The Combine Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
280 Posts
Discussion Starter #1
Hi all, we recently put a new fan motor on our 1740 bin, after 800 ha I’ve noticed it is already leaking fluid from the shaft seal.
There are 3 return lines.
1. Main fan return (big line straight out of the fan motor) dumps straight into case drain.
2. VR torque converter return (small line) dumps into the case drain.
3. Small line coming out of the back of the motor. I’ve got this one plugged into the return side of the remote running the fan circuit.
Am I setting this up correctly? I’m guessing there’s back pressure somewhere that’s causing the problem.
Running the rig on a t8.360.
TIA.
Hugh.
 

·
Registered
Joined
·
168 Posts
Main return should go into remote small line should go into case drain. Small line will be the one that relieves case pressure, unless you remember to kick the remote into float everytime you shut the fan off you'll eventually blow the seals.
 

·
Registered
Joined
·
339 Posts
Main return should go into remote small line should go into case drain. Small line will be the one that relieves case pressure, unless you remember to kick the remote into float everytime you shut the fan off you'll eventually blow the seals.
Correct. But better yet is to dump the fan return into a low-pressure return port (motor return port) rather than the SCV. Cuts down on heating from the backpressure.
 

·
Registered
Joined
·
280 Posts
Discussion Starter #4
Main return should go into remote small line should go into case drain. Small line will be the one that relieves case pressure, unless you remember to kick the remote into float everytime you shut the fan off you'll eventually blow the seals.
Correct. But better yet is to dump the fan return into a low-pressure return port (motor return port) rather than the SCV. Cuts down on heating from the backpressure.
Given the T8 has 2 low pressure return ports and the cart has 3 return lines which should go into the LP port and which into the scv?
Main return - out of the side of the motor
Fan motor secondary return
Roller motor return
 

Attachments

·
Premium Member
Joined
·
889 Posts
All three straight back to the tank. Don’t use cheap arse hose on the case drain like Flexi coil either, it’ll kink and blow the seal 😡
 

·
Registered
Joined
·
168 Posts
Roller motor return and fan secondary return to low pressure main return to the scv. Check both low pressure returns are actually that, one of my tractors what the dealer said was the low pressure return was actually the hydraulic trailer brake line one blown hypro motor later.
 

·
Registered
Joined
·
280 Posts
Discussion Starter #7
Roller motor return and fan secondary return to low pressure main return to the scv. Check both low pressure returns are actually that, one of my tractors what the dealer said was the low pressure return was actually the hydraulic trailer brake line one blown hypro motor later.
Cheers nicko, I’ll change the male connectors over and give it a try. Hopefully will fix the ongoing problem.
The 2 returns on the T8 both go into a block into a 3/4 steel line. Nothing slowing it down that I can see.
As an aside - what exactly is the purpose of the return line coming out of the back of the motor?
 

·
Registered
Joined
·
168 Posts
The Little line out the back is the case relief, it stops oil that escapes around the rotor inside the motor from building pressure and pushing out through the shaft seal. That's the important one not to have any back pressure on. The cv motor return being a single
line means it doesnt have an internal relief port so it also needs to go back to a pressure free line .The main return can either go into the scv or direct into the reservoir, but it depends on the internal plumbing on the tractor wether this puts extra strain on the hydraulic pump or not. Generally putting the bulk of the returning oil back into the scv means it goes directly back to the pump rather then having to circulate through the whole tractor.
 

·
Registered
Joined
·
280 Posts
Discussion Starter #9
The Little line out the back is the case relief, it stops oil that escapes around the rotor inside the motor from building pressure and pushing out through the shaft seal. That's the important one not to have any back pressure on. The cv motor return being a single
line means it doesnt have an internal relief port so it also needs to go back to a pressure free line .The main return can either go into the scv or direct into the reservoir, but it depends on the internal plumbing on the tractor wether this puts extra strain on the hydraulic pump or not. Generally putting the bulk of the returning oil back into the scv means it goes directly back to the pump rather then having to circulate through the whole tractor.
Just picked up the latest set of seals, my dealer told me to drop the fan scv into float when I shut it down. Is this common practice?
 

·
Registered
Joined
·
2,996 Posts
I have a somewhat newer cart then the one you listed and am pretty sure the fan case drain is tied in with the return low pressure line from the VR motors. That just seems odd somehow if I am to understand that your fan case drain is plumbed in with the return of the fan motor circuit as that would still have some back pressure on that line. On the mechanical meter type tanks of years back they had the separate line from the case drain of the motor all the way to the tractor to plug into a plumbed return to the hydraulic tank. I'd either re-plumb your unit or be tempted to run a hydraulic line right from your fan motor case drain to your tractor and tied into the tank return, using a hydraulic hose vs a rag hose would ensure the hose would not collapse by kinking or being crushed ( an issue with that low pressure hose on the VR carts ). Perhaps that sounds like overkill but that way you could be assured you do not create back pressure on that fan motor case drain.

I had tested the volume of oil coming out of the fan motor case drain when the VR cart was first bought used and there was next to nothing that comes out so certainly no worry about where that oil should flow to at the tractor, only that it be plugged into a no back pressure port to the hydraulic tank.

As to putting the circuit into float position I never did that with the older 2320 cart with mechanical drive or the newer VR cart and so far have never blown the seal on a motor. I don't know if the tractor hydraulic system in the SCV makes a difference between various tractors but two different JD tractors have been used on this last drill without issue.
 
1 - 10 of 10 Posts
Top