743 leaking axle

[Gbannish]

Hi, I'm new here, and to Bobcats, so please go easy on me! I bought an old 743 w/ 3700 hours last summer, ran it fine for just a tank or two of diesel. It hasn't seemed to leak any/much hydraulic fluid, but the chain case was quite low and had to add a few gallons to fill last month. This morning, I started her up, noticed a small puddle of oil around the left tires, but chose to ignore. I was loading stone and digging up dirt for a few hours. Then, while transferring a load of stone, the machine started to make a loud knocking/clicking sound on the left side wheels (not sure front or back). It sounded like a chain was skipping a gear or something, and the machine was lurching. This occurred whenever trying to make a right hand turn. I limped it back to the driveway, shut it off. Found the hydraulic fluid level was fine, so was the chain case fluid. I took a break, then went back and there was a pool of oil between the left tires. Going underneath, there is a slow but steady drip of oil coming from where the left rear tire/wheel meets the axle housing(?). Finally, I tried to start the machine but it wouldn't start. This is weird, as the machine always had started right up, especially when warmed up. I'm wondering if it isn't overheated, so will go try to start in a while, we'll see. Could anyone point me in the right direction as to what is wrong, and perhaps why? Thanks in advance!

 

[mmsllc]

Based on everything you said, I would recommend opening up the entire chain case. If it is popping & lurching, you most likely have damage inside & it will easily be cheaper to repair it now versus continuing to run it once it starts back up. I am certain that upon opening all of the access panels, you will find a few gears that are chewed up, along with a ton of metal shavings in the chain case. Congrats on finding it low on level & topping it off; I am not sure most operators / owners would even check that much out. The good news is that after you replace all of the axle seals, worn gears & stretched chains, then it should be good to go for another 20 years or so. Taking it all apart is a feat within itself, but will be a lot cheaper for you to do than someone else. The biggest thing here is to ASK a question ANYTIME you do not know what is going on. I would also suggest removing all of your wheel bearings (on each axle) to inspect them while the chain case is open & while all of the gears have to be inspected / replaced / removed. Do yourself a huge service & take your time to inspect everything. ALL of those parts are difficult to service one at a time, so replace everything that you find damaged. I would replace all of your chains because as you said the fluid level was low, that will add in the chains stretching out & possibly damaging new gears. Disregard the cost of the parts in favor of only doing this repair job once. Be sure to clean all of the crap out of the bottom of the chain case, too. Many people on here swear that the chain case fluid should be hydraulic fluid or even engine oil. I would call a BOBCAT dealership to ask them what your machine calls specifically for.

 

[Gbannish]

Based on everything you said, I would recommend opening up the entire chain case. If it is popping & lurching, you most likely have damage inside & it will easily be cheaper to repair it now versus continuing to run it once it starts back up. I am certain that upon opening all of the access panels, you will find a few gears that are chewed up, along with a ton of metal shavings in the chain case. Congrats on finding it low on level & topping it off; I am not sure most operators / owners would even check that much out. The good news is that after you replace all of the axle seals, worn gears & stretched chains, then it should be good to go for another 20 years or so. Taking it all apart is a feat within itself, but will be a lot cheaper for you to do than someone else. The biggest thing here is to ASK a question ANYTIME you do not know what is going on. I would also suggest removing all of your wheel bearings (on each axle) to inspect them while the chain case is open & while all of the gears have to be inspected / replaced / removed. Do yourself a huge service & take your time to inspect everything. ALL of those parts are difficult to service one at a time, so replace everything that you find damaged. I would replace all of your chains because as you said the fluid level was low, that will add in the chains stretching out & possibly damaging new gears. Disregard the cost of the parts in favor of only doing this repair job once. Be sure to clean all of the crap out of the bottom of the chain case, too. Many people on here swear that the chain case fluid should be hydraulic fluid or even engine oil. I would call a BOBCAT dealership to ask them what your machine calls specifically for.

Thanks MMSLLC, Not exactly the answer I was looking for, but thanks for that. So if I understand you correctly, you suggest the gears and chain are mostly likely bad. Any guess about whether the drive motor is toast or not, is there an easy/obvious way to inspect? I was wondering whether the drive motor had seized up or something, or maybe a valve problem somewhere, or even the hydrostatic pump? (My lack of understanding, and paranoia, is high!!). But happy to start by looking at the gears/chain. Also, do you know why the engine would not start? It had always started right up, anytime, before... I won't be able to look at it until the end of this week...

