thinking that the more correct way of diagnosing is to test the system and work to the root cause by a process of elimination. If the root cause is the swivel then so be it, but at least before tearing into it the finger would be firmly pointed in that direction as the culprit.
At 8000 hrs my thinking is the swivel will not be in to good of shape so I would just do it anyway. It not that big of a job
Done a bunch of them and not a bad job.I needed to lubricate my armpits anyway.
This comes down to personal preference informed by experience. If you have worked on a lot of these and established a history of bad swivel seals, you likely just take the short road and chance changing the swivel seals. If it works, you are a hero. If not, you start again doing as CMark has stated.
If you want to go halfway on the swivel test I do it by temp rise in the system. Start the machine cold and block the tracks however you like. Hold the travel control on for a few minutes then shut the machine down and do a temp check. If you have a buddy you can test while it’s running. If it’s leaking at the swivel the swivel will be warmer than the travel motors are . If it’s leaking on a motor case drain the case drain line will be warm. If it’s a crossover valve it will be warmer than the rest of the system. It’s not a perfect science but it costs nothing and takes very little time. Sometimes you will even hear it hissing at the swivel if it’s bad and you listen close.
I agree a heat gun will tell you
If these cats have a history of this yours had the seals totally gone like they where never there
Good afternoon folks, I'm have the same issue on my unit, serial # 6BL00625. Was wondering if someone could point me in the direction of the swivel rebuild parts and procedure. Thanks in advance!!!
See attached parts list plus R&I procedure.
If you will have troubles with parts but can measure grooves and come up with the seal sizes - you can contact Hercules Sealing Products about purchasing them. That’s what I do when messing with Altec bucket truck center pivots. Altec has ridiculous lead time ( probably not that ridiculous these days ), and I get my seals from Hercules within 2 days and made out of better materials ( bronze impregnated PTFE) and for the same price as Altec. Although I have to order non standard size seals to manufacture for me.
Thanks for the info guys!!!