We had a cylinder blow out a couple days ago and now it looks like we may have air trapped in the hydraulic fluid. Here's the story. Last week while I was out of town I got a call that the dozer blew a lift cylinder seal, no big deal just have it rebuilt,which they did and reinstalled it. Due to rain the dozer couldn't be ran or the tank topped off. When I got back I topped the tank off and brought the dozer to the house to do a few other repairs which didn't envolve the hydraulics. Yesterday my helper finally got to run it for about 4 hours. Today I went to check things out and noticed that the oil in the sight glass looked "milky". My first thought was water in the oil but now I'm thinking air bubbles. I took a sample off the bottom and top of the tank and both looked identical. Also the tank level was the same as when he left the shop with it. The dozer has only been run about 5 hours since the cylinder rebuild. Wondering if air got in the system and if so how to remove it. I did check the tank vent today also, it was dirty so I cleaned it. Dozer runs and operates fine the oil just looks milky. Dozer is a Case 850G and is being used to clear brush on the ranch. Sorry for the long post.
Drip a couple drops of the milky oil on a hot surface, moisture will sizzle, aerated oil will just smoke.
Just tried this test. The bubbles did come up and bust but didn't really sizzle, will try again when I get some fresh oil for comparison. It sure looks like water but kind of hard to believe seeing as how there was no change in the tank level.
Was it smoking hot? It doesn't take much water to make a milky oil, plus the water will defeat the additives that keep the foaming down. At least that's what I've read...
Delmer, I heated a piece of iron with a torch then poured a little oil on it. The first pour sizzled pretty good then smoked. I waited a few seconds and tried another pour this time the bubbles came up and popped but no sizzle just smoke. I got new oil, filter, and some Seafoam trans fluid cleaner today. Think I am going to pour a can of the Seafoam in and run for 30 min (per Seafoam website) then drain all the oil I can and replace with fresh oil and filter and add the Seafoam. I showed a sample of the oil to our local dozer mechanic today and he immediately said water, this was after he said it was probably air over the phone. It is probably water just funny how it just all of the sudden showed up. Oh well this is pretty much my luck. I will probably send a sample off so I will know, I'll update what I find.
I finally got time to get all the old fluid out and new fluid in. Wasn't a bad job but sure was messy bleeding and blowing out the lines. I think I got 99% of the old oil out. Hopefully this will fix things. Still not sure were the water came from though.
Just a thought that a cap might have been left off the hydraulic tank or the lift cylinder had a collection in it during the repair if it tilted back?
I'm kind of leaning towards a little fluid getting in the lines and cylinder during the repair. After changing the fluid I noticed how brown the old fluid was. It could have just gotten the smount of water it needed to turn milky. I did add 3 cans of Seafoam Trans Tune to the new fluid to help clean things up.