B5200 hydraulic pump keeps blowing front seal

[kjudd]

Hello,

My father has a B5200. When he first got it had milk for hydraulic fluid and wicked blow by. So we have have got the hydraulic oil back to normal. And thru my research on TBN we rebuilt the pump. Well that worked great up until a few weeks ago my dad was moving snow banks with it. and it started pushing hydraulic oil in the engine again. We have 2 theories. 1 its over pressuring the system and blowing the front seal out. 2 there is crap in the hydraulic system taking the front seal out.

For theory 1 does anyone know where the pressure relief valve is? and is it just the standard adding and removing washers to adjust it?

I haven't built a pressure gauge yet but I will. My plan is to also get a ready sleeve for it when we replace the seal just be safe. The shaft looked fine when we rebuilt before.

It will probably we a few weeks before we work on it again. Sap should be running again soon so that will take up all of our time.

Thanks
Ken

 

[Egon]

Are the bearings good?

 

[kjudd]

The pump has bushings. Everything is tight. You have to have it just right for it to go together. I will recheck it when I tear it apart again.

 

[oldnslo]

kjudd,
Blowing shaft seals is typically caused by one or two different things.
1) On most gear pumps the shaft seal is vented to the pump inlet. When you take the pump apart make certain this vent path is open. Some pumps will allow the seal to be pressed into the point where it can block this vent passage. Double check to make certain this pump is not one of those models.

2) Like Egon states Worn bearings allowing excessive leakage flow into the seal cavity. Check the bearings on both the drive shaft and the driven shaft. Are they worn egg shaped?

 

[kjudd]

judd,
On most gear pumps the shaft seal is vented to the pump inlet. When you take the pump apart make certain this vent path is open. Some pumps will allow the seal to be pressed into the point where it can block this vent passage. Double check to make certain this pump is not one of those models.

Thanks for the suggestion I will make sure to look for that.