743b noisy operations

[Wyatt743]

Have a 1990 743b that sure seams to make to much whining noise when running. Seams to whine way worse when turning, also when In reverse the machine pulls to the left. Not sure if a drive motor would whine thay bad or if it's the pump?

 

[brdgbldr]

Have a 1990 743b that sure seams to make to much whining noise when running. Seams to whine way worse when turning, also when In reverse the machine pulls to the left. Not sure if a drive motor would whine thay bad or if it's the pump?

Some of those models have in-line filters that never get changed. That's where I would start.

 

[Wyatt743]

I know about the hydraulic filter in the back, is there more than one?

 

[brdgbldr]

I know about the hydraulic filter in the back, is there more than one?

There may be an in-line filter that is in the hydrostatic circuit depending on how old your machine is. It looks like a small silver cylinder about 2" in diameter and about 4" long. It is under the cab.

Here is a link to the parts catalog:

Bobcat Parts Catalog - Find Diagrams for Your Equipment - Bobcat Company

Locate all parts and component information about your Bobcat equipment with detailed visual diagrams and illustrations with parts numbers and add to your list.

partscatalog.bobcat.com

Enter your serial number and look at the hydrostatic system. Then type in "filter" in the upper right and hit enter. You will see a schematic of the in-line filter if you have one and then you can look at the hydrostatic circuitry to find which line it is in.

 

[Wyatt743]

My machine does not appear to have a in line filter. The guy i bought it from a few months ago said he just changed the fluid and filter. The lift arms on the machine appear to be "spongy" as well, they seam to almost be able to bounce a inch or two. I know they are supposed to self bleed but do you think it could have air trapped in the system?

 

[brdgbldr]

My machine does not appear to have a in line filter. The guy i bought it from a few months ago said he just changed the fluid and filter. The lift arms on the machine appear to be "spongy" as well, they seam to almost be able to bounce an inch or two. I know they are supposed to self bleed but do you think it could have air trapped in the system?

There could still be air in the system depending on how much use the machine has had since the fluid change.

You can help bleed the air by slowly lifting and lowering the arms all the way up and down several times. Just make sure to keep checking the fluid level and add more as needed.

 

[Wyatt743]

I've used the machine quite a bit, enough to where I would think it would've bled itself out by now.

 

[Tlawdogg]

The in-line filter looks like this:
Sometimes its nasty dirt, oil covered and hard to find. Usually just before a drive motor.

 

[Wyatt743]

I looked again, definitely don't see any other filter.

 

[ward]

Don't forget that the suction line to the lift pump has to have a very good seal so it doesn't suck in air as that will give a sponge feeling to the system and make noise also the hydraulic tank vent needs to breathe freely, I had a John Deere that everyone thought had a cracked hydraulic tank, however the line in to the lift pump was lose the hydraulic oil would foam and come out the fill tube and dribble over which everyone thought it was just from spilling when being topped off in the field, after power washing the tank off and rechecked the suction hose was so stiff one could not tell the fitting in to the pump was lose, it was a 90 that had a o ring and nut to lock it in place, I found the nut was only finger tight, drained the hydraulic tank by putting a hose on the auxiliary line and started the unit and run at idle running the hydraulic fluid in to a 5 gallon bucket it till it stopped, then shut down the unit, if you have do this don't touch your drive and you won't harm it, the lift pump as far as I know is a gear pump and can run dry for a few seconds with out oil and not be damaged. I replaced the o ring reinstalled the 90 fitting topped off hydraulic oil and all was good.

 

[Wyatt743]

I can grab the hose going to the bottom of the tank and move the 90 by hand, so it definitely may be sucking some air. There is no oil leak though which is strange. But when I get some time I will drain the tank and see if I can snug up the fitting good.

 

[ward]

Air will always move more freely than oil, if the tank has a port fitting you will need to replace the o ring to ensure a good seal. If it is a pipe thread fitting that is a 90 it may be a swivel style that could be worn out by vibration, I know the John Deere that I worked on also was not leaking persay but was damp from oil, hydraulics can be strange at times. The line was about 1.5" to 1.75od.