743 Relief Valve

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uffda

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I would like to take out the Hydrostatic Relief Valves and see if they are rusty, plugged up, whatever. Do I need to drain the system, are they under pressure? It looks like a simple process. Or do I take it to the dealer? Any help appreciated..
 

Tazza

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they are not under pressure, just springs, the only issue is access, two are on top, the other two are underneath the pump i believe.
 

Tazza

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You need to pull the pump i'm afraid, what issues are you having that you suspect the relief valves?
 
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uffda

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Dealer says make sure the steering is tight , and he says there won't be any noise. He says it can't be the brake, so I reworked the steering with bushings, etc and it is pretty good, but when I step on the brake it makes a constant loud noise. I have read other comments that the relief valve on the hydrostatic pump gets rusty and the spring gets stuck. I watched a video about the pump and what the valve looks like so that's what I wanted to check
 

laurencen

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743 if I recall are on the valve body right side of machine, was a royal pain working with the motor in but to set pressures you need motor running, mine had broken spring
 
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uffda

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743 if I recall are on the valve body right side of machine, was a royal pain working with the motor in but to set pressures you need motor running, mine had broken spring
I thought you could take out the relief valve, look it over or replace, put back in. I thought the springs were all ready set, no pressure testing.
 

laurencen

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on ours yes you can get to the valves but a decent reach between the motor and side wall, you can adjust the pressure, remove the cap, loosen nut and adjust, we put a pressure gaugh on the aux port and watched pressure as adjusting
 

Iguana

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Was it a rattling kind of noise? Reason for asking is that i removed my pump and had it checked but couldnt find anything wrong with it. I have noticed that the noise gets worse when turning right when going left it was ok. Could that also be the relieve valve . Im thinkung its left drive motor. Also going to the left when driving in straight line. Sorry for hijacking your post but have been battling with my 743
Thanx
 

Tazza

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That noise is not your relief, that is your motors fighting against the brake.

Lift the machine off the ground so all wheels can move, start the engine and see if the wheels turn, if they move, your steering is not in neutral, i'd almost put money on that being your issue. Relief valves will cause a lack of power either forward or backwards, they limit the pressure that the pumps can apply to the drive motors.

You hear it when turning, what sort of revs are you running at? low speed, it makes more noise than when revved up?
 

Iguana

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Yes makes more noise at lower revs. When you lift the machine off the ground the wheels are standing still. No noise at all when standing still at idle or high revs. Only when pushing or pulling left handle to make it turn left in reverse or right going forward. Thanx for the help!
 
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uffda

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That noise is not your relief, that is your motors fighting against the brake.

Lift the machine off the ground so all wheels can move, start the engine and see if the wheels turn, if they move, your steering is not in neutral, i'd almost put money on that being your issue. Relief valves will cause a lack of power either forward or backwards, they limit the pressure that the pumps can apply to the drive motors.

You hear it when turning, what sort of revs are you running at? low speed, it makes more noise than when revved up?
Tazza: That is what my dealer said too. He said to work on the steering to get it in neutral. I will keep trying to find that neutral.
 

laurencen

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100% way I know how to set neutral, lift machine and block it so wheels are free, lift cab, at the back at the back right side are the forward/reverse levers, on them are blocks that push the drive valves, remove the 2 bolts in each and add a spring lock washer to them then tighten, back off about 1/2 thread, start machine, center levers and see which way the wheels turn, with someone holding lever to stop wheel turning use a long punch and tap the block tight against the drive valves, let go the lever and if it still turns repeat in small movements until the wheel no longer rotates, now repeat for the other side.

this method has worked 100% every time even when the dealer could not get it quite right
 
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uffda

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100% way I know how to set neutral, lift machine and block it so wheels are free, lift cab, at the back at the back right side are the forward/reverse levers, on them are blocks that push the drive valves, remove the 2 bolts in each and add a spring lock washer to them then tighten, back off about 1/2 thread, start machine, center levers and see which way the wheels turn, with someone holding lever to stop wheel turning use a long punch and tap the block tight against the drive valves, let go the lever and if it still turns repeat in small movements until the wheel no longer rotates, now repeat for the other side.

this method has worked 100% every time even when the dealer could not get it quite right
Are you talking about the bolts that hold the cams in place. Or is it the two adjusting bolts where you adjust the bars with the cams. What is the idea for the lock washers ???
 

laurencen

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yes the cams at the back, reason for the washers is you can have then tight and tap the blocks/cams just enough to fine neutral, if you just keep loosening moving and tightening its a never ending task getting neutral
 
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uffda

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I put lock washers on the bolts and got the creep to where it barely moves. However I still get that awful noise from the pump when I step on the brake. I even held the hand controls steady and stepped on the brake but that didn't help either. I think its going to the dealer come spring. Right now I need it for snow removal
 

laurencen

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even the smallest creep with brake on it will be noisy as motor is prevented from moving, if the noise starts does releasing brake stop the noise?
 
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