 

[mmsllc]

Thanks MMSLLC, Not exactly the answer I was looking for, but thanks for that. So if I understand you correctly, you suggest the gears and chain are mostly likely bad. Any guess about whether the drive motor is toast or not, is there an easy/obvious way to inspect? I was wondering whether the drive motor had seized up or something, or maybe a valve problem somewhere, or even the hydrostatic pump? (My lack of understanding, and paranoia, is high!!). But happy to start by looking at the gears/chain. Also, do you know why the engine would not start? It had always started right up, anytime, before... I won't be able to look at it until the end of this week...

On these machines, I have seen a multitude of reasons for them not starting. I always suggest checking the battery, battery terminals & battery cables FIRST! With the weather doing goofy things in regards to the varying air temperatures from day to day, a new battery may be in need. It is VERY difficult to try to convey why that seems to be the case, but it JUST is = very strange!! I also suggest checking all of the fuses. I have seen fuses on my 751 CORRODE to hell because it was missing the fuse covers. I would definetly check those as well. Assuming the battery, cables & fuses are good, I would "JUMP" the starter (very carefully) to see if it will rotate over while the key is ON. BEWARE = the engine "should" start once the starter is engaged, as long a everything else is in good condition. IF it does NOT crank over, then it is time to check the wiring to the starter for bad connections / corrosion. Any $hitty wiring will not carry good battery power & will become a problem, if not all ready. As for the chain case stuff, because the travel motors are far more expensive than opening up the chain case, START there! Remember that you said that you found that fluid level low, so it needs to be addressed now BEFORE it gets even more EXPENSIVE to repair. My bet is that because the fluid level got low, there will be normal damage to your chains & sprockets. It may not be the greatest news for your machine, but sooner versus later usually means "cheaper". A lot of other guys on here have done this type of job. It is somewhat hard, but mainly time consuming. If you find it worn out & you "re-seal" (replace ALL of the wearable seals), then you should be in great shape later on down the road. REPLACE all of the worn parts you find inside; DO NOT skimp on anything = it only bites you in the @$$ later on down the road at the worst possible time.

 

[Gbannish]

On these machines, I have seen a multitude of reasons for them not starting. I always suggest checking the battery, battery terminals & battery cables FIRST! With the weather doing goofy things in regards to the varying air temperatures from day to day, a new battery may be in need. It is VERY difficult to try to convey why that seems to be the case, but it JUST is = very strange!! I also suggest checking all of the fuses. I have seen fuses on my 751 CORRODE to hell because it was missing the fuse covers. I would definetly check those as well. Assuming the battery, cables & fuses are good, I would "JUMP" the starter (very carefully) to see if it will rotate over while the key is ON. BEWARE = the engine "should" start once the starter is engaged, as long a everything else is in good condition. IF it does NOT crank over, then it is time to check the wiring to the starter for bad connections / corrosion. Any $hitty wiring will not carry good battery power & will become a problem, if not all ready. As for the chain case stuff, because the travel motors are far more expensive than opening up the chain case, START there! Remember that you said that you found that fluid level low, so it needs to be addressed now BEFORE it gets even more EXPENSIVE to repair. My bet is that because the fluid level got low, there will be normal damage to your chains & sprockets. It may not be the greatest news for your machine, but sooner versus later usually means "cheaper". A lot of other guys on here have done this type of job. It is somewhat hard, but mainly time consuming. If you find it worn out & you "re-seal" (replace ALL of the wearable seals), then you should be in great shape later on down the road. REPLACE all of the worn parts you find inside; DO NOT skimp on anything = it only bites you in the @$$ later on down the road at the worst possible time.

Hi, Thanks for the suggestions, I'll plan to open up the chain case and inspect, and also to replace all of the wheel bearings (fun times, even bought a cheapo harbor freight 10 ton hydraulic puller for the project!). To clarify the motor issue, the motor would crank when I turned the starter, but it would not start. It always used to start right up immediately when warm, and pretty quickly when cold (so long as I heated the glow plugs for ~20 seconds first). I had added 5 gallons of diesel fuel before using the machine on the day it broke. Thinking the problem might be fuel related, I removed the fuel filter, then reattached, and attempted to bleed the system as per the owners manual (using the bulb pump thing and opening/closing the vent plug). The bulb seemed to be operating as expected. Still no start... One other thing, I had thought (incorrectly?) that the problem might be related to the hydraulic system, similar to how the auxiliary hydraulics can cause hard starting when inadvertently left on, and so messed with the auxillary hydraulics while cranking. When activated (right level pushed outwards), the cranking slowed down noticeably, but when inactivated (pushed inwards) sped up again. I interpreted that to mean that the problem is not related to the auxiliary hydraulics, and that might auxiliary hydraulics are turned off. Due to a nasty bought of poison ivy, these repairs may be delayed. Still confused...

