What causes hydraulic fluid to push past the reservoir breather and run down the side of it? Not a forklift, I know, but a Tennant floor sweeper I'm working on. It's an L.P. 4-cylinder Ford motor. The fluid levels are fine, and I've replaced the reservoir breather recently. I've checked the oil cooler, which is mounted behind the cooling radiator, and it's free of debris and obstructions. Any help is appreciated.