Bobcat 763 Help

[Hilbilly]

oldnslo
The owners manual that came with the motor has a graph showing side load info. So I'm guessing it is fine to use sprockets. I think I might do that so I can get the rpm's up on the blower.

I used the SS and the blower again today in some very heavy, wet snow. I had to go very slow and make sure the revs were up before engaging the snow or the chute would plug. After fighting with it for about 45 minutes I gave up. The lines were getting hot again and so was the motor. I used the IR to check it but don't trust the thing. It read the motor at 128 F but the QC only read 41F yet it was hot to the touch. Not warm but hot. I also checked the oil cooler temps and there only appeared to be about an 8* F change across the cooler. It read 116 F on the hot side and 106 on the cold side. Doesn't seem like much when the ambient temps are around 32 F. Anyways I switched the blower back the tractor and what a difference the extra HP and rev's make. With the SS at full throttle the blower would only throw the snow about 10'. On the tractor at PTO rpms the snow was blowing at least 20' probably more like 25'. I did note that just a few hundred RPM on the tractor made a big difference in how far the blower threw the snow. I think I need more speed from the hydraulic motor. I may have to switch to a sprocket setup and just use the SS when the snow is lighter, then switch to the tractor when the snow gets really heavy.

 

[bigdeano]

The IR thermometers don't give an accurate reading on a shiny object, like chrome plating.

 

[Hilbilly]

The IR thermometers don't give an accurate reading on a shiny object, like chrome plating.

I wasn't aware of this and thanks for the info.

I finally got around to changing the hydraulic motor to a sprocket mount setup. I used an 18 tooth sprocket on the motor and a 15 tooth on the blower input shaft. I got to try it out today as we had about 4" of snow overnight and this morning. Heavy wet stuff. Before trying it out, I used the digital tach to check the speed on the blower input shaft and it was running at 595 rpm at full throttle. I got the blower setup on my temporary mount to give it another try and it worked great. Success!!!!!!!. I had to travel fairly quickly to get that small amount of snow to load up the blower and when it did, it was throwing snow about 20' maybe 25'. I was very pleased with the results. I suspect it will not have the torque to plow through deep snow or to take full bites but I am fine with that since I can drive forward. One down side I can see using the SS is that I'm sitting lower and closer to the blower so I get a lot more blower mist in my face. Looks like I'll have to make a front plexiglass door for the SS.



I still appear to have a heat issue and I'll have to figure that out but probably not for a while. Snow blowing season is likely done and there are other more pressing things to get done.

 

[laurencen]

have you checked back pressure on the tractor, I run a bobcat snowblower and at no load full rpm the back pressure is less than 100 psi, under load a foot of snow brisk walking it increases to just over 250 psi, my guess you have a restriction in the return flow

 

[Hilbilly]

have you checked back pressure on the tractor, I run a bobcat snowblower and at no load full rpm the back pressure is less than 100 psi, under load a foot of snow brisk walking it increases to just over 250 psi, my guess you have a restriction in the return flow

I assume when you say tractor you are actually referring to my Bobcat skidsteer, as that is the machine with the hydraulic issues. You're the second person that has suggested there is a restriction in the hydraulic lines and I have no doubt your both right. oldnslo has suggested I follow the hydraulic system looking for a device or fitting that is creating heat (ie restriction) but I have not gotten very far with that yet. I have followed the lines to the back of the SS but have not yet tried chasing them under the cab. I guess that will need to be the next step. This will be tricky though. When I stop using the blower, the supply lines cool off very quickly so I might have a difficult time getting the cab lifted in time to find the hot item and I don't think I can run the blower with the cab up. I'll give it a try though.

Have you got any suggestions for finding the restriction? I'm open to ideas.

 

[b7610hsd]

Might be your cross over relief valve.

 

[Hilbilly]

Might be your cross over relief valve.

