766 Hydraulics

[Anonymous-0]

I have a 766 with 4500hrs on it that appears to be losing hydraulic pressure. It works fine when first started and as it is used and gets warmed up real good the hydraulics on the auxillary valves gets slow and you must rev it up to at least 2000 rpm to get the remote cylinder to lift. The fluid level is fine and I changed out the fluid and filter this Spring. The tractor is only used for haying and is not worked hard so have a major problem in the winter with condensation in the hydraulics. I am going to overfill with 5 gallons Hytran today to see if that helps when it gets warmed up on the baler. With out any test equipment what can I do to determine if the pump is bad or if it is something else I need to look at. Any and all suggestions are welcomed as I am of average mechanical ability. Taking to the dealer is very expensive and something I would hope to avoid. Thanks to everyone in advance for your help and suggestions, I am not on here often but learn a lot from what I read on this site.

 

[the tractor vet]

Well with out running it on a flow rater to see just how hot it is getting and the output of the pump and the pressure it is making . Or at least putting a gauge to see what you have cold then again hot . My guess is yep it is the pump. Is it hard to replace the pump ?? no ya got a 9/16th socket ?? , just drain the rear end remove the pump and unbolt the pump from the mounting plate remove the gear off the old pump replace all seals and gskt. and o/rings replace with new use two 3/8thsx4 guide studs to help slide the pump back on and hold the gskt in place replace the hyd. filter and fill with new Hy Tran and go . IF you don't like that idea then take it to someone that can test the system .

 

[J. Everett]

The problem may be a plugged filter, have you changed it?

 

[mkirsch]

It would get BETTER as it got hot if it was the filter.

As it stands, though, he already stated that the filter is new.

I agree, it's probably the pump.

The fluid would have to be like gritty, chunky, calf diarrhea in order to be so bad as to cause problems. Then, it wouldn't work at *ANY* temperature, *AND* the pump would be ruined anyway.

 

[Allan in NE]

If you have to replace that pump, consider the hi output unit.

Allan

 

[caterpillar guy]

It is not that expensive to get a pressure gage for about 2500-3000psi and screw it into a coupler plug it in and see what you have for pressure this will give you the pressure for the relief valve . If it is not about 2000-2200 either the pump or relief valve is shot. Then you can put a line to the coupler run it into a 5 gallon pail. Should have 2 of them. Put the line into a pail see what your volume is. You will have to time the oil flow. Also would need to over fill it so you don't damage things from lack of oil. You can also install a TEE in the line to the implement with the gage and see what you get there that would tell if the pump is not doing it's job.