Eagle Hydraulic Pump

[homermandy]

I have a question. I have the hydraulic pump design for running the radiator fan. There is an air cylinder attached to the pump which has a regulator set for 65psi. It looks like it is supposed to push on the pump and create belt tension from the pulley. It has a shutoff valve also. How do I test if this is working? If I switch the shutoff, the cylinder does not depress. I'm wondering if the tension on the belt is enough....

[justin25taylor]

Sounds like it is doing like it should. Leave the valve open. I THINK the thought was making belt changes easier (like the 60 series) If you need me to I can look it up in "Da Book"

[Tony LEE]

Assuming it is similar to the MCI system --

there is a spring inside the cylinder that will provide some tension during the airup stage.

With the engine off and no air pressure, squeeze the belt together by hand. There should be some resistance but the spring should re-tension the belt when you let go.
Air up the bus and switch the engine off and check the tension again by hand. Should be much more tension this time.

Operate the manual valve - cylinder should move to unload the belts completely.

Is there a pressure test port just on the outlet of the regulator - test with a tyre gauge.
Is there any pressure to the inlet of the regulator. At the outlet. At the non-piston end of the cylinder. Can get some idea by loosening the various fittings. Does air exhaust from the manual valve exhaust port as you switch the valve over.

Is the cylinder leaking so badly that it can't oppose the spring enough to unload when you operate the manual valve.

[homermandy]

Tony,
Yes, there is a tire like port. I will check the pressure. There is a shutoff valve also. When I turn it perpindicular to the line, it has a hissing sound and keeps hissing. I will do some diagnostics today and let you know. Thanks

[homermandy]

Also, there is a temperature sensor connected to the coolant pipe. 2 lines into it. I assume as coolant temp increases, it lets more fluid through to the motor to turn faster. I'm trying to diagnose whether this is working correctly. Short of a hard pull and heating up the system, getting out quickly and looking at how fast the fan is turning, any other suggestions? Also, I have seen people post issues with this sensor. Just wondering if you bypass the sensor and connect the hoses together whether the fan would turn 100% all the time?

[Tony LEE]

I had hissing on the bus AC system when I turned the manual valve -- turned out to be a hole in the line that un-tensions the belt - worn through by the belt.

My alternator used to only partially unload too. Also constant hissing. Turned out to be the manual valve so I removed it and just connected the hose from the regulator output to the end of the cylinder that does the tensioning. To change belts I would have to allow the air pressure to drop and then use a bar to swing the alternator to slacken the belts. Cheaper and easier than finding a replacement valve here.

I've eliminated the air tensioning on the AC compressor because of air leaks and the alternator will likely be next.

Does your cylinder have an airline to both ends. If it does and the air is coming out of the exhaust port on the manual valve then it probably means that the piston seals are worn. This will also mean the tensioning force is not as much as it should be.

It is quite likely that any air tensioning cylinders need the seals replaced. Not a difficult job and the bits are likely to be pretty cheap over there.

As I said, my bus is an MCI

[homermandy]

I checked the valve and it has 60psi. There is an adjustment valve and I could see the spring travel as I rotated the valve, so it works fine. Anyone know the tension on the belts for this setup? Thanks

[homermandy]

On a side note, I disconnected the two lines at the thermocouple and connected them together. I assumed since I was bypassing the thermocouple, I would have full fan speed. It didn't make much of a difference, meaning I was not getting blown away by the fan. Should this concern me? It also looks like the fan rotation and the fins would pull air into the engine bay. Sound correct?

[homermandy]

Excellent info.

http://domweb.sauer-danfoss.com/domdb/SauerLit.nsf/1526f939eb2e202286256c5b0062ff21/C1A469F4F55E628C86256CC7006AF540/$file/520L0824_Fan%20Drive%20Control%20ME_TI_Nov-2005_Rev%201.pdf

It's actually the reverse. As coolant temp increases, valve closes increasing pressure...