Bob cat 632 overheating hydrolics

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Vern 632

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Aug 23, 2016
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I have a Bob Cat 632 built in about 1982 when I first got it the previous owner used any hydrolic fluid that he could find, have have since changed to 10w40 motor oil that the book called for. in the past several years I have been having more and more trouble with hydrolic system over heating, it gets up to 220 degrees and quits working, the oil cooler is clear, the fins are clear and blower is working ok. In the past when I first got it when the bucket would get hungup it would cause the rear wheels to come off the ground it will not longer do that, also as it get hot is starts screaming like a banchee I have change the brass filteer several times also the Hydro. filter. what is going on with this machine?? Can any one give me some help??
 

Tazza

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It's possible that the pump is worn and causing cavetation which heats up the oil.
The screaming is a sign of cavetation, it will reduce the power of the machine and cause the pumps to heat up really fast. If you run it too long line this, it will casue more damage.
 
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Vern 632

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Aug 23, 2016
Messages
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It's possible that the pump is worn and causing cavetation which heats up the oil.
The screaming is a sign of cavetation, it will reduce the power of the machine and cause the pumps to heat up really fast. If you run it too long line this, it will casue more damage.
Thank you for the info I will be checking pump pressures
 
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Vern 632

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Thank you for the info I will be checking pump pressures
In checking pressures the repair manuel is not clear on where and how to check the pressure going to the drive motors, it shows how to check the charge pressure and the hydrolic pump pressure at the aux. port. it shows that the pressure switch on the port block is rated at 23-27 psi. and that the pressure at the aux port should be 1700-1800 psi but no place do I find the pressure for the lines going to the drive motors. Any ideas??
 

Tazza

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In checking pressures the repair manuel is not clear on where and how to check the pressure going to the drive motors, it shows how to check the charge pressure and the hydrolic pump pressure at the aux. port. it shows that the pressure switch on the port block is rated at 23-27 psi. and that the pressure at the aux port should be 1700-1800 psi but no place do I find the pressure for the lines going to the drive motors. Any ideas??
The only way to check the drive pump pressur is to remove the lines to the motors and install a gauge. Slowly push the stucks forward to build up pressure, it should get to about 5,000 PSI.
You may still be getting to this figure, but if it's cavetating, it will heat up.
 
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Vern 632

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Aug 23, 2016
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7
The only way to check the drive pump pressur is to remove the lines to the motors and install a gauge. Slowly push the stucks forward to build up pressure, it should get to about 5,000 PSI.
You may still be getting to this figure, but if it's cavetating, it will heat up.
Thyanks I will try that also I am checking for air leaks in the incomming lines and port block which may cause the cavation
 
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Vern 632

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Thyanks I will try that also I am checking for air leaks in the incomming lines and port block which may cause the cavation
So far the olny pressure test I have been able to do is the charge pressure test it is 80psi with the sysem just starting up oil silll cool but as soon as I put the machine under load trying to go up a small hill the pressure drops to any where between 20 and 0 psi at this time the machine is screaming as soon as I take the load off it it goes back up to 80 should this pressure be doing that?? if Not then this means that the vane pump is going bad?? any one know what is happening ???
 

Tazza

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So far the olny pressure test I have been able to do is the charge pressure test it is 80psi with the sysem just starting up oil silll cool but as soon as I put the machine under load trying to go up a small hill the pressure drops to any where between 20 and 0 psi at this time the machine is screaming as soon as I take the load off it it goes back up to 80 should this pressure be doing that?? if Not then this means that the vane pump is going bad?? any one know what is happening ???
It's normal for the pressure to dip some, but not to zero. It could be a bad main pump or the drive pumps could be worn too.
If the lift/tilt work well, i don't believe the main drive/charge pump are at fault. The pump gets it's charge pressure from the returning oil from the main hydraulic pump.
 

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