Any hydraulics experts around?

I have a tipping trailer with a simple two way maunual lever operated pump and a two stage ram.

It was very cold here overnight and when I tried to operate the pump this morning the lever failed to pump. Eventually it managed to work a bit but wouldn’t pressurise into the second ram stage. When it came down a milky emulsion came out through the tank breather along with some air bubbles.

The rams had new seals last year and it’s not been used a lot since then. Could the cold have an effect on the oil. Is the milky emusion caused by water mixing with the oil and possibly freezing?

Yes, cold weather and cold oil, not a good combination. probably need to let the vehicle run for some time before trying to tip the trailer,when I lived in the USA and it was minus daft every morning in the winter we had to let tractors run for an hour to get warm before we could run the snow blower. also sounds like some water contamination has got into the system

Yep, seals harden on the cold and don’t work as well until they’ve warmed a bit (remember the space shuttle?). Sounds like they are letting water and air into your system.

Thanks for that.

All the hydraulics are mounted to the trailer, so there is no way of warming the oil. I can see how the water could get in through the breater hole in the filler.

Milky emulsion means water in the oil, drain it and replenish with fresh hydro oil.