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.

 

[Xfaxman]

Good luck. :thumbsup:

 

[oldnslo]

Sure hope it is a simple hose failure. And yes skid loafers are 10 lbs of crap stuffed in 5 lb package

 

[laurencen]

have you got the hydraulic circuit diagram>

 

[Hilbilly]

have you got the hydraulic circuit diagram>

Sort of .......... the dealer gave me an electronic version of the service manual but it has expired so I can't see the entire page any more. I'll just have to chase hydraulic lines and try to find the leak. Problem is, the SS has had a slow leak since I got it and there is oil all over the place, making it hard to see where it's coming from. If I can't find it I may have to try using a pressure sprayer to see if I can clean away some of the oil from inside the cavity.

 

[Hilbilly]

I'm pretty sure I found the leak. It may not be the only one but it is definitely a significant one. It is between the pump side of the 45* male x male elbow and the female part of the female x male adapter that screws into the pump housing.



Does anyone know what type fittings these are. I can't get it apart to see for myself. I'll need to run into the city to get some special tools for this and would like to get the right replacement parts while i'm there. Maybe I'll just stop by the Bobcat dealer and get the parts there. They can probably tell me what tool they use to get access to these fittings too.

 

[Xfaxman]

It is a 45 degree, O-ring face seal fitting: http://blog.worldwidemetric.com/products/an-overview-on-o-ring-face-seal-orfs-fittings/

The O-ring is bad or overtightened.

Do a search for how to measure the size, or check the Bobcat online parts manual.

 

[Hilbilly]

It is a 45 degree, O-ring face seal fitting: http://blog.worldwidemetric.com/products/an-overview-on-o-ring-face-seal-orfs-fittings/

View attachment 543541

The O-ring is bad or overtightened.

Do a search for how to measure the size, or check the Bobcat online parts manual.

Thanks Xfaxman. I didn't know there was an online parts manual. That really helped. Now I can see how it goes together plus I can follow the hydraulic circuitry. The seal must have blown when the pump deadheaded. If I'm lucky that will be the only thing that blew.

After I get this fixed I might take the SS to the dealer and have them perform a flow / pressure / fluid temp check, just to make sure the auxiliary system is operating properly.

 

[Hilbilly]

Next problem.

I can't get the above fitting loose. I can get a 1 1/16" open end wrench on the bend but the wrench ends up against some piping and doesn't leave room to turn it. I can't get a wrench or socket on the nut that is screwed into the pump and I can't find a 1 1/4" crow foot wrench anywhere in the local town or the closest city. So I made this, hoping it would do the job.

I got the wrench over the nut and the fit was good but even with a 1/2" breaker bar and a box wrench over the end of the breaker bar I couldn't get the nut to break free. I have some WD40 soaking on it now and will give it another go. I'm thinking of using an air impact gun on the end of the wrench I made but I'm not sure if that is a really bad idea because the center of rotation is offset or if it has a chance of working.

Thoughts or experienced advise are welcomed. I certainly don't want to damage this. I can imagine this could really expensive in a hurry.

 

[oldnslo]

Hillbilly
I mean this as no insult to your intelligence but are you sure you are turning the nut the correct direction. I know that while standing on your head trying to work things can get mixed up or at least I hope that don稚 happen to just me.

 

[Hilbilly]

Hillbilly
I mean this as no insult to your intelligence but are you sure you are turning the nut the correct direction. I know that while standing on your head trying to work things can get mixed up or at least I hope that don稚 happen to just me.

A very good question and no offensive taken. Unless this is a left hand thread, I'm sure I'm trying to turn it the right way, ie. counterclockwise. I managed to get the swivel fitting to turn but for the life of me can't get the bend or the nut (they may be one piece based on the pic that Xfaxman posted) that screws into the pump to budge.

What do you think about trying an impact?