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Bobcat  > Skid Steers  > hydraulic pressure relief  
 
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 Author Thread: hydraulic pressure relief
ksapp is not online. Last active: 4/27/2010 8:42:56 PM ksapp
Joined: 31 Mar 2010
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hydraulic pressure relief
Posted: 03/31/2010 01:15 PM
I have a 91 7753, but apparently the hyd. pressure relief valve is not working--I can't get the hydraulic lines to attach. When I turn the key to release there is no solenoid or relay click. Is there a manual relief? Can I jump across the two wire connections on the relief valve, or from one contact to ground? Thanks for any assistance. K
Tazza is not online. Last active: 10/22/2014 3:19:17 PM Tazza
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Re: hydraulic pressure relief
Posted: 03/31/2010 02:01 PM

There should be a button on the dash (aux pressure release i think it says) with the machine running at idle, press and hold this button, it should shut down and release the pressure.

The other way is turn the key, engage the aux hydraulics with the button and move the thumb switch both ways, that should do the same.... Hopefully!


Bobcat 763 burntSadbut i'm working on it!, 04 S150 with air and a smooshed cab, S250 turbo.
mrfixitpaul is not online. Last active: 11/25/2012 4:08:16 PM mrfixitpaul
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Re: hydraulic pressure relief
Posted: 03/31/2010 02:20 PM
The Aux relief on the 7753 would be to run the engine at idle, shut the engine down and hold the key to the left ('accessory position') while the engine is stopping and for at least 5 seconds after everything has stopped. I believe this will only relieve the pressure to one of the other couplers, by design. I don't think jumping the solenoids will do anything after the engine is stopped, the solenoid is allowing hydraulic pressure to activate the aux spool...if that makes any sense. Of course you can hold a rag over the coupler and push in on the poppet on each coupler to relieve the pressure when the engine is off....as long as you don't have the flush face couplers
Tazza is not online. Last active: 10/22/2014 3:19:17 PM Tazza
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Re: hydraulic pressure relief
Posted: 03/31/2010 04:39 PM
Good point, they use charge pressure apparently to operate the main spool, not just the stem. My bad.

Bobcat 763 burntSadbut i'm working on it!, 04 S150 with air and a smooshed cab, S250 turbo.
ksapp is not online. Last active: 4/27/2010 8:42:56 PM ksapp
Joined: 31 Mar 2010
Total Posts: 3
 
Re: hydraulic pressure relief
Posted: 04/01/2010 02:38 AM
Thanks for your helpful comments. I had already tried left turning the ign key at idle to release pressure. Also with the switch on but not running I had toggled the button on the right stick. Finally, I released the bobcat pressure at the connector by unscrewing the fitting. There was almost no pressure, maybe none since only a few drops of fluid came out. The problem is [I think] with the attachment, a grapple. After all the above, I still could not attach the flat face lines. So I unscrewed the fitting on the attrachment which was under pressure and which bled fluid. After all that the hookup went ok. I had work to do which went ok, so I didn't obsess over the problem. Might be I failed to release and equalize pressure before I shut down last time I used the grapple. I think I'll look into some sort of release valve for the grapple if this problem recurs. Thanks for your advice and help. Ken
mrfixitpaul is not online. Last active: 11/25/2012 4:08:16 PM mrfixitpaul
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Re: hydraulic pressure relief
Posted: 04/01/2010 03:46 AM
If you couple the 2 hoses on the attachment together when when you are removing the attachment, it helps keep the pressure from building up.
skidsteer.ca is not online. Last active: 7/21/2014 8:31:40 PM skidsteer.ca
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Re: hydraulic pressure relief
Posted: 04/01/2010 05:53 AM

Ken

If you leave you grapple jaws open a bit, when you relieve the pressure inside the machine the jaws should close on their own from gravity. If they will close with the engine off, there should be a vaccum inside the line to make conection easier next time.

If you push the jaws tight shut, and pop the couplers, you may have a fight on your hands next time, epsecially if its a hot day and the oil has expanded.

Still on ocasion I find a wrench to loosen the hose is the only way.

Ken


NH LS 160, S150, S185 Hoe Brusher Grapple Auger, Mixer Tiller Soil Conditioner Trencher Tracks Snow Blade Wood Splitter Stump Grinder Land Plane. Dealer Virnig Erskine Componets Plus Wallenstein Bauma Lite
ksapp is not online. Last active: 4/27/2010 8:42:56 PM ksapp
Joined: 31 Mar 2010
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Re: hydraulic pressure relief
Posted: 04/01/2010 09:28 AM
Thanks again. Two more good ideas. I had not taken into account the much warmer temperature. And I probably did disconnect with the jaws shut. I remember once my son took a 2 x 4 and levered up the top claw, easing the connection. Thanks again. Ken
gtstang462002 is not online. Last active: 1/15/2013 5:58:57 PM gtstang462002
Joined: 27 Mar 2010
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Re: hydraulic pressure relief
Posted: 04/01/2010 08:35 PM
Another suggestion that I read on another site was to unhook your hydraulic lines when the fluid is hot. This will allow for the fluid to cool and contract almost making a vacuum for the next hookup, even on a hot sunny day.

Bobcat T300, Possible 751 on the way
Jeff3624 is not online. Last active: 12/30/2011 9:52:17 AM Jeff3624
Joined: 07 Apr 2010
Total Posts: 18
 
Re: hydraulic pressure relief
Posted: 04/07/2010 07:27 PM
by couplers that you can release under pressure. They are awesome. i have them on all my attachments
bobbie-g is not online. Last active: 5/3/2013 7:51:31 PM bobbie-g
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Re: hydraulic pressure relief
Posted: 04/08/2010 09:18 PM
Jeff, which pressure relief couplers did you buy? I tried, but I couldn't tell they worked. On-line source? Smiley RC

RC in Trinidad, CO - 1995 751C (Peugeot engine), 1999 863G, Thomas 4-in-1 bucket, Versatec brush grapple, antique backhoe attachment, 4-way snow blade, home-built stump grubber, forks, Dymax tree shear, Ammbusher mower
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