View Full Version : How to properly purge/bleed a hydralic system.

Ruben Rocha
08-13-2010, 08:00 PM
I have read a lot of posts on this but I did not get the warm comfy feeling.

I am replacing a wheel motor due to the bearing is really bad.

And at the same time I am replacing a pump trunnion seal for the other side.

Drives and pumps seem to be fine other than to much slop on the bearing on one drive and the pump seal leaking on the other side.

So I will drain the fluid on the system and replace same.
At the same time replace the filter
So other than pre-fill the filter. Do I need to attempt to pre-fill the motor?
Also then what is the proper way to bleed the system?

Did I miss a step?

08-13-2010, 08:37 PM
Fill the motor as much as possible. I ground plug wires and crank until the level in the tank starts to drops. Then top off if needed, open tow valves (with wheels elevated) and run at mid throttle until level stabilizes. The close vales and stroke the system.

08-13-2010, 09:24 PM
what is the proper way to bleed the system?

Well Ruben, I've been told different ways by different equipment manufacturers.

Here's what Hydro-Gear has to say about the subject, This pertains to their BDP series pumps;


If you have a different pump on this unit post the numbers and I'll be happy to look up Hydro-Gear's recommended purging procedure.

08-13-2010, 09:43 PM
This site has a wealth of Hydro-Gear info.http://www.m-and-d.com/Hydro-Gear_parts.html

SAVE IT!!!!!

08-13-2010, 11:46 PM
This site has a wealth of Hydro-Gear info

I do too ! :weightlifter: . :laugh:

Ruben Rocha
08-14-2010, 04:54 PM
It is a hydogear bdp pump and white ce motor.
So I will go with your posted procedure.
So I guess it is not necessary to try and pre fill the motor?
FYI. The only reason I mentioned the pump is because I can't get to the darn seal without removing the pump.

Thanks everyone.

08-14-2010, 05:16 PM
So I guess it is not necessary to try and pre fill the motor?

Nope, you could, I don't usually. Just keep an eye on the oil bag.

Ruben Rocha
08-14-2010, 05:24 PM
Being the anal person I am I will probably attempt to do so.
Just not so sure if it will do any good.

08-15-2010, 12:26 PM
It will prevent you from introducing more air into the system. It will take take much longer to bleed the system, and the aerated oil is doing the system no good for sure.
Incredible. If one has no mechanical aptitude, they should use a little common sense.