Hello ! Today I started my dozer and moved it . Ran in for like 15 minutes. Then parked it and came back about 3 hours later . I opened the hydraulic tank cap and a good amount of pressure came out . The hydraulic oil also did a gargling/bubbling noise when I opened the cap. The noise lasted for a couple seconds. What can be causing this ? Is it normal? The sn is 4ls00504 cat d4c . Thanks
Try opening the cap when the tractor is cold. You should still get a small whoosh of air but not a lot. The tank pressurises to a small extent when the oil gets hot which aids the implement pump suction.
That is pretty normal, Cat uses a closed system and the air pressure as a cushion to prevent hydraulic shock.
There's always some pressure released on my 931B that isn't much different. Sometimes I leave the cap loose for 20 seconds or so to let the air escape. Never heard gurgelling but the filter is right there so could be some oil draining from the filter.
That's actually a positive thing, it says your system has no leaks.