Foil too much oil.
Operators, follow the word in TM 5-3805-248-14&P-1 when you check the hydraulic oil with the scraper idling and the cylinders retracted. Checking oil that way saves seals and the hydraulic reservoir's sight glass by making sure you don't overfill the reservoir.
Why idling? Oil expands as it warms up. Warm oil registers a little higher on the gauge than cold oil.
OK, but why retract cylinders? Oil used to extend the cylinders isn't in the reservoir to be measured. It's in the cylinders doing its job. If you measure the tank with the cylinders extended, it looks low.
If you overfill the tank for either reason, pressure builds up-blowing seals. Too much oil has even been known to blow out the hydraulic reservoir's sight glass.
So, before you add oil, make sure the scraper is in the parked position with all cylinders retracted. Let the scraper warm up a few minutes. The hydraulic oil level should show between the ADD and FULL marks.
If you overfill the reservoir, remove the excess with an AOAP vampire pump, NSN 4930-01-1194030.