bobcat 642 again

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drdent

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Nov 11, 2007
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Hi , I had the engine out of my bobcat, and tazza told me how to line up the splines to get it back in , thanks it worked out fine. Now, the reason i had the engineout was because i was running it and it started to make a clunking, clattering sound that I thought sounded like chain noise.. then it just stopped functioning altogether. the arms wouldn't lift and the wheels would not turn. when I pulled the engine I found that a square key that hold a spline to the front of the pump had sheared off. I replaced the key . I also pulled the plate to see if a chain had broken. The chains were intact. 3 of them were rather snug fitting but one chain had about 3 inches of play in it.I didn't see anyway to adjust the chain tighter so I changed the oil and put the plate back on. now I started it up and the machine can pull itself agian but there is still a loud clunking and clanging noise. what do I need to do now? Is it possible to losen the pump enough to get the other plate off without removing the engine and pump again? hope you can help . mike burnett
 

Tazza

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I think you can, i have had to re-seal my chain case cover under the pump. I removed the metal bracket on the front of the pump to gain access. You may be able to get enough access if you do it that way.
The chains really aren't adjustable but you can get even play between the back and front by loosening the gear box and moving it back or forth to get it equal then re-tightening the gear box.
I hate to say it, but the key being sheared on the back of the pump sounds like you may have a pump issue..... Honestly i would start with the pump and not the drive chains. It takes a LOT of force to shear a key normal operation should never cause this.
Do you only hear the noise when the machine is moving or when you operate the hydraulics?
It may be an idea to block the loader and move the wheels and see if they jump that could indicate you have something wrong with the chains.
 
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drdent

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Nov 11, 2007
Messages
18
I think you can, i have had to re-seal my chain case cover under the pump. I removed the metal bracket on the front of the pump to gain access. You may be able to get enough access if you do it that way.
The chains really aren't adjustable but you can get even play between the back and front by loosening the gear box and moving it back or forth to get it equal then re-tightening the gear box.
I hate to say it, but the key being sheared on the back of the pump sounds like you may have a pump issue..... Honestly i would start with the pump and not the drive chains. It takes a LOT of force to shear a key normal operation should never cause this.
Do you only hear the noise when the machine is moving or when you operate the hydraulics?
It may be an idea to block the loader and move the wheels and see if they jump that could indicate you have something wrong with the chains.
tazza thank you again. yes I only hear the clanging noise when I move the sticks forward or back. It seems alright lifting the bucket. I will block it up and check it again. You say it sounds like a pump problem, sounds expensive. if i remove the pump is there a way to check it or have it checked? I would hate to spend the money on a pump if that is not the problem. I was thinking if the one chain had 3 inches of play maybe it was jumping over the teeth on the gears. I will try again tomrrow and see what I find . thans for the info.. mike burnett
 

sterlclan

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May 1, 2004
Messages
528
tazza thank you again. yes I only hear the clanging noise when I move the sticks forward or back. It seems alright lifting the bucket. I will block it up and check it again. You say it sounds like a pump problem, sounds expensive. if i remove the pump is there a way to check it or have it checked? I would hate to spend the money on a pump if that is not the problem. I was thinking if the one chain had 3 inches of play maybe it was jumping over the teeth on the gears. I will try again tomrrow and see what I find . thans for the info.. mike burnett
to get the cover off loosen the bolts on the engine side of the pump and take the front ones out the sticks may need to come off too when you get the covers off run it (on blocks) and watch the chains. with that much play it may be an axle bearing or a damaged sprocket .....good luck.............Jeff
 

Tazza

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to get the cover off loosen the bolts on the engine side of the pump and take the front ones out the sticks may need to come off too when you get the covers off run it (on blocks) and watch the chains. with that much play it may be an axle bearing or a damaged sprocket .....good luck.............Jeff
It would be a good idea to test it that way actually. Block the machine and see how far you can rotate each tyre. Both front and back tyres should move the same amount on each side. Test one side at a time, testing both rear or both front will tell you nothing.
Hopefully it is just something with the drive line, its cheaper than the pump!
Just spinning the tyres while blocked may not give you the noise as its not under load, but still worth a shot!
 
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drdent

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Nov 11, 2007
Messages
18
It would be a good idea to test it that way actually. Block the machine and see how far you can rotate each tyre. Both front and back tyres should move the same amount on each side. Test one side at a time, testing both rear or both front will tell you nothing.
Hopefully it is just something with the drive line, its cheaper than the pump!
Just spinning the tyres while blocked may not give you the noise as its not under load, but still worth a shot!
Ok . I jacked up the machine and removed the first inspection plate. when I turn the wheels on the right,they both turn the same,and when i turn the left side , they also turn the same. but i can hear the clanging , clunking sound when i turn either side. the only thing I can find loose ,is `what I believe are the brake disc. they are flopping and rattling. are they supposed to be loose? mike
 

Tazza

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Ok . I jacked up the machine and removed the first inspection plate. when I turn the wheels on the right,they both turn the same,and when i turn the left side , they also turn the same. but i can hear the clanging , clunking sound when i turn either side. the only thing I can find loose ,is `what I believe are the brake disc. they are flopping and rattling. are they supposed to be loose? mike
They do run loose. This way they self adjust i guess, but this would make like a scraping sound not clattering like you are hearing..... All i can think of is the chains are making this noise when they go over the guides, some run metal some run plastic. The metal ones obviously are a little more noisy.
It wouldn't be a bad idea to pull the front plate off and turn the wheels and check the state of the chains. See if anything looks damaged.
 
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drdent

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Nov 11, 2007
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They do run loose. This way they self adjust i guess, but this would make like a scraping sound not clattering like you are hearing..... All i can think of is the chains are making this noise when they go over the guides, some run metal some run plastic. The metal ones obviously are a little more noisy.
It wouldn't be a bad idea to pull the front plate off and turn the wheels and check the state of the chains. See if anything looks damaged.
I did pull the plate off.the gears seem fine. the slack in the chains are the same now that I moved the wheels. are the brake disc suppoed to be loose? or should they be ridgid and firm on the gears. there is a lot of slop and noise in them.
 

jerry

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May 3, 2007
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I did pull the plate off.the gears seem fine. the slack in the chains are the same now that I moved the wheels. are the brake disc suppoed to be loose? or should they be ridgid and firm on the gears. there is a lot of slop and noise in them.
The brake discs in my 632 are loose on the spline also, the brake pucks are what keeps them in line. As long as you have the cover off drag a magnet through the oil to see if there are any bits and pieces of metal that may give you a clue as to what is going on.
 
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drdent

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Nov 11, 2007
Messages
18
The brake discs in my 632 are loose on the spline also, the brake pucks are what keeps them in line. As long as you have the cover off drag a magnet through the oil to see if there are any bits and pieces of metal that may give you a clue as to what is going on.
I did clean out all of the oil, and cleaned the bottom of the box,but there was no pieces found. ill check more tommorrow
 
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