Drive extremley poor and no boom lift....

[gary743]

Hi people,new here to the forum.I recently purchased a 743 very cheap I have worked out the machine is between numbers 501911001 to 501914999. there was no drive when I purchased the machine so complete service on engine and new oil and filter in hydraulic system! still now drive,replaced bronze cented filter in the alloy block on top of the first pump and now the machine will move only just but will not turn!The boom will not lift also.It has a 4 in 1 bucket and holding the aux lever on until bucket jaw is open and continually holding the aux lever on and moving the boom lift pedal the boom will only just move approx 1/3 of the way,the other controls for the bucket work fine. REplaced all case drain houses,pressure hoses and charge hoses{they had damage and old age wear and tear}also replaced front pump to hydrostatic O ring and all other Orings on bungs and fittings that I could get at.Removed the spool valve and replaced all O rings in spool valve assembly. I have not checked for pressures yet. Pumps don"t seem to be too noisy. Hydraulic oil seems to be slightly aerated. My questions are,1what pressures to check and where,what are the pressures! 2what i can look at before i check pressures! 3any ideas about the boom operation! 4I can see that the small front pump has been serviced recently! 5I can see that the back large pumps have been apart some time ago! 6any help would be appreciated Thanks

 

[flyerdan]

If the oil is foamy, there is likely a leak that allows air to be sucked in on the intake side and frothed up. That can seriously degrade hydraulic performance.
There are at least a couple of good books for the 743 in the manual thread, I'd suggest getting one and following the troubleshooting charts.

 

[gary743]

If the oil is foamy, there is likely a leak that allows air to be sucked in on the intake side and frothed up. That can seriously degrade hydraulic performance.
There are at least a couple of good books for the 743 in the manual thread, I'd suggest getting one and following the troubleshooting charts.

thanks Flyerdan for the reply,its pretty hard trying to get info on these older machines in aus,just another question on this 743 do you or anyone else have any contact information on where to buy parts in USA for the pumps on these machines other than through BOBCAT. thanks again.

 

[Tazza]

thanks Flyerdan for the reply,its pretty hard trying to get info on these older machines in aus,just another question on this 743 do you or anyone else have any contact information on where to buy parts in USA for the pumps on these machines other than through BOBCAT. thanks again.

loader parts source will be able to help you out with parts.

 

[gary743]

loader parts source will be able to help you out with parts.

thanks for the information.

 

[gary743]

thanks for the information.

hi,I want to thank everyone that replied about my problem. At this moment I havent solved this problem,but in saying that I think I have found what may be it. the previous owner had tried to fix things himself and made more problems than he had fixed,so the main relief on the control valve apperently has a ORING and a WASHER/BACKUP they can only be purchased in a BOBCAT kit #6661034 and are not available in Aussie,Loader Parts Source do not have them on there web,WHERE CAN I PURCHASE THEM..... thanks in advance for your help,hoping someone can have a contact for me????

 

[gary743]

hi,I want to thank everyone that replied about my problem. At this moment I havent solved this problem,but in saying that I think I have found what may be it. the previous owner had tried to fix things himself and made more problems than he had fixed,so the main relief on the control valve apperently has a ORING and a WASHER/BACKUP they can only be purchased in a BOBCAT kit #6661034 and are not available in Aussie,Loader Parts Source do not have them on there web,WHERE CAN I PURCHASE THEM..... thanks in advance for your help,hoping someone can have a contact for me????

PS for previous post I have no serial numbers on machine I have been using between #501911001-501914999 Control valve (on inlet block) is a Gresen CS on the Bobcat web site Thanks again?????

 

[Tazza]

PS for previous post I have no serial numbers on machine I have been using between #501911001-501914999 Control valve (on inlet block) is a Gresen CS on the Bobcat web site Thanks again?????

I'd like to think you can get seals from other places than bobcat, you're in australia?
I get my seals from a place in underwood, Brisbane. A&B Seals, they are very good at matching them, even if you need to post them, i'm actually off there today to see if they can help me with a seal for an engine.

 

[gary743]

Hello to all,well I have solved my problems,#1 no drive was solved partially by replacing the bronze filter in the square shaped aluminium block mounted to the hydraulic pump (sorry I can’t remember the correct name) after doing this I rebuilt both of the hydrostatic pumps this then solved the drive issues.
#2 prior to me purchasing the machine someone had the control valve apart and numerous other things,the pressure line for lift on the boom has a restriction valve in the pipe fitting on the control valve and someone has replaced it with the incorrect one causing a permanent restriction as it could not move off the seat to allow enough oil flow.
It took a lot of searching for this problem as apparently this machine only uses this control valve system in a small amount of models.
Thanks for the help and directions.

 

[ddbackhoe]

Hello to all,well I have solved my problems,#1 no drive was solved partially by replacing the bronze filter in the square shaped aluminium block mounted to the hydraulic pump (sorry I can’t remember the correct name) after doing this I rebuilt both of the hydrostatic pumps this then solved the drive issues.
#2 prior to me purchasing the machine someone had the control valve apart and numerous other things,the pressure line for lift on the boom has a restriction valve in the pipe fitting on the control valve and someone has replaced it with the incorrect one causing a permanent restriction as it could not move off the seat to allow enough oil flow.
It took a lot of searching for this problem as apparently this machine only uses this control valve system in a small amount of models.
Thanks for the help and directions.

Wow, Just read through this and you certainly have spent a fair deal of time and money fixing this one up. Nice to read that you didnt give up and rescued it.