621D Hydraulic Issues

[Sunesis1]

We are having a issue with the engine cooling fan not running. Last summer this machine was out of town and had a hydraulic tilt cylinder go bad. We contacted the local dealer for repair. They ended up installing a new barrel for the left tilt. After that we had complaints of the machine over heating. Once again we called the local dealer, they ended up replacing the brake pump and freeing up a relief valve on that circuit. We had the machine in the shop for winter work and a complete service. After it went to the job once again the cooling fan does not work. It only works when you first start the machine up then quits. I am affraid that the pump may have went bad again but was wondering if any one else had a issue. Thanks for the help.

 

[hunter29078]

I know this is old but did you ever figure it out? I'm having the same issue.

 

[FWD]

Sunesis has not been on this site in nearly 6 years.
FWD

 

[Coy Lancaster]

I know this is old but did you ever figure it out? I'm having the same issue.

Hey Hunter what is the serial number of your loader? Do you have any warning lights or error codes for brakes or hydraulics?

 

[hunter29078]

no warning light fan just stop turning. Can you explain how the reverse valve works. It has 2 sets of holes, should one set be completely blocked of and the other set completely opened?

 

[Coy Lancaster]

The fan gets its supply oil from brake valve. Do you know how to look up error codes on instrument cluster?

 

[hunter29078]

Sure don't. When it leaves the brake box it goes to a manifold with the reverse valve for the fan, pilot valves and pressure relief valves. I believe the issue is with the reverse valve in that box, or at least part of the problem. Won't know for certain until new one gets here.

 

[Coy Lancaster]

Ok on the top of your IC the two switches on the right is what you use to scroll through the screen. Push the left side of the first switch on right. Then the second switch is you count up/down switch. I forget which side does what, count will start slow but speed up after 10 counts. Scroll up to position 70 put first switch in center that will give you the hours the error occurred and position 71 will give you error code. After that even numbers are hours and odd numbers are codes up to 79 I believe. Do you have a service manual?

 

[Coy Lancaster]

Oh I forgot to tell you you have to push the first switch to left every time you count up and back to center to read screen.

 

[hunter29078]

There aren't any codes

 

[Coy Lancaster]

Hmmm Okay then. Have you checked the brake pressures and have you had someone flowmeter the brake pump?

 

[hunter29078]

I haven't. I see some ports on the brake box, is there a kit that I could buy to check?

I have also noticed the line from the brak box to the reverse box (manifold) seems to heat up faster that the other line.

 

[Coy Lancaster]

There are pressure kits you can buy online for hyd. pressure test. The flowmeter however is quite expensive so you may want to have local dealer to test it for you.

 

[hunter29078]

Does anyone know if from the brake valve hydraulic oil can return to the reservoir without going through the cooling fan?

 

[hunter29078]

There is in fact a line that runs from the brake valve to the reservoir. I am unsure if there is a serviceable valve that is responsible for building pressure. However, anyone that has a fan that is not working this may be the issue.

My issue is the fan stops turning at idle once the hydraulic fluid warms up. This is because the fluid is returning to the reservoir from the brake valve and essentially bypassing the cooling fan.

I have drained the hydraulic tank and inspected suction filter, replaced hydraulic filter, replaced brake pump (which was needed), replaced reverser box/manifold, replaced ran motor. The fan turn well enough to cool when machine is cold, the hydraulics heat up and fan stops causing unit to overheat. For future reference anyone struggling with the same issue look to the brake valve. There are 2 valves on the bottom of the brake valve I plan on taking out and inspecting, if they ar ok then the brake valve itself is around 3k for a reman.

I will post if there is a serviceable valve that fixes the issue.

Thanks,

 

[Coy Lancaster]

You probably have a bad brake pump. It supplies the fan and brake system. You need to have pump flow checked.

 

[hunter29078]

That was a problem. New pump is good, issue is brake valve. Fluid is going back to reservoir from brake valve before it gets to fan.

 

[Coy Lancaster]

Then you probably have a stuck spool in brake valve