I have recently purchased an old Bobcat 643 with a ford 1600cc engine. I am a first timer with skid steers so have very limited knowledge. The machine worked fine for an hour or two when I first got it but it has started to get a squeel when I turn. The problem has got progressively worse the next couple of times I tried to use it (Lift and tilt still seemed to work fine). Searching through other posts I discovered the bronze filter so I have taken that out (full of dirt) and try to clean as best I can. In the process of doing that I found a split hydraulic hose which I thought may have been the cause which has since been replaced. I put everything back together but it still has the same problem. To make matters worse all functions seem to produce a loud squeeling noise now even lift and tilt. From what I understand these are supposed to automatically bleed, is it possible it may have air in the system or could it be a pump problem? Any help very much appreciated. Thankyou Scott
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I forgot to mention the problems with the drive started after I cleaned the pump and surrounding area with a high pressure hose. I ran the bobcat today for about 15 minutes just lifting the boom up and down and tilting the bucket forward and back to try to bleed out any air. The lift seemed to improve although is still "chattering" a bit when going up. It will only drive on flat surfaces back and forward. Any attempt to turn or go up a slight incline only results in a total refusal and a loud squeal. After running I noticed the hydraulic fluid had bubbled up over the filler cap. Obviously there is a lot of air in the system so would this impede the hydrastatic drive this much? Thanks
OldMachinist
Well-known member
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Sounds like your sucking air into the system. Check the hose from the hydraulic tank to the pump. Maybe when you cleaned it up it exposed a crack in the hose.
With the filter, just cleaning will not always work. You can try leaving it out for a test, see if your drive power returns without it. I think they are pretty cheap from the dealer too.
The system will self bleed over time.
Thanks for your replys. I tried taking the bronze filter out this afternoon and it made a big difference. The bobcat will now go up small hills but still does not have enough power to turn on it axis etc. Both sides seem to be affected equally so I am guessing it must be a pump problem??? I am wondering if there is any other filters in the hydraulic system that may be clogged and restricting flow as the bronze filter was extremely dirty when I removed it the first time? What rpm should the engine be running to drive the pump effeciently? Mine at full throttle (I am guessing as no tacho hooked up) is about 3000 - 3500rpm. The other functions seem to be working normally although I did not try to lift much weight. Tazza where abouts in brisbane is the best (cheapest) place to get bobcat parts?
Another thing, the motor does not seem to "work" when the drive motors are under load like it does when the bucket functions are under load. Sorry about the double post just wanted to give you guys as much info as possible.
Not an issue about the extra post, its only an issue when people post the exact same thing in different sections hoping for faster replies....
Its possible the pump has scores in the wear plates reducing the power to the motors, but it shouldn't just happen, especially on both sides. Is the oil foaming at all? and is the pump getting hot quickly?
If you replaced the main filter in the engine bay, thats the only other filter there is.
As for a cheap place in Brisbane... no such place exists. I deal with clark equipment at Archerfield only when i need to. I did have a setup that they gave me 15% discount because my dad knew a guy there, but the powers higher up figured they are genuine parts, why should they offer a discount, so that went away. Because of that, they would have lost at least $15,000 in parts sales from me, if not more. If i bought pump parts, i would have paid $6,000 instead of the $1,200 shipped i ended up paying from a place in the USA.
Depending on what parts you need, there is a fair bit available for older machines aftermarket. Pump and motor parts especially. Seals can be bought cheaply locally too.
There really is no perfect speed for the pumps, at mid throttle it should work just fine, when the load increases the engine will bog down more, so give it a bit more.
As you did say it has been lower on power since you got it, its totally possible it is wear in the pump. If you have the time, you can use glass and wet and dry to remove most of these scores and hopefully get it back to how it should be.
The oil was foaming after I replaced the hose and put the bronze filter back in but I would say it just had a gutful of air in the lines. The pump gets warm (can touch without burning hand) within a couple of minutes. My thinking is that it may be something simple as it went from running fine to having problems overnight. I removed the main filter today so I will replace that and see what happens. Do you know if there is an aftermarket filter Repco, Ryco etc or do I have to use genuine bobcat? The part no is 6515541. I can see one suspect hose near the battery so I may need to replace that aswell. Best to start with the simple things first and fingers crossed it works.
If you call somewhere like queensland diesel spares they should be able to cross it for you to a fleetguard or donaldson. I'm pretty sure the price you will get will be very close if not more than bobcat is. Bobcat have priced their hydraulic filters are pretty well actually.
The drive is far more forgiving for having air in the system than the hydraulics are. Even with foamy oil, it will drive pretty well. I really don't know what else it could be. Can you remove the pressure sender on the square block and install a pressure gague? this will check your charge pressure.
I got a new bronze filter and hydraulic filter from clarks which suprisingly was quite reasonably priced. I installed and run the machine for about 10 minutes. For the first five minutes or so the machine actually worked like it should actually turning without complaining too much. As it started to heat up the howling started to come back when trying to turn. If the plates were worn would it cause problems as soon as I start it? What is involved in removing them and inspecting for wear? The machine does seem to be improving every time I use it so hopefully after a couple more uses it may return to normal. If not i will try the pressure guage. Is the pressure sender in the fitting on the right hand side(looking at from the front of bobcat) on the front of the square block? Mine looks to have been cut off! Thanks for your help.
Its not always the way, when the oil is cold its thicker than when its warm. As you stated it runs well when cold it probably isn't only wear causing your issue. The pressure sender should be on the front of the square block, if the sender is not there anymore there will be a plug in it. Charge pressure has a lot to do with the drive circuit, if its too low it will howl and not move.
Hopefully its just air that is bleeding out, but i highly doub it from what you describe its doing. Its working fine then not....
To check for wear you need to remove the main pump and pull it down and inspect the rotating groups and wear plattes, there is no easy way i'm afraid.
Bobcatt643
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I have the exact problem with the same machine 643. I going to change the bronz and hydro filter but Im not sure if it will work becouse my bronze filter was not so bad. From where can i see is the oil foam, from the cap of the reservoir? I have spme spots that colecting dust seems like leaks one is on the supply hose from the reservoir and Im thinking to change it. Could this noise be from dameged seals on a drive motor?
Not sure you'd get noise from bad drive motor seals, but i guess it is possible.