In order to eliminate the cross over as a potential problem I had previously removed it from the circuit and ran a line directly between the 2 remotes, with a pressure gauge in the line. The result was that at idle I got about 50 psi line pressure and at full throttle there was 600 psi. So there are 3 possibilities; 1) this is normal but I don't think so, despite the Bobcat dealer telling me it is, 2) this is due to line and fitting loses or 3) there is a restriction in the hydraulic system. As several people on this forum have pointed out, their machines run with significantly less back pressure. So I am inclined to agree with those that suggest a restriction somewhere. I just need to find it somehow.

Yesterday when I was setting up the cross over relief valve, the SS stopped suddenly. Like the pump deadheaded. I had the outlet ports plugged, so all the flow was passing through the valve. It was set at 2900 psi when it happened and I left it set there. The pump is only rated for 2973 psi continuously. It ran fine after getting the hydraulics all hooked back up to the blower, with the relief valve in place but it still got hot.

Other than taking it to a dealer and handing over my wallet I can't think of another approach. Maybe if I go back to a direct connection between the remotes and then go looking for hot spots with the SS running.

 

[Xfaxman]

In order to eliminate the cross over as a potential problem I had previously removed it from the circuit and ran a line directly between the 2 remotes, with a pressure gauge in the line. The result was that at idle I got about 50 psi line pressure and at full throttle there was 600 psi. So there are 3 possibilities; 1) this is normal but I don't think so, despite the Bobcat dealer telling me it is, 2) this is due to line and fitting loses or 3) there is a restriction in the hydraulic system. As several people on this forum have pointed out, their machines run with significantly less back pressure. So I am inclined to agree with those that suggest a restriction somewhere. I just need to find it somehow.

-------------------------------.

Your machine will develop full pressure at idle. Full flow happens at max RPM. Resistance to flow causes pressure to increase.

The 600 psi reading may be from the tee fitting the gauge is on. Can you post a picture and give the size of the tee?

 

[Hilbilly]

Your machine will develop full pressure at idle. Full flow happens a max RPM. Resistance to flow causes pressure to increase.

The 600 psi reading may be from the tee fitting the gauge is on. Can you post a picture and give the size of the tee?

Sorry, I didn't get a pic of the test setup and it has been dismantled. But it consists of a 6' length of 1/2" ID hydraulic hose connected to the 1/2" Pioneer QC at the remote and the other end connected to a 1/2" x 1/2" x 1/2" tee. The other end of the T has the same setup back to the other 1/2" Pioneer QC.

I was in the City today and stopped at the Bobcat dealer. Great news ........... the awesome parts guy is back. I BS'd with him for a bit then discussed the issues with him. He called one of their mechanics to the counter to help and after a few minutes a second mechanic showed up and we went through my experiences. They think the temps might be ok but can't confirm there is a back pressure or not because the way they test the machines is different. I think I might just run the Bobcat in and get them to do a flow / pressure / fluid temp check. Sounds like it wouldn't be too expensive and will definitely shed some light on whether or not there are issues I need to be concerned with or if this is simply a matter of me not knowing what is normal. The 2 mechanics said when the do tests on skidsteers and excavators it is not uncommon for the fluid temps to be 140*F.

 

[Hilbilly]

Well the great news was short lived. I used the SS with the blower for about 15 minutes and all seemed to be going well until I got out to check something and noticed an orange colored fluid under the machine. I watched for a few minutes and it was obvious that there is a significant hydraulic fluid leak somewhere. I lifted the cab and could see a lot of fluid on the piping under the left side of the pump but I couldn't see any obvious location for the source. I guess tomorrow I will have to get it in the shop and start climbing around under the cab to see if I can locate the source. Sure hope it is something simple like a loose fitting or a cracked hose and not something serious like a cracked pump. The reason I mention a cracked pump is because one of the mechanics at the Bobcat dealer said he has seen that happen before when a pump deadheads, like mine did yesterday.

I've also read that there is a hose under the pump, in this model, that has a history of failing due to rubbing against the frame. Apparently the easiest way to get access to the hose is to pull the diesel engine.:irked:

Keep your fingers crossed.