What causes grease to leak out of grease gun?

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Originally Posted By: rooflessVW
Grease is just oil mixed with a thickener. They separate over time. Some worse than others.


Truth.
 
It's especially bad with cheap grease guns, I have a couple Stewart Warner-Alemite guns that don't leak much at all. At the shop we use SKF-Alemite 555-E guns.....They don't sit long enough for the grease to separate! But I'm sure they would be better than a cheaper gun.
 
I think it's the constant pressure from the spring. I have never had grease separate in the tube. I have some that are 20+ years old and in perfect condition, even sitting in the Florida heat. Some are a lot worse than others but they all leak eventually if left in the gun.
 
Originally Posted By: rooflessVW
Grease is just oil mixed with a thickener. They separate over time. Some worse than others.


That pretty much sums it up. In hot weather it can be worse. Some brands, I won't mention names because it isn't worth the flame war that will follow, are worse than others. Not pulling back on the plunger after using the gun can also contribute more to it as well.
 
You don't have to name names, we all know it's Mobil.

I switch whole fleet of Helicopters from Mobil 28 over to Aeroshell 22 because the Mobil leaked out of everything like crazy in the desert heat.
 
Originally Posted By: motor_oil_madman
Like say for example, the grease is red, so it will leak a red liquid out the bottom of the gun.

funny you mention red. mine leaked all over the place and was light red/ strawberry color. not sure what brand it is but I now leave it in a big bucket. I bought it to grease my truck's drivetrain since the dealer "forgot" to do it every time!
 
The oil will separate from the thickener. Has nothing to do with the grease gun amd everything to do with the grease. When you look at product data sheets this chatacteristic is often listed. Some can have 10% separation, and others 0% separation.

2 options to combat this....one is change your grease to one that does not separate. Other option is pull the plunger on your grease gun when you store it to take the pressure off the grease.
 
One word.... HEAT. Here in Arizona in the Summer, if you park 2 hot vehicles in a 2 car garage, the inside air temperature can easily reach 130F+. You learn real quick to store your loaded grease guns in a heavy gauge plastic bag, or else a plastic storage bin. If you don't you'll end up with a huge mess. This regardless of the type of grease you are working with. They will ALL leak under these high temperatures. Unused unopened grease in tubes must be stored inside. Otherwise the liquid will start leaking out.
 
My grease gun just did this to me last night and it’s been stored in my cool basement the entire time with a tube of Valvoline black grease. Granted it’s about five years old now, but it happened to me just due to age and definitely not caused by heat.
 
Buy a better grease. mine stays in my $15 gun in the combine cab and leaks not a drop. also stays in my $50 gun. and in the tube. and machinery. If the grease doesn't separate, even a cheap gun wont leak... and your equipment is better protected!
 
Originally Posted By: Jddan
Buy a better grease. mine stays in my $15 gun in the combine cab and leaks not a drop. also stays in my $50 gun. and in the tube. and machinery. If the grease doesn't separate, even a cheap gun wont leak... and your equipment is better protected!


Have a recommendation?

Ive had this happen with Mobil 1, Amsoil, and Valvoline synpower greases.

All seemingly "good" greases.

All seemingly NOT making a mess for use upon use, hot and cold cycles after one another...

Until one day its a huge mess.

I do pull the plunger on mine, BTW... Doesnt help.

I now just wrap in paper and leave in a foil tray. Its not if but when... I dont go through a lot of grease, which doesnt help.
 
jhzr2- I currently use Texas Refinery 880 crown and chassis. have not yet had the need for their paragon 3000 or moly paragon or moly 880. I may at some point try one of these but will not be switching brands. my personal opinion- if the grease cannot stand up to the grueling requirements if staying in the gun... Hows it gonna stay in the equipment?
 
Minor oil separation in a bulk container of grease such as a drum is called bleeding. Oil that is squeezed from the thickener due to thickener shrinkage is called syneresis. Often cracks will occur in the grease as oil separates due to syneresis. Oil separating from a grease when the grease is under pressure as in a lube system or grease gun is called migration. The oil moves through the grease due to the pressure. This can cause lube system blockages is the thickener concentrates to that point. Oil can also be separated from by centrifugal force which may possibly be considered to be a form of migration with the force being increased gravity. AGMA coupling standards limit centrifugal separation.
 
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