 

[Tazza]

Hi, Thanks for the suggestions, I'll plan to open up the chain case and inspect, and also to replace all of the wheel bearings (fun times, even bought a cheapo harbor freight 10 ton hydraulic puller for the project!). To clarify the motor issue, the motor would crank when I turned the starter, but it would not start. It always used to start right up immediately when warm, and pretty quickly when cold (so long as I heated the glow plugs for ~20 seconds first). I had added 5 gallons of diesel fuel before using the machine on the day it broke. Thinking the problem might be fuel related, I removed the fuel filter, then reattached, and attempted to bleed the system as per the owners manual (using the bulb pump thing and opening/closing the vent plug). The bulb seemed to be operating as expected. Still no start... One other thing, I had thought (incorrectly?) that the problem might be related to the hydraulic system, similar to how the auxiliary hydraulics can cause hard starting when inadvertently left on, and so messed with the auxillary hydraulics while cranking. When activated (right level pushed outwards), the cranking slowed down noticeably, but when inactivated (pushed inwards) sped up again. I interpreted that to mean that the problem is not related to the auxiliary hydraulics, and that might auxiliary hydraulics are turned off. Due to a nasty bought of poison ivy, these repairs may be delayed. Still confused...

Not sure why it wouldn't start, did it crank but not catch or was it bogged down?
There are axle seals on all 4 axles, there is a seal on both drive motors between the motor and the chain case.

 

[7LBSSMALLIE]

Not sure why it wouldn't start, did it crank but not catch or was it bogged down?
There are axle seals on all 4 axles, there is a seal on both drive motors between the motor and the chain case.

i think the point not expressed was if its bogged down. two possible causes 1. aux hyds may have been inaverdantlet engaged. #i problem on the 743. aux engaged by rihgt stick left into detenet. @2 steering componets comprimised (lik trying to start a standard without the clutch. and in first gear.

 

[Gbannish]

i think the point not expressed was if its bogged down. two possible causes 1. aux hyds may have been inaverdantlet engaged. #i problem on the 743. aux engaged by rihgt stick left into detenet. @2 steering componets comprimised (lik trying to start a standard without the clutch. and in first gear.

Thanks guys, the machine cranked but was not bogged down. But the reason it wouldn't start is because I'm a moron and didn't push back down the fuel shutoff knob when shutting the machine off! I was so distraught at the gear/drive problem that I must've forgot. Once realized, but after I had disassembled/reassembled the fuel filter, the machine fired up, but only for 30 seconds. I then noticed a reasonably bad leak at the primer bulb. At that point, I decided I either did not adequately bleed the fuel out or the leak was introducing new fuel, and that I would order a new primer bulb. So once I get the bulb and stop that leak, I think/hope I can bleed the lines and start her up.

 

[Tazza]

Thanks guys, the machine cranked but was not bogged down. But the reason it wouldn't start is because I'm a moron and didn't push back down the fuel shutoff knob when shutting the machine off! I was so distraught at the gear/drive problem that I must've forgot. Once realized, but after I had disassembled/reassembled the fuel filter, the machine fired up, but only for 30 seconds. I then noticed a reasonably bad leak at the primer bulb. At that point, I decided I either did not adequately bleed the fuel out or the leak was introducing new fuel, and that I would order a new primer bulb. So once I get the bulb and stop that leak, I think/hope I can bleed the lines and start her up.

HEHE
Been there! i was sitting in the seat thinking what the hell have i done? then i noticed the shut off cable, then it fired right up. You are not the first to be caught, and will not be the last.

 

[7LBSSMALLIE]

HEHE
Been there! i was sitting in the seat thinking what the hell have i done? then i noticed the shut off cable, then it fired right up. You are not the first to be caught, and will not be the last.

been there. myself forest for the trees thing

 

[Gbannish]

been there. myself forest for the trees thing

I got her started and very happy about that! It was hard for me and took 1/2 day. Here's what I did. I replaced some but not all of the fuel lines. Specifically the line from the fuel shutoff to the bulb, put in a new bulb, then from the bulb to the fuel filter. Also replaced the line from the fuel filter to the injection pump, and another short piece at the injection pump. The bleed bolt on the fuel filter worked great and I was able to squeeze the new bulb and bleed out air from the fuel filter. But the injection pump bleed screw was either broken, isn't working, or I don't know how to use it, because no fluid would leak out. That's what took me forever to diagnose. Finally, I loosened the nut/bolt that the bleeder screws into, and then diesel and bubbles came out. I also cracked open the fuel injection nuts on the first 3 cylinders. Then she fired right up. Big relief, as I was convincing myself that the injection pump must be bad...! (PS- the state of the rubber fuel lines was pretty bad, and I'm planning shortly to replace every piece of supply and return line in the system. Already bought the stuff for inside the tank...).