Stupid NF hydraulic lift...
 

I'm about ready to tear this thing out and throw it on ebay I've had so many problems with it. I swear I've had the pump apart three times now. I've got the problems mostly worked out, and to its credit it works great, but I can't get it to stop leaking around the input shaft. The shaft itself is a brand new hunk of 1/2" steel rod from Mcmaster. I have two seals installed. Any chance I put them in backwards?

Tear it all apart again and take photos!!

We like photos!!:biggrin2:

If you just used cold rolled, not machined rod, the rod could be inaccurate enough to cause leaking past a seal (or two!!):bigthink:

That is possible, there is also the chance that the seals got torn upon install or the shaft you got is to small. I know the one on my 123 has a small leak( never done anything to it) I just keep am eye on the oil if it's not making a huge mess. How bad is yours leaking?

It is machined rod, but there is a little bit of slop in the hole the shaft goes through due to wear. I thought about boring it out and pressing in a bronze bushing, not sure if that would help though.

I know the seals are good. I was very careful when I installed them. I'll rip the pump apart (AGAIN!) and take some pics tonight.

It's leaking pretty bad. There's a nice puddle on the bracket under the pump after about an hour of mowing.

Check your valve as well, it can leak out of it and look like it's coming out of your shaft.

A machined rod is not going to be smooth enough not to tear up the seals. If it was turned on a lathe, the surface is like a very fine pitch screw thread. What you need is chrome-plated rod meant for hydraulic cylinders. McMaster-Carr carries metric sizes specifically for that application, but the inch stuff they have may or may not work for a hydraulic cylinder. I can't tell from reading the description.

Matt G. you are right about the pitch on the shaft. All seal surfaces on spinning shafts are plunge ground as not to put a lead in the surface. I machine shafts for a high end gear boxes and lead in the seal surface will cause a seal to leak bad! It will actually pull the oil out of the seal. If its ground stock from Mcmaster then it was ran threw a centerless grinder which means it was ran threw as a spiral and you can probably see it if you hold it in the light just right. Our ruff stock comes in like that and sometimes you can actualy feel the grooves left in the grinding process.

Great info guys! This is the rod I ordered is 1346K17 on the mcmaster site - sorry, I can't get it to direct link to it.

Says the surface finish is 4-8 rms. Not sure what that really means but is sure looks pretty dang smooth to me.

I'll pull this thing apart in a few hours and post back tomorrow...

The problem with that is it is unfinished, and therefore is going to rust and tear up the seals. These are chrome plated for a reason, so 7936K331 would be a better choice. It appears to meet the specs required for hydraulic cylinder rod chrome plating after a quick google search.

Sorry, Matt, I disagree.

Is the shaft on your Cub Cadet engine plated? There is a seal there!

The shaft on your mower deck has seals, it is not plated.

You can not show an example of a pump with a plated shaft, unless it was improperly designed. None of the major manufacturers plate pump shafts.

A pulley or a coupling will not stay on a chrome plated surface.

Maybe you were thinking the OP was talking about a cylinder.

:bash2: Work must have worn me out more than I thought...

Yep, that's right...I read cylinder somehow.

On seals the finish is usually 2 to 4 micron finish. If it is to smooth then the seals will not break in properly and will leak over time. If its to ruff then it will wear out the seal to fast. When Installing new seals its best to lubricate them with grease so they wont be dry upon first start up.

I know everybody likes pics so here's a few....

The patient with my awesome leaf sucker in tow:
http://img.photobucket.com/albums/v6...107_210056.jpg

The mess:
http://img.photobucket.com/albums/v6...107_204341.jpg

Pump on the bench:
http://img.photobucket.com/albums/v6...107_205535.jpg

The input shaft:
http://img.photobucket.com/albums/v6...107_212444.jpg

Two pics of the seals, it was tough to get these, them things are pretty small.
http://img.photobucket.com/albums/v6...107_212352.jpg

http://img.photobucket.com/albums/v6...107_212436.jpg

What do you guys think? I was leaning toward me having the seals in backwards but I remember when putting them in it woulda been tough to put them in the other way - there's a radius on the "front" and not on the back which woulda made it hard to put them in the other way.

The seals don't expand around the shaft much when I stick it in (heh), it seems as if the seal ID was a little smaller they'd seal better.

It looks to me that the seals are in backwards. The Lip should open up to the side that you want to keep the fluid on.

Kinda like a wheel seal on a trailer hub, the "tough to start" side goes in first!!??

That's what I was thinking, the internal pressure should make the seal lip want to clamp tighter around the shaft rather than open up like it is now.

Sweet pics!

Oh yeah! :beerchug:

spring always goes to the wet side. Also there should be no pressure on the reservoir side.

These seals are so small there isn't a spring. And since the shaft leads to the pocket where the gears are, I'd think there would be at least some pressure there? I guess unless the seals are on the intake part of the circuit...

So the general consensus here is that I put 'em in backwards? I'll try to pull them without damaging them - I'd hate to have to order and wait for two new ones...

If there is room for two seals, and they could (should) be on the suction side, maybe you should only reverse one of them.

Then you are covered both ways.

One other thought before you put the pump back together.

I had a friend that cut the end of an engine shaft to shorten it.

He did not get it straight, the engine had a bushing, not a bearing on the output.

The seal leaked. The mfgr said it was due to the out of balance shaft caused by the angle cut. He cut the shaft straight, the seal stopped leaking.

There is a lot of material ground off one side of the shaft. Could it be out of balance!!?? Put that shaft in a 2500rpm hand drill and spin it, you will feel a lot of out of balance vibration.

Just something to think about as those pumps have very little bearing area and spread.

Well guys, after much effort I finally got it licked. Here are the steps I took:

1) Take pump apart and reverse the outer seal. Still leaks, but not as bad.

2) Take pump apart again and reverse the inner seal. Front shaft is not leaking - yay! But after having this thing apart so many times the seal at the back of the reservoir started leaking. Grrrr...

3) Go to auto parts store and pick up some rubber/steel drain plug washers. Take pump apart again and find out they're too big (I got the smallest ones they had). Say screw it and slap some permatex on the old washer and stick it back together.

It worked! Finally, NO LEAKS! :beerchug:

Glad you got it fixed! :beerchug:

Glad to here it's not leaking.

Same here! You've had a time with this lift!